gsm document
DESCRIPTION
TRANSCRIPT
GSM Basic Radio parameters
ZTE University
Objectives
At the end of this course, you will be able to:
Understand the meaning of various radio parameters
Grasp the setting of radio parameters
State the effect to radio network performance of various
kind of radio parameters
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
Roles of identification parameters
Enable the MS to correctly identify the ID of the current
network
Enable the network to be real time informed of the correct
geographical location of the MS
Enable the MS to report correctly the adjacent cell
information during the conversation process
MCC LAC
Cell Global Identity
MNC
3 Digits 2-3 Digits Max 16 Bits
CI
Max 16 bits
LAI
CELL GLOBAL IDENTITY (CGI)
Cell Global Identity (CGI)
It is used for identifying individual cells within an LA
ROLES OF CGI
The CGI information is sent along the system broadcasting
information in every cell.
When the MS receives the system information, it will
extract the CGI information from it and determines whether
to camp on the cell according to the MCC and MNC
specified by the CGI.
It judges whether the current location area is changed,
then determines whether to take the location updating
process.
SETTING OF CGI
MCC(Mobile Country Code):
consists of 3 decimal digits, and the value range is the decimal
000 ~ 999.
MNC(Mobile Network Code):
consists of 3 decimal digits, and the value range is the decimal
00 ~ 999.
LAC(Location Area Code):
The range is 1-65535.
CI(Cell Identity):
The range is 0-65535.
NCC BCC
3 Bits 3 Bits
BSIC
NCC Network/ National Color Code Value Range: 0~7
BCC Base Station Color Code Value Range: 0~7
BASE STATION IDENTITY CODE (BSIC)
Base Station Identity Code (BSIC)
It enables MSs to distinguish between
neighboring base stations
NCC and BCC ROLES
NCC:
In the connection mode (during conversation), the MS
must measure the signals in the adjacent cells and
report the result to the network. As each measurement
report sent by the MS can only contain the contents of
six cells, so it is necessary to control the MS so as to
only report the information of cells factually related to
the cell concerned. The high 3 bits (i.e. NCC) in the
BSIC serve this purpose.
BCC:
The BCC is used to identify different BS using the same
BCCH in the same GSMPLMN.
C B A
F E D
BSIC CONFIGURATION PRINCIPLE
In general, it is required that Cells A, B, C, D, E and
F use different BSIC when they have same BCCH
frequency. When the BSIC resources are not
enough, the cells close to each other may take the
priority to use different BSIC.
ROLES OF BSIC
Inform the MS the TSC used by the common signaling
channel of the cell.
As the BSIC takes part in the decoding process of the
random access channel (RACH), it can be used to prevent
the BS from mis-decoding the RACH, sent by the MS to
an adjacent cell, as the access channel of this cell.
When the MS is in the connection mode (during
conversation), it must measure the BCCH level of adjacent
cells broadcasting by BCCH and report the results to the
BS. In the uplink measurement report, MS must show
BSIC of this carrier it has measured to every frequency
point.
BA LIST (BCCH ADJACENT LIST)
Adjacent cell BCCH table
At most 32 adjacent cell
Carried by BCCH when MS is idle, by SACCH
when MS is dedicated
The MS will first search carriers from this table
and if none is found it will turns to find any of 30
carriers with highest levels.
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
RANDOM ACCESS
Random access is the process that messages
being transmitted on RACH when a MS turns
from “idle” to “dedicate” mode. The main
parameters includes:
MAXRETRANS
Tx_Integer
AC
MAX RETRANS
When starting the immediate assignment process
(e.g, when MS needs location updating,
originating calls or responding to paging calls), the
MS will transmit the "channel request" message
over the RACH to the network. As the RACH is an
ALOHA channel, in order to enhance the MS
access success rate, the network allows the MS to
transmit multiple channel request messages
before receiving the immediate assignment
message. The numbers of maximum
retransmission (MAX RETRANS) are determined
by the network.
MAX RETRANS
The MAX RETRANS is often set in the following ways:
For areas (suburbs or rural areas) where the cell radius is more
than 3km and the traffic is smaller, the MAX RETRANS can be
set 11 (i.e. the MAX RETRANS is 7).
For areas (not bustling city blocks) where the cell radius is less
than 3km and the traffic is moderate, the MAX RETRANS can be
set 10(i.e. the MAX RETRANS is 4).
For micro-cellular, it’s recommend that the MAX RETRANS be
set 01(i.e. the MAX RETRANS is 2).
For microcellular areas with very high traffic and cells with
apparent congestion, it’s recommend that the MAX RETRANS
be set 00(i.e. the MAX RETRANS is 1).
Transmission Distribution Timeslots
(Tx_integer)
The Tx_integer parameter is the interval in timeslots at which
the MS continuously sends multiple channel request messages.
The parameter S is an intermediate variable in the access
algorithm, and is to be determined by the Tx_integer parameter
and the combination mode of the CCCH and SDCCH
Format of Tx_Integer
MS starts the first channel request message : {0, 1, ...,
MAX (Tx_integer, 8)-1}
The number of timeslots between any two adjacent
channel request messages {S, S+1, ..., S+Tx_integer-1}
The Tx_integer is a decimal number, which can be 3~12,
14, 16, 20, 25, 32 and 50 (default). The values of the
parameter S are shown as below:
Tx_integer
CCH Combination Mode
CCCH Not Shared with SDCCH CCCH Shared with SDCCH
3, 8, 14, 50 55 41
4, 9, 16, 76 52
5, 10, 20, 109 58
6, 11, 25, 163 86
7, 12, 32, 217 115
ACCESS CONTROL AC
The access levels are distributed as follows:
C 0~C9: ordinary subscribers;
C11: used for PLMN management;
C12: used by the security department;
C13: public utilities (e.g. water, gas);
C14: emergency service;
C15: PLMN staff.
SETTING OF AC
In the BS installation and commissioning process or in the
process of maintaining or testing some cells, the operator
can set C0~C9 as 0 to forcedly forbid the access of
ordinary subscribers so as to reduce the unnecessary
effects on the installation or maintenance work.
In some cells with very high traffic, the congestion will
occur in busy hours. For example, the RACH conflict
happens frequently, the AGCH is overloaded and the Abis
interface flow is overloaded. The network operator can set
proper access control parameters(C0~C15)to control
the traffic of some cells.
CCCH_CONF
CodingMeanings
CCCH message
blocks in one
BCCH
0 CCCH use one basic physical channel, not shared with SDCCH 9
1 CCCH use one basic physical channel, shares with SDCCH 3
10 CCCH use two basic physical channels, not shared with SDCCH 18
100 CCCH use three basic physical channels, not shared with SDCCH 27
110 CCCH use 4 basic physical channels, not shared with SDCCH 36
Others Reserved
CCCH_CONF
The CCCH can be one or more physical channels. The
CCCH and SDCCH can share the same physical channel.
The combination mode of the common control channel in a
cell is determined by the CCCH_CONF
CCCH_CONF
The CCCH_CONF is determined by the telecom
operation department according to the traffic
model of a cell.
If a cell has 1 TRX, we recommend that the CCCH
uses one basic physical channel and shares it with the
SDCCH
If a cell has 2 ~ 8 TRX, we recommend that the CCCH
uses one basic physical channel but does not share it
with the SDCCH.
AGBLK
Since the CCCH consists of the access grant
channel (AGCH) and paging channel (PCH), it is
necessary to set how many blocks of the CCCH
information blocks are reserved and dedicated to
the AGCH, the access grant reserve blocks
(AGBLK).
AGBLK is represented in decimal numerals, and
its value range is:
CCCH is not combined with SDCCH: 0~7.
CCCH is combined with SDCCH: 0~2.
AGBLK
SETTING AND IMPACT OF AGBLK
The AGBLK setting principle is: given that the AGCH is
not overloaded, try to reduce the parameter as much as
possible to shorten the time when the MS responds to
the paging and improve the quality of service of the
system.
The recommended value of AGBLK is usually 1 (when
the CCCH is combined with the SDCCH), 2 or 3 (when
the CCCH is not combined with the SDCCH).
BS-PA-MFRMS
According to the GSM specifications, every mobile
subscriber belongs to a paging group. the MS calculates
the paging group to which it belongs by its own IMSI.
In an actual network, the MS only "receives“ the contents
in the paging subchannel to which it belongs but ignores
the contents in other paging subchannels. (i.e. DRX
source).
The BS-PA-MFRMS refers to how many multi-frames are
used as a cycle of a paging subchannel. This parameter in
fact determines how many paging sub-channels are to be
divided from the paging channels of a cell.
BS-PA-MFRMS
Multiframes of the same
paging group that cycle
on the paging channel
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
BS-PA-MFRMS (2)
BS-PA-MFRMS is represented in decimal
numerals and its value range is 2~9, its unit is
multiframe (51 frames), its default value is 2
PERIODIC UPDATING TIMER (T3212)
The frequency of periodic location update is
controlled via the network and the period length is
determined by the parameter T3212.
The T3212 is a decimal number, within the range
of 0~255, in the unit of six minutes (1/10 hours).
If the T3212 is set to 0, it means that the cell
needs no periodical location update.
NCCPERM
In the connection mode (during the conversation), the MS will report the measured signals of the adjacent cells to the BS, but each report may contain at most 6 adjacent cells.
Therefore, let the MS only report the information of the cells that may become the hand-over target cells.
The above functions can be fulfilled by limiting the MS to merely measure the cells whose NCC have been specified. The NCCPERM lists the NCCs of cells to be measured by the MS.
NCCPERM will affect handover
RADIO LINK TIMEOUT (RLT)
GSM specification stipulates that the MS must have a timer
(S), which is assigned with an initial value at the start of
the conversation, that is, the “downlink radio link timeout”
value.
Every time the MS fails to decode a correct SACCH
message when it should receive the SACCH, the S is
decreased by 1. On the contrary, every time the MS
receives a correct SACCH message, the S is increased by
2, but the S should not exceed the downlink radio link
timeout value. When the S reaches 0, the MS will report
the downlink radio link failure.
The radio link timeout is a decimal number, within the
range of 4 ~ 64, at the step of 4, defaulted to 16.
MBCR (1)
The parameter "multiband indication (MBCR)" is
used to notify the MS that it should report the
multiband adjacent cell contents.
The value is 0-3
MBCR (2)
0: Based on the signal strength of adjacent cells, the MS reports the
measurement results of 6 adjacent cells whose signals are the strongest,
whose NCC are known and allowed no matter in which band the adjacent
cells lie. The default value is “0”
1: The MS should report the measurement result of one adjacent cell in
each band (not including the band used by the current service area) in the
adjacent table, whose signal is the strongest and whose NCC is already
known and allowed.
MBCR (3)
2: The MS should report the measurement results of two adjacent cells
in each band (not including the band used by the current service area)
in the adjacent table, whose signals are the strongest and whose NCC
are already known and allowed.
3: The MS should report the measurement results of three adjacent cells
in each band (not including the band used by the current service area)
in the adjacent table, whose signals are the strongest and whose NCC
are already known and allowed.
Application of MBCR
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
CELL SELECTION C1
When the MS is turned on, it will try to contact a
public GSM PLMN, so the MS will select a proper
cell and extract from the cell the control channel
parameters and prerequisite system messages.
This selection process is called cell selection.
The quality of radio channels is an important factor
in cell selection. The GSM Specifications defines
the path loss rule C1. For the so-called proper cell,
C1>0 must be ensured.
C1 = RXLEV - RXLEV_ACCESS_MIN
- Max(MS_TXPWR_MAX_CCH - P ,0)
CELL SELECTION C1
where:
RXLEV_ACCESS_MIN is the minimum received level the
MS is allowed to access the network
MS_TXPWR_MAX_CCH is the maximum power level of
the control channel (when MS sending on RACH);
RXLEV is average received level;
P is the maximum TX power of MS;
MAX(X, Y)=X; if X Y.
MAX(X, Y)=Y; if Y X.
RxLevAccessMin
The RXLEV_ACCESS_MIN is a decimal number,
within the range of -110dBm ~ -47dBm
Default value is 0 (-110dBm).
RXLEV_ACCESS_MIN Meaning
-47 dBm > -48 dBm (level 63)
-46 dBm -49 ~ -48 dBm (level 62)
... ...
-108 dBm -109 ~ -108 dBm (level 2)
-109 dBm -110 ~ -109 dBm (level 1)
-110 dBm <-110 dBm (level 0)
Setting and Influence
For a cell with traffic overload, you can appropriately
increase the RXLEV_ACCESS_MIN
RXLEV_ACCESS_MIN value cannot be set to too high a
value. Otherwise, “blind areas” will be caused on the
borders of cells.
It is suggested that the RXLEV_ACCESS_MIN value
should not exceed -90 dBm.
CELL RESELECTION C2
Cell Reselection (C2) is a process when MS change its
service cell in idle mode.
When the MS selects a cell it will begin to measure the
signal levels of the BCCH TRX of its adjacent cells (at
most 6)
When given conditions are met, the MS will move from the
current cell into another one. This process is called cell
reselection.
When C2 Parameter Indicator (PI) indicates YES,the MS
will get parameters (CRO, TO and PT) , from BCCH, to be
used to calculate C2(channel quality criterion), which serves
as cell reselection norm. The equation is as follows:
Where T is a timer. When a cell is recorded by MS as one
of the six strongest cells, timer starts counting, otherwise, T
is reset to zero.
C2=C1+CRO-H(PT-T)×TO, when PT≠ 31
C2=C1-CRO , when PT= 31
CELL RESELECTION C2
PARAMETER INDICATOR (PI)
PI is used to notify the MS whether to use C2 as the cell
reselect parameter and whether the parameters calculating
C2 exist.
PI consists of 1 bit. “1”means the MS should extract
parameters from the system message broadcasting in the
cell to calculate the C2 value, and use the C2 value as the
standard for cell reselect; “0” means the MS should use
parameter C1 as the standard for cell reselect (equivalent
to C2=C1).
CRO, PT AND TO
The cell reselection initiated by the radio channel quality regards C2
as the standard. C2 is a parameter based on C1 plus some artificial
offset parameters.
The artificial influence is to encourage the MS to take the priority in
accessing to some cells or prevent it from accessing to others. These
methods are often used to balance the traffic in the network.
In addition to C1, there are three other factors influencing C2, namely:
CELL_RESELECT_OFFSET (CRO), TEMPORARY_OFFSET (TO)
and PENALTY_TIME (PT).
Format of CRO, PT and TO
The CRO is a decimal number, in dB, within the range
of 0 ~ 63, meaning 0 ~ 126 dB, at the step of 2 dB.
The TO is a decimal number, in dB, within the range of
0 ~ 7, meaning 0 ~ 70 dB, at the step of 10 dB, where
70 means infinite.
The PT is a decimal number, in seconds, within the
range of 0 ~ 31, meaning 20 ~ 620 seconds for 0 ~ 30,
and at the step of 20 seconds. The value of 31 is
reserved to change the direction of effect that the CRO
works on the C2 parameter.
C2 TYPICAL APPLICATIONS
For cells where the traffic is very heavy or the
channel quality is very low. the PT may be set 31,
making TO invalid, so C2=C1-CRO.
For cells where the traffic is moderate, the
recommended value for CRO is zero and PT=31,
thus causing C2=C1, i. e. no artificial impact will
be imposed.
C2 TYPICAL APPLICATIONS
For cells with light traffic, it’s recommended that CRO
be ranged from 0 to 20dB. The greater the CRO, the
more possible the cells will be reselected ,and vice
versa. It’s also suggested that TO is equal or a little
higher than CRO. PT, whose main role is to avoid
frequent cell reselection by MS, is generally
recommended to be set at 20 seconds or 40 seconds.
CELL SELECTION HYSTERESIS (1)
When a MS reselects a cell, if the old cell and the target
cell are in different locations, then the MS must initiate a
location updating process after cell reselection.
Due to the fading features of the radio channel, the C2
values of two adjacent cells measured along their borders
will fluctuate greatly.
MS will frequently conduct the cell reselection, which will
not only increase the network signaling flow and lead to
low efficiency use of radio resources, but reduces the
access success rate of the system, as the MS cannot
respond to paging calls in the location updating process.
CELL SELECTION HYSTERESIS (2)
To minimize the influence of this issue, the GSM
specifications put forward a parameter called
ReselHysteresis,
The cell selection hysteresis is represented in
decimal numerals, its unit is dB, its range is 0~14,
its step length is 2dB, and its default value is 4.
CELL RESELECTION PRINCIPLE
If the MS calculates that the C2 value of an adjacent cell (Same location area) surpasses the C2 value of the serving cell and maintains for 5s or longer, the MS will start cell reselection .
If the MS detects a cell that is not in the same location area with the current cell, the calculated C2 value surpasses the sum of the C2 value of the current cell and the ReselHysteresis parameter and if it remains for 5s or longer, the MS will start the cell reselection .
The cell reselection caused by C2 should be originated at least at the interval of 15s.
In the system message broadcasting in each cell, there is a bit
information indicating whether to allow the MS to access to it, which
is called cell bar access (CBA). The parameter CBA is to indicate
whether the cell bar access is set in a cell.
The CBA bit is a parameter for the network operator to set. Usually
all the cells are allowed to be accessed by MS , so the bit is set
NO. However, in special cases, the telecom operator may want to
assign a certain cells for handover service only, then the bit can be
set YES.
CELL BAR ACCESS (CBA)
Area A
MS A
BTS B
BTS C
CELL BAR ACCESS (CBA)
CELL BAR QUALIFY (CBQ)
In areas where the cells overlay with each
other and differ in capacity, traffic and
functions, the telecom operator often hopes
that the MS can have priority in selecting
some cells, that is, the setting of cell priority.
This function is set by way of the parameter
"Cell Bar Qualify" (CBQ).
C1 and C2 States with CBA and CBQ Configurations
CBQ CBACell Selection
Priority
Cell Reselection
State
No No Normal Normal
No Yes Barred Barred
Yes No Low Normal
Yes Yes Low Normal
CELL BAR QUALIFY (CBQ) 2
B A
EXAMPLE OF CBQ SETTING
For some reasons, the traffic of Cells A and B is apparently higher
than that of other adjacent cells. To balance the traffic in the whole
area, you can set the priority of Cells A and B as low, and set the
priority of the rest cells as normal so that the traffic in the shade
area will be absorbed by adjacent cells. It must be noted that the
result of this setting is that the actual coverage of Cell A and Cell B
is narrowed. However, this is different from reducing the transmitting
power of Cell A and Cell B, the latter may cause blind areas of the
network coverage and the reduction of communication quality.
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
LIMITn
According to GSM Specification 05.08, the BTS must
measure the interference levels of the upward links of all
the free channels for the purpose of providing basis for
managing and allocating radio resources.
Moreover, the BTS should analyze its measured results,
divide the interference levels into 5 grades and report them
to the BSC. The division of the 5 interference grades (i.e.
the so-called interference bands) is set by the operator
through the man-machine interface. The parameter
"Interference band border(LIMITn)” determines the borders
of the 5 interference bands.
Value Range Specified dBm Level
0 <-110 dBm
1 -110 dBm ~ -109 dBm
2 -109 dBm ~ -108 dBm
…
61 -50 dBm ~ -49 dBm
62 -49 dBm ~ -48 dBm
Default: LIMIT1:4 LIMIT2:8 LIMIT3:15 LIMIT4:25
LIMITn
The division of the interference bands should be favorable in
describing the interference in the system. Generally the default values
are recommended. In the ordinary situations, the free channel
interference level is smaller, so the LIMIT1~4 value should be
smaller. When apparently large interference appears in the system,
you can properly increase the LIMIT1~4 values in order to know the
exact interference.
INTAVE
Due to the randomness of the radio channel
interference, the BTS must average the measured
uplink interference levels within the specified
period, and this average cycle is determined by
the INTAVE parameter.
This parameter is a decimal number, in SACCH
multi-frames, within the range of 1 ~ 31.
New Cause Indication (NECI)
The NECI is a decimal number, within the range of
0 ~ 1, with the meaning described as below:
When the NECI is 0, it means that the cell does not
support the access of half-rate services.
When the NECI is 1, it means that the cell supports the
access of half-rate services.
RE-ESTABLISHMENT ENABLE (RE)
For the drop calls caused by the radio link fault, the MS can start the call reestablishment process to resume the conversation, but the network is entitled to determine whether the call reestablishment is allowed or not. “0”=Yes, “1”=No.
In some special circumstances, the drop call may occur when the MS goes through a blind area during the conversation. If the call reestablishment is allowed, the mean drop call rate will be reduced. However, the call reestablishment process will occupy a longer period of time, most of the subscribers have hung up before the reestablishment process is over, as a result, the call reestablishment failed to achieve its purpose and wasted many radio resources. We recommend that the call reestablishment be not allowed in the network except for some individual cells.
GSM Coverage problem & Solution
ZTE university
Objectives
To know different kinds of coverage problem, their
causes and solutions.
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Overview of coverage problem
Weak coverage
Over coverage
No-serving cell coverage
Too small coverage range will cause high
call drop rate and a large number of
customer complaints.
Too large coverage will result in frequent
handovers, and mutual interference as
well, if it’s rather serious, and network
indicators will also be affected.
When cell reselection parameters and
handover scenarios are similar, or there
are 2 or more cells with similar signal
strength ,Pingpong handover is easy to be
caused during calls.
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Main causes of weak coverage
Weak coverage
too small BTS power
too low antenna height
too small down-tilt
hardware problem
Obstruction of buildings
Main causes of over coverage
too high antenna height
inappropriate down-tilt
poor antenna performance
Causes of no-serving cell coverage unreasonable planning
of antenna parameters
inappropriate type of antenna
too large or too small
carrier transmission power
shrunk coverage caused
by equipment problem
influence of changes
in radio environment
unreasonable setting
of handover parameters
unreasonable setting of
cell reselection parameters
no-serving cell coverage
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Procedures of Handling Coverage Problem
Check setting of problem BTS’ radio parameters
Check if strong interference source exists
Check hardware
Check antenna system
Analyze the local geographical environment to
see if site location and type of site are appropriate
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Poor coverage at cold storage warehouse
【Problem description 】
Subscribers complained about the poor coverage around a cold storage warehouse of animal foodstuff; it was difficult to detect signal even when they were not far from the warehouse.
【Problem analysis】
According to subscriber’s complaint, we confirmed there was problem with coverage around the warehouse. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality data distribution were normal. Hardware operated normally, as shown in OMCR warning report.
Hardware engineers went to the site and checked the system of the BTS, tested power amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.
Through DT on site, network engineers found that the signal strength of the antenna main lobe was weak, while that of the side lobes was stronger, so they tentatively confirmed the problem was due to antenna fault.
Poor coverage at cold storage warehouse
【Problem handling】
After the antenna was replaced with a new one, the coverage improved
greatly, so did the speech quality.
Poor coverage of a BTS
【Problem description 】 Subscribers complained about weak signal strength around a Food
Bureau (near a BTS).
【Problem analysis 】 According to subscriber’s complaint, we confirmed there was
problem with the BTS' coverage. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality distribution were normal. Hardware operated normally, as shown in OMCR warning report.
Hardware engineers went to the site and checked the system of the BTS, tested amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.
Through DT on site, network optimization engineers found that the BTS’ coverage was in normal condition. While the Food Bureau, where subscribers complained about the signal, was 4km away from the BTS, and only indoor signal was weak (covered by Cell2).
Coverage shrinking after BTS starts operation
【Problem description 】
After Cell3 of a BTS started to operate, its coverage range was
found shrunk. On highway 3km away from the BTS, where the BTS
tower was visible, MS could not detect Cell3’s signal. MS could
receive signal when it’s around the BTS, and the signal level was
about -60dB.
【Problem analysis 】
We checked in radio resource management centre and found
Cell3’s static power class was set 2, which meant its static power
was reduced by 4dB, so we reset it to be 0. The next day, MS on
highway 3km away from the BTS could receive Cell3’s signal, and
its level was -60—70; and the signal level around the BTS was
strong, which was about -40dB.
we concluded that the cell’s coverage shrinking was caused by
wrong setting of static power control at OMCR.
High handover failure rate due to skip-zone
coverage 【Problem description 】
Configuration of a mountain site was S11, and the local network was single band GSM900. From indicator statistics of the past week, we found handover success rate of Cell2 under the BTS kept very low, which was around 80%, while TCH allocation failure rate was completely normal.
【Problem analysis 】 First, we could exclude the possibility of hardware problem and
interference, because there were no TCH assignment failures, which explained that MS could successfully occupy TCHs assigned to it by BSC; from DT analysis, we could see when signal level was above -90dbm, no call drops happened to MS, and speech quality was good, which could prove that no serious interference existed. Through further analysis, we found the target cell for handover was a bit far from Cell2; and probably adjacent cell relations were not set right during assignment planning, which resulted in isolated-island effect.
we could make area A and area B become adjacent cells to Cell2; while Cell2 coverage at A and B was already very weak, so Cell2 should not be adjacent cell to A and B .
After adjustment, handover success rate of Cell2 increased greatly, from 80% to 96%.
High handover failure rate due to skip-zone
coverage
Cell2
Cell1
Questions for thinking
Which parameters can be adjusted to improve
coverage?
GSM/GPRS/EDGE Basic Principles
ZTE University
Objective
At the end of this course, you will be able to:
Learn GSM development history
Learn and master network structure of GSM system and
functions & principles of different portions
Learn and be familiar with GSM wireless channel and
protocol
Learn and be familiar with main service call process for
GSM
Content
Chap.1: GSM Overview
Chap.2: GSM Network Structure
Chap.3: Interfaces and Protocols
Chap.4: GSM Radio Channel
Chap.5: Basic Service and Signaling Process
Chap.6: Voice Processing and Key Radio
Technology
Chap.7: GPRS and EDGE
GSM Overview
This chapter mainly introduces some basic
information for GSM, including GSM development
history, supported service type, specification, and
system features.
GSM Basic Concepts
Services Supported by GSM System
GSM Specification
GSM Overview
This section introduces network structure of GSM
system and basic functions of various NEs.
GSM Area Division Concepts
GSM composition
Mobile Switching System (MSS)
Base Station Subsystem (BSS)
Operation & Maintenance Subsystem (OMS)
Mobile Station (MS)
GSM System Number
GSM Area Division Concepts
Relationship between Areas in GSM
GSM System Composition
IBM
IBM
BSS MSS
MS
MS
PSTN
Other
PLMN
Um
Interfac
e
A
Interf
ace
GSM composition
Mobile Switching System (MSS)
The MSS consists of such entities as the mobile
switching center (MSC), home location register
(HLR), visitor location register (VLR), equipment
identity register (EIR), authentication center (AUC)
and short message center (SMC).
Base Station Subsystem (BSS)
BSS serves as a bridge between the NSS and MS.
It performs wireless channel management and
wireless transceiving. The BSS includes the Base
Station Controller (BSC) and Base Transceiver
Station (BTS).
Operation & Maintenance Subsystem (OMS)
The OMS consists of two parts: Operation &
Maintenance Center – System (OMC-S) and OMC-
Radio (OMC-R). The OMC-S serves the NSS, while
the OMC-R serves the BSS.
Mobile Station (MS)
The MS consists of mobile terminals and Subscriber
Identity Module (SIM) card.
GSM System Number
GSM system number contains:
Mobile Subscriber ISDN Number (MSISDN)
International Mobile Subscriber Identity (IMSI)
Mobile Subscriber Roaming Number (MSRN)
Handover Number
Temporary Mobile Subscriber Identification (TMSI)
Location Area Identification (LAI)
GERAN interfaces
This chapter introduces GERAN interfaces, User
plane/control plane protocol stack at PS and CS.
Interfaces
PS-Domain Protocol Stack
CS-Domain Protocol Stack
GSM interfaces
Interfaces
User plane protocol stack at PS domain
PS-Domain Protocol Stack
Control plane protocol stack at PS
domain
PS-Domain Protocol Stack
User plane protocol stack at CS domain
CS-Domain Protocol Stack
Control plane protocol stack at CS
domain
CS-Domain Protocol Stack
GSM Working Frequency Band
This section introduces GSM radio frame, channel
concept, division & function for different channels,
mapping combination mechanism between
channels.
GSM Working Frequency Band
Structure of GSM Radio Frame
Physical Channel and Logical Channel
System Messages
GSM Working Frequency Band
Currently, the GSM communication system works at
900MHz, extended 900MHz and 1800MHz.
1900MHz band is adopted in some countries.
1 hyper frame = 2048 super frames =2715648 TDMA frame
1 hyper frame = 1326 TDMA frame (6.12s)
(=51 (26 frames) multi-frames or 26 (51 frames) multi-frames
1 (26 frames) multi-frame = 26 TDMA frame (120ms) 1 (51 frames) multi-frame = 51 TDMA frame (3036/13 ms)
TDMA Frame
Hierarchical frame structure in GSM system
Structure of GSM Radio Frame
There are five layers for structure of GSM radio frame, that
is, timeslot, TDMA frame, multiframe, super frame, and
hyper frame.
GSM uses TDMA and FDMA technologies for physical
channel, as shown in the figure below.
Time
Frequency
Frequency
Time
Physical Channel and Logical Channel
System Messages
System message falls into 12 types: type1, 2, 2bis,
2ter, 3, 4, 5, 5bis, 5ter, 6, 7, 8.
Basic Service and Signaling Process
This section introduces GSM terminal start,
position register / update, service call and
handover service implementation and signaling
interaction process.
Mobile subscriber state
Location Update
Typical Call and Handover Process
Basic Signaling Process
Mobile subscriber state
The mobile subscriber has three states as follows:
MS starts, network does "Attach" marks on it
MS shutdowns, separated from network
MS Busy
Location Update at Same MSC Office
BSC
(2)
(1)
(3) (4)
MSC/VLR
LAI
1
LAI
2
M
S
M
S
Location update between different MSCs
(5)
(2)
(3) (1)
(4)
HLR
MSC/VLR1
MSC/VLR2
M
S
M
S
Location Update
Call process
Typical Call and Handover Process
Handover process
Typical Call and Handover Process
Location Update Process of MS
RLC
RLSD
DT1:CIPH MODE CMD
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:LOC UPD REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:LOC UPD ACCEPT
Basic Signaling Process
IMSI Detach Process
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
CREF
CR:IMSI DETACH EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
Basic Signaling Process
Mobile-Originated Call and Called
Party On-hook Process
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:CM SERV REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:SETUP
DTAP:CALL PROC
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
DTAP:CM SERV ACCP
Basic Signaling Process
Mobile-Terminated Call and Calling
Party On-hook Process
UDT:PAG PAG CMD PAG REQ
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:PAG RES EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
DTAP:SETUP
DTAP:CALL CONF
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
BSC MSC BTS MS
Basic Signaling Process
Inter-cell Handover Process
DT1:HO PERF
HO CMD
CH ACT
MEAS REP
RF CH REL ACK
RF CH REL
DI:HO COM
EST IND
HO DET
CH ACT ACK
MS BTS1 BTS2 BSC MSC
MEAS RES
DR:HO CMD
HO ACCESS
PHY INFO
SABM
UA
HO COM
Basic Signaling Process
key radio enhanced technologies
This section describes basic voice processing for
GSM, and several key radio enhanced
technologies.
Voice Processing
Frequency multiplexing
Adaptive equalizing
Diversity Receiving
Discontinuous Transmission (DTX)
Power Control
Timing Advance
Frequency Hopping Technology
Voice Processing
Voice Processing in the GSM System
Frequency multiplexing
Frequency multiplexing is the core concept of the cellular
mobile radio system. In a frequency multiplexing system,
users at different geographical locations (different cells)
can use channels of the same frequency at the same time
(see the figure above).
Adaptive equalizing
Equalizer can do equalizing at frequency domain
and time domain. GSM uses time domain
equalizing, enabling the better performance in
whole system.
Diversity Receiving
Diversity reception technology is commonly used in GSM.
Diversity consists of different forms: Space diversity,
frequency diversity, time diversity and polarity diversity.
Discontinuous Transmission (DTX)
The DTX mode accomplishes two objectives: Lower the total
interference level in the air and save the transmitter power.
Speech Frame Transmission in DTX Mode
Power Control
Power control means to control the actual transmitting power (keep it
as low as possible) of MS or BS in radio propagation, so as to reduce
the power consumption of MS/BS and the interference of the entire
GSM network.
Power Control Process
Timing Advance
In the GSM, the MS requires three intervals between timeslots when
receiving or transmitting signals. See the figure below.
Uplink and Downlink Offset of TCH
Frequency Hopping Technology
Frequency hopping (FH) refers to hopping of the carrier frequency
within a wide frequency band according to a certain sequence.
Basic Structure of FH
section describes evolution of GSM
technologies
This section describes evolution of GSM
technologies: basic concept, network structure,
radio channel, and basic application of GPRS and
EDGE.
Definition and Feature
Inheritance and Evolution
GPRS Radio Channel
Radio Link and Media Access Control Flow
Terminal and Application
Definition and Feature
The General Packet Radio Service (GPRS) is the
packet data service introduced in GSM Phase2+.
The GPRS has the following features:
Seamless connection with IP network
High rate
Always online and flow charging
Mature technology
Definition and Feature
Enhanced Data Rate for GSM Evolution (EDGE) is a kind
of technology for transition of GSM to 3G.
The EDGE has the following features:
EDGE neither changes GSM or GPRS network structure nor
introduces new network element, but only upgrades the BSS.
EDGE does not change the GSM channel structure, multiframe
structure and coding structure.
EDGE supports two data transmission modes: packet service (non-
real time service) and circuit switching service (real time service).
EDGE adopts octal 8PSK modulation technology, supports 303%
of GMSK payload, and provides higher bit rate and spectral
efficiency.
Compared with GPRS, EDGE adopts new coding mode.
GPRS Radio Channel
This section introduces GPRS physical channel,
GPRS logic channel, mapping of logical channel
combination in the physical channel, and GPRS
channel coding.
Radio Link and Media Access Control Flow
This section introduces paging flow, TBF setup
flow, GPRS suspend/resume flow, and TBF
release flow.
Terminal and Application
The GPRS MSs fall into three categories: Type A,
B, and C.
GSM Handover Problems & Solutions
ZTE university
Objectives
To master different types of handover and their
signaling flows;
To master handover statistical signaling point and MR
tasks;
To know common handover problems and the handling
procedures.
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Aims of handovers
Why there are handovers?
To keep calls going on during movement;
To improve network service quality;
To decrease call drop rate;
To decrease congestion rate.
Handover classification
Inter-MSC
Inter-BSC
Intra-BSC
Intra-cell
Handover
classification
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Intra-cell handover
Air A
TCBTS
BSC
New Channel
Old Channel
Signaling flow of intra-cell handover
MS BTS BSC MSC
1、Measurement Report(SACCH)
2、Measurement Report
3、Channel Activation
4、Channel Activation Ack
5、Assigment Command (FACCH)
6、SABM(FACCH)
8、UA(FACCH)
7、Establish Indication
9、Assigment Complete(FACCH)
10、Receiver Ready(FACCH)11、HO Performed
12、RF Channel Release
13、RF Channel Release Ack
Air A
TCBTS
BTS
BSC
Old Cell / BTS New Cell / BTS
Inter-cell handover within one BSC
Signaling flow of inter-cell handover within one BSC
MS Old BTS BSC MSC
1、Measurement Report(SACCH)2、Measurement Report
5、HO Command
7、HO Access(FACCH)
12、UA(FACCH)
13、HO Complete(FACCH)
14、Receiver Ready(FACCH)
16、HO Performed17、RF Channel Release
18、RF Channel Release Ack
New BTS
3、Channel Activation
4、Channel Activation Ack
6、HO Command(FACCH)
8、HO Detect
9、Physical info(FACCH)
10、SABM(FACCH)
11、Establish Indication
15、HO Complete
Air A
BTS
Old Cell / BTS
New Cell / BTS
BTS
BSC TC
BSC TC
VLRMSC
Inter-BSC handover
Signaling flow of inter-BSC handover
MS Old BTS Old BSC MSC
14、HO ommand
6、HO Command
13、UA(FACCH)
New BTS
3、Channel Activation
4、Channel Activation Ack
10、HO Detect
11、Physical info(FACCH)
12、SABM(FACCH)
New BSC
1、HO_REQ
2、HO_REQ
5、HO_REQ_ACK
7、HO Command8、HO Command
9、HO Access(FACCH)
15、HO Command16、HO Command
17、HO Command
Air A
BTS
Old Cell / BTS
New Cell / BTS
BTS
BSC TC
BSC TC
VLRMSC
VLRMSC
Inter-MSC handover
Basic signaling flow of Inter-MSC handover
MS/BSS-A
MSC-A MSC-B
MAP-Prep-Handover req. MAP-Allocate-Handover-Number req.
A-HO-REQUEST
A-HO-REQUIRED
BSS-B/MS
VLR-B
A-HO-REQUEST-ACK
MAP-Send-Handover-Report req.
MAP-Prep-Handover resp.
IAM
MAP-Send-Handover-Report resp.
ACM A-HO-COMMAND
A-HO-DETECT
A-HO-COMPLETE
MAP-Process-Access-Sig req.
MAP-Send-End-Signal req. A-CLR-CMD/COM
ANSWER
RELEASE End of call
MAP-Send-End-Signal resp.
MS/BSS-B
MSC-A MSC-B
MAP-Prep-Sub-Handover req. A-HO-REQUIRED
BSS-A/MS
VLR-B
A-HO-COMMAND MAP-Prep-Sub-Handover resp.
A-HO-REQUEST-ACK
A-HO-DETECT
A-HO-COMPLETE MAP-Send-End-Signal resp. A-CLR-CMD/COM
A-HO-REQUEST
Release
Signaling flow of inter-MSC back-handover
MSC-B
A-HO-REQUIRED
VLR-B
A-HO-COMMAND
MAP-Prep-Sub-Handover req.
A-HO-DETECT
A-HO-COMPLETE
MSC-A
MS/BSS
MSC-B’ VLR-B’
MAP-Prepare-Handover req.
MAP-Prepare-Handover resp.
MAP-Allocate-Handover-Number req.
MAP-Send-Handover-Report req.
IAM
MAP-Send-Handover-Rep. resp. (1)
MAP-Prep-Sub-Ho resp.
MAP-Process-Access-Signalling req.
MAP-Send-End-Signal req.
ACM
Answer
Release
MAP-Send-End-Signal resp.
MAP-Send-End-Signal resp.
Release
(end of call)
A-CLR-CMD/COM
Signaling flow of inter-MSC handover to a third MSC
Basic flow of handover signaling
Inter-cell handover
within BSC
There is no “HO-Request” message for intra-BSC handover; all
information is analyzed within BSC; Once a target cell in the
BSC fulfilling handover conditions is found, send “Channel
activation” message directly;
Inter-BSC handover
within MSC
BSC reports CGI and handover cause of original cell and target
cell to MSC through “HO-Request”;
After MSC finds target cell LAC, it sends “HO-Request” to the
BSC which the target cell belongs to;
Target BSC activates channel in target cell, and executes the
following flow.
Basic flow of handover signaling
Inter-MSC handover
MSC inquires “REMOTLAC sheet” (including LAC and
route address of adjacent MSC);
MSC sends (Prepare-HO) message to the target
MSC-B according to the route address;
According to the (Prepare-HO) message, target
MSC-B requests for Handover number from VLR-B,
then sends “HO-Request” message to BSC-B;
After the target BSC-B receives “HO-Request ACK”, it
sends (Prepare-HO ACK)message to the original
MSC, and executes the following flow.”
MSC participates
or not
CGI is carried
or not
Inter-
BSC
handover
Intra-
BSC
handover
MSC transmits “HO-REQ” message,
and CGI of original cell and target cell
is carried in the message;
As for inter-BSC handover, MSC
participates in it since “HO-Request”;
As for intra-BSC handover, “HO-
Performed” message is sent to MSC
only after the handover is
completed; MSC doesn’t participate
before that;
For intra-BSC handover, CGI isn’t
carried in any message, it’s handled
within BSC.
Main differences between intra-BSC handover
and inter-BSC handover
MS BTS BSC MSC
BCCH
frequency
point, BSIC
and level
values of
the six
adjacent
cells (with
strongest
level) and
serving cell;
UL MR
Process of MR
Confirmation of
adjacent cell CGI
Execution of
handover decision
Selection of
target cell
Channel activation
External cell?
HO
req
uest
Intra-MSC
handover
Target MSC Target BSC
BA2 sheet
List of cells
under one LAC
HO
req
uest
HO
req
uest
No
Yes
Flow of handover algorithm
Common timers at BSC
T3107
Suitable for: intra-cell handover
Start-up: BSC sends “assignment command”
Stop counting: when “assignment completed” or
“assignment failure” is received;
A1
BSCBTS:TRXMS
ASSIGNMENT COMMAND
CHANNEL ACTIVATE
A2
CHANNEL ACTIVATE ACK
SET T3107
T3107
Timeout
Common timers at BSC
T3103
Suitable for: inter-cell handover
Start-up: BSC sends “handover command”
Stop counting: when “handover completed” or “handover failure” is
received;
A1
BSCOld BTS:MS
HANDOVER COMMAND
CHANNEL ACT
A2
CHANNEL ACT ACK
New BTS
HANDOVER COMMANDSET T3103
T3103
Timeout
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
MR cycle
MR is sent to BTS in SACCH UL direction;
When MS is in SDCCH, MR cycle is 470ms/time;
When MS is in TCH, MR cycle is 480ms/time.
12TCH 12TCH 1SACCH 1 idle
480ms 26 multi-
frames of 4
TCHs
Indicator definition of handover success rate
KPI name Handover success rate
Indicator
definition
( busy hour number of handover success times /busy hour total
number of handover request times)*100%
V6.20 (C900060098+C900060102+C900060120+C900060094
+C900060096)*100/(C900060097+C900060213+C9000
60214+C900060215+C900060099+C900060100+C900
060101+C900060216+C900060119+C900060093+C900
060095)
Signaling statistical point of handover success
C900060098 C900060102
C900060120
A
BTSBSC
HO_ COM
BSC-controlled inter-cell incoming handover success
A
BSCMSC BTS
HO_COM
HO_COM
MSC-controlled incoming handover success
A
BSC BTS
ASS_COM
ASS_CMD
Intra-cell handover success
C900060096
A
MSCBSC
CLEAR_CMD
No. of MSC-controlled outgoing handover success times
Signaling statistical point of handover success
C900060094
MS
HO_CMD
BTS(Src)
CHL_ACT
BSC
HO_CMD
MEAS_RESMEAS_RES
SABM
UA
HO_COM
MSC
HO_COM
EST_IND
HO_PERFORM
HO_ACCESS
BTS(Target)
CHL_ACT_ACK
HO DETECT
Phy Info
A
BSC-controlled inter-cell outgoing handover success
Signaling statistical point of handover request
C900060097
A
BTSBSC
CHL_ACTIV_ACK
BSC-controlled inter-cell incoming handover execution
C900060213
C900060214
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Forced release attempt
,Resource Available
Execution of forced release
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Cell queuing
,Resource Available
Execution of cell queuing
C900060215
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Force handover attempt
,Resource Available
Execution of force handover
Signaling statistical point of handover request
C900060099 C900060100
C900060101
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACK
CHL_ACTIV_ACK
CHL_ACTIV
MSC BSC-controlled incoming handover execution
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACKCHL_ACTIV_ACK
CHL_ACTIV
Forced release attempt,
resource available
Execution of forced release
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACKCHL_ACTIV_ACK
CHL_ACTIV
Cell queuing, resource available
Execution of queuing
A
BSCBTS
ASSIGN_ CMD
CHL_ ACTIV_ACK
Execution of intra-cell handover
C900060119
Signaling statistical point of handover request
C900060216 C900060095
C900060093
BTS
A
MSC
HO_CMD
BSC
HO_CMD
No. of MSC-controlled outgoing handover execution times
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Force handover attempt
,Resource available
Execution of force handover
MS
HO_CMD
BTS(Src)
CHL_ACT
A
BSC
HO_CMD
MEAS_RESMEAS_RES
SABM
UA
HO_COM
MSC
HO_COM
EST_IND
HO_PERFORM
HO_ACCESS
BTS(Target)
CHL_ACT_ACK
HO DETECT
Phy Info
No. of BSC-controlled inter-cell outgoing handover execution times
Handover-related measurement tasks
Handover
causes
measurement
Measure the frequency of MS handovers caused by various kinds of
reasons, so as to examine radio environment of a cell;
Common
handover
measurement
Measure the process of MS handover to inspect handover success or
failure and abnormal situations causing failures, so as to improve the
cell’s radio configuration and observe traffic dispersion, etc.;
Measurement
of adjacent
cell handover
Measure the number of times of incoming/outgoing handover
attempt/success/failure from/to certain cells, and number of times of
handover caused by different reasons, so as to get the handover
situations of the serving cell and its adjacent cells and to optimize their
radio configurations correspondingly;
Sub cell
statistical
measurement
Focus on traffic load of the second subcell.
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Analysis handover problems
Analysis of handover problems
Location method of handover problems
Common handover problems
Common handover problems
Possible influences
Handover nonoccurrence
• Result in call drop;
Handover failure • Affect call quality and result in call
drop;
Frequent handover • Affect call quality, and increase
system load;
Handover hysteresis • Affect call quality and result in
call drop;
Discovery of handover problems
Meters at A interface
Traffic statistics analysis
Customer complaints
DT/CQT tests
TOPN analysis
Abnormal number of handover times
Call drop
Poor speech quality
Bad coverage
Handover problem Slow handover
Handover to best cell inhibited
No handover
Handover failure
Frequent handover
Flow of handover problem checking Too high TCH
handover failure rate
of a cell
Complete
Any antenna
problems?
Solve
antenna
problems
Eliminate
equipment
faults
Check &
eliminate
interference
Is radio
parameter setting
reasonable?
Interference
exists?
Any equipment
faults?
No
Yes
Adjust
parameters
Yes
Yes
Coverage
problem exists?
Improve
coverage
Yes
Location methods of handover problems
Analyze traffic statistics Conduct handover statistics measurement, identify
problem range: If just some cells fail to make handovers to the cell, check
handover data, check if co-channel and co-BSIC exist;
If the cell fails to take handovers from all other cells, check its data.
Check warnings: single board malfunction, transmission and clock malfunctions, etc.;
Check if radio parameters are set reasonably If co-channel or co-BSIC exist among adjacent cells;
If handover parameters are set reasonably;
If data configuration of external cells is correct.
Location methods of handover problems
Interference checking
DT analysis
Signaling analysis: Um interface、Abis interface 、 A interface;
Hardware checking: like DCU, transceiver, clock generator, RF
connection lines between boards;
Antenna system checking
Analysis of handover problems
Coverage & interference
Antenna system
BTS software & hardware
transmission
BSC software & hardware
A interface malfunction
Busy target cell
Connection & adaptation to equipment from different suppliers
Coverage & interference
Coverage:
Poor coverage: due to influence from forest, complex
landforms, houses, indoor coverage, etc.;
Isolated site: no adjacent cells around;
Skip-zone coverage: no adjacent cells available due to
isolated-island effect;
Interference:
It makes MS unable to access in UL, or DL signal
receiving problem will be resulted.
Handover nonoccurance due to isolated-
island effect
Adjacent cell N3
adjacent cell N2
adjacent cell N1
Non-adjacent
cell
Non-adjacent
cell
Non-adjacent
cell
Serving cell
Handover can’t happen due to lack of adjacent cells.
Skip-zone
coverage leads to
isolated island.
Antenna system problems
Too large VSWR
Reversed installation of antenna
Non-standard antenna installation
Unreasonable azimuth, down-tilt
Below-standard antenna insulation
Twisted cables, loosened connectors and wrong
connections;
BTS software/hardware
Problems about :
Single board
Clock generator malfunction
Internal communication cable malfunction
BTS software malfunction
Transmission and BSC problems
Transmission fault
Unstable transmission
Too high transmission error rate
BSC hardware/software malfunctions
Clock generator malfunction: unconformity among clocks in
different BTSs due to clock generator malfunction;
Problem about single board
Wrong data configuration
Unreasonable setting of handover threshold
CGI, BCCH and BSIC values in “external cell data sheet” do not
match up to those in the corresponding BSC;
Wrong BSC signaling point in “list of cell under a LAC” in MSC; co-
channel& co-BSIC adjacent cells exist.
A interface malfunction
A interface malfunction
Abnormal handover due to lack of link resource, abnormal calls;
Busy target cell
Abnormal handover due to lack of link resource, abnormal calls;
handover between equipment from different suppliers
Difference in signaling at interface A and interface E between ZTE
and other suppliers’ equipment, causing non-recognition or non-
support problem, including speech version, handover code and
addressing mode (CGI or LAI) etc., which will result in handover
failure.
Typical case 1- frequency interference
Problem description:
The data in performance report shows that Cell 1 under
a BTS suffers from low handover success rate.
Problem analysis
Examine the problem cell, discover that 2 cells under a
BTS co-channel and co-BSIC, and close to each other,
which results in low handover success rate in the cell.
Problem handling
After adjustment of frequency point, handover success
rate obviously increases, and number of handover times
reduces.
Typical case 1- frequency interference
Changes of HO indicators before & after Frequency point adjustment
0
30
60
90
120
150
180
9-4 9-5 9-6 9-7 9-8 9-9 9-10 9-11
Number of HO Req./number of HO success
0%
20%
40%
60%
80%
100%
120%
HO success rate
切换请求总次数 切换成功总次数 切换成功率(%)No. of HOReq. HO success
rate
No. of HOsuccess
Typical case 2- clock malfunction
Problem description For a newly-commissioned BTS, handover nonoccurrence appears
during DT: the MS occupies a channel in cell A; during DT from cell A to cell B, cell B can’t be observed in the adjacent cell list, and it doesn’t start normal handovers.
Problem analysis It’s a common network problem that handover nonoccurrence
appears in many cells;
It’s a newly-commissioned BTS; handover parameters are as default in the system;
Check adjacent cells relation, no problem found;
Observe from test MS, find out that adjacent cell frequency appears in the adjacent cell, but BSIC can’t be decoded. Since adjacent cell is searched through BA2 table during a call, and
BA2 relies on BCCH and BSIC to confirm an adjacent cell, when the adjacent cell’s BSIC is unobtainable, BSC is unable to locate it, thus handover won’t be started.
Typical case 2- clock malfunction
Problem analysis
Process of MS decodeing on DL channel
decode FCCH decode SCH(SCH comprises MS frame
synchronous information and BSIC.
MS can show adjacent cell frequency point, but not BSIC. It’s
suspected that adjacent cell’s SCH information can’t be decoded
by MS due to clock or transmission fault.
Check clock and transmission
BTS adopts network clock
BSC traces superior clock
MSC traces superior GPS clock through long-distance satellite link
The long-distance satellite link is found unstable, which leads to
high error rate on the meter, and warning of clock deterioration
appears on MSC.
Typical case 2- clock malfunction
Problem handling
Decide that it’s handover problem
caused by poor clock quality.
Bring new GPS clock device and
adopt the local one, thoroughly
solve clock malfunction.
Problem of handover
nonoccurrence is solved.
Experience conclusion
If no high accuracy clock
available, clock in BTS can be
used; calibration of each BTS
must be made by using
frequency meter and LMT to
ensure that frequency deviation
meets precision requirement.
Typical case 3-HO parameter setting problem
Problem description
During DT at a BTS, we find slow handover problem is
common (>10S), which affects speech quality and even
causes call drops.
Problem: level of cell 2 is higher than that of cell 3 by
20dB, total handover time is 15s.
Typical case 3-HO parameter setting problem
Problem analysis and handling
Slow handover seriously affects network quality. Make adjustment of handover parameters accordingly:
Change adjacent cell handover threshold to improve timeliness of handover trigger;
Adjust the whole network’s handover window to be 2, so as to accelerate handover speed;
Adjust the whole network’s handover preprocess to 2, so as to accelerate handover speed.
Parameter Before
adjustment
After adjustment
Level threshold
(HOMARGINRXLEV)
30 28
Quality threshold
(HOMARGINRXQUAL)
30 26
Result
Test after adjustment shows that handover time is reduced to 5s; the slow
handover problem is solved and speech quality is improve.
Questions for thinking
Please simply illustrate effects on handover due to
changing T3103、T3107.
Suggestions on parameter settings of handovers on
highway.
GSM Network Interference &
Solutions
ZTE university
Training goals
To know the classification of interference;
To master the analytical methods of interference
problem;
To master the flow of handling interference problem;
To know the analytical tool of interference problem;
To be able to handle common interference problems.
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
GSM Frequency Allocation
Frequenc
y band
UL
frequency
DL
frequency
Duplex
interval
Band
width
Carrier
frequenc
y interval
EGSM+G
SM900
880MHz
~915MHz
925MHz~9
60MHz 45MHz 35MHz 200kHz
DCS1800 1710MHz~1
785MHz
1805MHz~
1880MHz 95MHz 75MHz 200kHz
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Phenomena of Interference
Call drop
Unable to
establish calls Metallic noise
On-and-off
speech
Poor
speech
quality
Phenomena
Classification of Interference
Internal interference
Internal interference refers to unreasonable frequency planning
and equipment hardware faults, which could lead to decrease in
network service quality.
External interference
External interference refers to unknown signal source out of the
network, whose existence could seriously disturb the network’s
signals and lead to decrease in service quality.
UL interference
DL interference
Internal Interference _Causes
Unreasonable frequency planning
Equipment faults
Skip-zone coverage
Internal
interference
Internal Interference
_due to unreasonable frequency planning
Unreasonable frequency planning :
Frequency and adjacent cell relation may be set
unreasonable in network planning because of planning
tools or human mistakes .
Interference will be reflected in too large DL_RxQuality,
MS unable to access into network, poor speech quality,
and call drop.
Internal Interference
_due to unreasonable frequency planning
Check and confirm problem: Use planning tool to check if co-channel exists; co-
channel is easy to be detected if it does exist.
As for cells in boundary areas, we can block co-
channel cells in the network; meanwhile, make tracing
test with DT devices at areas with emergence of large
DL_RxQuality. If co-channel interference does exist, the
DL_RxQuality value shall become smaller after the
blocking of co-channel cells, thus we can adjust the
cell’s frequencies to eliminate the interference.
Internal Interference _due to skip-zone
coverage
Interference caused by skip-zone coverage
If the actual cell coverage greatly exceeds requirement,
interference will be increased.
Incorrect setting of engineering and network
parameters may lead to skip-zone coverage.
Internal Interference _due to skip-zone
coverage
Unreasonable setting of engineering parameters:
Wrong antenna type, down-tilt and azimuth may result
in over large cell coverage, which exceeds actual
coverage need;
Unreasonable setting of network parameters:
Network parameters include: minimum access level,
BTS transmission power, MS max transmission power,
handover thresholds, etc..Improper setting of these
parameters will result in skip-zone coverage problem
and interference as well.
Internal Interference _ due to equipment
fault
Interference caused by equipment fault:
Radio fault of BTS is mainly caused by defective UL
unit parts.
External Interference
Definition: External interference refers to other interferences caused by
external factors, but not due to equipment fault or unreasonable
frequency planning.
Common external interferences:
due to wide-band repeater;
due to CDMA system (trailing signal);
due to signal jammer;
Characteristic:
It’s hard to detect this kind of interference without
specific devices.
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Flow of Handling Interference Problem
Confirm
interference
range
Check
frequency,
change
frequency
points
Complete
Poor speech
quality due
to
interference
Check and
change
TRX
Check
external
interference
Check
VSWR/antenna/divider/dupl
exer
One cell
Interference
exists
One
TRX
Interference
exists
Interference
exists
Any new sites? If thorough change
of frequency parameters taken
recently?
Several
cells
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Analytical Methods of Interference
Problem
Analytical
Methods of
Interference
Problem
Statistical
analysis of
network
performance
indicators
Analysis of
parameter
checking
Investigation
of hardware
fault
Drive Test
and Dialing
Test
External
interference
test
Analytical Methods of Interference Problem - Statistical analysis of network performance
indicators
Statistical analysis of network performance indicators
Statistics of interference band : When TCHs are in idle status, UL noise/interference is constantly being measured BTS, and the measurement result will be analyzed, and interference level will be sent to BSC in 6 levels. 。
Statistics of handover due to UL/DL interference : We can judge whether interference exists through statistics of handover caused by UL/DL interference.
Collection of UL/DL RQ samples during speeches : RxQual is an indicator to reflect speech quality, which is based on error rate and falls into 8 grades (0~7).
Analytical Methods of Interference Problem - Statistical analysis of network performance
indicators
Corresponding relation between RxQual and Ber
Analytical Methods of Interference Problem
- Analysis of parameter checking
Check
parameters
related to
transmitting
power
Check antenna
engineering
parameters
Check frequency
planning
parameters
Check
parameters
related to skip-
zone coverage
Parameter
checking
Analytical Methods of Interference Problem
- Checking hardware fault
Checking hardware fault
OMCR warning analysis
Checking latent equipment fault
Analytical Methods of Interference Problem
- Checking latent equipment fault
Block the two
input ways of
TRX, observe
UL
interference
band; if it’s 0,
it’s proved
that TRX
hasn’t
brought UL
interference.
Input the two
stimulations
of TRX
without
connecting
them to
power
amplifier,
observe UL
interference
band; if it’s
0, it means
external
interference
doesn’t exist.
If serious UL
interference exists
even though there
is no stimulation
imposed on
power amplifier,
disconnect rack
top feeder cables,
if the interference
disappears, we
can infer that the
problem is caused
by external
factors.
Disconnect the
rack top feeder
cables, and
observe UL
interference
band; if the
interference
isn’t fading at
all, then we can
conclude that
the problem is
with the divider
unit.
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test
Drive Test and Call Quality Test
Drive test can effectively detect the location
and degree of interference, which is
convenient for analyzing the cause of
interference.
In CQT, we can actually feel the speech
quality at areas being interfered, and we can
see call quality class on the test phone.
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test
DT parameters:
C/I: co-channel carrier-to-interference ratio
RxQual 0 1 2 3 4 5 6 7
C/I[dB] 23 19 17 15 13 11 8 4
0
5
10
15
20
25
0 1 2 3 4 5 6 7
C/I[dB]
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test DT parameters:
SQI:SPEECH QUALITY INDEX is the comprehensive description of BER, FER and HANDOVER EVENT by TEMS.
Analytical Methods of Interference Problem
- Test of external interference Confirm external interference with
SITEMASTER : Test of UL interference;
Connect the input port of frequency-sweep generator to the output port of divider to increase the degree of sensitivity, as shown in the figure.
Analytical Methods of Interference Problem
- Test of external interference
Confirm external interference with SITEMASTER :
persistent strong level exists within the bandwidth of 20MHz, we can conclude that serious UL interference exists.
Analytical Methods of Interference Problem
- Test of external interference
Confirm external interference with YBT250:
Make UL interference analysis of GSM 900M UL frequency band with frequency scanning meter-NetTek Analyzer(TEK company). The model we usually use is YBT250.
Connection method of YBT250:
One is to use its own test antenna ;
One is to obtain interference information through connection to
the output port of divider.
Analytical Methods of Interference Problem
- Test of external interference
Connection method using YBT250 to test UL
interference:
Antenna
CDU
YBT 250
Feeder
Analytical Methods of Interference Problem
- Test of external interference
Wave graph of UL interference tested by YBT250: This output is the average value of the test results of
one minute, which shows the frequency and strength of interference. Persistent observation is needed to confirm if the interference continues.
Analytical Methods of Interference Problem
- Test of external interference Time scatter graph of UL interference tested by YBT250:
TEK frequency scanning meter features in three dimensional recording of time, frequency and signal.The vertical bold red lines in the graph represent the time duration, signal level strength and frequency .
vertical
axis=time
Colour
spectrum
=strengt
h
horizontal
axis=frequency
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Typical case 1: Problem description
Since March 2005, an operator has received a lot of
complaints about poor speech quality; sometimes calls
even couldn’t be setup; the caller could hear the
counterpart, but could not be heard.
Typical case 1: Problem analysis
At the
beginning we
thought it was
caused by
poor signal.
After on-site
test, we found
it wasn’t
coverage
problem.
When the level
tested by MS was
-85dbm, UL call
problem
occurred, which
was displayed as
on-and-off
speech, silence,
metallic noise
and current noise,
so we concluded
that the problem
was caused by
interference.
Performanc
e statistics
at OMCR
showed that
the rank of
idle channel
interference
band was
high.
Confirmed the
problem was
caused by
interference
Typical case 1: Problem handling process—
STEP1 Test UL interference with YBT250 connected to CDU. CDMA wave
form was strong when wave filter wasn’t used, the peak value reached
about -35dbm (average about -60dbm), which was close to GSM UL
wave band and could cause UL interference to GSM network.
Typical case 1: Problem handling process—
STEP1 In the three dimensional graph of interference tested by YBT250, the
CDMA wave form was strong and the wave form of GSM background
noise on the right was high in a long period of time.
Typical case 1: Problem handling process—
STEP2
Use CDMA wave filter to eliminate CDMA
interference.
Antenna Common
CDU
YBT 250
Feeder
CDMA wave
filter
Typical case 1: Problem handling process—
STEP2 When CDMA wave filter was adopted, CDMA wave
form was obviously weakened, but it was still strong at
some certain point; the background noise in GSM
frequency band was also reduced.
Typical case 1: Problem handling process—
STEP2
Because of CDMA wave filter, the UL interference in GSM
frequency band reduced greatly.
Typical case 1: Problem handling process—
STEP3
With the aim to eliminate CDMA interference, adopt IRCDU
+CDMA wave filter.
Antenna CDMA wave
filter
YBT 250
IR CDU
Typical case 1: Problem handling process—
STEP3 Adoption of IRCDU+CDMA wave filter can effectively
filter CDMA waves to below -104dbm. This kind of filtering
effect can help completely avoid CDMA network interfering
GSM UL network.
Typical case 1: Problem handling process—
STEP3 Adoption of IRCDU+CDMA wave filter can eliminate
CDMA wave form to a great extent; during the test period,
CDMA interference was almost eliminated.
Typical case 1: Summary
The interference source was from CDMA system.
Through comparisons of tests above, we can see after
IRCDU+CDMA wave filter was used, call quality
obviously improved.
Questions for thinking
How is interference resulted from wrong setting of transmitting power-related parameters?
What is the flow of checking external interference?
SDCCH Assignment Analysis
& Solutions
Zte university
Contents
Overview
Analysis of signaling and counters related to
immediate assignment
Radio parameters
Instructions on checking of SDCCH assignment
failure
Typical cases on SDCCH assignment
Definition of SDCCH
SDCCH: the Standalone Dedicated Control Channel is used to transmit information like channel assignment, which falls into the following two types: SDCCH/8: the standalone dedicated control channel;
SDCCH/4: the SDCCH that is combined with CCCH.
In brief, the following processes shall be taken into consideration in the process of occupying SDCCH: Location update, periodical location update;
IMSI attach/detach
Call setup
SMS
Signaling flow of immediate assignment
Counters related to SDCCH assignment &
corresponding signaling messages V3
C900060242
Number of
SDCCH
assignment
success
Function:
After BSC sends out the immediate assignment message (IMM_ASS), this counter counts the number of successful MS accesses to the corresponding SDCCH.
Sampling:
when BSC receives the correct EST_IND or the message of assignment complete.
C900060243
Number of
SDCCH
assignment
failure
Function:
After BSC sends out the immediate assignment message (IMM_ASS), this counter counts the number of failed MS accesses to the allocated SDCCH.
Sampling:
when BSC receives the wrong EST_IND, or when T3101 expires.
SDCCH assignment success rate
KPI SDCCH assignment success rate
Definition Number of successful SDCCH assignments*100/(Number of successful
SDCCH assignments + Number of failed SDCCH assignments)
Counter
formula
V2 C11644*100%/( C11644+ C11645)
V3 V6.2 C900060242*100%/(C900060242+C900060243)
Difference: Random access success rate
Definition: Number of successful random accesses / Number of random access requests*100%
Number of random access requests Definition: MS applies for a channel in the idle mode.
Trigger point: it counts the message of CHANNEL REQUIRED received by BSC from MS. (A1)
Number of successful random accesses Definition: BSC successfully assigns a dedicated
channel for MS.
Trigger point: it counts the message of IMMEDLATE ASSIGNMENT sent from BSC to MS. (A2)
Contents
Overview
Analysis of signaling and counters related to
immediate assignment
Radio parameters
Instructions on checking of SDCCH assignment
failure
Typical cases on SDCCH assignment
Analysis of Channel Request cause
Establishment Cause
Analysis of Channel Request cause
Establishment Cause (continued)
Analysis of Channel Request cause
Summary on Establishment Cause
Emergency call
Call re-establishment
Paging response(MTC)
Mobile originating call(MOC)
Location update (LOC)
Other access causes
One-step access
LMU service
MBMS service
Channel Required
Channel Required
Request Reference
RA(Random access reference): it continues to use the Cause and
Random Reference in the Channel Request.
Byte 3 and 4 (T1, T2, T3): receive the frame number(42432) of the
burst pulse.
Channel Required
Access Delay
The estimated TA
Physical Context
including Rxlev_UL
Immediate Assignment Page Mode = same as before
Packet Response Type and Dedicated mode or TBF
Downlink assignment to mobile in Ready state: no meaning
TBF or dedicated mode: this message assigns a dedicated mode resource
PR Type: immediate assignment procedure for RR connection establishment
Channel Description
Type = SDCCH/8[0]
Timeslot Number: 1
Training Sequence Code: 0h
ARFCN: 104
Request Reference
Random Access:
Establish Cause: E0h = Originating call and TCH/F is needed, or originating call and the network does not set NECI bit to 1
Random Reference: 12h
N32: 13h; N51: 1Fh; N26: 0Dh
Timing Advance: 1 = 0,6 km
Mobile allocation
Establish Indication
Establish Indication
T represents the sub-channel number.
Establish Indication
Establish Indication
Information on layer3:
CM SERVICE REQUEST
LOCATION UPDATING REQUEST
IMSI DETACH
PAGING RESPONSE
CM RE-ESTABLISHMENT REQUEST
NOTIFICATION RESPONSE
IMMEDIATE SETUP
RR INITIALISATION REQUEST
Establish Indication
CM SERVICE REQUEST
Originate call
Emergency call (Access statistics show that emergency
call is not included in MOC )
SMS
Supplementary service
Group call establishment
Voice broadcast call
Access counters
Basic measurement
Counter Number Counter name
C900060001 Number of MTC access requests
C900060002 Number of MTC access successes
C900060131 Number of CM SERVICE REQ of MOC
C900060136 Number of MOC access requests
C900060137 Number of accesses due to paging response
C900060236 Number of MOC access successes
Access counters
Radio access measurement (I)
Counter Number Counter name
C901110001 Number of invalid access requests
C901110003 Number of successful process for MOC access
C901110006 Number of successful process for MTC access
C901110008 Number of call re-establishment access requests
C901110009 Number of successful process for call re-
establishment access
C901110010 Number of call re-establishment access success
C901110011 Number of emergency call access requests
C901110012 Number of successful process for emergency call
access
C901110013 Number of emergency call access success
C901110014 Number of LOC access requests
C901110015 Number of successful process for LOC access
C901110016 Number of LOC access success
C901110017 Number of access requests due to other causes
C901110018 Number of successful process for other causes’
access
C901110019 Number of access success of other causes
Access counters
Radio access measurement (II)
C901110020 Number of LMU Establishment access requests
C901110021 Number of successful process for LMU Establishment access
C901110022 Number of LMU Establishment access success
C901110023 Number of accesses due to location update
C901110024 Number of accesses due to CM SERVICE REQ
C901110026 Number of Emergency Call (CM SERVICE REQ) accesses
C901110027 Number of SMS (CM SERVICE REQ ) accesses
C901110028 Number of supplementary service (CM SERVICE REQ) accesses
C901110029 Number of accesses for LCS (CM SERVICE REQ ) accesses
C901110031 Number of accesses due to call re-establishment
C901110032 Number of accesses due to IMSI de-activation
C901110033 Number of accesses due to other causes
Contents
Overview
Analysis of signaling and counters related to
immediate assignment
Radio parameters
Instructions on checking of SDCCH assignment
failure
Typical cases on SDCCH assignment
TxInteger
Before response to the previous “channel request”
is received, MS waits for a period of time at
random and sends the request again after
expiration. TxInteger is to decide the random
waiting time.
The interval (number of timeslots) from MS originating
the immediate assignment to the transmission of the
first “channel request” message is a random number
among { 0,1,…,Max(T,8)-1 }.
The interval (number of timeslots) between two
consecutive “channel request” is a random number
among {S,S+1,…,S+T-1}.
TxInteger
T(Number of
timeslots
Of TxInteger)
S
(CCCH is NOT
combined with
SDCCH)
S
(CCCH is
combined with
SDCCH)
3, 8, 14,50 55 41
4, 9, 16 76 52
5,10,20 109 58
6,11,25 163 86
7,12,32 217 115
TxInteger Number of
timeslots (T)
0 3
1 4
2 5
3 6
4 7
5 8
6 9
7 10
8 11
9 12
10 14
11 16
12 20
13 25
14 32
15 50
MaxRetrans
Because RACH is a ALOHA channel, in order to
improve MS access success rate, the network
allows MS to send several Channel Request
messages before it receives the Immediate Assign
message. The max number of Channel Requests
sent by MS is decided by MaxRetrans. MaxRetrans Max number of retransmission
0 1
1 2
2 4
3 7
TaAllowed
It represents the max TA allowed for access to the
cell.
It is used to filter out fake accesses.
RachAccessMin
New parameter for iBSC 6.20.100e
Used to filter out fake access, but not
recommended because it will affect the paging
performance.
Contents
Overview
Analysis of signaling and counters related to
immediate assignment
Radio parameters
Instructions on checking of SDCCH
assignment failure
Typical cases on SDCCH assignment
Explanation on common causes of SDCCH
assignment failure
MS frequently originates location update due to
poor downlink quality;
Improper setting of Tx-Integer;
High SD assignment failure rate due to LAPD
delay
Co-channel/co-BSIC interference
Uplink interference
Overshooting
Improper setting of Tx-Integer
The default of Tx-Integer is 14, which is also the
max value.
Usually, the one-way signaling transmission delay
at Abis interface is 60ms~100ms; there should be
a delay of about 240ms from MS originates
Channel Request till it receives Immediate Assign.
When the transmission link delay is long, while
TxInteger is set with a small value, it will result in
MS sending too many access requests. However,
MS only responds to the first Immediate Assign it
receives.
Improper setting of Tx-Integer
Flow chart of repeated assignment failure
Channel Request
Channel Required
M S
Channel Active
Channel Active Ack
Imm Assign(OK) Imm Assign Cmd
B T S
Channel Request(Re-Send)
TxInteger
Lapd
Delay
Channel Required
Channel Active
Channel Active Ack
Imm Assign Cmd Imm Assign(Fail)
MS change
to SDCCH
B S C
LAPD delay
Possible causes of LAPD delay Application of LAPD 1:4 multiplexing will lead to the situation that
several BCCH TRXs are multiplexed on one LAPD, which will cause heavy flow on the LAPD and hence delay.
Heavy flow on LAPD leads to delay. For example, improper LAC division will lead to large amount of paging and hence LAPD flow control.
Transmission equipment fault leads to loss of messages on LAPD or long LAPD delay. These phenomena are often accompanied with SDCCH assignment failure.
The transmission equipment’s own delay, such as the delay caused by satellite transmission at Abis interface.
Impact of PS service: PS service is more sensitive to network delay. Any LAPD delay will leads to re-transmission of PS service message, which increases the flow on LAPD and causes longer LAPD delay, then a malicious circle will be resulted.
Co-channel & co-BSIC
Two cells have same BCCH and same BSIC
The Channel Request sent by MS is received by two
cells and they assign SDCCH at the same time, but MS
can only accept one SDCCH, therefore, one of the two
cells will inevitably experience SDCCH assignment
failure.
For RACH coding, first add in 6bit color code, which is
obtained through taking mod2 of 6bit BSIC and 6bit
parity checking code. Therefore, co-BCCH and co-BSIC
may cause the BTS to incorrectly decode MS access
bursts to other sites, which will lead to SDCCH
assignment failure
Co-channel & co-BSIC
Two cells have same BSIC and the TCH Arfcn of one cell
is same as the BCCH Arfcn in the other cell.
The handover access request occurring on the TCH timeslot is
received as Channel Request by the other cell, which thereafter
performs assignment. This certainly leads to SDCCH assignment
failure.
It’s stipulated in protocols that the MS-started handover access
information and the random access request share the same format,
which is AB frame; the difference is that the handover access
information content (RA) in one handover started by MS is the
same, and the FN is in consecution.
Signaling related to this problem displays that the RA is the same,
TA is in consistence and FN in consecution. It’s confirmed that all
the large amount and consecutive Channel Requests are fake
accesses caused by handovers between co-channel cells.
Overshooting
If the coverage of cell is too large, the DL Rxqual at the cell margin will be poor. In this case, BTS can receive Channel Request sent by MS, but MS can not receive Immediate Assign sent by BTS, for BTS is more sensitive than MS,
If the coverage of cell is too large, the cell may share channel and BSIC with the cell which is far away.
Solution to overshooting: Adjust the engineering parameters of antenna to limit the cell
coverage.
TA_allowed can effectively decrease SDCCH assignment failures caused by overshooting. The side effect it brings is that the distant MS is not able to access network. Therefore, the threshold of TA_allowed shall be set a bit higher than the cell’s actual coverage. Besides, we should take into account the transmission distance of repeater when calculating the cell coverage range.
Uplink Interference --- Fake Access
BTS receiving sensitivity is -112dbm~-125dbm. If the random access signal
strength received by BTS is lower than BTS sensitivity, it usually is confirmed to
be interference. The interference can be decoded as random access, which is
called as fake access, and will definitely lead to SDCCH assignment failure.
Another feature of fake access is that TA is larger than that needed for the actual
coverage range.
Solution: TA_allowed
Note:
① RachAccessMin is not recommended to use
② As for TA-allowed, the corresponding name used by Nortel is RNDACCTIMADVTHRESHOLD,
whose description is as follows: adjust the parameter according to the cell’s actual coverage range.
Fake RACH request can be filtered out through setting proper threshold, therefore unnecessary
SDCCH assignment can be avoided. Test results prove that if TA-allowed is set 35Km for cells with
small coverage radius, fake RACH (the system demodulate the noise into RACH pulse by mistake)
accounts for almost 30% of all RACH requests. After rndAccTimAdvThreshold is changed to 2, fake
RACH is totally filtered out.
Frequent location update started by MS
If MS needs to make location update, while the
radio environment is poor, it will retransmit
Channel Request with the cause of location
update again and again, but it can never receive
Immediate Assign message.
The frequent location update will cause
fluctuations in SDCCH assignment indicators.
Frequent location update started by MS
Number of SDCCH
assignment
successes
Number of SDCCH
assignment failures
SDCCH assignment
success rate
Number of
MOC access
requests
Number of
MOC access
successes
Number of
MTC access
requests
Number of
MTC access
successes
Number of
SDCCH
occupation
attempts (for
assignment)
(MOC+MT
C)
assignment
success rate
(MOC+MT
C)
proportion
Reference
indicators
Troubleshooting instructions
Check TxInteger of the problem cell, along with LAPD delay observed from signaling.
Check whether the LAPD link of BCCH TRX in the problem cell is multiplexed with that of other cells.
Check whether any of the adjacent cells have same Arfcn and BSIC with the problem cell.
Check whether the value of counter “number of access attempts due to other causes” is big. If so, and the counter “number of access successes due to other causes” is zero, it is possible that “handover access” on other TCH TRXs are decoded as “channel request” by the problem cell.
Error Report with Channel Number 0x88 is available in the mplog file.
Troubleshooting instructions
Check SDCCH allocation KPIs and transmission
alarms.
If SDCCH &TCH assignment indicators are all bad,
the problem shall be related to radio environment.
Analyze signaling and check if Channel Request
with large TA, if so, fake access exist and
TA_allowed restriction can be used.
Contents
Overview
Analysis of signaling and counters related to
immediate assignment
Radio parameters
Instructions on checking of SDCCH assignment
failure
Typical cases on SDCCH assignment
LAPD delay—Case 1: Large amount of
paging
Problem description: It’s found through performance
analysis that ZTE BSC3 has low SD assignment success
rate, which is only about 60% on late busy hours.
Problem analysis:
It’s observed that all the cells are experiencing high SD assignment
failure rate, so impact from radio parameters is excluded.
Indicators of other BSCs are normal; the SD assignment success
rate is low in only BSC3 and the Siemens BSC, both of which are
under MSC7.
The paging success rate in MSC7 is also very low; as the traffic
volume increases, the amount of paging increases as well.
LAPD delay—Case 1: Large amount of
paging
Adjustment measure:
Add one LAC under MSC7. After the adjustment, the SD assignment
success rate of BSC3 returns to normal, reaching above 95%.
50%
60%
70%
80%
90%
100%
0
20000
40000
60000
80000
100000
3月10日 3月11日 3月12日 3月13日 3月14日 3月15日
BSC3 SDCCH指配成功率对比
SDCCH指配成功次数 SDCCH指配失败次数 SD指配成功率
LAPD delay—Case 2: Satellite transmission
Problem description: 4BTSs are under BSC01, but
belong to different peripheral modules. The SD
assignment failure rate of the 4BTSs reaches as
high as 50%.
The time stamp shows that it takes an average of
0.58s to successfully activate a channel.
LAPD delay—Case 2: Satellite transmission
How to confirm that two Channel Requests are
started by the same call attempt?
They should have the same Establish Cause;
The same Access Delay;
The frame number interval corresponds to the setting of
TxInteger:
Calculation formula: FN=T1*26*51+((T3-T2)mod 26)*51+T3
LAPD delay—Case 3: Transmission equipment fault
Problem description: Massive SDCCH assignment
failures occur in 3 cells of a site, accompanied
with lots of SDCCH allocation failures.
Problem analysis: SDCCH allocation failure
usually means transmission equipment fault.
After checking mpLog printing, there are lots of LAPD
Errors.
Also There are a lot of transmission alarms.
Improper setting of Tx-Integer
A cell’s ordinary SDCCH assignment failure rate remains at around 20% and hits 30% in busy hour. However, other KPIs(such as TCH assignment failure rate, handover success rate) are all good.
Problem analysis: After analyzing the cell’s signaling, we find there usually are Channel Request messages appearing in couples in the cell (with the same TA and cause). The Imm Assignment corresponding to the first Channel Request was successful, but the one corresponding to the second Channel Request failed.
Improper setting of Tx-Integer
Problem analysis:
Tx-Integer=12, which means “channel request”
retransmission interval is 109~128
FN of the first Channel Request is 964; that of the second
Channel Request is 1086; there is a difference of 124 frames.
It’s confirmed that the two Channel Requests are sent by the
same MS.
Solution: change Tx-Integer to be 14. After the
adjustment, the SDCCH assignment failure rate drops
to below 10%.
Access of interference signal—Case 1: TA
exceeding the actual coverage range
Problem description: the SDCCH assignment
success rate in a cell is very poor.
Time Alias
11644(Number of
SDCCH Assignment
Success)
11645(Number of
SDCCH Assignment
Failure)
2007-4-26 19:15 Cell A 191 15
2007-4-26 19:30 Cell A 190 24
2007-4-26 19:45 Cell A 177 33
2007-4-26 20:00 Cell A 192 26
Access of noisy signal—Case 1: TA exceeding the
actual range
Problem analysis: analyze ABIS signaling; the TA of
failed random access Immediate Assign failure is as
follows; the neighboring sites are near each other ,
with a distance less than 1 Km.
Serial No. TA Cause
Corresponding time stamp for sending Immediate Assign
1 35 MOC 06-08-55.375
2 36 MTC 06-08-55.562
3 35 MOC 06-08-55.984
4 34 MTC 06-08-56.578
5 32 MOC 06-09-11.640
6 30 MTC 06-09-24.546
7 27 MTC 06-09-38.031
8 27 MTC 06-09-38.578
9 27 MTC 06-09-39.109
10 0 MOC 06-09-57.171
11 24 MOC 06-09-57.828
12 10 MOC 06-11-15.406
13 2 MOC 06-12-12.781
14 0 MOC 06-12-52.671
15 0 MOC 06-12-53.218
16 1 LAC update 06-15-13.140
Access of noisy signal—Case 2: the Rxlev
lower than BTS sensitivity
Problem description: A cell’s SDCCH assignment
failure rate keeps high, but the TCH assignment
rate is acceptable.
SDCCH
assign
successful
number
SDCCH
assign
failure
number
SDCCH
assign
failure rate
TCH
Assignment
Success
Number
TCH assign
failure
number
TCH assign
failure rate
14479 4490 23.63 4678 122 2.54
Access of noisy signal—Case 2: the Rxlev
lower than BTS sensitivity
Problem analysis: The Physical Context carried by
Channel Required message reports the Rxlev of random
accesses, in which we find lots of Channel Request
messages whose Rxlev is -135dbm(0x87).
Co-BCCH & co-BSIC— Overshooting
Problem description: the SDCCH assignment failure rate
in many cells exceeds 25%.
Process procedure:
After all the hardware is changed, the problem still exists.
Through signaling trace we find that the co- BCCH/co-BSIC
signals received when TA=20 lead to SDCCH assignment failure.
Based on the above finding, re-plan the BSIC of more than 10
cells in the network. After the re-planning, coverage of the cells
returns to normal.
Solution:
Temporary solution: the CMM of cells with high reset failure rate
enables the clock to reset, which lead to synchronous malposition
of SDCCH timeslot.
Ultimate solution: to avoid co-channel/co-BSIC.
Co-Channel & co-BSIC—Handover
Problem description: a cell experiences a sudden
increase of SDCCH assignment failure rate in
busy hour; the TCH assignment indicators are
good.
Cell ID Pmdatatime SDCCH assign
failure rate
TCH assign
faliure rate
Cell A 19:00-20:00 15.85 0.68
Cell A 21:00-22:00 12.78 0.71
Cell A 20:00-21:00 11.27 1.36
Co-Channel & co-BSIC—Handover
Problem analysis: Through signaling trace, we find that there is a
large number of continuous random accesses; these Channel
Requests have the same RA, TA, and consecutive frame numbers.
Solution: After checking frequency planning, we find there are co-
channel & co-BSIC cells which are located 14km away from the BTS.
After re-planning of frequency, the problem disappears.
Weak coverage
Problem description:
The SDCCH assignment failure rate in a cell reaches
58% in busy hour, and TCH assignment failure rate
56%; handover success rate in only 20%.
Network performance statistics of fore-and-aft days
display that the TCH assignment failure rate, call drop
rate and handover failure rate have remained high.
UserLabel Handover
success rate(%)
SDCCH assign
failure rate
TCH assign
failure rate
Cell A 20 58.67 56.19
Weak coverage
Problem analysis: DT result shows that the problem cell not only experiences weak
coverage, but also overshooting and co-channel interference.
Signaling trace shows a large number of abnormal accesses of
consecutive Channel Requests with TA =63.
Consecutive LOC update request
Problem description: some sites at LAC boundaries and suburb
experience sudden increase of SDCCH assignment failure rate, which
moves in no certain pattern; while other indicators of the cell are quite
normal.
Problem analysis:
The basic measurement data shows that LOC access attempts and
failures count for a large proportion of the SDCCH assignment failures.
Consecutive LAC update access request
Problem analysis:
Signaling analysis shows that MS continuously starts Channel
Requests with cause of LAC update, which all end in failure.
GSM Radio network planning principle
ZTE University
Objectives
At the end of this course, you will be able to:
Describe the contents of information collection
State capacity planning
State coverage planning
Describe steps to notices of site survey
Master frequency planning and anti-interference
technology
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Overview
Mobile service forecast
Subscriber forecast, distribution
Network equipment &
operation profile
MSC,BSC,BTS
Traffic statistic, quality
City planning
City type, map
Population
Economic development plan
Road and transport condition
Information Collection
Radio propagation survey
Geographic environment
Plantation
Network traffic distribution
Industrial, commercial, residential
area
Coverage and quality analysis
Coverage and quality (DT)
Statistic of A, Abis and OMCR
Interference analysis
Frequency allocation
Frequency scanning test
Analysis and survey
Frequency Other Traffic Model Capacity Coverage
Limited
frequency
Available
bandwidth
Frequency
resources
Coverage
KPI
Traffic
distributing
Coverage
size
Redundancy
and other
requirements
traffic
distributing
Traffic and
system
capacity
Data traffic
model
Voice traffic
model
Site
configuration
Propagation
environment
Electronic
map exists ?
Requirement analysis
Summary
Network planning information collecting
template
Inadequate
info
1. What is necessary information?
2. What is supplementary info?
?
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Basic concepts
Traffic volume
Traffic model
Erland
Call loss rate
Erlang B table
Erlang B table 2% 5%
1 0.020 0.0532 0.223 0.3813 0.602 0.8994 1.092 1.5255 1.657 2.2186 2.276 2.9607 2.935 3.7388 3.627 4.5439 4.345 5.37010 5.084 6.21611 5.842 7.07612 6.615 7.95013 7.402 8.83514 8.200 9.73015 9.010 10.63316 9.828 11.54417 10.656 12.46118 11.491 13.33519 12.333 14.31520 13.182 15.24921 14.036 16.18922 14.896 17.13223 15.761 18.08024 16.631 19.03025 17.505 19.985
Capacity Planning Procedures
Confirm subscriber
number
Site numbers and
configuration
Traffic distribution
ratio
Site distribution and
their latitude and
longitude
Reach target of
capacity planning
1 2 3 4 5
Network scale Capacity information
collection Site layout Traffic distribution
analysis
Site type and
number
Capacity Planning
Information collection
Network type: GSM900, DCS1800, dual-band network or WLL network?
System capacity requirement. No of subscriber and the traffic?
Traffic model of the voice service?
Equipment type: V2/V3? Model? Indoor or outdoor? DPCT applied in V3 or not?
Data service required? EDGE TRX? Data service penetration rate? Traffic model of data service?
Frequency resource range ? Is there frequency that are prohibited? Maximum site configuration ?
Forecast and investigation traffic density and define traffic distribution ratio.
Traffic density distribution
Traffic distribution analysis is to categorize the planning
area into areas of different service levels based on
forecast and survey of traffic density distribution
● how many phases and what is the ratio of
subscribers in each phase
● what is the planning area range and the
traffic distributing ratio in DU/MU/SU/RU.
● Provide existing sites and their
configuration and performance statistics
report data
扇面 1
41%
扇面 2
26%
扇面 3
15%
扇面 4
11%
扇面 5
7%
Service level by radio propagation environment
Area Topographic features
Dense
urban
Average height of surrounding buildings is more than 30 metres (over 10 storey)
and average distance between buildings is 10-20 metres. Usually the buildings
are crowded around the site with the height of 10-20 stories and the ambient
roads are not considerably wide.
urban
Average height of surrounding buildings is about 15-30 metres (5-9 storey) and
average distance between buildings is 10-20 metres. The buildings are evenly
distributed around the site. Mostly are below 9 stories and some are over 9
stories and the ambient roads are not considerably wide.
suburb
Average height of surrounding buildings is about 10-15 metres (3-5 storey) and
average distance between buildings is 30-50 metres. The buildings are evenly
distributed around the site. Mostly are 3-4 stories and some are over 4 stories.
Roads around are wide.
rural Average height of surrounding buildings is below 10 metres. They are dispersed
and mainly are 1-2 storey high. There are spacious space between.
Service level by service distribution area
Area Distribution Features
Dense
urban
Traffic is heavy with high data service
rate, mainly for data service
development
Mean
urban
Traffic is relatively heavy and date
rate should be comparatively high.
Data service is required
Suburb Traffic is low and only low-speed
data service
Rural Traffic is quite low. Site is for
coverage purpose and data service
quality are not ensured.
Both radio propagation
environment and service
distribution factors should all
be taken into consideration.
Number of BTS sites-1
No. of BTS for capacity limited area
Maximum site type by frequency reuse pattern
Traffic per site by traffic model, Erlang-B table
Total number of BTS: Total traffic / single site
traffic
Number of BTS sites-2
No. of BTS for coverage limited area
Total area / single site coverage (according to service
level)
Cell traffic = Cell coverage * traffic density
TCH number (Erlang-B table)
SDCCH number
TRX number
Start
Frequency resources
Capacity of each cell
Capacity per site
Site configuration & number
Frequency reuse pattern
Maximum Site type
Channel planning & data service
Erlang B table
Traffic model
Site configuration
Traffic & distribution
Network Scale Coverage Planning
Site type and number
No of SDCCH
Suppose SDCCH average process time is 3s,Location updating
process is 9s,BHCA=2
The traffic of SDCCH per subscriber is:
(3×2 + 9) / 3600 = 0.0042 Erlang
4SDCCH call loss=2% can support 1.092Erlang,
(1.092 / 0.0042 = 260sub) ×0.025 Erlang = 6.5Erlang
look up in Erlang-B,call loss=2%, 6.5Erlang need 12TCH(2TRX)
8SDCCH call loss=2% can support 3.627Erlang
(3.627 / 0.0042 = 863sub) ×0.025 Erlang = 21.6Erlang
Look up in Erlang-B,call loss=2%,21.6Erlang need 30
TCH(4TRX)
SDCCH configuration
TRX Channel SDCCH type SDCCH TCH TCH traffic
(GOS=2%)
1 8 SDCCH/8 1 6 2.28
2 16 SDCCH/8 8 14 8.2
3 24 2*SDCCH/8 16 21 14.9
4 32 2*SDCCH/8 16 29 21
5 40 2*SDCCH/8 16 37 28.3
6 48 2*SDCCH/8 16 45 35.6
7 56 3*SDCCH/8 24 52 43.1
8 64 3*SDCCH/8 24 60 49.6
9 72 3*SDCCH/8 24 68 57.2
10 80 4*SDCCH/8 32 75 64.9
LA planning
LA border
Paging capacity in LA
Paging capacity calculation
Influence by Short message
LA border
Avoid dense city with high traffic area
Avoid area with high mobility of subscribers
Cross the road slantwise
Consider traffic expansion
Paging capacity
IMSI/TMSI
Second paging(local paging、global paging)
Paging group:
(BS-AG-BLK-RES)
(BS_PA_MFRAMS)
Paging blocks/ per second =(9-AGB)/0.2354
Paging number / per paging block : B = 2 or 4
Paging capacity calculation
Paging numbers per second(P)
P =(9-AGB)/0.2354 * B
Suppose:
Average time of call:60s,ie:1/60Erl
Traffic of LA(T)
75%of MS response first paging,25% of MS response
second paging
Paging congestion when 50% of maximum paging.
T*30%/(1/60)*1.25 = P*50% = 59.47*3600*50%
Influence by short message
3/per sub/per day
30% retransmit
Convergence factor:0.12
Subscriber in LA:100000
SM number in busy hour
100000×3×0.12×(1+30%)=46800
Consider holiday case: 8 times
Coverage
Planning
Capacity
Planning
Network
Scale
Summary
Capacity planning is
just an initial plan,
Add or reduce sites
based on radio
coverage planning
and analysis.
Capacity planning is
a repeated, gradual
process helping to
decide site number
and type.
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Coverage Planning flow
Set parameters Estimated
coverage radius of
each site
Allowable max path
loss
Information of site
distribution ,
latitude & longitude
of sites
Target of coverage
1 2 3 4 5
Network scale Network
parameter
Site layout &
coverage emulation Link budget Coverage radius
estimate
1
Network parameter
Confirm network parameters
Network category: GSM900,DCS1800, dual-band or WLL network?
Equipment type: V2 or V3? Model? Indoor or outdoor? Apply DPCT in V3? DPCT ratio?
Carrier Transmission power is 40W,60W,80W? Are data service required? EDGE carrier frequency?
Antenna model: antenna gains, horizontal and vertical beam width, antenna downtilt, polarization mode and electrical downtilt etc.
Antenna parameter: antenna available height, directional angle and downtilt.
Apply tower top amplifier?
Feeder type: 7/8 feeder or 15/8 feeder?
Maximum site configuration is? Are there special requirements toward configuration of combining and distribution unit?
What is KPI? What is level and area coverage rate? Which new technology will be adopted in V3 site, DDT? IRC? or FWDR?
2
Link Budget
Link budget
Definition:
Link budget is the calculation of loss and gains on one
communication link.
Target:
Maximum power of the site, avoid invalid downlink
coverage, reduce interference and system noise.
Allowable maximum indoor & outdoor path loss of uplink
and downlink Uplink Downlink
PA
Feeder loss Transmission
loss
Antenna gain Penetration loss
Site sensitivity
Fading margin
Body loss MS power
Link budget
Template
Losses
Margin reservation
Gains
Network Type & Equipment
Link Budget
Transmission power and reception
sensitivity of MS/BTS
CDU type
Fast fading margin
Slow fading margin
Interference margin
Site antenna gain
MS antenna gain
TMA gain
Path loss
Body loss
Vegetation
loss
Building penetration
loss
Feeder and
connector loss
Combiner and
splitter loss
Link budget
Link budget-Equipments
MS transmission power is showed as follows:
Power
class
GSM 900
Nominal
Maximum output
power
DCS 1800
Nominal
Maximum output
power
PCS 1900
Nominal
Maximum output
power
1 1 W (30 dBm) 1 W (30 dBm)
2 8 W (39 dBm) 0.25 W (24 dBm) 0.25 W (24 dBm)
3 5 W (37 dBm) 4 W (36 dBm) 2 W (33 dBm)
4 2 W (33 dBm)
5 0.8 W (29 dBm)
Link budget-Equipments Series Modulation Transmission power Reception
sensibility
Biggest site
BTS
V3
B8018 GMSK 60 W 47.78 dBm
-112 dBm S18/18/18 8PSK 31 W 45 dBm
B8112 GMSK 60 W 47.78 dBm
-112 dBm S12/12/12 8PSK 31 W 45 dBm
M8202 GMSK 30 W 44.78 dBm
-110 dBm S2/2/2 or O6 8PSK 20 W 43 dBm
BTS
V2
GMSK 40W 46 dBm -110 dBm S12/12/12
GMSK 80W 49 dBm -110 dBm S6/6/6
8PSK 30W 44.78 dBm -110 dBm S12/12/12
(EDGE) GMSK 60W 47.7 dBm -110 dBm S12/12/12
OB06 GMSK 40W 46 dBm -110 dBm S6/6/6
BS30 GMSK 40W 46 dBm -110 dBm S2/2/2
BS21 GMSK 40W 46 dBm -110 dBm S2/2/2
GMSK 80W 49 dBm -112 dBm S1/1/1
Link budget-Loss
Path loss
Body loss
Vehicle loss
Plantation loss
Building penetration loss
Feeder and connector
loss
Combining and
distributing unit loss
Link budget-Loss
Path loss
Radio wave loss caused by the transmission distance.
Body loss
Voice service, body loss 3 dB
Data service, 0dB.
Vehicle loss
Usually it is 8~10dB.
Link budget-Loss
Plantation loss
Inside the forest, the loss of 900MHz is 0.2dB/m; the
loss of 1800MHz is 0.3dB/m
Through forest or diffraction, the loss is 20dB/dec
Forest around the antenna and the antenna is lower
than the forest, around 10dB
Building penetration loss
Averagely it’s 10 – 20 dB,relying on building material
and thickness.
Link budget-Loss
Feeder cable loss
Type loss(dB/100m)
900M 1800/1900M
1/2 soft jumper 7.22 11.3
7/8 feeder 3.89 6.15
15/8 feeder 2.34 3.84
Link budget-Loss
Combiner & Splitter loss
Unit (900M) Insertion loss
CDUG 4.4dB
CEUG 3.5dB
CENG 5.3dB
CENG/2 5.3dB
ECDU 0.9-1.0dB
Unit(1800M) Insertion loss
CDUD 4.6dB
CEUD 3.6dB
CEND 5.5dB
CEND/2 5.5dB
ECDU 0.9-1.0dB
Link budget-Gain
BTS Antenna gain
Area Antenna gain
(dBi)
urban 15.5
suburb 15.5~17
rural 17~18
Express way or
long & narrow
valley
18~21
Hills and
highland
17~18
MS antenna gain
usually is 0
remark:special attention
should be paid to antenna gain
in MS in GSM WLL network
Antenna may be indoor,
outside door or on the roof.
So antenna gain and height
should be checked, which
will affect coverage greatly.
TMA gain
Link budget-Margin
Fast fading & deterioration storage
walking:2.0--5.0dB
fast moving:0dB
In GSM system, fast fading for voice and data service is
supposed to be 3dB.
Interference margin
The interference margin is generally supposed to be
3dB.
Link budget-Margin
Slow fading (shadow fading) margin
shadow fading is based on
standard deviation
margin coverage probability.
slow fading standard deviation is related to propagation
condition. In cities, it’s about 8~10 dB, while in suburbs
or rural areas,6~8dB.
Marginal coverage
probability(%)
70 75 80 85 90 95 98
Slow fading margin/dB 0.53σ 0.68σ 0.85σ 1.04σ 1.29σ 1.65σ 2.06σ
Link budget
Parameter Symbol
MS transmitting power A
Body loss B
Building loss C
MS reception sensibility D
MS antenna gain E
TMA gain F
Diversity gain G
Feeder loss H
Combiner/divider unit
loss
I
Fast fading margin J
Slow fading margin K
Noise margin L
Path loss indoor M=A-B-C-D+E+F+G-H-I-J-
K-L
Path loss outdoor N=M+C
Path loss difference
between uplink and
downlink is 3-5dB
3
Coverage
radius estimate
Estimate coverage radius
Maximum allowable path loss
Propagation model
Okumura-Hata model
Cost231-Hata model
Universal model
Cost231-Walfish-Ikegami model
Estimate
coverage
radius Max allowable loss Propagation model selection
4
Site layout &
coverage emulation
Site
distribution
Electronic map
Planning area size
Planning site number
Link budget
radius estimate
Distribution map
Distribution info
Latitude & longitude
Site layout & emulation
**** Input Output
Coverage &
emulation
**** Input Output
Electronic map
Planning map
latitude & longitude
Antenna height/direction angle
Antenna selection
Propagation model
Link budget
Existing network data
Site distribution map
Site coverage effect map
Height info map
Existing network coverage map
Coverage probability statistics table
4
Site layout &
coverage emulation
5
Network scale
Coverage
planning
Capacity
planning
Network
scale
Summary
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Site layout & survey procedure
coverage planning
+ capacity planning
=>
network scale
Distribute site on Mapinfo
or PLANET/EET E-map,
decide site theoretic
location, latitude &
longitude and other para of
sites
Based on theoretic location of
sites, make sites survey.
Confirm site location, site type &
location, antenna type, height,
direction angle, downtilt, CDU,
TTA and feeder etc.
Site survey
Optical measurement
Construction environment and natural
environment
Frequency spectrum measurement
Electromagnetism environment
Site investigate
Installation condition of antenna and equipment
Power and transmission supply
Preparation
Try to collect materials relating to the project
include:
Engineering files, background information,
existing network situation, map and
configuration list
Get tools ready
Digital cameral, GPS satellite receiver,
compass, ruler and PC.
Site layout & survey
When select site location, take the following aspects into
consideration
Previous Network condition
Population distribution and habits
City layout and distribution
Main streets and traffic volume
Natural environment such as Hills, lakes, rivers and coastline
Growing trend
Select high traffic area and
dense population area
population
Traffic distribution
Customer mobility trend
Principles of site selection
Surrounding environment
Signaling transmission
quality
Careful select high hills, radar,
radio station, gas station, forest
and power plant
Main principles to select sites
Site should be at the best place of regular mesh with deviation less than a quarter of the site radius.
Select existing facilities for cost saving and period reduction purpose on the premise that it doesn’t affect site distribution.
City edge or High-altitude hills(100 m or 300 m higher than city construction) in suburbs are not supposed to be sites, as first to control coverage scope, second to make construction and maintenance easier.
Newly-constructed sites should better be at place where transportation is convenient, commercial power supply available, safe environment and take less farmland.
Avoid construct sites near high power radio transmitter, radar station or other interference sources.
Better far from forest to avoid fast fading of received signaling.
Pay attention to the effect of signaling reflection and dispersion when in hills, steep slopes, dense lake area, mountainous region and high metallic buildings.
When in cities, utilize the height of the building to realize division of network hiberarchy
There are less sites in the initial stage of network construction, so good coverage of key areas should be guaranteed.
CDU
Feeder design
Antenna
Height, direction
Frequency range,
gain
Polarization
3dB beam width
Down tilt
To increase
receiving sensitivity of
BTS
TMA Feeder
Antenna and feeder
City site
Suburb
site
Antenna selection
Site in city
Select directional antenna with horizontal 3dB bandwidth of 60~65°
Select medium gain antenna of about 15dBi
Best to select antenna with electrical tiltdown of 3~6°
Recommend dual-polarized antenna
Site in suburb
Select direction antenna with horizontal 3dB bandwidth of 65°or
90°
Generally select medium or high gain antenna 15~18dBi
Preset downtilt or not based on actual condition
Select dual polarized or vertical polarized antenna
City site
Suburb
site
Antenna selection
Site in rural area
Select directional antenna of 90°、120°or omni antenna
High gain of directional antenna (16~18dBi)
Generally don’t select downtilt antenna. For high sites, zero filling
antenna is the best choice.
Vertical polarized antenna is recommended
Road site
Select narrow-beam, high gain directional antenna. 8-shape
antenna, omni antenna or deformation omni antenna based on
actual condition
Generally don’t select downtilt antenna because road site has
higher requirements to coverage distance.
Vertical polarized antenna is recommended.
Principle for antenna height
Antenna of different cell of the same site can be different
due to installation conveniences or cell planning
requirements.
For flat urban area, height of antenna is around 25m.
For suburbs, antenna height can be elevated to 40m.
Antenna can not be too high
Reduce coverage level near the antenna especially for omni
antenna
Easy cause problems affecting network quality like over coverage,
co-channel interference or adjacent-channel interference.
Principle for Antenna direction
Try to keep the direction of three-sector site same in urban area.
Antenna main lobe should direct at dense traffic area
Main lobe deviate from co-frequency cell to control interference effectively.
Overlapping depth of urban adjacent sectors should not exceed 10%.
Overlapping area for suburb and country adjacent cells shouldn’t be too deep and the antenna angle between two adjacent sector of the same site should not less than 90 degree
Antenna main lobe of dense city area should avoid pointing straight to the street in case over coverage because of wave guide effect.
Principles of antenna tiltdown
Antenna tiltdown is the basic method to enhance
frequency reuse ability.
Control coverage and reduce interference
Electrical or mechanical tiltdown.
Mechanical tiltdown angle < 15°
Space diversity distance
Distance between two receiving antenna is 12~18λwhen
antenna is diversified by space.
Generally distance between diversity antenna is 0.11 times
of the antenna height.
To achieve the same effect, distance of vertical diversity
must be 5 to 6 times of horizontal diversity.
To reduce the interaction of the two antennas, horizontal
distance of diversity antenna should be over 3 m
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Coverage
emulation
**** Input Output
Coverage emulation
Electronic map
Planning area
Latitude & longitude of sites
Antenna height & direction angel
Antenna model
Link budget
Existing network data
Sites distribution map
Site coverage effect map
Height information map
Existing network
coverage map
Coverage rate statistics
table
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
GSM working frequency band
GSM900
Uplink 890 915 MHz
Downlink 935 960 MHz
duplex separation is 45MHz,carrier frequency separation is 200KHz
EGSM
Uplink 880 890 MHz
Downlink 935 935 MHz
duplex separation is 45MHz, carrier frequency separation is 200KHz
DCS1800
Uplink 1710 1785 MHz
Downlink 1805 1880 MHz
duplex separation is 95MHz, carrier frequency separation is 200KHz
P-GSM900
Fl (n) = 890 + 0.2n MHz
Fu (n) = Fl(n) + 45 MHz 1 n 124
n stands for ARFCN
E-GSM900
Fl (n) = 890 + 0.2(n-1024) 975 n 1023
Fu (n) = Fl(n) + 45 MHz 0 n 124
DCS1800
Fl (n) = 1710.2 + 0.2(n-512) MHz
Fu (n) = Fl(n) + 95 MHz 512 n 885
ARFCN
Basic Concept
Frequency Reuse Cluster
Frequency Reuse Factor
Frequency Reuse Distance
C/I and C/A
Frequency reuse distance
The following equation is used to estimate frequency reuse
distance:
D = 3 N * R
D —— frequency reuse distance
R —— cell radius
N - frequency reuse factor.
Definition of C/I and C/A
Co-channel Interference C/I:
C/I refers to the interference of another cell using the
same frequency to the current cell. The ratio of carrier
to interference is called C/I.
GSM specification regulates that C/I >9dB. In
implementing, it requires C/I>12dB.
Adjacent channel interference C/A
C/A refers to interference of adjacent channel to the
current channel. The ratio is called C/A. The GSM
specification regulates that C/A>-9dB.
Calculation of C/I
Where, Pown_cell is the signal strength of current
cell; Pi_BCCH is BCCH signal strength of interfering
cell i measured by MS.
Frequency reuse pattern
Ordinary (group) frequency reuse: ―43‖, ―33‖ and
more close ―26‖ and ―13‖.
MRP: different layers adopt different frequency reuse
patterns.
Concentric: the Underlay and Overlay adopt different
frequency reuse patterns respectively.
―4×3‖multiplex
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
A3
B1
B3B2
A1
A2
A3
B1
A1
A2A3
D2B1
D1
D3
A1
A2
A1
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
dB
dBI
C
18
)2.7(2)8(
2log10
)(
44
4
18dB>12dB
―3×3‖multiplex
A3
C2B1
C1
C3
B3B2
A1
A2
A3
C2B1
C1
C3
B3B2
A1
A2A3
C2B1
C1
C3
B3B2
A1
A2
A3 C1
A1
A2
A3
C2B1
C1
C3
B3B2
A1
A2
A3 C1
A1
A2
A3
B1
B3B2
A1
A2
dB
dBI
C
3.13
)57.5(2)7(2
2log10
)(
44
4
13.3dB>12dB
Multiple reuse pattern(MRP)
BCCH can use 43 or higher reuse coefficient to
ensure the BCCH quality, while the TCH will use
relatively dense reuse mode.
The division of BCCH and TCH layer frequency
bands reduces the planning workload and
facilitate the layered planning.
Reserve some frequency for the micro cell.
Simplify the configuration of BA tables
The relative independence of the BCCH and TCH
layers facilitates the maintenance and expansion
of each layer.
TCH2
FRF=6
BCCH FRF=12
TCH1 FRF=9
For Microcell
FRF: Frequency reuse factor
Bandwidth=6 MHz
MRP
BCCH
“4×3”
TCH1
“3×3”
TCH2
“2×3”
TCH3
“1×3”
MRP
Application of MRP
China mobile: MRP
Frequency bandwidth: 7.2MHz
AFN:(60~95),
Divide 36 carrier frequencies into 4 group as per
12/9/8/7
Channel
type
Logic channel
TCH1 service
channel
TCH2 service
channel
TC3 service
channel
Channel
number
60 61 62 63 64 65
66 67 68 69 70 71
72 73 74 75 76 77
78 79 80
81 82 83 84 85
86 87 88
89 90 91 92
93 94 95
60
64
68
62
66
7063
67
7161
65
69
72
75
78
73
76
7972
75
787477
80
89
91
93
9092
94 9092
9489
91
93
8183
85
8284
8682
84
8183
85
86
1) BCCH 4 3 2) TCH1 3 3
4) TCH3 2 3 3) TCH2 2 3
Application of MRP
2 2
2
2
2
2
2 2 2
2
2 2
2
2
2
Concentric
Concentric
The coverage of Underlay is the same as that of ordinary cell, while the Overlay use small transmitting power and thus has smaller coverage.
The frequency reuse factor of overlay differs from that of underlay.
The BCCH and SDCCH are used by Underlay, in which the call will be set up.
The absorbing of traffic by overlay is limited by traffic lay-out and coverage. It will increase the capacity by 10-30%
A brand new switching algorithm should be added.
2 2
2
2 2
2 2
2
2
2 2
2
2
2
2
2
2
2 2
2
2
2
2
2
Intelligent Concentric IUO
IUO
IUO has the same network structure as ordinary
concentric, consisting of Overlay and Underlay.
Underlay and Overlay of IUO both use the same
transmitting power.
IUO adopts a handover algorithm based on C/I
It’s very suitable for absorbing traffic inside building.
Comparison
Concentric
Overlay smaller
transmitting power
Handover based on
power or TA
Overlay coverage is
fixed but not reasonable
Absorb limited traffic
Handover algorithm is
easy
IUO
U/O same transmitting
power
Handover algorithm
based on C/I
Overlay coverage is
fixed and reasonable
Absorb more traffic
Handover algorithm is
complicated
TCH frequency plan
The frequency in same site can not be reused
In same cell, the frequency distance between BCCH and
TCH is at least 400khz
Frequency can not be reused in its directly adjacent sites if
it is not 1*3 pattern
Opposite cells should not be co-channel and avoid
adjacent channel.
High hill in the middle shall not be considered as
neighboring sites while broad water in the middle shall be
considered as neighboring sites.
Avoid to set same BSIC to BCCH with same frequency
Neighboring cell configuration
Centered on the cell, at most two-circle cells
can be neighbor cells
Neighboring cells shall not be more than 32.
Modify unreasonable neighboring cells
according to drive test.
Handover cells shall not be co-channel.
Avoid one way neighboring relationships
Avoid two neighboring cells with the same
BCCH and the same BSIC.
Attention
Reserve frequencies for
Test in propagation,
Replacement frequency in the interference test,
Micro cell frequency in hot spot area.
Generally BCCH should use higher continuous frequencies.
Allocate frequency based on different areas.
Allocate frequency for sites in different areas such as urban,
suburb and rural.
Focus should be put on cities to avoid interference.
Make planning in urban areas before suburbs and rural areas.
Divide urban area into small areas if there are many sites.
Check manually after frequency assignment via automatic frequency
planning.
Anti-interference technique
Dynamic power control (DPC)
Discontinuous transmit (DTX)
Diversity receiving
FH technique
Discontinuous transmit (DTX)
DTX encodes the voice at 13kbit/s during the
voice active period, it encodes the comfort
noise at 500bit/s during the quiet period.
DTX
DTX contributes very little to the interference
during the quiet period, its power can be
regarded as 0 (inactive state).
Suppose the DTX active factor is , then the
gain
log10log10log10)(/ IC
ICdBIC
Dynamic power control (DPC)
From the figure we
can see that, in the
dynamic power
control situation,
when the interfering
MS is only at the
cell borders, the
BTS can work with
the maximum
transmitting power.
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2A3
A1
A2
A3
A1
A2
A3
A1
A2
DPC
Obviously, the interfering MS location is a
probability. This case is especially apparent in
the frequency hopping situation.
Suppose the DPC factor is p:
pdBICIC
pIC log10log10log10)(/
(FH)
Frequency hopping is to avoid external
interference. In other words, it is to prevent or
greatly reduce co-channel interference and
frequency selective fading effect by
converting frequencies to an extent that
interference cannot catch up with.
Baseband and synthesized FH
Parameters
HSN(hopping sequence number)
MAIO(mobile assignment index offset)
Function
The advantage of the frequency hopping is the so-called
effect of Frequency Diversity and Interference Diversity.
The former actually expands the network coverage scope,
and the latter improves the network capacity.
Frequency diversity gain
For static or slow moving MS. about 6.5dB gain can
be provided.
For fast moving MS, the difference of two connected
bursts of a channel in time and place is enough to
make them uncorrelated to Rayleigh change, that is,
they are almost not subject to the influence of the
same fading, at this time, the slow hopping can
provide very little frequency diversity gain.
Gain=1.5-6.5dB
Interference diversity gain
In consideration of the above figure, suppose the MS talks by
using fk at the time t, in this case, the probability of the
interfered cell fk is
m
n
I
C
pI
CdBIC log10log10log10)(/ 增益
nmCCp mn
mn //1
1
Hopping set MA:},...,,,{ 321 nffff
,
TRX number:m (mn)
Interfering cell
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2A3
A1
A2
A3
A1
A2
A3
A1
A2
C/I= 9.43 dB
1*3+FH+DPC+DTX
Most densely reuse pattern
BCCH (4*3)
Combined with anti-
interference technology
Generally,only use 50%
of the whole available
frequency
1*3+FH+DPC+DTX
Compared to ―4×3‖ multiplex, the ―1×3‖ multiplex brings about the
interference degradation:
CIR 4×3- CIR 1×3 =18 - 9.43 8.57 dB
―1×3‖hopping, 50% frequency load brings about the interference
diversity gain:
10log10(2/1) = 3dB
Suppose the frequency hopping length is 12 frequency points, then
the frequency diversity gain is about 2dB
Suppose the DTX active factor is 0.5, then the gain is:
-10log10(0.5) = 3dB
Suppose the DPC factor is 0.9, then the gain is: -10log10(0.9)
=0.5dB
The total gain is: 3+2+3+0.5=8.5dB
GSM Network Planning
Info
collection
Capacity
planning
Coverage
planning
Site layout
& survey Frequency
planning
Radio
network
Summary
Case Analysis on GSM Network
Optimization
ZTE University
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
Severe call drops caused by the illegal user
Description:
2 cells of the GSM network in XX had severe call drop
problem, about dozens of times per hour in the day time.
Cause Analysis & Procedure:
According to the 24-hour performance statistics, most
of the call drops were in the daytime. While very few of
them were in the night. So the engineer suspected that
the problem was related with the user behavior.
Severe call drops caused by the illegal user
After tracing the Abis interface signaling, we found:
(1) The handsets with the call drop problem all used the same IMEI number.
(2) The dialed numbers were all the emergency number: 112;
(3) The call drop occurred about 10s after the call was connected. After the call drop, the user continued to dial 112 again and again.
Based on the above factors, we made the judgment: the call drop was caused by the user himself. For example, the workers in a factrory were testing the batteries of handsets, and they took out the battery while the call was still going on. So if we disable the emergency call function of the cell, the user will try to use another operator's network. After the operation, we found that the amount of call drops in the cell was greatly reduced. After we enabled the emergency call function later, the call drop problem didn't occur any more, becasue the user selected another operator's network.
Severe call drops caused by the illegal user
Summary:
By analyzing the Abis signaling file, we can make
judgement about the call drop problem and find out the
regularity of the problem. The network performance
index and user experience may be harmed when the
network resource is occupied by some illeagle user.
We can find out the illeagle user by signal tracing or
analyzing the CDR from the switching side.
Call drops caused by handover failure of the
handset
Description:
After the equipment been swapped to the GSM
network, one subscriber complained that under the
mobile environment, his call was automatically hanged
up within one minute after connection. The subscriber's
handset is HS-D907 and it worked normally under the
MOT equipment network before the swap. Another
subscriber complained that when he made a call by HS-
D907 on the highway, the call was frequently hanged up
about dozens of seonds after connection. In addition,
the subscriber said the handset never had the above
problem in other places.
Call drops caused by handover failure of the
handset
Cause Analysis & Procedure: The engineer traced the Abis interface MM signaling from the
switching side.
When the XX handset is the calling party, it enters the Conversation state after receiving "connect Ack". Several seconds later, the BSSAP entity sends a "cbclearcmdEvent" message to the handset, and the handset automatically hangs up.
When the XX handset is the called party, it enters the Conversation state after receiving "connect Ack". Several seconds later, the BSSAP entity also sends a "cbclearcmdEvent" message to the handset, and the handset automatically hangs up.
According to the signaling tracing analysis, the core network makes the judgement that the connection is actively released by the wireless side. The releasing reason is 1, and the meaning of this value is:
1=Radio interface failure(1)
Call drops caused by handover failure of the
handset
The engineer traced the Abis interface signaling
from the OMCR side.
After tracing the signaling in the 900/1800 area of Cell 3
and conducting call trace by MA10 software, we found
that the handset released the channels after the
handover failure, and the handovers were all
simultaneous handovers
During the conversation, every time when the handover
command was initiated, the handset pointed to "full rate
or half rate version 3", then the handover was failed.
Call drops caused by handover failure of the
handset
After comparing the version with the BSC voice version, the core network engineer found that the preferred full rate voice version for the wireless side was version 2, while the switching side only supported voice version 1 and 3, voice version 2 was not selected.
Steps: In "Configure the relation between BSC and trunk
group", the engineer added the TFRV2 to the property of all trunk groups of the 79 and 80 BSC from the switching side. After that, the automatic hang up never happened again during the dialing test.
Call drops caused by handover failure of the
handset
Under the AMR mode, the HS-D907 handset misunderstands the
encrypted fields in the handover command, so the handover will be
failed. Once the encrypted fields contain non-encription information,
the handset will report invalid mandatory filed, then the handover is
failed, and the call drop occurs.
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
Slow handover caused by improper handover
parameters
Description: During the drive test, the engineer found that the handover
from the Negotiation Building (covered by the 1800 network) to the Hongyan Primary School (covered by the 900 network) was too slow.
The testing vehicle moved from the north to the south, and the MS occupied the Cell5 (CI:10355,BCCH:700) of the Negotiation Building for conversation. When the vehicle moved on, the MS gradually entered the coverage of G1 cell of Hongyan Primary School (CI:11551, BCCH:115), and the level of the serving cell gradually turned to be -86db and became lower and lower. From the table, we can see that the level of the G1 cell was -50db, but the serving cell was not switched to the G1 cell of the school. So the level turned to be worse, and the quality also became worse.
Slow handover caused by improper handover
parameters
Tmicro timer
The 900 network and the 1800 network were set to be
on the same layer, and the Tmicro timer was set to be
8S. So when the handset occupied the cell 5 of the
Negotiation Building under the 1800 network, it could
not be switched to the 900 network at the same layer
within 8S after it sent the PBGT handover request. And
after 8S, since the frame error rate became higher, the
device couldn't decode the corresponding neighbor cell.
In order to solve the problem of slow PBGT handover
from the 1800 network to the 900 network, we need to
reduce the value of the Tmicro timer.
Slow handover caused by improper handover
parameters Pre-processing Parameter
Description: The survey report contains the large amount (message amount) of Abis interface information. Preprocess of the survey report can be transferred to BTS to reduce the burden of Abis interface link. After preprocess, BTS averages the survey data of MS by its own, and reports to BSC in a lower frequency. Average reporting period can be two, three or four SACCH multi-frames (480 ms). That is, the frequency decreases from the original twice/s to once/2 s, so the message amount of Abis interface decreases. However, the decrease of message amount still depends on whether the message length before preprocess is same as that after preprocess. This parameter determines whether to execute pre-processing or not, and it also determines the period of pre-processing.
Reducing the period of pre-processing will greatly impact the handover. It will speed up the handover, as well as increase the times of handover.
When the pre-processing period is 3, the average window is 4, and the P/N value is 2/3, the handover decision will take 9S. When the pre-processing is turned off , the average window is 6, and the P/N value is 3/4, the handover decision will take 4.5S.
Slow handover caused by improper handover
parameters
The related parameters may be
adjusted as follows:
Parameters O r i g i n a l
Value Adjustment value
Tmicro 8s 5s
Pre-processing window 3 0
Slow handover caused by improper handover
parameters
Summary:
After the adjustment of related parameters, the problem
of slow handover from the Negotiation Building to the
Hongyan Primary School was solved.
Accoring to the site conditions, we can adjust the pre-
processing parameter, the decision window and the
Tmicro timer to ensure the prompt handover and
prevent the call drop.
Inter-MSC Trunk Congestion Leading to Low
Handover Success Rate
Description:
One network uses dual bands, 900M is our equipment
and 1800 M is Nokia. Recently one IBSC was
commissioned, kept under the new MSC. Performance
statistics shows that handover success rate of this IBSC
is low, specifically, its outgoing handovers are basically
normal, and its incoming handover success rate is low.
Based on the handover statistics of the cells in this
IBSC with low handover success rate, most failures
happen during handovers from Nokia 1800M to 900M of
our company.
Inter-MSC Trunk Congestion Leading to Low
Handover Success Rate
Cause Analysis & Procedure: Based on the observation and performance statistics of our
MSC, the handover failures causes are mainly mchMapCauseErr_M.
From the failure observation of the core network, we found that when the failure occurs, the MSC-B has already sent MAP-Prep-HO Rsp containing the handover number to the MSC-A. The MSC-A should send IAM to the MSC-B according to the handover number, then MSC-B send the ACM to the MSC-A to indixate that the inter-office trunk is ready. And then the MSC-A will send HO Cmd to the BSC to inform the BSC to initiate the handover.
At this time, if MSC-A, due to some reasons, such as trunk congestion, can not send the IAM message, the MAP interface timer will time out and release MAP. MSC-A will not send HO Cmd message, and the handover fails.
Inter-MSC Trunk Congestion Leading to Low
Handover Success Rate
Based on the field test, the inter-MSC trunk between our MSC and Nokia MSC are congested, and the traffic volume of each line is more than 0.9 Erl. Thus, it can be concluded that the low inter-MSC
handover success rate is caused by the trunk congestion from Nokia MSC to our MSC, leading to acquisition failure of inter-MSC trunk and then handover failure.
We perform the capacity expansion of the inter-MSC trunk, and the traffic volume of every line is reduced and IBSC6 handover success rate becomes normal.
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
SDCCH congestion caused by group sending
SMS
Description:
As shown from the performance report, one site has
heavy congestion on the SDCCH channel. But the TCH
traffic volume of the site is not high and the site is not at
the bordering sections of several location areas. We
think the SDCCH congestion may be caused by the
huge amount of SMS.
SDCCH congestion caused by group sending
SMS
Cause Analysis & Procedure: At first, we tried the signaling tracing. And the result
showed that most of the CM service requests are SMS.
Then we conducted CALL TRACE. After we conducted CALL TRACE for two continuous requests, we found both of them were initiated by the IMSI:460028703084110, and the interval between the two requests was very short. So we thought the IMSI was group-sending the SMS.
According to the signaling trace, the cell has initiated 4536 requests (including the calling/called request, the SMS request and data service request) in total during the traced period. The amount of SMS requests was 3454 (including 3125 SMS requests initiated by that IMSI), and the amount of location update request was 247.
So we were sure that the SDCCH congestion was caused by the group sending of SMS from the IMSI number.
Serious SD congestion caused by core
network module problem
Description
About one third of the cells on 2 iBSC of the XX site had
serious SDCCH congestion. The cell-level statistics
shows that nearly one third of the cells have serious
congestion for all the time. The rate of successful
paging was decreased from 80% to 50%.
Serious SD congestion caused by core
network module problem
Troubleshooting process According to our analysis, the data configuration of the cell
was normal, the alarming of the BSC was normal, and the CPU usage was normal. Compared with the core network, the data of the cell was OK. And the load on the A interface was not increased.
After checking the basic CS measurement of the cell, we found the amount of calling /called attempts was small, and most of the attempts were about location update.
After analyzing the signaling of the cell, we found that a lot of location updates were failed. The handset didin't receive responses after sending the identity response. After the T3120 timer timed out,the channel was released. During this period, the SD channel was occupied for about 20s.
In mormal location update, the handset will receive the response from the network in about 100ms after it sends the identity response:
Serious SD congestion caused by core
network module problem
In mormal location update, the handset will receive the response from the network in about 100ms after it sends the identity response:
Since the failed location update occupied the SD channel for long time, serious congestion occurred on the SD channel. Due to the 3210 Timer on the handset timed out, the failed location update occupied the channel for 20s.
After the handset sent the location update request, there were ID request and ID response between the core network and the handset. It means the SCCP layer is OK, but the core network didn't respond to the handset.
Serious SD congestion caused by core
network module problem
Conclusion
After troubleshooting, the core network found two
modules were in problems. After the supporting A5/1
encryption algorithms of all the cells were disabled by
the wireless side, the SD congestion was temporarily
settled. And the congestion problem did not happen
after the algorithms was enabled again.
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
Handling the shrinking of BTS coverage
Description: According to the statement from the network
optimization engineer of China Unicom in ZhouKou, the coverage of ZTE's BTSs in some counties shrinked after certain period of operation, thus some originally covered areas became coverage holes or areas with weak coverage. This situation has great impact especially for the sub-urban areas, since the sub-urban areas had more omni-directional BTSs, and the distances between the BTSs in sub-urban areas are wider. The shrinked coverage can easily lead to coverage holes. Therefore, the operator may frequently receive complaint from the subscriber that the signal in some area becomes weak.
Handling the shrinking of BTS coverage
Cause Analysis & Procedure:
According to the subscriber's complaint, we conducted
drive test for the BTS with serious problem of shrinked
coverage. According to our analysis on the drive test
data, the coverage of some BTSs indeed shrinked,
especially for those BTSs that had been commissioned
for long time.
Problem 1: The coverage of the BTS in
FuCaoLou shrinked badly
Description From the table of project parameters, we found that the
BTSs in FuCaoLou Town of Taikang County were 40W omni-directional stations with the height of 50m. This kind of BTS generally can cover a distance of 4 km. According to the above figure, we can see that the coverage of the BTS (frequency point 124) in FuCaoLou is too small. The receiving level of the handset decrerases to -85dBm when the handset is 1 km away from the BTS.
Cause analysis We found that the BTS in FuCaoLou had been
commissioned for more than 2 years. However, the dust filter of the cabinet had never been cleaned during the period. Since lots of dusts were accumulated on the dust filter, the ventilation and cooling function of the fan on the cabinet was greatly affected, thus the working of the carrier, power amplifier and combiner were affected.
Problem 2: The BTS in Wulikou has different
coverage in different direction
Description 从From the Rxlev chart, we can see that the BTS in
Wulikou has different coverage in different direction. The coverage to the east is very samll, about 1 km, while the coverage to the north-easte reaches 5 km.
Cause analysis There are 2 platforms on the tower of the BTS. This site
is shared by the BTSs of CDMA network and GSM network. The CDMA network was commissioned earlier, it uses the upper platform, then the omni-directrional antennas of the GSM network were placed on the lower platform. So some omni-directrional antennas were obstructed by the iron tower, and the coverage in that direction is smaller.
Coverage became weaker due to repeater
frequency is inconsistent
Description: A subscriber from Shao Yang city complained that due to the
unstable signals at ShenJiaCun, he couldn't make a call untill he climed to the top of his building.
Cause Analysis & Procedure: According to our test at the site, the strength of the signal
from the repeater is -90dbm and the signal disappears randomly. After several times of dialing test, we confirmed the reported problem.
From the BTS side, we found the equipment was working normally. After querying, we found that the data of the repeater were not updated after the BTS was changed from omni-directional to directional. Then the repeater didn't work, and the signal strength became weak.
After we changed the frequency of the repeater to be the frequency of the signal source, the problem was solved.
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
"The subscriber is not in the service area"
caused by large CRO value
Description:
Some subscribers complained that the signal was very
weak near the BTS. For most of the handsets, the
signal strength was only 2 grids when the handset was
500 m away from the BTS. The maintenance engineer
said, the signal strength displayed on the handset was
normal, but when the subscriber was called, the calling
party got the response "the subscriber is not in the
service area".
"The subscriber is not in the service area"
caused by large CRO value
Cause Analysis & Procedure: According to our analysis, the above problem of subscriber not in the
service area was caused by "no response to paging". The possible causes are as follows:
1 The system was congested or over-loaded
If the MSC, the Abis interface signaling link, the BSC, the TRX or the wireless interface is overloaded, "no response to paging" may occur.
2 The cell was interferred by radio signal
If the cell is interferred by strong radio signal for a long time, "no response to paging" may occur.
3 The communication equiment is failed or working unsteadily
If the LAPD link, the uplink or downlink signal from the BTS is poor, "no response to paging" may occur.
If the handset has some problem itself, "no response to paging" may occur, and there will also be problems when the handset is the calling party.
"The subscriber is not in the service area"
caused by large CRO value
4 The BSC has data configuration error
It mainly refers to that the "Cell Module Information Table" is in error. The content of the table should be in consistency with all the modules of the BSC.
5 The handset was executing other processes, so it didn't respond to the paging
It's a coincidence that a new call is inintiated when the location update, SMS, call releasing process is not completed. This kind of "no response to paging" cannot be avoided in the GSM system. In this case, the calling party only needs to redial the number later.
6 The subscriber is indeed not in the service area or the handset is power-off
In this case, "The subscriber is not in the service area" is the correct response from the GSM.
"The subscriber is not in the service area"
caused by large CRO value For the complaint of the signal was very weak near the BTS, the
engineer suspected that the RF system and antenna feeder system had problems. But no problem was found when the engineer checked the hardwares of the BTS, the RF connection cable and the antenna feeder system. And the signal was not improved when the engineer adjusted the pitch angles of the antenna. Then the engineer tested the handset and found that the serving cell used by the handset belonged to the neighbor BTS in area B. The signal strength of the serving cell was only -85dBm, but the CRO was set to be 40. So it is very easy for the subscriber to select this BTS. Then the level of the serving cell was too low, it was easy to cause "The subscriber is not in the service area" . After the CRO setting was changed from the background, the problem was solved.
Generally, the CRO value should not be too large, especially for the sub-urban areas. Because the signal received by the MS is depending on the actually received level. If the two cells around the MS have similar C2 value and the actually received levels are quite different, it is very easy to cause cell reselection, thus lead to the problem of unstable signal when the MS is in idle state.
"The subscriber is not in the service area"
caused by cross-location-area cell reselection
Description:
The subscribers in one office building complained that
they often received the response " the subscriber is
powered off" or "the subscriber isnot in the service area"
when the signal on the handset of the called party was
very good.
"The subscriber is not in the service area"
caused by cross-location-area cell reselection
The office buiding is a high-rise building. Most of
the complaint are from the subscribers on the 10th
floor to 13th floor. According to the observation at
11th floor, the level received by the test handset is
-70dbm to -90dbm. However, the handset
detected multiple frequencies, including 900M and
1800M. And the signal strengths of different
frequencies were quite similar. There were many
900M frequence points taht belonged to different
location area. The handset frequently reselected
the cell in idle state.
"The subscriber is not in the service area"
caused by cross-location-area cell reselection
Cell reselection is needed in the following conditions:+
(1) Great loss of radio path occurs on the current registered
cell (C1<=0);
(2) The downlink of current registered cell failed;
(3) The current registered cell is blocked;
(4) According to C2, another cell in the same location area is
better than the current registered cell; Or according to CRH,
a cell in another location area in the selected netrwork is
better than the current regitered cell.
(5) The handset has not accessed the current regidtered cell
successfully after the random access times reached the
maximum number broadcasted on the BCCH.
"The subscriber is not in the service area"
caused by cross-location-area cell reselection
When the handset is in idle state, it frequently reselects the cell. If the cell reselection is crossing different location areas, a location update will be initiated. After times of dialing tests, we found that "the subscriber is not in the service area" may occur if the handset frequently conducts the location update.
According to the dialing test, some 900M frequence points are from a BTS that is in different location area. So there are two location areas for the 900M nertwork. Added by the location area of the 1800M network, the office building receives signals from 3 different location areas. So the cross-location-area cell reselection frequently occurs on the handset. The number of complaints were significatntly reduced after we requested the operator to adjust the downtilt angle of the 900M BTS antenna, since the office building cannot receive the signals from that
BTS.。
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
Interference caused by Excessive Strong
Back Signals of the Directional Antenna
Description:
During the drive test performed in one GSM network
optimization process, it was found that the area which
was more than one kilometer away from the site (S122)
and should be covered by cell 3 received stronger
signals from cell 1. Cell 1 signals brought severe
interference to other sites.
Interference caused by Excessive Strong
Back Signals of the Directional Antenna
Cause Analysis & Procedure:
1. The engineers first walked 100 meters away from the site, circled the BTS tower to test the signals with the MS. and the signals of all directions were found normal.
2. The engineers walked one kilometer away from the site and performed the test. It was found that the areas which should be covered by cell 3, was covered by cell 1, and the signals from cell 1 were about 5 dB stronger than that of cell 3.
3. The engineers first suspected that the jumper connection of the antenna system was wrong, and cross connection might exist. They checked the jumper and no problem was found.
4. The engineers checked the jumpers of the antenna and found no problem. This problem will not affect the transmission of the TRX and the VSWR, which can not located by SITEMASTER.
5. Therefore the engineers suspected that the directivity of the directional antenna of one cell is poor, and the back signals are not shielded. Because the site is space diversity, change the TRX/Main antenna with the diversity receiving antenna.
Interference caused by Excessive Strong
Back Signals of the Directional Antenna
Then it showed that the directivity of the antenna was poor,
the back signals of the antenna were not shielded, which
led to the great transmission strength of the opposite
coverage direction of the cell.
Because this cell was one TRX cell, and the power did not
deteriorated through using the combiner. Therefore the
areas which should be covered by cell 1 received better
signals from cell 1.
The antennas of cell 1 had 3 degree depression angle and
the test near the site did not show. The areas which should
be covered by cell 2 were not severely affected, because
the TRX of cell 2 is blocked from that of cell 3 by the tower.
Bad KPI of the Cell Caused by External
Interference
Description:
In one project, cells such as KBL029 had very poor
voice quality, high call drop rate and high handover
failure rate. KPIs were as follows:
Cause Analysis & Procedure:
KBL used PGSM as BCCH (105-124), and TCH used
EGSM 1*3 frequency hopping (975-995). Based on
TRX measurement, idle interference band of these cells
were distributed on TCH TRX instead of BCCH TRX,
assignment failed and most were on TCH TRX.
Bad KPI of the Cell Caused by External
Interference
It was decided that the cells with strong interference were the cells marked in red in the following figure:
Bad KPI of the Cell Caused by External
Interference Therefore the interference existed in the red areas, and the
interference is only on the TCH TRX that used the EGSM. The engineers were required to performe a scanning test
Bad KPI of the Cell Caused by External
Interference
The result shown that the EGSM frequency used
by ET was strongly interfered externally and the
interference power level was about -8 dB.
The scanning result was submitted to ET, and the
government confirmed that it was caused by the
military troops of one country and therefore the
problem could not be solved.
Contents
Call Drop
Handover
Congestion
Coverage
Paging
Interference
Allocation Failure
Long delay in receiving the "recharging is
successful" message
Description
One subscriber complained that he had to wait for a
long time to receive the "recharging is successful".
Long delay in receiving the "recharging is
successful" message Signaling of the core network: the core network releases the CC
connection after sending the short message, then it sends the short mesage, and after sending the short mesage, it releases the RR connection.
Long delay in receiving the "recharging is
successful" message Even if the handset has hanged up, the core network will continue to send
the message. After receiving the clear request 12s later, it will release the connection. If the sending of short message is failed, the core network will resend the "recharging is successful" when the handset is in Idle state.
Long delay in receiving the "recharging is
successful" message
Cause for the failure of sending the message
for the first time
From the signaling of the Abis interface, we found that
after receiving the "release complete" message for 10s,
the handset sent a "release indication" message to
clear the connection. So the sending of "recharging is
successful" was failed.
The handset cleared the connection 10s after receiving
the "release complete", because the T3240 timer of the
handset was timed out then.
Long delay in receiving the "recharging is
successful" message
Judging form the process, we can see the handset
will receive the "recharging is successful" if it
receives the CP-DATA message within 10s.
The engineer recorded the signaling of the
recharging process again. According to the air
interface signaling, it takes10s in total for the BTS
to send the "recharging is successful" to the
handset in 11 steps.
Long delay in receiving the "recharging is
successful" message
T3240 was started when the handset released the connection. And it was stopped when the handset received the CP-DATA messagem T3240. In the signaling, the interval between receiving " release complete" and "release indication" was 10s, that means the timer was not stopped.
There are two possible reasons. One is that the BTS had not send the CP-DATA
message to the handset in time.
The other one is that the handset may have some problem itself, that it didn't stop the T3240 timer after it received the CP-DATA message.
Long delay in receiving the "recharging is
successful" message
Conclusion Based on the above analysis, if the handset actively hangs
up after the recharging, it cannot receive the CP-DATA message within the time specified by the T3240 timer, and it will release the connection, so it will not receive "the recharging is successful" message. According to the subscriber behavior, most subscribers hang up the handset after they hear "the recharging is successful". So the first time of sending the message is failed.
So there are two solutions for this problem: One is to shorten the message of recharging success, so as
to let the total time of message sending + link creation be less than the value of T3240.
The other one is to change the time for sending the message. The core network will send "the recharging is successful" to the handset when the handset is in idle state after the recharging.
Antenna System
ZTE University
Objective
By the end of this course, you will be able:
To Understand the concept of dipole
To state GSM antenna specifications
To comprehend the principle of antenna selection
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Blah
blah
blah bl ah
Radio Waves
A form of electromagnetic radiation typically
generated as disturbances sent out by
oscillating charges on a transmitting antenna
Definition
An Antenna is any
device used to
collect or radiate
Electromagnetic
Waves
Linear antennas are
used:
Monopole (Slab)
Dipole Elements
Mobile Phones
Base Tranceiver
Station Antenna
• Single Monopole
• Patch Antenna
• Array of dipoles
Antenna for mobile communication
Antenna basic structure
Antenna are generally
composed of stacked of dipole
bundling their radiated power
to form a desired antenna
pattern in vertical plains
around the antenna
Depending on the gain desired
that wants to be achieved
several of those diploes can
be arranged on top of one
another
DIPOLES
Wavelength
1/2 Wavelength
1/4 Wavelength
1/4 Wavelength
1/2 Wavelength
Dipole
1800MHz :166mm
900MHz :333mm
Generation of radio waves
1个 dipole Received Power:1mW
Multiple dipole matrix Received Power:4 mW
GAIN= 10log(4mW/1mW) = 6dBd
Half wave dipole
Gain=10log(8mW/1mW) = 9dBi
“Omnidirectional array”
Received power:1mW
(Overlook
Antenna
“Sector antenna”
Received power:8mW
Isotropic antenna
Dipole
Ideal radiating dot source
(lossless radiator)
0dBd = 2.15dBi
2.15dB
dBd and dBi
dBd and dBi
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Antenna electrical properties
Operating Frequency Band
Input impedance
VSWR
Polarization
Gain
Radiation Pattern
Horizontal/Vertical beamwidth
Downtilt
Front/back ratio
Sidelobe suppression and null filling
Power capability
3rd order Intermodulation
Insulation
Type Frequency Range
GSM 900 890 - 960 MHz
GSM 1800 1710 - 1880 MHz
890 - 960 MHz
1710 - 1880 MHzGSM Dual Band
GSM antenna frequency range
BANDWIDTH = 960 - 890 = 70MHz
Optimum 1/2 wavelength
for dipole at 925MHz
at
960
MHz
Antenna
Dipole
at
890
MHz
GSM antenna frequency range
Standard Value: 50
Cable
50 ohms
Antenna
50 ohms
Impedance
9.5 W 80
ohms 50 ohms
Forward: 10W
Backward: 0.5W
Return Loss: 10log(10/0.5) = 13dB
VSWR (Voltage Standing Wave Ratio)
Voltage standing wave ratio (VSWR)
VSWR1.5
= (VSWR-1)/(VSWR+1)
RetureLoss = -20lg
Calculation of VSWR
120°
(eg) Peak
Peak - 10dB
Peak - 10dB
10dB Beamwidth
60° (eg) Peak
Peak - 3dB
Peak - 3dB
3dB Beamwidth
Bandwidth
Directional Antenna:65°/90°/105°/120°
Omni:360°
Omni-directional Directional
3dBm horizontal beamwidth
Omni-directional Directional
3dBm vertical beamwidth
Omni-directional Directional
Antenna structure types
Vertical Horizontal
+ 45degree slant - 45degree slant
Polarization
Space diversity
V/H (Vertical/Horizontal) Slant (+/- 45°)
Polarization diversity
Linear Polarization,vertical X Polarization, 45
Types of antenna
Antenna down tilt
Mechanical down tilt
Fixed electronic down tilt
Adjustable electronic down tilt
Mechanical down tile
It is achieved by physically
tilting the antenna out of the
perpendicular by using down
tilt kit
PROS: Cost efficient and
flexible
CON: Has no effect on the
side-lobe characteristics of the
antenna
Input Signal
Electrical down tilt
Electrical downtilt can be fixed or adjustable
Fixed is tuned by the manufacturer
Adjustable allows adjustment in a certain level on the rear of the
antenna
Non down tilt Electronic downtilt Mechanical
downtilt
Down tilt
Antenna tilt development
F/B = 10 log(FP/BP) typically : 25dB
Back power Front power
FRONT-TO-BACK Ratio
Ratio of maximum mainlobe to maximum
sidelobe
Upper sidelobe suppression and null fill
Upper sidelobe suppression and null fill
913 MHz 936 MHz 959 MHz 982 MHz
IMD@243dBm
f1, f2, 2f1-f2, 2f2-f1
Intermodulation
It occurs when two signals of a different frequency mix in a
non-linear device
It can be a problem at any site that has two or more
transmitters
It can be caused by a transmitter of the same system or by a
transmitter in another site that is co-sited or has a site in the
neighborhood
1000mW ( 1W) 1mW
10log(1000mW/1mW) = 30dB
Isolation
Antenna mechanical properties
Size
Weight
Radome material
Appearance and color
Working temperature
Storage temperature
Windload
Connector types
Package Size
Lightning Protection
Dimension
LWH
Length:connected with vertical bandwidth and gain
Width:connected with horizontal bandwidth
Height:connected with techniques adopted
Weight
A factor that can affect transport and
deployment
PVC, Fiberglass
Anti-temperature, water-proof , anti-
aging,weather resistant
Radome materials
Good-looking
Environment-protecting
Color
Temperature range
Operation and storage
Typical range:-40°C — +70°C
Connector type
7/16”DIN,N,SMA
Female/male
Mast diameter 45-
90mm
Mast
Direct Ground
Lightning protection
Antenna types
By frequency band: GSM900, GSM1800,
GSM900/1800
By polarization: Vertical, Horizontal, ±45º linear
polarization, circle polarization
By pattern: Omni-directional, directional
By down-tilt: Non, mechanical, electronic
adjustment, remote control
By function: Transmission, receiver,
transceiver
7/8” Main feeder
Feeder cable
1/2” (JUMPER CABLE)
Jumper cable
7/16”DIN-F(DIN CONNECTOR)
7/16”DIN-M(DIN & N CONNECTOR)
Connector
Rf port 2
Grounding
Lightning arrestor
Accessories
Trimming Tool or Hand Tool Kit
Clamp
Earthing Kit
Wall Glands
Hoisting Stocking
Universal Ground Bar
Antenna
7/16 Din Connector
7/8“ Cable
Grounding
1/2“ Jumper
Cabinet
EMP
Grounding clip
Grounding bar
1/2 Clamp
Tower Top
Amplifier
7/8“ Cable
Machine house
1/2 Jumper
Antenna system
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Radio propagation in cities
Environment features:
Densely deployed BTS,small coverage area
Decrease over coverage and interference, increase
frequency reuse factor
Antenna selection in cities
Polarization Dual-polarization (Installation space)
Direction Directional antenna (Frequency reuse factor)
3dB bandwidth 60~65°(Control coverage)
Gain 15-16dBi
Tilt down angle Fixed electrical tilt down
Radio propagation in suburb/rural area
Environment features:
Loosely deployed BTS
light traffic
large coverage
Antenna selection in suburb/rural area
Polarization Both dual-polarized and vertical
Direction directional
3dB bandwidth 90°105°
Gain 16-18dBi directional
or 9-11dBi omni
Tilt down angle Mechanical tilt down; 50m high; null fill
Radio propagation in road/highway environment
Environment features:
Low traffic
Fast moving
subscribers
Focus on coverage.
Strip coverage
Two sectors
Omni-cell when pass
towns or tourist site
Antenna selection for highway
Polarization Both dual-polarized and vertical
Direction Narrow beamwidth directional
3dB
bandwidth 30°
Gain 18dBi-22dBi
Tilt down
angle No tilt down
Radio propagation in mountainous environment
Environment features:
Block by mountains
Big propagation loss
Difficult to cover
Antenna selection in mountainous area
Polarization Both dual-polarized and vertical
Direction Omni or directional
3dB bandwidth Big 3db verticle bandwidth
Gain Omni (9-11dBi)
Directional (15-18dBi)
Tilt down angle Null fill & electrical tilt down
GSM/GPRS/EDGE Basic Principles
ZTE University
Objective
At the end of this course, you will be able to:
Learn GSM development history
Learn and master network structure of GSM system and
functions & principles of different portions
Learn and be familiar with GSM wireless channel and
protocol
Learn and be familiar with main service call process for
GSM
Content
Chap.1: GSM Overview
Chap.2: GSM Network Structure
Chap.3: Interfaces and Protocols
Chap.4: GSM Radio Channel
Chap.5: Basic Service and Signaling Process
Chap.6: Voice Processing and Key Radio
Technology
Chap.7: GPRS and EDGE
GSM Overview
This chapter mainly introduces some basic
information for GSM, including GSM development
history, supported service type, specification, and
system features.
GSM Basic Concepts
Services Supported by GSM System
GSM Specification
GSM Overview
This section introduces network structure of GSM
system and basic functions of various NEs.
GSM Area Division Concepts
GSM composition
Mobile Switching System (MSS)
Base Station Subsystem (BSS)
Operation & Maintenance Subsystem (OMS)
Mobile Station (MS)
GSM System Number
GSM Area Division Concepts
Relationship between Areas in GSM
GSM System Composition
IBM
IBM
BSS MSS
MS
MS
PSTN
Other
PLMN
Um
Interfac
e
A
Interf
ace
GSM composition
Mobile Switching System (MSS)
The MSS consists of such entities as the mobile
switching center (MSC), home location register
(HLR), visitor location register (VLR), equipment
identity register (EIR), authentication center (AUC)
and short message center (SMC).
Base Station Subsystem (BSS)
BSS serves as a bridge between the NSS and MS.
It performs wireless channel management and
wireless transceiving. The BSS includes the Base
Station Controller (BSC) and Base Transceiver
Station (BTS).
Operation & Maintenance Subsystem (OMS)
The OMS consists of two parts: Operation &
Maintenance Center – System (OMC-S) and OMC-
Radio (OMC-R). The OMC-S serves the NSS, while
the OMC-R serves the BSS.
Mobile Station (MS)
The MS consists of mobile terminals and Subscriber
Identity Module (SIM) card.
GSM System Number
GSM system number contains:
Mobile Subscriber ISDN Number (MSISDN)
International Mobile Subscriber Identity (IMSI)
Mobile Subscriber Roaming Number (MSRN)
Handover Number
Temporary Mobile Subscriber Identification (TMSI)
Location Area Identification (LAI)
GERAN interfaces
This chapter introduces GERAN interfaces, User
plane/control plane protocol stack at PS and CS.
Interfaces
PS-Domain Protocol Stack
CS-Domain Protocol Stack
GSM interfaces
Interfaces
User plane protocol stack at PS domain
PS-Domain Protocol Stack
Control plane protocol stack at PS
domain
PS-Domain Protocol Stack
User plane protocol stack at CS domain
CS-Domain Protocol Stack
Control plane protocol stack at CS
domain
CS-Domain Protocol Stack
GSM Working Frequency Band
This section introduces GSM radio frame, channel
concept, division & function for different channels,
mapping combination mechanism between
channels.
GSM Working Frequency Band
Structure of GSM Radio Frame
Physical Channel and Logical Channel
System Messages
GSM Working Frequency Band
Currently, the GSM communication system works at
900MHz, extended 900MHz and 1800MHz.
1900MHz band is adopted in some countries.
1 hyper frame = 2048 super frames =2715648 TDMA frame
1 hyper frame = 1326 TDMA frame (6.12s)
(=51 (26 frames) multi-frames or 26 (51 frames) multi-frames
1 (26 frames) multi-frame = 26 TDMA frame (120ms) 1 (51 frames) multi-frame = 51 TDMA frame (3036/13 ms)
TDMA Frame
Hierarchical frame structure in GSM system
Structure of GSM Radio Frame
There are five layers for structure of GSM radio frame, that
is, timeslot, TDMA frame, multiframe, super frame, and
hyper frame.
GSM uses TDMA and FDMA technologies for physical
channel, as shown in the figure below.
Time
Frequency
Frequency
Time
Physical Channel and Logical Channel
System Messages
System message falls into 12 types: type1, 2, 2bis,
2ter, 3, 4, 5, 5bis, 5ter, 6, 7, 8.
Basic Service and Signaling Process
This section introduces GSM terminal start,
position register / update, service call and
handover service implementation and signaling
interaction process.
Mobile subscriber state
Location Update
Typical Call and Handover Process
Basic Signaling Process
Mobile subscriber state
The mobile subscriber has three states as follows:
MS starts, network does "Attach" marks on it
MS shutdowns, separated from network
MS Busy
Location Update at Same MSC Office
BSC
(2)
(1)
(3) (4)
MSC/VLR
LAI
1
LAI
2
M
S
M
S
Location update between different MSCs
(5)
(2)
(3) (1)
(4)
HLR
MSC/VLR1
MSC/VLR2
M
S
M
S
Location Update
Call process
Typical Call and Handover Process
Handover process
Typical Call and Handover Process
Location Update Process of MS
RLC
RLSD
DT1:CIPH MODE CMD
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:LOC UPD REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:LOC UPD ACCEPT
Basic Signaling Process
IMSI Detach Process
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
CREF
CR:IMSI DETACH EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
Basic Signaling Process
Mobile-Originated Call and Called
Party On-hook Process
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:CM SERV REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:SETUP
DTAP:CALL PROC
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
DTAP:CM SERV ACCP
Basic Signaling Process
Mobile-Terminated Call and Calling
Party On-hook Process
UDT:PAG PAG CMD PAG REQ
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:PAG RES EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
DTAP:SETUP
DTAP:CALL CONF
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
BSC MSC BTS MS
Basic Signaling Process
Inter-cell Handover Process
DT1:HO PERF
HO CMD
CH ACT
MEAS REP
RF CH REL ACK
RF CH REL
DI:HO COM
EST IND
HO DET
CH ACT ACK
MS BTS1 BTS2 BSC MSC
MEAS RES
DR:HO CMD
HO ACCESS
PHY INFO
SABM
UA
HO COM
Basic Signaling Process
key radio enhanced technologies
This section describes basic voice processing for
GSM, and several key radio enhanced
technologies.
Voice Processing
Frequency multiplexing
Adaptive equalizing
Diversity Receiving
Discontinuous Transmission (DTX)
Power Control
Timing Advance
Frequency Hopping Technology
Voice Processing
Voice Processing in the GSM System
Frequency multiplexing
Frequency multiplexing is the core concept of the cellular
mobile radio system. In a frequency multiplexing system,
users at different geographical locations (different cells)
can use channels of the same frequency at the same time
(see the figure above).
Adaptive equalizing
Equalizer can do equalizing at frequency domain
and time domain. GSM uses time domain
equalizing, enabling the better performance in
whole system.
Diversity Receiving
Diversity reception technology is commonly used in GSM.
Diversity consists of different forms: Space diversity,
frequency diversity, time diversity and polarity diversity.
Discontinuous Transmission (DTX)
The DTX mode accomplishes two objectives: Lower the total
interference level in the air and save the transmitter power.
Speech Frame Transmission in DTX Mode
Power Control
Power control means to control the actual transmitting power (keep it
as low as possible) of MS or BS in radio propagation, so as to reduce
the power consumption of MS/BS and the interference of the entire
GSM network.
Power Control Process
Timing Advance
In the GSM, the MS requires three intervals between timeslots when
receiving or transmitting signals. See the figure below.
Uplink and Downlink Offset of TCH
Frequency Hopping Technology
Frequency hopping (FH) refers to hopping of the carrier frequency
within a wide frequency band according to a certain sequence.
Basic Structure of FH
section describes evolution of GSM
technologies
This section describes evolution of GSM
technologies: basic concept, network structure,
radio channel, and basic application of GPRS and
EDGE.
Definition and Feature
Inheritance and Evolution
GPRS Radio Channel
Radio Link and Media Access Control Flow
Terminal and Application
Definition and Feature
The General Packet Radio Service (GPRS) is the
packet data service introduced in GSM Phase2+.
The GPRS has the following features:
Seamless connection with IP network
High rate
Always online and flow charging
Mature technology
Definition and Feature
Enhanced Data Rate for GSM Evolution (EDGE) is a kind
of technology for transition of GSM to 3G.
The EDGE has the following features:
EDGE neither changes GSM or GPRS network structure nor
introduces new network element, but only upgrades the BSS.
EDGE does not change the GSM channel structure, multiframe
structure and coding structure.
EDGE supports two data transmission modes: packet service (non-
real time service) and circuit switching service (real time service).
EDGE adopts octal 8PSK modulation technology, supports 303%
of GMSK payload, and provides higher bit rate and spectral
efficiency.
Compared with GPRS, EDGE adopts new coding mode.
GPRS Radio Channel
This section introduces GPRS physical channel,
GPRS logic channel, mapping of logical channel
combination in the physical channel, and GPRS
channel coding.
Radio Link and Media Access Control Flow
This section introduces paging flow, TBF setup
flow, GPRS suspend/resume flow, and TBF
release flow.
Terminal and Application
The GPRS MSs fall into three categories: Type A,
B, and C.
GSM Network optimization overview
Objectives
At the end of this course, you will be able to:
State network optimization flow and the Content
Master common network optimization problems analysis
and solution
Understand Dual-Band Network and its peculiar
problems and solutions
Contents
Overview of radio network optimization
Introduction of network performance evaluation
Flow of Radio Network Optimization
Routine network optimization tasks
Common network optimization problems
Dual-Band network optimization
Object Purpose
The upcoming network
Network in operation
Improve system performance
Maximize service quality under existing
system configuration
Maximize benefit of existing network
Suggestion of network future
maintenance and planning
Network
Optimization
Data
Collection
Data
Analysi
s
Confirm
Reason
Make
Solution
Solution
Implement
Network Optimization Concept
Cause of Network
Optimization
End-user changes
New calling model
Subscriber distribution change
Environment change
New Building,Road,Vegetation
Network structure changes
Coverage , Capacity
Application of
New Technology
New Equipment
New Standard
Why Optimization
Network Optimization Position
Position in mobile communication
Specific working flow of mobile
networks
Throughout network planning,
implementation and daily
maintenance
Closed-loop management of network
quality
Necessary and effective approach of
Improving network operation quality
Relation with Maintenance
Maintenance is the foundation of
network optimization
Network optimization is the
further development based on
maintenance
Maintenance focus on equipment,
Network optimization focus on
network,
Maintenance work is the network
value-keeping process
Optimization is the network
value-added process
Network optimization category
Commission and maintenance optimization
ZTE equipments were not
used in network optimization,
but network operator wants
us (as the third party) to do
network quality evaluation,
optimization adjustment,
complementary planning,
etc.
Independence Optimization
Network
optimization
category
Engineering network
optimization
Maintenance network
optimization
Content
Overview of radio network optimization
Introduction of network performance
evaluation
Flow of Radio Network Optimization
Routine network optimization tasks
Common network optimization problems
Dual-Band network optimization
Network
Evaluation
Object
Network in
operation
Means Check and analyze: •Collection customers’ complain, •frequency allocation •radio parameter, •BTS equipment •MSC data •System performance data
Objectives Output reasonable and objective evaluation •network planning quality, • network running condition, • network operation question, the hidden danger, • network investment utilization factor
Concept
Drop call rate
TCH/SDCCH congestion rate
TCH allocation success rate
Handover success rate
Radio coverage
Traffic
Channel available rate
Optimization
Voice quality
KPI
Network performance KPI
Performance
evaluation
Analyze network KPI and output optimization suggestion
Resource
utilization
evaluation
By traffic statistic, export Traffic, calculate the utilization of network
resources. Reflect the capacity of network
Network
layout
evaluation
Network size, types of coverage, the feature / topographic
distribution, network architecture, site / Traffic density, indoor coverage
strategy
Network
test
evaluation
Through DT and CQT test, simulate users calling process. Reflect
the user’s feeling of communication
Voice
quality
evaluation
Evaluate voice quality by MOS
Network evaluation content
Contents
Overview of radio network optimization
Introduction of network performance evaluation
Flow of Radio Network Optimization
Routine network optimization tasks
Common network optimization problems
Dual-Band network optimization
1 2 3 4 5
Detailed Flow
Data
analysis
Require
analysis Data
collection
Preparation Equipment
check
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Requirement analysis
Network status: coverage, voice quality,radio KPI,
topographic and geographic feature, population
distribution, traffic hot spot
The most important problem of existing network
Expected performance KPI and dead line
Working interface with operator
Analysis Framework
2 1 3 4 5
Data
analysis
preparation Data
collection
Require
analysis
Equipment
check
8 6
Adjust
plan
Summary
acceptance
7
Result
verifies
Goals Detail
requirement
Expectations indicators Estimate time Special requests
Further detail
operator
requirement
Prepare data &
equipment
History P&O report Digital map Site information Network Index DT and related test equipment
…………
Preparation
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection
Require
analysis
preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verifies
Avoid the
Hardware
problems to affect
overall network
performance
Checking object
BTS hardware fault Antenna and feeding cable Clock problem Unstable power supply system Working environment condition
BSC/OMCR fault
Equipment check
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection
Require
analysis
Preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Current service condition
System performance data
Field test data
Subscriber complaints
Signaling trace
The data directly related to call processing of
mobile system in MSC
Data collection
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection
Require
analysis
Preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Traffic
statistics Drive test
Longer period
data
Comprehensive
analysis of
relative KPI
Reflect
downlink
signal
situation
Signaling data
Analysis coordination
between system entity
Provide essential clue
for network failure
Subscriber complaints
The non-
professional data
Need confirmation
again
Data analysis
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection Require
analysis preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Make plan
Risk control Avoid frequent
adjustment Partial experiment plan Quickly rollback plan Implementation step Backup
Reasonable time Agreement from operator
Check plan
Audit by the
expert and
operator
Confirm feasible
solution
Implementation
Detailed record
optimization
process and
results
Adjust optimization plan
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection
Require
analysis preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Performance
Comparison
Comparison of
test
Compare DT result. Compare CQT result.
At the same test
period and route
Compare and
analyze the data
before and after
adjustment
Verify result
Analysis Framework
3 1 2 4 5
Data
analysis
Equipment
check
Data
collection
Require
analysis preparation
8 6
Adjust
plan
Summary
acceptance
7
Result
verify
Optimization
report
Project
acceptance
Accept on
standard
Operator involved Signed by
operator
Project
summary
Knowledge
transfer Job evaluation
Document
backup
The work done
The achievement
obtained
Summary and acceptance
Contents
Overview of radio network optimization
Introduction of network performance evaluation
Flow of Radio Network Optimization
Routine network optimization
Common network optimization problems
Dual-Band network optimization
RF
Optimization
Three kind of routine work
Performance statistics
CCCH
Radio resource
assignment
Channel mode Dedicated channel
assignment
Handover
Channel release
Channel establish
Several important counters
Abis interface
A interface
BSC
cell
Neighbor cell list
Several key network element
Some specific event can
trigger corresponding counter
to do add 1 for counting,
through the observation of
counters in a specific period of
time, We can know the
network running status
Network monitor
Statistics report table
Concept
Network performance statistics report come from the
calculation of counters.
Quality KPI Statistical report reflect faults and solution
Drop call
Handover
Can’t call (block,
interference...)
Network access (large
coverage, indoor
coverage...)
Voice quality
Hard fault:Failed board or partial failure of
equipment. Generally hard faults can generate
obvious warning information on OMC-R
Soft fault:System still running, but part of system is unstable or not in the best status
Network monitor
Other monitor methods
DT and
CQT
Subscrib
er feeling
and
customer
complaints
Environment
New
building
External
interference
Network monitor
Network identification parameters System control parameters
Cell selection and re-selection parameters Network function parameters
Radio
parameter
Identify MS and network
The parameters related to
system configuration. Which
will Influence the service load
and signaling flow of the
system (capacity)
The parameters related to cell
selection and cell re-selection,
which will affect coverage
The parameters that provide various system functions
BSS parameter adjustment
BSS parameter adjustment
Selection and reselection
parameters
System control parameters
Network function
parameters
Network
identification
parameters Radio
parameter
CGI:
BSIC: BSIC=NCC&BCC
BSS parameter adjustment
Selection and
reselection
parameters
System
control
parameters
Network function parameters
Network identification
parameters
Radio
parameter
IMSI attach detach
Common control channel configuration (CCCH CONF)
Access allowed reserved blocks (BS AG BLKS RES)
Paging channel multiplexing frames (BS PA MFRMS)
Periodic location update timer (T3212)
Radio Link Timeout
Permitted network color code (NCC PERMITTED)
Maximum retransmission times (MAX RETRANS)
Transmission distributed timeslots (TX INTEGER)
Cell access barring(CBA)
Wait time(T3122)
Multi-band indication (MULTIBNAD )
BSS parameter adjustment
Selection and reselection
parameters
System control
parameters
Network function
parameters
Network identification
parameters
Radio
parameter
Additional re-selection
parameter indication (ACS)
Reselection parameter indication (PI)
Cell barring qualifying (CBQ)
Cell reselection offset (CRO)
Temporary offset (TO)
Penalty time (PT)
Cell reselection hysteresis (CRH)
Maximum power level of the control
channel (MS TXPWR MAX CCH)
Allowed access minimum receiving
(RXLEV ACCESS MIN)
Selection and
reselection
parameters
System control
parameters
Network function
parameters
Network identification
parameters
Radio
parameter
Power control indication (PWRC)
discontinuous transmission
(DTX)
New establishment cause
indication (NECI)
Call reestablishment allowance
(RE)
BSS parameter adjustment
Some BSC timers
T3111: Timer
between channel release
and RF deactivation.
T3101: Waitting
timer used in immediate
assignment process.
T3103:Intra-BSC
handover timer to hold TCH
both in original and target
cells
T3109:used limit
SACCH release time in
case of a radio link
timeout.
T3107:used to restrict
the TCH assignment time
BSS parameter adjustment
Check balance
of UP/DOWN link
Feeder cable check
Check interference
of UP/DOWN link
Antenna check
Azimuth
Tiltdown angle
Height
Isolation
Cross connection
VSWR high
Connector loose
Signal leakage
RF
Optimization
RF Optimization
Check balance
of UP/DOWN link
Feeder cable check
Check interference
of UP/DOWN link
Antenna check RF
Optimization
Uplink Interference
Check the ratio of un-decoded
RACH and uplink signal quality
handover to determine internal or
external uplink interference.
Repeated change frequency
Check idle channel interference
band
Frequency scanner
Downlink
Interference
Cell coverage test
Adjacent channel scan
Co-channel interference
detection
RF Optimization
Check balance
of UP/DOWN link
Feeder check
Check interference
of UP/DOWN link
Antenna check
RF
Optimization
Preparation information :
Link budget used in radio
design
BTS functions : DPC,DTX
Cell main parameter
BTS debugging report
Field data
collection
Abis signaling trace by
OMCR
Signaling analysis by MA10,
retain measurement report
message
RF Optimization
Contents
Overview of radio network optimization
Introduction of network performance evaluation
Flow of Radio Network Optimization
Routine network optimization
Common network optimization problems
Dual-Band network optimization
Call drop
handover
coverage
interference
congestion
Common Network Optimization Problem
1
Common phenomenon
Overshooting
Blind spot Sector cell
Overlaps
Coverage
2
Investigation
Power
Control
Measure
Rx_LEV
Measure
Drop
Call
Measure
Neighbo
r Cell
Measure
Undefin
ed
neighbor
cell
(lonely
island)
Locate
reason
Cell
perform
ance
measure
Cell
handover
out
measure
Coverage
3
Problem solution
Add new
site
Adjust
antenna
and feeder
Coverage
solution
Increase power
of TRX,MHA
Adjust network
parameter
Coverage
1
Common phenomenon
High call
drop rate
Bad voice
quality Ping-pong
handover
Handover
failure
Interference
2
Investigation
Handover failure but reestablish Also fail
Interference
3
Solution
Increase
the
distance
of co-
channel
or
adjacent
channel
cell
Reduce
BTS
power
Avoid
external
interference
frequency
Adjust
antenna
height
azimuth
down
tilt
Adjust
frequency
plan
Solution Narrow
beamwidth
antenna
Use
frequency
hopping,
DTX,
DPC
Interference
1
Common phenomenon
Difficult to originate
a call
Incoming
handover
failure
Low calling
success rate
Congestion
Congestion
2
Investigation -SDCCH congestion
Unreasona
ble access
parameter
Unreaso
nable
LAC
Small
T3212
SDCCH
frequency
interferen
ce
SDCCH
number
Wrong
LAC
setting
Too
many
SM
2
Investigation -
TCH congestion
•Check equipment hardware
•Check TCH Congestion rate
Locate
reason
Congestion
3
Solution -
TCH congestion
Adjust
antenna
height,
direction,
down tilt
Change
BTS
power
Open
half rate
function
Open
traffic-
based
handover
,
direction
al retry
function
solution
Expand
TRX or
add new
site
Adjust cell
access,
reselection
and
handover
parameter
3
Solution - SDCCH congestion
Check cell
CRH of
LAC
boundary
Rational
division of
LAC
Increase
SDCCH
Check
LAC
setting solution
Adjust cell
access
parameter
increase
T3212
Check
frequency
interference
Congestion
1
Common phenomenon
HO failure
or HO slow Unreasonable
Proportion of out/in HO
Frequent
handove
r
Handover
Neighbor cell
setting check
Define neighbor
cell for lonely
island
2 Investigation and
solution
Very high HO
failure rate
Neighbor cell high
load
Neighbor cell TRX
fault
Neighbor cell
transmission fault
Same frequency
and same BSIC for
nearby cells
Lonely island
Interference No enough
overlap area
between source
cell and target cell
Work out
hardware problem
Work out neighbor
cell problem
Improve radio
environment
Improve coverage
1 2 3 4 5
coverage Hardware Bad radio
environment Neighbor cell Congestion and transmission fault
Handover
2
Investigation and
solution
Two transmitting
antennas of same
cell cover scope is
different.
HO aarameters
unreasonable or
mismatch
Repeater only
enlarged part of
frequency of a cell.
Check MSC
REMOTELAC
table
A interface
signaling load
congestion, lead
HO signaling lost
Check antenna
condition,
Check and adjust
HO parameters
Adjust or replace
Repeater
Complete LAC
info in MSC
Expansion
6 7 8 9 10
Signaling link Heavy load
Antenna
problem LAC Not defined in MSC
Repeater problem
Parameter setting problem
Handover
1
Three type
MS can not decode
SACCH result in RLT
timeout and dropped
calls.
Radio link timeout
HO timer timeout,MS is unable to
access the target
channel, and can
not return to the
original channel as
well.
Handover call drop
Equipment failure
cause the call
dropped, Such as
LAPD link break
and so on
LAPD call drop
Call drop
3 Investigation and
solution
Blind spot
Poor indoor
coverage
overshooting
co-channel
interference
Adjacent channel
interference
Unreasonable
parameters.
Neighbor cell not
complete
Same BCCH/ BSIC
Traffic Congestion
Clock asynchronous
Feeder mistake
connection
Azimuth and
downtilt inconsistent
Antenna, feeder
damage, leak water
The transmission
break, Interrupt,
high BER
Adjust radio para.
Adjust engineer
para.
Solve hardware
problem
Adjust engineering para.
or frequency plan
Open DTX、FH、DPC
Solve equipment
problems
Adjust para.
Balanced traffic
Calibration Clock
Analysis traffic
statistics
Examination
alarm
On-stie check
Observation
transmission and
board alarm
Transmission path
checks
1 2 3 4 5
Transmission Coverage Antenna and feeder
Handover Interference
Call drop
3
Investigation and
solution
such as
inconsistent
software
version
RLT ,Min-Acc-
Min, Minimum
level of RACH,
RACH busy
threshold.
Upgrade software check and
adjust radio
parameters
6 7
Unreasonable radio para.
Other reasons
Call drop
Contents
Overview of radio network optimization
Introduction of network performance evaluation
Flow of Radio Network Optimization
Routine network optimization
Common network optimization problems
Dual-Band network optimization
GSM900 macro GSM1800 macro
900 micro 1800 micro
P-cell P-cell
GSM900/1800 umbrella-like cell macro
A lot of cells are
available for choice.
Concept
Ideal dual-band network
MS roaming in two band network
MS can seamless handover between two band network
Traffic balance in the dual-band network
Avoid frequent re-election and normal location update
Avoid frequent unnecessary handover between dual-band
network
Dual-band network unique problem
Traffic is not balance
Ideal dual-band network
Frequent location
update
Frequent HO and
reselection
Traffic management
principle
Selection principle Traffic balance principle
Layer principle
Automatic traffic
balance technology
based on dynamic
priority to prevent
traffic congestion.
900 networks and 1,800 networks in different layer
MS idle: Select the 1800 cell first
MS busy: Remain in the layer
where the call is originated,
and avoid unnecessary
handover between layers.
1800 layer
900 layer
The basic principle
Balance the traffic in
dual-band network
Traffic Balance
While covered by dual-
band cells ,try to reduce
the frequent handover
and location update,
reduce network signaling
flow
The efficient use of
resources
Traffic control principle
Objective
Adjust cell engineering parameters Adjust cell radio parameters
BTS transmit power
Antenna height, azimuth and
downtilt
Antenna type
Through modifying the signal level of dual band cells in the same position,
change priority and direction of cell selection, reselection and handover.
Balance traffic of dual band cells.
Cell selection :C1,CBA,CBQ
Cell re-selection :C2
Dual-band handover :
• PBGT handover control
• Handover priority
The main optimization method
900M cell:CBQ = 1,CBA = 0,C1=15
1800M cell:CBQ = 0,CBA = 0,C1=10
Power on the MS to make cell selection
Application of Cell Selection
MS select 1800 network first, set the 1800 cell to a
normal priority cell CBQ = 0,CBA = 0
Set the 900 cell to a low priority cell CBQ = 1,CBA = 0
900M cell:C1=15,C2=5
1800M cell:C1=10,C2=20
Cell re-selection in the idle mode
Application of Cell Selection
MS Reselects the 1800 network, set a large
offset for the 1800 cell and a small offset for
the 900 cell.
1800 cell
900 cell
PBGT
handover
Bar Inter-layer PBGT Handover
Multi-path fading
can cause a
large number of
PBGT handover
80% handover is
PBGT, it must be
barred.
Different layer use different
handover priority
Other policies
Automatic traffic balance
policy based on dynamic
priority
Traffic-based handover
Directed retry between
different bands
Fast fading handoff
algorithm
Set handover protection
time
Other optimization policies
GSM Radio network planning principle
ZTE University
Objectives
At the end of this course, you will be able to:
Describe the contents of information collection
State capacity planning
State coverage planning
Describe steps to notices of site survey
Master frequency planning and anti-interference
technology
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Overview
Mobile service forecast
Subscriber forecast, distribution
Network equipment &
operation profile
MSC,BSC,BTS
Traffic statistic, quality
City planning
City type, map
Population
Economic development plan
Road and transport condition
Information Collection
Radio propagation survey
Geographic environment
Plantation
Network traffic distribution
Industrial, commercial, residential
area
Coverage and quality analysis
Coverage and quality (DT)
Statistic of A, Abis and OMCR
Interference analysis
Frequency allocation
Frequency scanning test
Analysis and survey
Frequency Other Traffic Model Capacity Coverage
Limited
frequency
Available
bandwidth
Frequency
resources
Coverage
KPI
Traffic
distributing
Coverage
size
Redundancy
and other
requirements
traffic
distributing
Traffic and
system
capacity
Data traffic
model
Voice traffic
model
Site
configuration
Propagation
environment
Electronic
map exists ?
Requirement analysis
Summary
Network planning information collecting
template
Inadequate
info
1. What is necessary information?
2. What is supplementary info?
?
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Basic concepts
Traffic volume
Traffic model
Erland
Call loss rate
Erlang B table
Erlang B table 2% 5%
1 0.020 0.0532 0.223 0.3813 0.602 0.8994 1.092 1.5255 1.657 2.2186 2.276 2.9607 2.935 3.7388 3.627 4.5439 4.345 5.37010 5.084 6.21611 5.842 7.07612 6.615 7.95013 7.402 8.83514 8.200 9.73015 9.010 10.63316 9.828 11.54417 10.656 12.46118 11.491 13.33519 12.333 14.31520 13.182 15.24921 14.036 16.18922 14.896 17.13223 15.761 18.08024 16.631 19.03025 17.505 19.985
Capacity Planning Procedures
Confirm subscriber
number
Site numbers and
configuration
Traffic distribution
ratio
Site distribution and
their latitude and
longitude
Reach target of
capacity planning
1 2 3 4 5
Network scale Capacity information
collection Site layout Traffic distribution
analysis
Site type and
number
Capacity Planning
Information collection
Network type: GSM900, DCS1800, dual-band network or WLL network?
System capacity requirement. No of subscriber and the traffic?
Traffic model of the voice service?
Equipment type: V3/SDR? Model? Indoor or outdoor? DPCT applied in V3 or not?
Data service required? EDGE TRX? Data service penetration rate? Traffic model of data service?
Frequency resource range ? Is there frequency that are prohibited? Maximum site configuration ?
Forecast and investigation traffic density and define traffic distribution ratio.
Traffic density distribution
Traffic distribution analysis is to categorize the planning
area into areas of different service levels based on
forecast and survey of traffic density distribution
● how many phases and what is the ratio of
subscribers in each phase
● what is the planning area range and the
traffic distributing ratio in DU/MU/SU/RU.
● Provide existing sites and their
configuration and performance statistics
report data
扇面 1
41%
扇面 2
26%
扇面 3
15%
扇面 4
11%
扇面 5
7%
Service level by radio propagation environment
Area Topographic features
Dense
urban
Average height of surrounding buildings is more than 30 metres (over 10 storey)
and average distance between buildings is 10-20 metres. Usually the buildings
are crowded around the site with the height of 10-20 stories and the ambient
roads are not considerably wide.
urban
Average height of surrounding buildings is about 15-30 metres (5-9 storey) and
average distance between buildings is 10-20 metres. The buildings are evenly
distributed around the site. Mostly are below 9 stories and some are over 9
stories and the ambient roads are not considerably wide.
suburb
Average height of surrounding buildings is about 10-15 metres (3-5 storey) and
average distance between buildings is 30-50 metres. The buildings are evenly
distributed around the site. Mostly are 3-4 stories and some are over 4 stories.
Roads around are wide.
rural Average height of surrounding buildings is below 10 metres. They are dispersed
and mainly are 1-2 storey high. There are spacious space between.
Service level by service distribution area
Area Distribution Features
Dense
urban
Traffic is heavy with high data service
rate, mainly for data service
development
Mean
urban
Traffic is relatively heavy and date
rate should be comparatively high.
Data service is required
Suburb Traffic is low and only low-speed
data service
Rural Traffic is quite low. Site is for
coverage purpose and data service
quality are not ensured.
Both radio propagation
environment and service
distribution factors should all
be taken into consideration.
Number of BTS sites-1
No. of BTS for capacity limited area
Maximum site type by frequency reuse pattern
Traffic per site by traffic model, Erlang-B table
Total number of BTS: Total traffic / single site
traffic
Number of BTS sites-2
No. of BTS for coverage limited area
Total area / single site coverage (according to service
level)
Cell traffic = Cell coverage * traffic density
TCH number (Erlang-B table)
SDCCH number
TRX number
Start
Frequency resources
Capacity of each cell
Capacity per site
Site configuration & number
Frequency reuse pattern
Maximum Site type
Channel planning & data service
Erlang B table
Traffic model
Site configuration
Traffic & distribution
Network Scale Coverage Planning
Site type and number
No of SDCCH
Suppose SDCCH average process time is 3s,Location updating
process is 9s,BHCA=2
The traffic of SDCCH per subscriber is:
(3×2 + 9) / 3600 = 0.0042 Erlang
4SDCCH call loss=2% can support 1.092Erlang,
(1.092 / 0.0042 = 260sub) ×0.025 Erlang = 6.5Erlang
look up in Erlang-B,call loss=2%, 6.5Erlang need 12TCH(2TRX)
8SDCCH call loss=2% can support 3.627Erlang
(3.627 / 0.0042 = 863sub) ×0.025 Erlang = 21.6Erlang
Look up in Erlang-B,call loss=2%,21.6Erlang need 30
TCH(4TRX)
SDCCH configuration
TRX Channel SDCCH type SDCCH TCH TCH traffic
(GOS=2%)
1 8 SDCCH/8 1 6 2.28
2 16 SDCCH/8 8 14 8.2
3 24 2*SDCCH/8 16 21 14.9
4 32 2*SDCCH/8 16 29 21
5 40 2*SDCCH/8 16 37 28.3
6 48 2*SDCCH/8 16 45 35.6
7 56 3*SDCCH/8 24 52 43.1
8 64 3*SDCCH/8 24 60 49.6
9 72 3*SDCCH/8 24 68 57.2
10 80 4*SDCCH/8 32 75 64.9
LA planning
LA border
Paging capacity in LA
Paging capacity calculation
Influence by Short message
LA border
Avoid dense city with high traffic area
Avoid area with high mobility of subscribers
Cross the road slantwise
Consider traffic expansion
Paging capacity
IMSI/TMSI
Second paging(local paging、global paging)
Paging group:
(BS-AG-BLK-RES)
(BS_PA_MFRAMS)
Paging blocks/ per second =(9-AGB)/0.2354
Paging number / per paging block : B = 2 or 4
Paging capacity calculation
Paging numbers per second(P)
P =(9-AGB)/0.2354 * B
Suppose:
Average time of call:60s,ie:1/60Erl
Traffic of LA(T)
75%of MS response first paging,25% of MS response
second paging
Paging congestion when 50% of maximum paging.
T*30%/(1/60)*1.25 = P*50% = 59.47*3600*50%
Influence by short message
3/per sub/per day
30% retransmit
Convergence factor:0.12
Subscriber in LA:100000
SM number in busy hour
100000×3×0.12×(1+30%)=46800
Consider holiday case: 8 times
Coverage
Planning
Capacity
Planning
Network
Scale
Summary
Capacity planning is
just an initial plan,
Add or reduce sites
based on radio
coverage planning
and analysis.
Capacity planning is
a repeated, gradual
process helping to
decide site number
and type.
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Coverage Planning flow
Set parameters Estimated
coverage radius of
each site
Allowable max path
loss
Information of site
distribution ,
latitude & longitude
of sites
Target of coverage
1 2 3 4 5
Network scale Network
parameter
Site layout &
coverage emulation Link budget Coverage radius
estimate
1
Network parameter
Confirm network parameters
Network category: GSM900,DCS1800, dual-band or WLL network?
Equipment type: V3/SDR? Model? Indoor or outdoor?
Carrier Transmission power is 40W,60W,80W? Are data service required? EDGE carrier frequency?
Antenna model: antenna gains, horizontal and vertical beam width, antenna downtilt, polarization mode and electrical downtilt etc.
Antenna parameter: antenna available height, directional angle and downtilt.
Apply tower top amplifier?
Feeder type: 7/8 feeder or 15/8 feeder?
Maximum site configuration is? Are there special requirements toward configuration of combining and distribution unit?
What is KPI? What is level and area coverage rate?
2
Link Budget
Link budget
Definition:
Link budget is the calculation of loss and gains on one
communication link.
Target:
Maximum power of the site, avoid invalid downlink
coverage, reduce interference and system noise.
Allowable maximum indoor & outdoor path loss of uplink
and downlink Uplink Downlink
PA
Feeder loss Transmission
loss
Antenna gain Penetration loss
Site sensitivity
Fading margin
Body loss MS power
Link budget
Losses
Margin reservation
Gains
Network Type & Equipment
Link Budget
Transmission power and reception
sensitivity of MS/BTS
Fast fading margin
Slow fading margin
Interference margin
Site antenna gain
MS antenna gain
TMA gain
Path loss
Body loss
Vegetation
loss
Building penetration
loss
Feeder and
connector loss
Combiner and
splitter loss
Link budget
Link budget-Equipments
MS transmission power is showed as follows:
Power
class
GSM 900
Nominal
Maximum output
power
DCS 1800 Nominal Maximum
output power
1 1 W (30 dBm)
2 8 W (39 dBm) 0.25 W (24 dBm)
3 5 W (37 dBm) 4 W (36 dBm)
4 2 W (33 dBm)
5 0.8 W (29 dBm)
Link budget-Equipments Series Modulation Transmission power Reception
sensibility
Biggest site
BTS
V3
B8018 GMSK 60 W 47.78 dBm
-112 dBm S18/18/18 8PSK 31 W 45 dBm
B8112 GMSK 60 W 47.78 dBm
-112 dBm S12/12/12 8PSK 31 W 45 dBm
M8202 GMSK 30 W 44.78 dBm
-110 dBm S2/2/2 or O6 8PSK 20 W 43 dBm
Link budget-Loss
Path loss
Body loss
Vehicle loss
Plantation loss
Building penetration loss
Feeder and connector
loss
Combining and
distributing unit loss
Link budget-Loss
Path loss
Radio wave loss caused by the transmission distance.
Body loss
Voice service, body loss 3 dB
Data service, 0dB.
Vehicle loss
Usually it is 8~10dB.
Link budget-Loss
Plantation loss
Inside the forest, the loss of 900MHz is 0.2dB/m; the
loss of 1800MHz is 0.3dB/m
Through forest or diffraction, the loss is 20dB/dec
Forest around the antenna and the antenna is lower
than the forest, around 10dB
Building penetration loss
Averagely it’s 10 – 20 dB,relying on building material
and thickness.
Link budget-Loss
Feeder cable loss
Type loss(dB/100m)
900M 1800/1900M
1/2 soft jumper 7.22 11.3
7/8 feeder 3.89 6.15
15/8 feeder 2.34 3.84
Link budget-Loss
Combiner & Splitter loss
Unit (900M) Insertion loss
CDUG 4.4dB
CEUG 3.5dB
CENG 5.3dB
CENG/2 5.3dB
ECDU 0.9-1.0dB
Unit(1800M) Insertion loss
CDUD 4.6dB
CEUD 3.6dB
CEND 5.5dB
CEND/2 5.5dB
ECDU 0.9-1.0dB
Link budget-Gain
BTS Antenna gain
Area Antenna gain
(dBi)
urban 15.5
suburb 15.5~17
rural 17~18
Express way or
long & narrow
valley
18~21
Hills and
highland
17~18
MS antenna gain
usually is 0
remark:special attention
should be paid to antenna gain
in MS in GSM WLL network
Antenna may be indoor,
outside door or on the roof.
So antenna gain and height
should be checked, which
will affect coverage greatly.
TMA gain
Link budget-Margin
Fast fading & deterioration storage
walking:2.0--5.0dB
fast moving:0dB
In GSM system, fast fading for voice and data service is
supposed to be 3dB.
Interference margin
The interference margin is generally supposed to be
3dB.
Link budget-Margin
Slow fading (shadow fading) margin
shadow fading is based on
standard deviation
margin coverage probability.
slow fading standard deviation is related to propagation
condition. In cities, it’s about 8~10 dB, while in suburbs
or rural areas,6~8dB.
Marginal coverage
probability(%)
70 75 80 85 90 95 98
Slow fading margin/dB 0.53σ 0.68σ 0.85σ 1.04σ 1.29σ 1.65σ 2.06σ
Link budget
Parameter Symbol
MS transmitting power A
Body loss B
Building loss C
MS reception sensibility D
MS antenna gain E
TMA gain F
Diversity gain G
Feeder loss H
Combiner/divider unit
loss
I
Fast fading margin J
Slow fading margin K
Noise margin L
Path loss indoor M=A-B-C-D+E+F+G-H-I-J-
K-L
Path loss outdoor N=M+C
Path loss difference
between uplink and
downlink is 3-5dB
3
Coverage
radius estimate
Estimate coverage radius
Maximum allowable path loss
Propagation model
Okumura-Hata model
Cost231-Hata model
Universal model
Cost231-Walfish-Ikegami model
Estimate
coverage
radius Max allowable loss Propagation model selection
4
Site layout &
coverage emulation
Site
distribution
Electronic map
Planning area size
Planning site number
Link budget
radius estimate
Distribution map
Distribution info
Latitude & longitude
Site layout & emulation
**** Input Output
Coverage &
emulation
**** Input Output
Electronic map
Planning map
latitude & longitude
Antenna height/direction angle
Antenna selection
Propagation model
Link budget
Existing network data
Site distribution map
Site coverage effect map
Height info map
Existing network coverage map
Coverage probability statistics table
4
Site layout &
coverage emulation
5
Network scale
Coverage
planning
Capacity
planning
Network
scale
Summary
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Site layout & survey procedure
coverage planning
+ capacity planning
=>
network scale
Distribute site on Mapinfo
or PLANET/EET E-map,
decide site theoretic
location, latitude &
longitude and other para of
sites
Based on theoretic location of
sites, make sites survey.
Confirm site location, site type &
location, antenna type, height,
direction angle, downtilt, CDU,
TTA and feeder etc.
Site survey
Optical measurement
Construction environment and natural
environment
Frequency spectrum measurement
Electromagnetism environment
Site investigate
Installation condition of antenna and equipment
Power and transmission supply
Preparation
Try to collect materials relating to the project
include:
Engineering files, background information,
existing network situation, map and
configuration list
Get tools ready
Digital cameral, GPS satellite receiver,
compass, ruler and PC.
Site layout & survey
When select site location, take the following aspects into
consideration
Previous Network condition
Population distribution and habits
City layout and distribution
Main streets and traffic volume
Natural environment such as Hills, lakes, rivers and coastline
Growing trend
Select high traffic area and
dense population area
population
Traffic distribution
Customer mobility trend
Principles of site selection
Surrounding environment
Signaling transmission
quality
Careful select high hills, radar,
radio station, gas station, forest
and power plant
Main principles to select sites
Site should be at the best place of regular mesh with deviation less than a quarter of the site radius.
Select existing facilities for cost saving and period reduction purpose on the premise that it doesn’t affect site distribution.
City edge or High-altitude hills(100 m or 300 m higher than city construction) in suburbs are not supposed to be sites, as first to control coverage scope, second to make construction and maintenance easier.
Newly-constructed sites should better be at place where transportation is convenient, commercial power supply available, safe environment and take less farmland.
Avoid construct sites near high power radio transmitter, radar station or other interference sources.
Better far from forest to avoid fast fading of received signaling.
Pay attention to the effect of signaling reflection and dispersion when in hills, steep slopes, dense lake area, mountainous region and high metallic buildings.
When in cities, utilize the height of the building to realize division of network hiberarchy
There are less sites in the initial stage of network construction, so good coverage of key areas should be guaranteed.
CDU
Feeder design
Antenna
Height, direction
Frequency range,
gain
Polarization
3dB beam width
Down tilt
To increase
receiving sensitivity of
BTS
TMA Feeder
Antenna and feeder
City site
Suburb
site
Antenna selection
Site in city
Select directional antenna with horizontal 3dB bandwidth of 60~65°
Select medium gain antenna of about 15dBi
Best to select antenna with electrical tiltdown of 3~6°
Recommend dual-polarized antenna
Site in suburb
Select direction antenna with horizontal 3dB bandwidth of 65°or
90°
Generally select medium or high gain antenna 15~18dBi
Preset downtilt or not based on actual condition
Select dual polarized or vertical polarized antenna
City site
Suburb
site
Antenna selection
Site in rural area
Select directional antenna of 90°、120°or omni antenna
High gain of directional antenna (16~18dBi)
Generally don’t select downtilt antenna. For high sites, zero filling
antenna is the best choice.
Vertical polarized antenna is recommended
Road site
Select narrow-beam, high gain directional antenna. 8-shape
antenna, omni antenna or deformation omni antenna based on
actual condition
Generally don’t select downtilt antenna because road site has
higher requirements to coverage distance.
Vertical polarized antenna is recommended.
Principle for antenna height
Antenna of different cell of the same site can be different
due to installation conveniences or cell planning
requirements.
For flat urban area, height of antenna is around 25m.
For suburbs, antenna height can be elevated to 40m.
Antenna can not be too high
Reduce coverage level near the antenna especially for omni
antenna
Easy cause problems affecting network quality like over coverage,
co-channel interference or adjacent-channel interference.
Principle for Antenna direction
Try to keep the direction of three-sector site same in urban area.
Antenna main lobe should direct at dense traffic area
Main lobe deviate from co-frequency cell to control interference effectively.
Overlapping depth of urban adjacent sectors should not exceed 10%.
Overlapping area for suburb and country adjacent cells shouldn’t be too deep and the antenna angle between two adjacent sector of the same site should not less than 90 degree
Antenna main lobe of dense city area should avoid pointing straight to the street in case over coverage because of wave guide effect.
Principles of antenna tiltdown
Antenna tiltdown is the basic method to enhance
frequency reuse ability.
Control coverage and reduce interference
Electrical or mechanical tiltdown.
Mechanical tiltdown angle < 15°
Space diversity distance
Distance between two receiving antenna is 12~18λwhen
antenna is diversified by space.
Generally distance between diversity antenna is 0.11 times
of the antenna height.
To achieve the same effect, distance of vertical diversity
must be 5 to 6 times of horizontal diversity.
To reduce the interaction of the two antennas, horizontal
distance of diversity antenna should be over 3 m
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
Coverage
emulation
**** Input Output
Coverage emulation
Electronic map
Planning area
Latitude & longitude of sites
Antenna height & direction angel
Antenna model
Link budget
Existing network data
Sites distribution map
Site coverage effect map
Height information map
Existing network
coverage map
Coverage rate statistics
table
Contents
Network planning information collection
Capacity Planning
Coverage Planning
Site layout & Survey
Coverage Emulation
Frequency Planning
GSM working frequency band
GSM900
Uplink 890 915 MHz
Downlink 935 960 MHz
duplex separation is 45MHz,carrier frequency separation is 200KHz
EGSM
Uplink 880 890 MHz
Downlink 935 935 MHz
duplex separation is 45MHz, carrier frequency separation is 200KHz
DCS1800
Uplink 1710 1785 MHz
Downlink 1805 1880 MHz
duplex separation is 95MHz, carrier frequency separation is 200KHz
P-GSM900
Fl (n) = 890 + 0.2n MHz
Fu (n) = Fl(n) + 45 MHz 1 n 124
n stands for ARFCN
E-GSM900
Fl (n) = 890 + 0.2(n-1024) 975 n 1023
Fu (n) = Fl(n) + 45 MHz 0 n 124
DCS1800
Fl (n) = 1710.2 + 0.2(n-512) MHz
Fu (n) = Fl(n) + 95 MHz 512 n 885
ARFCN
Basic Concept
Frequency Reuse Cluster
Frequency Reuse Factor
Frequency Reuse Distance
C/I and C/A
Frequency reuse distance
The following equation is used to estimate frequency reuse
distance:
D = 3 N * R
D —— frequency reuse distance
R —— cell radius
N - frequency reuse factor.
Definition of C/I and C/A
Co-channel Interference C/I:
C/I refers to the interference of another cell using the
same frequency to the current cell. The ratio of carrier
to interference is called C/I.
GSM specification regulates that C/I >9dB. In
implementing, it requires C/I>12dB.
Adjacent channel interference C/A
C/A refers to interference of adjacent channel to the
current channel. The ratio is called C/A. The GSM
specification regulates that C/A>-9dB.
Calculation of C/I
Where, Pown_cell is the signal strength of current
cell; Pi_BCCH is BCCH signal strength of interfering
cell i measured by MS.
Frequency reuse pattern
Ordinary (group) frequency reuse: ―43‖, ―33‖ and
more close ―26‖ and ―13‖.
MRP: different layers adopt different frequency reuse
patterns.
Concentric: the Underlay and Overlay adopt different
frequency reuse patterns respectively.
―4×3‖multiplex
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
A3
B1
B3B2
A1
A2
A3
B1
A1
A2A3
D2B1
D1
D3
A1
A2
A1
A3
D2B1
D1
D3
C1B3
C2
B2
C3
A1
A2
dB
dBI
C
18
)2.7(2)8(
2log10
)(
44
4
18dB>12dB
―3×3‖multiplex
A3
C2B1
C1
C3
B3B2
A1
A2
A3
C2B1
C1
C3
B3B2
A1
A2A3
C2B1
C1
C3
B3B2
A1
A2
A3 C1
A1
A2
A3
C2B1
C1
C3
B3B2
A1
A2
A3 C1
A1
A2
A3
B1
B3B2
A1
A2
dB
dBI
C
3.13
)57.5(2)7(2
2log10
)(
44
4
13.3dB>12dB
Multiple reuse pattern(MRP)
BCCH can use 43 or higher reuse coefficient to
ensure the BCCH quality, while the TCH will use
relatively dense reuse mode.
The division of BCCH and TCH layer frequency
bands reduces the planning workload and
facilitate the layered planning.
Reserve some frequency for the micro cell.
Simplify the configuration of BA tables
The relative independence of the BCCH and TCH
layers facilitates the maintenance and expansion
of each layer.
TCH2
FRF=6
BCCH FRF=12
TCH1 FRF=9
For Microcell
FRF: Frequency reuse factor
Bandwidth=6 MHz
MRP
BCCH
“4×3”
TCH1
“3×3”
TCH2
“2×3”
TCH3
“1×3”
MRP
Application of MRP
China mobile: MRP
Frequency bandwidth: 7.2MHz
AFN:(60~95),
Divide 36 carrier frequencies into 4 group as per
12/9/8/7
Channel
type
Logic channel
TCH1 service
channel
TCH2 service
channel
TC3 service
channel
Channel
number
60 61 62 63 64 65
66 67 68 69 70 71
72 73 74 75 76 77
78 79 80
81 82 83 84 85
86 87 88
89 90 91 92
93 94 95
60
64
68
62
66
7063
67
7161
65
69
72
75
78
73
76
7972
75
787477
80
89
91
93
9092
94 9092
9489
91
93
8183
85
8284
8682
84
8183
85
86
1) BCCH 4 3 2) TCH1 3 3
4) TCH3 2 3 3) TCH2 2 3
Application of MRP
2 2
2
2
2
2
2 2 2
2
2 2
2
2
2
Concentric
Concentric
The coverage of Underlay is the same as that of ordinary cell, while the Overlay use small transmitting power and thus has smaller coverage.
The frequency reuse factor of overlay differs from that of underlay.
The BCCH and SDCCH are used by Underlay, in which the call will be set up.
The absorbing of traffic by overlay is limited by traffic lay-out and coverage. It will increase the capacity by 10-30%
A brand new switching algorithm should be added.
2 2
2
2 2
2 2
2
2
2 2
2
2
2
2
2
2
2 2
2
2
2
2
2
Intelligent Concentric IUO
IUO
IUO has the same network structure as ordinary
concentric, consisting of Overlay and Underlay.
Underlay and Overlay of IUO both use the same
transmitting power.
IUO adopts a handover algorithm based on C/I
It’s very suitable for absorbing traffic inside building.
Comparison
Concentric
Overlay smaller
transmitting power
Handover based on
power or TA
Overlay coverage is
fixed but not reasonable
Absorb limited traffic
Handover algorithm is
easy
IUO
U/O same transmitting
power
Handover algorithm
based on C/I
Overlay coverage is
fixed and reasonable
Absorb more traffic
Handover algorithm is
complicated
TCH frequency plan
The frequency in same site can not be reused
In same cell, the frequency distance between BCCH and
TCH is at least 400khz
Frequency can not be reused in its directly adjacent sites if
it is not 1*3 pattern
Opposite cells should not be co-channel and avoid
adjacent channel.
High hill in the middle shall not be considered as
neighboring sites while broad water in the middle shall be
considered as neighboring sites.
Avoid to set same BSIC to BCCH with same frequency
Neighboring cell configuration
Centered on the cell, at most two-circle cells
can be neighbor cells
Neighboring cells shall not be more than 32.
Modify unreasonable neighboring cells
according to drive test.
Handover cells shall not be co-channel.
Avoid one way neighboring relationships
Avoid two neighboring cells with the same
BCCH and the same BSIC.
Attention
Reserve frequencies for
Test in propagation,
Replacement frequency in the interference test,
Micro cell frequency in hot spot area.
Generally BCCH should use higher continuous frequencies.
Allocate frequency based on different areas.
Allocate frequency for sites in different areas such as urban,
suburb and rural.
Focus should be put on cities to avoid interference.
Make planning in urban areas before suburbs and rural areas.
Divide urban area into small areas if there are many sites.
Check manually after frequency assignment via automatic frequency
planning.
Anti-interference technique
Dynamic power control (DPC)
Discontinuous transmit (DTX)
Diversity receiving
FH technique
Discontinuous transmit (DTX)
DTX encodes the voice at 13kbit/s during the
voice active period, it encodes the comfort
noise at 500bit/s during the quiet period.
DTX
DTX contributes very little to the interference
during the quiet period, its power can be
regarded as 0 (inactive state).
Suppose the DTX active factor is , then the
gain
log10log10log10)(/ IC
ICdBIC
Dynamic power control (DPC)
From the figure we
can see that, in the
dynamic power
control situation,
when the interfering
MS is only at the
cell borders, the
BTS can work with
the maximum
transmitting power.
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2A3
A1
A2
A3
A1
A2
A3
A1
A2
DPC
Obviously, the interfering MS location is a
probability. This case is especially apparent in
the frequency hopping situation.
Suppose the DPC factor is p:
pdBICIC
pIC log10log10log10)(/
(FH)
Frequency hopping is to avoid external
interference. In other words, it is to prevent or
greatly reduce co-channel interference and
frequency selective fading effect by
converting frequencies to an extent that
interference cannot catch up with.
Baseband and synthesized FH
Parameters
HSN(hopping sequence number)
MAIO(mobile assignment index offset)
Function
The advantage of the frequency hopping is the so-called
effect of Frequency Diversity and Interference Diversity.
The former actually expands the network coverage scope,
and the latter improves the network capacity.
Frequency diversity gain
For static or slow moving MS. about 6.5dB gain can
be provided.
For fast moving MS, the difference of two connected
bursts of a channel in time and place is enough to
make them uncorrelated to Rayleigh change, that is,
they are almost not subject to the influence of the
same fading, at this time, the slow hopping can
provide very little frequency diversity gain.
Gain=1.5-6.5dB
Interference diversity gain
In consideration of the above figure, suppose the MS talks by
using fk at the time t, in this case, the probability of the
interfered cell fk is
m
n
I
C
pI
CdBIC log10log10log10)(/ 增益
nmCCp mn
mn //1
1
Hopping set MA:},...,,,{ 321 nffff
,
TRX number:m (mn)
Interfering cell
A3
A1
A2
A3
A1
A2
A3
A1
A2
A3
A1
A2A3
A1
A2
A3
A1
A2
A3
A1
A2
C/I= 9.43 dB
1*3+FH+DPC+DTX
Most densely reuse pattern
BCCH (4*3)
Combined with anti-
interference technology
Generally,only use 50%
of the whole available
frequency
1*3+FH+DPC+DTX
Compared to ―4×3‖ multiplex, the ―1×3‖ multiplex brings about the
interference degradation:
CIR 4×3- CIR 1×3 =18 - 9.43 8.57 dB
―1×3‖hopping, 50% frequency load brings about the interference
diversity gain:
10log10(2/1) = 3dB
Suppose the frequency hopping length is 12 frequency points, then
the frequency diversity gain is about 2dB
Suppose the DTX active factor is 0.5, then the gain is:
-10log10(0.5) = 3dB
Suppose the DPC factor is 0.9, then the gain is: -10log10(0.9)
=0.5dB
The total gain is: 3+2+3+0.5=8.5dB
GSM Network Planning
Info
collection
Capacity
planning
Coverage
planning
Site layout
& survey Frequency
planning
Radio
network
Summary
GSM Signaling System
Objectives
At the end of this course, you will be able to:
Know GSM system signaling model
State various types of GSM protocol messages
Understand GSM system basic signaling procedure
Content
GSM System Signaling Model
GSM protocol message
Basic Signaling Procedure
GSM Interface
SGSN
Abis Um
BTS
BSC
TRAU
GGSN
MSC/VLR/GMSC
NSMU FSMU
Ater A
OMC
Qx
HLR/AUC
EIR SMC
PSTN / PLMN /
PSPDN / ISDN
BTS
BTS
BTS
Gb
GSM System Signaling Model
GSM system signaling model adopts the lowest three
layer of OSI seven layer protocol model, from low to
high:
Application layer
Link layer/Network layer
Physical layer
Physical Layer
The physical layer provides error protection
transmission. It defines the electric parameters of
transmission.
In ZTE-GSM digital mobile communication
systems, The physical layer of Um interface
between MS and BTS is Radio link. Abis interface
physical layer adopts 75-ohm coaxial cable or
120-ohm symmetrical twisted pair whose rate is
2Mbit/s.
Data Link Layer
The data link layer major functions: frame
transmission、error-free transmission and realize
end-to-end bits transfer between two connective
entities. Open、 maintenance and close the
connection of two connective entities.
The link layer protocol used by the GSM system at
the radio interface is the LAPDm protocol (Dm
channel link access procedure). The data link
layer of Abis interface between BTS and BSC is
LAPD (D channel link access procedure).
Application Layer
Application Layer
CM MM RR
CC SS SMS
Application Layer
Radio Resources (RR) management handles the
establishment, maintenance and release of physical
channels. Its major functions are performed by BSC. Part
of functions are performed by BTS.
Mobility Management (MM) deals with the mobile station’s
register and the identify of the mobile subscriber, The
function are performed by MSC.
The CM Layer is composed of three functional entities:
Call Control (CC), deals with the functions to establish、maintenance and release the call;Short Message Service
support (SMS) and Supplementary Service support (SS).
Mobile
Switching
Centre
(MSC)
) ) )
Base
Transceiver
Station
(BTS)
Base
Station
Controller
(BSC)
Equipment
ID
Register
(EIR)
Visitor
Location
Register
(VLR)
Home
Location
Register
(HLR)
Authenti-
cation
Centre
(AUC)
Mobile
Switching
Centre
(MSC)
Public Switched
Telephone Network
(PSTN)
MAP/TCAP + ISUP/TUP
To other VLR
ISUP/TUP
DTAP + BSSMAP
MAP/TCAP
MAP/TCAP MAP/TCAP
BTSM
A-bis interface A interface
GSM protocol
DTAP
DTAP Direct Transfer Application Part BSSMAP BSS Management Application Part CM Call Management MM Mobile Management RR Radio Resource Management
SCCP Signalling Connection Control Part MAP Mobile Application Part TCAP Transaction Capability Application Part ISUP ISDN User Part MTP Message Transfer Part
CM
MM
RR
Sig. layer 2
Layer 1 (air)
Sig. layer 2
Sig. layer 1
MTP
SCCP
BSSMAP RR
(CM+MM)
MS BSC
MTP MTP
SCCP SCCP
CM
MM
BSSMAP TCAP
MAP
I
S
U
P
MSC
Sig. layer 2
Layer 1 (air)
BTS
(CM)
(MM)
(RR)
(CM)
(MM)
(RR)
(CM)
(MM)
(LAPDm) (LAPDm) (LAPD) Sig. layer 2
Sig. layer 1
(LAPD)
BTSM BTSM RR'
BTSM BTS Management
Um Interface Abis Interface A Interface Inter-MSC
Interface
GSM Protocol Architecture
Content
GSM System Signaling Model
GSM protocol message
Basic Signaling Procedure
Um interface protocol stack
CM
MM
RR
LAPDm
Layer1 Layer1
LAPDm
RR
MSBTS
Um interface
LAPDm frame format
The address field contains the service
access point identifier (SAPI).
SAPI = 0 represents the signaling link
SAPI = 3 represents the short message link
In the control field,
N (S) represents the sending serial number
N (R) represents the receiving serial number
Address Control Information
SAPI N(S) N(R)
Operation mode
Acknowledged mode: Requires the confirmation
from the receiver. This mode provides a whole set
of control mechanism for error recovering and flow
control, the establishment mechanism and release
mechanism for multi-frame operations.
Unacknowledged mode: The receiver is not
required to send a confirmation upon reception of
a UI frame. This operation mode does not provide
flow control or error recovering mechanism.
RR messages
Type Message
Channel establishment message Immediate assignment
Immediate assignment reject
Ciphering message Ciphering mode command
Ciphering mode complete
Handover message
Handover command
Handover complete
Handover failure
Handover access
Channel release message Channel release
Paging message Paging request
Paging response
System info System info:1~8
MM messages
Type Message
Registration messages
IMSI detach indication
Location updating accept
Location updating reject
Location updating request
Security messages
Authentication reject
Authentication request
Authentication response
Identity request
Identity response
TMSI reallocation command
TMSI reallocation complete
Connection-management messages
CM service accept
CM service reject
CM service request
CC messages
Type Message
Call establishment messages
Alerting
Call confirmed
Call proceeding
Connect
Call clearing messages
Disconnect
Release
Release complete
Miscellaneous messages
Congestion control notify
Start DTMF
Stop DTMF
Abis Interface Protocol stack
Abis
BTS
BTSM
LAPD
Layer1
BSC
interface
Layer1
LAPD
BTSM
RR
LAPD Protocol
SAPI = 0 represents the signaling link,
SAPI = 62 represents the O&M link, and
SAPI = 63 represents the management link of the LapD layer.
flag Address Control Information FCS flag
SAPI TEI N(S) N(R)
1 0-260 2 1
A interface protocol stack
BSC
MTP3
MTP2
Layer1
MSC
A interface
Layer1
MTP2
MTP3
RR
SCCP SCCP
BSSAP BSSAP
MM
CM
Relationship between SCCP and OSI model
MTP-1
MTP-2
MTP-3
SCCP
ISP
TCAP
INAP OMAP MAP BSSAP ISUP TUP
HLR VLR
Layer1
Layer2
Layer3
4~6
Layer 7
BSSAP
MTP
SCCP
Distribution
BSSMAP DTAP
BSSAP
RR
MM
CC
MTP
SCCP
Distribution
BSSMAP DTAP
BSSAP
L1
LAPDm
RR
CC
MM
RR
LAPDm
L1
MSC BSS
MS
DTAP
BSSMAP: DTAP:
SCCP message
CR Connection request
CC Connection confirm
CREF Connection refused
RLSD Released
RLC Release complete
DT1 Data form 1
UDT Unit data
UDTS Unit data service
BSSMAP Message -1
Assignment messages (setup of traffic channels) Assignment request
Assignment complete
Assignment failure
Handover messages Handover request (to BSC: request for handover to that BSC)
Handover required (to MSC: inter BSC/MSC handover required)
Handover request ack. (to MSC: acknowledge of handover request)
Handover command (to BSC: contains new radio channel/BTS for the MS)
Handover complete (to MSC: commanded handover successful)
Handover failure (to MSC: commanded handover unsuccessful)
Handover performed (to MSC: BSC has performed internal handover)
Handover candidate enquiry (to BSC: MSC requests list of MS that could be handed
over to another cell)
Handover candidate response (to MSC: answer to handover candidate enquiry)
Handover required reject (to BSC: required handover unsuccessful)
Handover detect (to MSC: commanded handover successful)
BSSMAP Message -2
Release messages Clear command (release of traffic channel)
Clear complete
Clear request
SAPI “n” clear command (control of layer 2 SAPI “n” on the radio interface)
SAPI “n” clear complete
SAPI “n” reject
General messages Reset (initialisation of BSS or MSC due to failure)
Reset acknowledge
Overload (processor or CCCH overload)
Trace invocation (start production of trace record
Reset circuit (initialisation of single circuit due to failure)
Terrestrial resource messages Block (management of circuits/time slots between MSC and
BTS)
Blocking acknowledge
Unblock
Unblocking acknowledge
BSSMAP Message -2
Radio resource messages
Resource request (available radio channels in
BSS cells)
Resource indication
Paging (paging of MS)
Cipher mode command (start encryption)
Classmark update (change of MS power class)
Cipher mode complete
Queuing indication (indicates delay in
assignment of tch)
Content
GSM System Signaling Model
GSM protocol message
Basic Signaling Procedure
Mobile Originating Call Establishment Procedure -1
MS BTS BSC MSCCH REQ(1)
CH RQD(2)
CH ACT(3)
IMM ASS(6)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(7)
UA(10)EST IND(8)
CM SERV REQ(9)
AUTH REQ(11)
AUTH REQ(12)
AUTH RSP(13)AUTH RSP(14)
CIPH MODE CMD(16)
CIPH MODE CMP(18)CIPH MODE CMP(19)
CIPH MODE CMD(17)
CIPH MODE CMD(15)
Mobile Originating Call Establishment Procedure -2
MS BTS BSC MSC
TMSI REALL CMD(20) TMSI REALL CMD(21)
TMSI REALL CMP(22)TMSI REALL CMP(23)
SETUP(24) SETUP(25)
CALL PRO(26) CALL PROCEEDING(27)
ASSIGN REQ(28)CH ACT(29)
CH ACT ACK(30)
ASSIGNMENT COMMAND(31)
SABM(32)
UA(34)EST IND(33)
ASSIGNMENT COMPLETE(35)ASSIGN CMP(36)
RF CH REL(37)
RF CH REL ACK(38)
Mobile Originating Call Establishment Procedure -3
MS BTS BSC MSCALERTING(39)
ALERTING(40)
DEACT SACCH(55)
CONNECT ACK(43)CONNECT ACK(44)
RELEASE(49)
CONNECT(41) CONNECT(42)
MEAS REPORT(45)MEAS REPORT(46)
DISCONNECT(47)DISCONNECT(48)
RELEASE(50)
RELEASE COMPLETE(51)RELEASE CMP(52)
CLEAR CMD(53) CHANNEL RELEASE(54)
DISC(56)
UA(57)REL IND(58)
RF CH REL(59)
RF CH REL ACK(60)CLEAR CMP(61)
SCCP REL(62)
SCCP REL ACK(63)
Mobile Terminating Call Establishment Procedure -1
MS BTS BSC MSC
CH REQ(4)CH RQD(5)
CH ACT(6)
IMM ASS(9)
CH ACT ACK(7)
IMM ASS CMD(8)
SABM(10)
UA(13)EST IND(11)
PAGE RSP(12)
AUTH REQ(14)
AUTH REQ(15)
AUTH RSP(16)AUTH RSP(17)
CIPH MODE CMD(19)
CIPH MODE CMP(21)CIPH MODE CMP(22)
CIPH MODE CMD(20)
CIPH MODE CMD(18)
PAGING CMD(1)PAGING CMD(2)
PAGING RQT(3)
Mobile Terminating Call Establishment Procedure -2
MS BTS BSC MSC
TMSI REALL CMD(23) TMSI REALL CMD(24)
TMSI REALL CMP(25)TMSI REALL CMP(26)
ASSIGN REQ(31)CH ACT(32)
CH ACT ACK(33)
ASSIGNMENT COMMAND(34)
SABM(35)
UA(37)EST IND(36)
ASSIGNMENT COMPLETE(38)ASSIGN CMP(39)
RF CH REL(40)
RF CH REL ACK(41)
SETUP(27) SETUP(28)
CALL CONFIRMED(29)CALL CONF(30)
Mobile Terminating Call Establishment Procedure -3
MS BTS BSC MSC
DEACT SACCH(58)
RELEASE(52)
MEAS REPORT(48)MEAS REPORT(49)
DISCONNECT(50)DISCONNECT(51)
RELEASE(53)
RELEASE COMPLETE(54)RELEASE CMP(55)
CLEAR CMD(56) CHANNEL RELEASE(57)
DISC(59)
UA(60)REL IND(61)
RF CH REL(62)
RF CH REL ACK(63)CLEAR CMP(64)
SCCP REL(65)
SCCP REL ACK(66)
ALERTING(42)ALERTING(43)
CONNECT(44)CONNECT(45)
CONNECT ACK(46) CONNECT ACK(47)
Location Update Procedure -1
MS BTS BSC MSCCH REQ(1)
CH RQD(2)
CH ACT(3)
IMM ASS(6)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(7)
UA(10)EST IND(8)
LOC UPDATE REQ(9)
AUTH REQ(15) AUTH REQ(16)
AUTH RSP(17)AUTH RSP(18)
IDENTITY REQ(11) IDENTITY REQ(12)
IDENTITY RSP(13)IDENTITY RSP(14)
CIPH MODE CMD(20)
CIPH MODE CMP(22)CIPH MODE CMP(23)
CIPH MODE CMD(21)
CIPH MODE CMD(19)
Location Update Procedure -2
MS BTS BSC MSC
LOC UPDATE ACC(24) LOC UPDATE ACCEPT(25)
TMSI REALL CMP(26)TMSI REALL CMP(27)
DEACT SACCH(30)
CLEAR CMD(28) CHANNEL RELEASE(29)
DISC(31)
UA(32)REL IND(33)
RF CH REL(34)
RF CH REL ACK(35)CLEAR CMP(36)
SCCP REL(37)
SCCP REL ACK(38)
Intra Cell Handover Procedure
MS BTS BSC MSCMEASURE REPORT(1)
MEASURE REPORT(2)
CH ACT(3)
CH ACT ACK(4)
SABM(6)
UA(8)EST IND(7)
RECEIVE READY(10)
ASSIGNMENT COMMAND(5)
ASSIGNMENT COMPLETE(9)
HO PERFORMED(11)
RF CH REL ACK(13)
RF CH REL(12)
Intra BSC Handover Procedure
MS BTS1 BSC MSCMEAS REPORT(1)
MEAS REPORT(2)
CH ACT ACK(4)
CH ACT(3)
PHYSICAL INFO(9)
HO ACCESS(7)
HO PERFORMED(16)
HO CMP(15)
BTS2
HO CMD(5)HO CMD(6)
HO DETECT(8)
SABM(10)
EST IND(11)
UA(12)
HO CMP(13)
RECEIVER READY(14)
RF CH REL ACK(18)
RF CH REL(17)
Inter BSC Handover Procedure MS BTS1 BSC1 BSC2
MEAS REPORT(1)MEAS REPORT(2)
CH ACT(5)
CH ACT ACK(6)
HO CMD(8)
HO REQUIRED(3)
BTS2
HO REQ(4)
HO CMD(9)
HO ACCESS(10)
MSC
HO REQ ACK(7)
HO DETECT(11)
HO DETECT(12)
PHYSICAL INFO(13)
SABM(14)
EST IND(15)
UA(16)
HO CMP(17)
RECEIVER READY(18)
HO CMP(19)
HO CMP(20)
CLEAR COMMAND(21)
RF CH REL(22)
RF CH REL ACK(23)
CLEAR COMPLETE(24)
Call Re-establishment Procedure
MS BTS BSC MSC
CONN FAIL IND(1)
CLEAR CMD(3)
CLEAR REQ(2)
CHANNEL REQ(5)
CM RE-EST REQ(6)
CIPH MODE CMD(7)
CIPH MODE CMP(8)
STATUS(12)
STATUS ENQUIRY(11)
CLEAR CMP(4)
ASS REQ(9)
ASS CMP(10)
Directed Retry Procedure
MS BTS1 BSC MSC BTS2 MSCH REQ(1)
CH RQD(2)
CH ACT(3)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(6)
UA(7)
EST IND(8)
CR(9)
CC(10)
CM SERVICE ACCEPTED(11)
SETUP(12)
CALL PROCEEDING(13)
ASS REQ(14)
CHANNEL ACT(15)
CHANNEL ACT ACK(16)
HANDOVER COMMAND(17) HO ACCESS(18)
HO DETECT(19)
PHY INFO(20)
SABM(21)
UA(23)
EST IND(22)
HO CMP(24)
ASS CMP(25)
Short Message Procedure On SDCCH When MS Is
Calling -1
MS BTS BSC MSCCH REQ(1)
CH RQD(2)
CH ACT(3)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(6)
UA(7)EST IND(8)
CM SERV REQ(9)
AUTH REQ(11)
AUTH RSP(12)
CC(10)
SABM(SAPI3)(13)
UA(14)EST IND(SAPI3)(15)
CIPH MODE CMD(16)
CIPH MODE CMP(17)
CP DATA(18)
CP ACK(19)
Short Message Procedure On SDCCH When MS Is
Calling -2
MS BTS BSC MSC
CP DATA(20)
CP ACK(21)
DEACT SACCH(24)
CLEAR CMD(22) CHANNEL RELEASE(23)
DISC(25)
UA(26)REL IND(27)
RF CH REL(28)
RF CH REL ACK(29)CLEAR CMP(30)
SCCP REL(31)
SCCP REL ACK(32)
Short Message Procedure On SDCCH When MS Is
Called -1
MS BTS BSC MSC
CH REQ(3)CH RQD(4)
CH ACT(5)
CH ACT ACK(6)
IMM ASS CMD(7)
SABM(8)
UA(10)EST IND(9)
CM SERV REQ(11)
AUTH REQ(13)
AUTH RSP(14)
CC(12)
CIPH MODE CMD(15)
CIPH MODE CMP(16)
PAGING CMD(1)PAGING CMD(2)
CP DATA(17)EST REQ(SAPI3)(18)
SABM(19)
UA(20)EST CMP(SAPI3)(21)
Short Message Procedure On SDCCH When MS Is
Called -2
CP DATA(22)
CP ACK(23)
DEACT SACCH(28)
CLEAR CMD(26) CHANNEL RELEASE(27)
DISC(29)
UA(31)REL IND(30)
RF CH REL(32)
RF CH REL ACK(33)CLEAR CMP(34)
SCCP REL(35)
SCCP REL ACK(36)
CP DATA(24)
CP ACK(25)
MS BTS BSC MSC
Short Message Procedure On SACCH When
MS Is Calling
MS BTS BSC MSC
CM SERVICE REQ(1)
CM SERVICE ACC(2)
SABM(SAPI3)(3)
UA(4)EST IND(SAPI3)(5)
CP DATA(6)
CP ACK(7)
CP DATA(8)
CP ACK(9)
ACTIVE CALL
ACTIVE CALL
Short Message Procedure On SACCH When
MS Is Called
MS BTS BSC MSC
SABM(3)
UA(4)EST CNF(SAPI3)(5)
CP DATA(8)
CP ACK(9)
CP DATA(6)
CP ACK(7)
ACTIVE CALL
ACTIVE CALL
CP DATA(1)EST REQ(SAPI3)(2)
Summary of radio network planning
ZTE University
Objectives
At the end of this course, you will be able to:
Describe the contents and flow of site survey
State the basic principle of site selection
Master the using of site survey tools
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data audit and documents output
Site survey tools
Site survey instances
Function
Provide basic data for planning and imitation;
Make planning more reasonable and reduce risk;
Reduce the cost of network
Goals
Know the feature of field, landform and
subscribers, estimate the subscriber number and
traffic;
Integrate coverage, traffic density, site condition
and cost
Output BTS site type, site location , distribution
and antenna configuration which satisfying
customer’s requirements.
Make site survey of each site and prepare three
candidate sites for substitution
Working flow
Single site record
Collection and check
Execution
Site survey plan
preparation
Right data ?
Requirement
analysis
Output Site survey
report
Site survey report
N
Y
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data audit and documents output
Site survey tools
Site survey instances
Requirement analysis
Target of network (coverage and capacity)
Customer’s suggestion on site type (micro cell,
repeater, indoor coverage etc.)
Existing network situation of coverage area (site
distribution of other operators)
Working interface with customers
Schedule and resource of site survey
Output of requirements analysis
Collect and analyze all the requirements form
customer, combined with network planning and
site survey documents. Output report of
requirements analysis.
Tools Function
necessary
GPS Altitude, latitude and longitude of BTS
Compass direction and environment
Digital camera photo the environment of site
ruler For measurement
vehicle One vehicle for each team
Not
necessary
map Digital map, scan map, paper map
Range finder Measure distance
telescope Increase sight scope
test equipment Test the coverage of site
Tools
Site survey plan
According to the project and requirements report,
make detail site survey plan, including goal,
organization, personnel, tools, schedule and
outputs.
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data process and documents output
Site survey tools
Site survey instances
Site survey flow
Site location
selection
Information
collection and
analyzing
‘Site adjust Not suitable
Cell parameters
design
Site survey
record table
end
start Site initial
information
Site initial information
Latitude and longitude of sites from planning
Site location provided by operators
The location of old substitute sites
Sites of other operators
No. Common principle for site selection
1 Site should be in the ideal position of honeycomb structure
2 The BTS density should match the traffic density
3 The height of BTS should lower then the highest building and higher then the average building
4 Avoid high buildings or potential blocking constructions, which may affect the coverage
5 Avoid radio station, radar or other strong interference equipments
6 Avoid choose the top of hill or woods
7 Necessary condition for site building
8 Select the equipment rooms with little expansion cost or buildings with less rent
9 Try to select the existing telecom station, micro wave station, so to reuse the power supply
10 The feasibility, cost and performance should be considered before the microwave is used as transmission
11 Dual band sites should be at same site in urban area
Principle of site selection
Information collection and analysis
Traffic distribution survey
Traffic distribution in serving area
Economy level, average income and consumption
habits.
Forecast subscriber increase trend
Radio propagation environment survey
Location information of BTS (longitude, latitude, altitude)
Description of the overall environment
Description of barriers
Cell parameter design
BTS type
Site configuration
Antenna parameters
Antenna height
Azimuth
Tilt down angle
Site survey record table
Altitude, longitude and precision of GPS
Geographic description of BTS
Important area
Direction
Transmission system
Repeater basic information
Co-site description
Picture of site
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data audit and documents output
Site survey tools
Site survey instances
Data audit and documents output
After the site survey, all the documents should be
collected by team leader, who will pass them to
network planning technical manager
After check and audit, Network planning manager
will pass these documents to project manager.
Check and audit
Check and audit from technical view, make sure
the site survey result is true, accurate, reasonable
and feasible:
Fill up <Radio network site survey report>
If there is any questions about sites, communicate with
customers and put it into MOU.
If the environments is not good for sites, suggestion
must be given to customers for improvement.
Output report
After gather and audit, provide the following
information in the final report
BTS site survey report(Chinese, English)
Coverage area list
BTS site information list
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data audit and documents output
Site survey tools
Site survey instances
GPS
Main indices
Receive sensitivity
Navigation
Physical index
Power
Keys on panel
Power key
Turn page
Input
Exit
GPS
Basic operate
power on, light, shut down
Automatic location
Location and navigation operation
Navigation on route
GPS
Notes for longitude/latitude measurement
GPS needs 3 satellites for location
The measurement mode is WGS84
The angle unit is degree
Try close to site to measure
Deviation compared with digital map
The precision of digital map
GPS measurement deviation
The test spot is not same as planned
Compass
Main function
Direction and tilt down angle
Landform measurement: include orientation, slope
degree, fix level
Vertical angle
1.viewfinder 2.Aim board 3.Magnetic needle 4.Horizontal
dial 5.Vertical dial 6.Vertical scale indicator 7.Vertical level organ 8.batholith level organ 9.Magnetic needle fix helix 10.thimble 11.lever
12.Glass cover
13.Box and needle round board
Structure
Magnetic needle
Horizontal dial
Vertical dial
Aim board
Viewfinder
Compass
Antenna direction
Stand under the antenna or tower with instrument in
hand
Make the upper cover face you, aim board point to
antenna
Wait for the needle stop, the degree of the needle “N
pole” is the direction of antenna.
Antenna tiltdown
Keep the compass close to the character surface of
antenna, and keep the bleb in the middle for some time
Read the degree, which represent the tiltdown angle of
this character surface.
Contents
Site survey summary
Preparation of site survey
Working flow of site survey
Data audit and documents output
Site survey tools
Site survey instances
Unreasonable location
BTS site close to high voltage cable
Wrong: One BTS is close to a high voltage cable,
antenna is at the same level as power cable and the
distance to power cable is no more than 10 meters.
Right: move the BTS 50 meters away from the power
cable for safety
BTS is on the hill in urban
In order to cover a city, a BTS is built on a hill with 300
meters high.
As the BTS is so high that all the MS in this city can
receive the signal, which make other BTS traffic idle,
This site is congestion, and cause many MS fail to call.
Unreasonable planning
Less BTS sites in dense urban area
Total 29 frequencies available for one city, so only 5
sites were build.
Limited by frequency resources, there is no large
capacity sites which can’t satisfy the traffic requirement.
Solution: Another 8 new BTS sites were built to fit the
large traffic.
Antenna System
ZTE University
Objective
By the end of this course, you will be able:
To Understand the concept of dipole
To state GSM antenna specifications
To comprehend the principle of antenna selection
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Blah
blah
blah bl ah
Radio Waves
A form of electromagnetic radiation typically
generated as disturbances sent out by
oscillating charges on a transmitting antenna
Definition
An Antenna is any
device used to
collect or radiate
Electromagnetic
Waves
Linear antennas are
used:
Monopole (Slab)
Dipole Elements
Mobile Phones
Base Tranceiver
Station Antenna
• Single Monopole
• Patch Antenna
• Array of dipoles
Antenna for mobile communication
Antenna basic structure
Antenna are generally
composed of stacked of dipole
bundling their radiated power
to form a desired antenna
pattern in vertical plains
around the antenna
Depending on the gain desired
that wants to be achieved
several of those diploes can
be arranged on top of one
another
DIPOLES
Wavelength
1/2 Wavelength
1/4 Wavelength
1/4 Wavelength
1/2 Wavelength
Dipole
1800MHz :166mm
900MHz :333mm
Generation of radio waves
1个 dipole Received Power:1mW
Multiple dipole matrix Received Power:4 mW
GAIN= 10log(4mW/1mW) = 6dBd
Half wave dipole
Gain=10log(8mW/1mW) = 9dBi
“Omnidirectional array”
Received power:1mW
(Overlook
Antenna
“Sector antenna”
Received power:8mW
Isotropic antenna
Dipole
Ideal radiating dot source
(lossless radiator)
0dBd = 2.15dBi
2.15dB
dBd and dBi
dBd and dBi
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Antenna electrical properties
Operating Frequency Band
Input impedance
VSWR
Polarization
Gain
Radiation Pattern
Horizontal/Vertical beamwidth
Downtilt
Front/back ratio
Sidelobe suppression and null filling
Power capability
3rd order Intermodulation
Insulation
Type Frequency Range
GSM 900 890 - 960 MHz
GSM 1800 1710 - 1880 MHz
890 - 960 MHz
1710 - 1880 MHzGSM Dual Band
GSM antenna frequency range
BANDWIDTH = 960 - 890 = 70MHz
Optimum 1/2 wavelength
for dipole at 925MHz
at
960
MHz
Antenna
Dipole
at
890
MHz
GSM antenna frequency range
Standard Value: 50
Cable
50 ohms
Antenna
50 ohms
Impedance
9.5 W 80
ohms 50 ohms
Forward: 10W
Backward: 0.5W
Return Loss: 10log(10/0.5) = 13dB
VSWR (Voltage Standing Wave Ratio)
Voltage standing wave ratio (VSWR)
VSWR1.5
= (VSWR-1)/(VSWR+1)
RetureLoss = -20lg
Calculation of VSWR
120°
(eg) Peak
Peak - 10dB
Peak - 10dB
10dB Beamwidth
60° (eg) Peak
Peak - 3dB
Peak - 3dB
3dB Beamwidth
Bandwidth
Directional Antenna:65°/90°/105°/120°
Omni:360°
Omni-directional Directional
3dBm horizontal beamwidth
Omni-directional Directional
3dBm vertical beamwidth
Omni-directional Directional
Antenna structure types
Vertical Horizontal
+ 45degree slant - 45degree slant
Polarization
Space diversity
V/H (Vertical/Horizontal) Slant (+/- 45°)
Polarization diversity
Linear Polarization,vertical X Polarization, 45
Types of antenna
Antenna down tilt
Mechanical down tilt
Fixed electronic down tilt
Adjustable electronic down tilt
Mechanical down tile
It is achieved by physically
tilting the antenna out of the
perpendicular by using down
tilt kit
PROS: Cost efficient and
flexible
CON: Has no effect on the
side-lobe characteristics of the
antenna
Input Signal
Electrical down tilt
Electrical downtilt can be fixed or adjustable
Fixed is tuned by the manufacturer
Adjustable allows adjustment in a certain level on the rear of the
antenna
Non down tilt Electronic downtilt Mechanical
downtilt
Down tilt
Antenna tilt development
F/B = 10 log(FP/BP) typically : 25dB
Back power Front power
FRONT-TO-BACK Ratio
Ratio of maximum mainlobe to maximum
sidelobe
Upper sidelobe suppression and null fill
Upper sidelobe suppression and null fill
913 MHz 936 MHz 959 MHz 982 MHz
IMD@243dBm
f1, f2, 2f1-f2, 2f2-f1
Intermodulation
It occurs when two signals of a different frequency mix in a
non-linear device
It can be a problem at any site that has two or more
transmitters
It can be caused by a transmitter of the same system or by a
transmitter in another site that is co-sited or has a site in the
neighborhood
1000mW ( 1W) 1mW
10log(1000mW/1mW) = 30dB
Isolation
Antenna mechanical properties
Size
Weight
Radome material
Appearance and color
Working temperature
Storage temperature
Windload
Connector types
Package Size
Lightning Protection
Dimension
LWH
Length:connected with vertical bandwidth and gain
Width:connected with horizontal bandwidth
Height:connected with techniques adopted
Weight
A factor that can affect transport and
deployment
PVC, Fiberglass
Anti-temperature, water-proof , anti-
aging,weather resistant
Radome materials
Good-looking
Environment-protecting
Color
Temperature range
Operation and storage
Typical range:-40°C — +70°C
Connector type
7/16”DIN,N,SMA
Female/male
Mast diameter 45-
90mm
Mast
Direct Ground
Lightning protection
Antenna types
By frequency band: GSM900, GSM1800,
GSM900/1800
By polarization: Vertical, Horizontal, ±45º linear
polarization, circle polarization
By pattern: Omni-directional, directional
By down-tilt: Non, mechanical, electronic
adjustment, remote control
By function: Transmission, receiver,
transceiver
7/8” Main feeder
Feeder cable
1/2” (JUMPER CABLE)
Jumper cable
7/16”DIN-F(DIN CONNECTOR)
7/16”DIN-M(DIN & N CONNECTOR)
Connector
Rf port 2
Grounding
Lightning arrestor
Accessories
Trimming Tool or Hand Tool Kit
Clamp
Earthing Kit
Wall Glands
Hoisting Stocking
Universal Ground Bar
Antenna
7/16 Din Connector
7/8“ Cable
Grounding
1/2“ Jumper
Cabinet
EMP
Grounding clip
Grounding bar
1/2 Clamp
Tower Top
Amplifier
7/8“ Cable
Machine house
1/2 Jumper
Antenna system
Content
Antenna overview
Antenna specifications
Principle of antenna selection
Radio propagation in cities
Environment features:
Densely deployed BTS,small coverage area
Decrease over coverage and interference, increase
frequency reuse factor
Antenna selection in cities
Polarization Dual-polarization (Installation space)
Direction Directional antenna (Frequency reuse factor)
3dB bandwidth 60~65°(Control coverage)
Gain 15-16dBi
Tilt down angle Fixed electrical tilt down
Radio propagation in suburb/rural area
Environment features:
Loosely deployed BTS
light traffic
large coverage
Antenna selection in suburb/rural area
Polarization Both dual-polarized and vertical
Direction directional
3dB bandwidth 90°105°
Gain 16-18dBi directional
or 9-11dBi omni
Tilt down angle Mechanical tilt down; 50m high; null fill
Radio propagation in road/highway environment
Environment features:
Low traffic
Fast moving
subscribers
Focus on coverage.
Strip coverage
Two sectors
Omni-cell when pass
towns or tourist site
Antenna selection for highway
Polarization Both dual-polarized and vertical
Direction Narrow beamwidth directional
3dB
bandwidth 30°
Gain 18dBi-22dBi
Tilt down
angle No tilt down
Radio propagation in mountainous environment
Environment features:
Block by mountains
Big propagation loss
Difficult to cover
Antenna selection in mountainous area
Polarization Both dual-polarized and vertical
Direction Omni or directional
3dB bandwidth Big 3db verticle bandwidth
Gain Omni (9-11dBi)
Directional (15-18dBi)
Tilt down angle Null fill & electrical tilt down
GSM Basic Radio parameters
ZTE University
Objectives
At the end of this course, you will be able to:
Understand the meaning of various radio parameters
Grasp the setting of radio parameters
State the effect to radio network performance of various
kind of radio parameters
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
Roles of identification parameters
Enable the MS to correctly identify the ID of the current
network
Enable the network to be real time informed of the correct
geographical location of the MS
Enable the MS to report correctly the adjacent cell
information during the conversation process
MCC LAC
Cell Global Identity
MNC
3 Digits 2-3 Digits Max 16 Bits
CI
Max 16 bits
LAI
CELL GLOBAL IDENTITY (CGI)
Cell Global Identity (CGI)
It is used for identifying individual cells within an LA
ROLES OF CGI
The CGI information is sent along the system broadcasting
information in every cell.
When the MS receives the system information, it will
extract the CGI information from it and determines whether
to camp on the cell according to the MCC and MNC
specified by the CGI.
It judges whether the current location area is changed,
then determines whether to take the location updating
process.
SETTING OF CGI
MCC(Mobile Country Code):
consists of 3 decimal digits, and the value range is the decimal
000 ~ 999.
MNC(Mobile Network Code):
consists of 3 decimal digits, and the value range is the decimal
00 ~ 999.
LAC(Location Area Code):
The range is 1-65535.
CI(Cell Identity):
The range is 0-65535.
NCC BCC
3 Bits 3 Bits
BSIC
NCC Network/ National Color Code Value Range: 0~7
BCC Base Station Color Code Value Range: 0~7
BASE STATION IDENTITY CODE (BSIC)
Base Station Identity Code (BSIC)
It enables MSs to distinguish between
neighboring base stations
NCC and BCC ROLES
NCC:
In the connection mode (during conversation), the MS
must measure the signals in the adjacent cells and
report the result to the network. As each measurement
report sent by the MS can only contain the contents of
six cells, so it is necessary to control the MS so as to
only report the information of cells factually related to
the cell concerned. The high 3 bits (i.e. NCC) in the
BSIC serve this purpose.
BCC:
The BCC is used to identify different BS using the same
BCCH in the same GSMPLMN.
C B A
F E D
BSIC CONFIGURATION PRINCIPLE
In general, it is required that Cells A, B, C, D, E and
F use different BSIC when they have same BCCH
frequency. When the BSIC resources are not
enough, the cells close to each other may take the
priority to use different BSIC.
ROLES OF BSIC
Inform the MS the TSC used by the common signaling
channel of the cell.
As the BSIC takes part in the decoding process of the
random access channel (RACH), it can be used to prevent
the BS from mis-decoding the RACH, sent by the MS to
an adjacent cell, as the access channel of this cell.
When the MS is in the connection mode (during
conversation), it must measure the BCCH level of adjacent
cells broadcasting by BCCH and report the results to the
BS. In the uplink measurement report, MS must show
BSIC of this carrier it has measured to every frequency
point.
BA LIST (BCCH ADJACENT LIST)
Adjacent cell BCCH table
At most 32 adjacent cell
Carried by BCCH when MS is idle, by SACCH
when MS is dedicated
The MS will first search carriers from this table
and if none is found it will turns to find any of 30
carriers with highest levels.
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
RANDOM ACCESS
Random access is the process that messages
being transmitted on RACH when a MS turns
from “idle” to “dedicate” mode. The main
parameters includes:
MAXRETRANS
Tx_Integer
AC
MAX RETRANS
When starting the immediate assignment process
(e.g, when MS needs location updating,
originating calls or responding to paging calls), the
MS will transmit the "channel request" message
over the RACH to the network. As the RACH is an
ALOHA channel, in order to enhance the MS
access success rate, the network allows the MS to
transmit multiple channel request messages
before receiving the immediate assignment
message. The numbers of maximum
retransmission (MAX RETRANS) are determined
by the network.
MAX RETRANS
The MAX RETRANS is often set in the following ways:
For areas (suburbs or rural areas) where the cell radius is more
than 3km and the traffic is smaller, the MAX RETRANS can be
set 11 (i.e. the MAX RETRANS is 7).
For areas (not bustling city blocks) where the cell radius is less
than 3km and the traffic is moderate, the MAX RETRANS can be
set 10(i.e. the MAX RETRANS is 4).
For micro-cellular, it’s recommend that the MAX RETRANS be
set 01(i.e. the MAX RETRANS is 2).
For microcellular areas with very high traffic and cells with
apparent congestion, it’s recommend that the MAX RETRANS
be set 00(i.e. the MAX RETRANS is 1).
Transmission Distribution Timeslots
(Tx_integer)
The Tx_integer parameter is the interval in timeslots at which
the MS continuously sends multiple channel request messages.
The parameter S is an intermediate variable in the access
algorithm, and is to be determined by the Tx_integer parameter
and the combination mode of the CCCH and SDCCH
Format of Tx_Integer
MS starts the first channel request message : {0, 1, ...,
MAX (Tx_integer, 8)-1}
The number of timeslots between any two adjacent
channel request messages {S, S+1, ..., S+Tx_integer-1}
The Tx_integer is a decimal number, which can be 3~12,
14, 16, 20, 25, 32 and 50 (default). The values of the
parameter S are shown as below:
Tx_integer
CCH Combination Mode
CCCH Not Shared with SDCCH CCCH Shared with SDCCH
3, 8, 14, 50 55 41
4, 9, 16, 76 52
5, 10, 20, 109 58
6, 11, 25, 163 86
7, 12, 32, 217 115
ACCESS CONTROL AC
The access levels are distributed as follows:
C 0~C9: ordinary subscribers;
C11: used for PLMN management;
C12: used by the security department;
C13: public utilities (e.g. water, gas);
C14: emergency service;
C15: PLMN staff.
SETTING OF AC
In the BS installation and commissioning process or in the
process of maintaining or testing some cells, the operator
can set C0~C9 as 0 to forcedly forbid the access of
ordinary subscribers so as to reduce the unnecessary
effects on the installation or maintenance work.
In some cells with very high traffic, the congestion will
occur in busy hours. For example, the RACH conflict
happens frequently, the AGCH is overloaded and the Abis
interface flow is overloaded. The network operator can set
proper access control parameters(C0~C15)to control
the traffic of some cells.
CCCH_CONF
CodingMeanings
CCCH message
blocks in one
BCCH
0 CCCH use one basic physical channel, not shared with SDCCH 9
1 CCCH use one basic physical channel, shares with SDCCH 3
10 CCCH use two basic physical channels, not shared with SDCCH 18
100 CCCH use three basic physical channels, not shared with SDCCH 27
110 CCCH use 4 basic physical channels, not shared with SDCCH 36
Others Reserved
CCCH_CONF
The CCCH can be one or more physical channels. The
CCCH and SDCCH can share the same physical channel.
The combination mode of the common control channel in a
cell is determined by the CCCH_CONF
CCCH_CONF
The CCCH_CONF is determined by the telecom
operation department according to the traffic
model of a cell.
If a cell has 1 TRX, we recommend that the CCCH
uses one basic physical channel and shares it with the
SDCCH
If a cell has 2 ~ 8 TRX, we recommend that the CCCH
uses one basic physical channel but does not share it
with the SDCCH.
AGBLK
Since the CCCH consists of the access grant
channel (AGCH) and paging channel (PCH), it is
necessary to set how many blocks of the CCCH
information blocks are reserved and dedicated to
the AGCH, the access grant reserve blocks
(AGBLK).
AGBLK is represented in decimal numerals, and
its value range is:
CCCH is not combined with SDCCH: 0~7.
CCCH is combined with SDCCH: 0~2.
AGBLK
SETTING AND IMPACT OF AGBLK
The AGBLK setting principle is: given that the AGCH is
not overloaded, try to reduce the parameter as much as
possible to shorten the time when the MS responds to
the paging and improve the quality of service of the
system.
The recommended value of AGBLK is usually 1 (when
the CCCH is combined with the SDCCH), 2 or 3 (when
the CCCH is not combined with the SDCCH).
BS-PA-MFRMS
According to the GSM specifications, every mobile
subscriber belongs to a paging group. the MS calculates
the paging group to which it belongs by its own IMSI.
In an actual network, the MS only "receives“ the contents
in the paging subchannel to which it belongs but ignores
the contents in other paging subchannels. (i.e. DRX
source).
The BS-PA-MFRMS refers to how many multi-frames are
used as a cycle of a paging subchannel. This parameter in
fact determines how many paging sub-channels are to be
divided from the paging channels of a cell.
BS-PA-MFRMS
Multiframes of the same
paging group that cycle
on the paging channel
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
BS-PA-MFRMS (2)
BS-PA-MFRMS is represented in decimal
numerals and its value range is 2~9, its unit is
multiframe (51 frames), its default value is 2
PERIODIC UPDATING TIMER (T3212)
The frequency of periodic location update is
controlled via the network and the period length is
determined by the parameter T3212.
The T3212 is a decimal number, within the range
of 0~255, in the unit of six minutes (1/10 hours).
If the T3212 is set to 0, it means that the cell
needs no periodical location update.
NCCPERM
In the connection mode (during the conversation), the MS will report the measured signals of the adjacent cells to the BS, but each report may contain at most 6 adjacent cells.
Therefore, let the MS only report the information of the cells that may become the hand-over target cells.
The above functions can be fulfilled by limiting the MS to merely measure the cells whose NCC have been specified. The NCCPERM lists the NCCs of cells to be measured by the MS.
NCCPERM will affect handover
RADIO LINK TIMEOUT (RLT)
GSM specification stipulates that the MS must have a timer
(S), which is assigned with an initial value at the start of
the conversation, that is, the “downlink radio link timeout”
value.
Every time the MS fails to decode a correct SACCH
message when it should receive the SACCH, the S is
decreased by 1. On the contrary, every time the MS
receives a correct SACCH message, the S is increased by
2, but the S should not exceed the downlink radio link
timeout value. When the S reaches 0, the MS will report
the downlink radio link failure.
The radio link timeout is a decimal number, within the
range of 4 ~ 64, at the step of 4, defaulted to 16.
MBCR (1)
The parameter "multiband indication (MBCR)" is
used to notify the MS that it should report the
multiband adjacent cell contents.
The value is 0-3
MBCR (2)
0: Based on the signal strength of adjacent cells, the MS reports the
measurement results of 6 adjacent cells whose signals are the strongest,
whose NCC are known and allowed no matter in which band the adjacent
cells lie. The default value is “0”
1: The MS should report the measurement result of one adjacent cell in
each band (not including the band used by the current service area) in the
adjacent table, whose signal is the strongest and whose NCC is already
known and allowed.
MBCR (3)
2: The MS should report the measurement results of two adjacent cells
in each band (not including the band used by the current service area)
in the adjacent table, whose signals are the strongest and whose NCC
are already known and allowed.
3: The MS should report the measurement results of three adjacent cells
in each band (not including the band used by the current service area)
in the adjacent table, whose signals are the strongest and whose NCC
are already known and allowed.
Application of MBCR
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
CELL SELECTION C1
When the MS is turned on, it will try to contact a
public GSM PLMN, so the MS will select a proper
cell and extract from the cell the control channel
parameters and prerequisite system messages.
This selection process is called cell selection.
The quality of radio channels is an important factor
in cell selection. The GSM Specifications defines
the path loss rule C1. For the so-called proper cell,
C1>0 must be ensured.
C1 = RXLEV - RXLEV_ACCESS_MIN
- Max(MS_TXPWR_MAX_CCH - P ,0)
CELL SELECTION C1
where:
RXLEV_ACCESS_MIN is the minimum received level the
MS is allowed to access the network
MS_TXPWR_MAX_CCH is the maximum power level of
the control channel (when MS sending on RACH);
RXLEV is average received level;
P is the maximum TX power of MS;
MAX(X, Y)=X; if X Y.
MAX(X, Y)=Y; if Y X.
RxLevAccessMin
The RXLEV_ACCESS_MIN is a decimal number,
within the range of -110dBm ~ -47dBm
Default value is 0 (-110dBm).
RXLEV_ACCESS_MIN Meaning
-47 dBm > -48 dBm (level 63)
-46 dBm -49 ~ -48 dBm (level 62)
... ...
-108 dBm -109 ~ -108 dBm (level 2)
-109 dBm -110 ~ -109 dBm (level 1)
-110 dBm <-110 dBm (level 0)
Setting and Influence
For a cell with traffic overload, you can appropriately
increase the RXLEV_ACCESS_MIN
RXLEV_ACCESS_MIN value cannot be set to too high a
value. Otherwise, “blind areas” will be caused on the
borders of cells.
It is suggested that the RXLEV_ACCESS_MIN value
should not exceed -90 dBm.
CELL RESELECTION C2
Cell Reselection (C2) is a process when MS change its
service cell in idle mode.
When the MS selects a cell it will begin to measure the
signal levels of the BCCH TRX of its adjacent cells (at
most 6)
When given conditions are met, the MS will move from the
current cell into another one. This process is called cell
reselection.
When C2 Parameter Indicator (PI) indicates YES,the MS
will get parameters (CRO, TO and PT) , from BCCH, to be
used to calculate C2(channel quality criterion), which serves
as cell reselection norm. The equation is as follows:
Where T is a timer. When a cell is recorded by MS as one
of the six strongest cells, timer starts counting, otherwise, T
is reset to zero.
C2=C1+CRO-H(PT-T)×TO, when PT≠ 31
C2=C1-CRO , when PT= 31
CELL RESELECTION C2
PARAMETER INDICATOR (PI)
PI is used to notify the MS whether to use C2 as the cell
reselect parameter and whether the parameters calculating
C2 exist.
PI consists of 1 bit. “1”means the MS should extract
parameters from the system message broadcasting in the
cell to calculate the C2 value, and use the C2 value as the
standard for cell reselect; “0” means the MS should use
parameter C1 as the standard for cell reselect (equivalent
to C2=C1).
CRO, PT AND TO
The cell reselection initiated by the radio channel quality regards C2
as the standard. C2 is a parameter based on C1 plus some artificial
offset parameters.
The artificial influence is to encourage the MS to take the priority in
accessing to some cells or prevent it from accessing to others. These
methods are often used to balance the traffic in the network.
In addition to C1, there are three other factors influencing C2, namely:
CELL_RESELECT_OFFSET (CRO), TEMPORARY_OFFSET (TO)
and PENALTY_TIME (PT).
Format of CRO, PT and TO
The CRO is a decimal number, in dB, within the range
of 0 ~ 63, meaning 0 ~ 126 dB, at the step of 2 dB.
The TO is a decimal number, in dB, within the range of
0 ~ 7, meaning 0 ~ 70 dB, at the step of 10 dB, where
70 means infinite.
The PT is a decimal number, in seconds, within the
range of 0 ~ 31, meaning 20 ~ 620 seconds for 0 ~ 30,
and at the step of 20 seconds. The value of 31 is
reserved to change the direction of effect that the CRO
works on the C2 parameter.
C2 TYPICAL APPLICATIONS
For cells where the traffic is very heavy or the
channel quality is very low. the PT may be set 31,
making TO invalid, so C2=C1-CRO.
For cells where the traffic is moderate, the
recommended value for CRO is zero and PT=31,
thus causing C2=C1, i. e. no artificial impact will
be imposed.
C2 TYPICAL APPLICATIONS
For cells with light traffic, it’s recommended that CRO
be ranged from 0 to 20dB. The greater the CRO, the
more possible the cells will be reselected ,and vice
versa. It’s also suggested that TO is equal or a little
higher than CRO. PT, whose main role is to avoid
frequent cell reselection by MS, is generally
recommended to be set at 20 seconds or 40 seconds.
CELL SELECTION HYSTERESIS (1)
When a MS reselects a cell, if the old cell and the target
cell are in different locations, then the MS must initiate a
location updating process after cell reselection.
Due to the fading features of the radio channel, the C2
values of two adjacent cells measured along their borders
will fluctuate greatly.
MS will frequently conduct the cell reselection, which will
not only increase the network signaling flow and lead to
low efficiency use of radio resources, but reduces the
access success rate of the system, as the MS cannot
respond to paging calls in the location updating process.
CELL SELECTION HYSTERESIS (2)
To minimize the influence of this issue, the GSM
specifications put forward a parameter called
ReselHysteresis,
The cell selection hysteresis is represented in
decimal numerals, its unit is dB, its range is 0~14,
its step length is 2dB, and its default value is 4.
CELL RESELECTION PRINCIPLE
If the MS calculates that the C2 value of an adjacent cell (Same location area) surpasses the C2 value of the serving cell and maintains for 5s or longer, the MS will start cell reselection .
If the MS detects a cell that is not in the same location area with the current cell, the calculated C2 value surpasses the sum of the C2 value of the current cell and the ReselHysteresis parameter and if it remains for 5s or longer, the MS will start the cell reselection .
The cell reselection caused by C2 should be originated at least at the interval of 15s.
In the system message broadcasting in each cell, there is a bit
information indicating whether to allow the MS to access to it, which
is called cell bar access (CBA). The parameter CBA is to indicate
whether the cell bar access is set in a cell.
The CBA bit is a parameter for the network operator to set. Usually
all the cells are allowed to be accessed by MS , so the bit is set
NO. However, in special cases, the telecom operator may want to
assign a certain cells for handover service only, then the bit can be
set YES.
CELL BAR ACCESS (CBA)
Area A
MS A
BTS B
BTS C
CELL BAR ACCESS (CBA)
CELL BAR QUALIFY (CBQ)
In areas where the cells overlay with each
other and differ in capacity, traffic and
functions, the telecom operator often hopes
that the MS can have priority in selecting
some cells, that is, the setting of cell priority.
This function is set by way of the parameter
"Cell Bar Qualify" (CBQ).
C1 and C2 States with CBA and CBQ Configurations
CBQ CBACell Selection
Priority
Cell Reselection
State
No No Normal Normal
No Yes Barred Barred
Yes No Low Normal
Yes Yes Low Normal
CELL BAR QUALIFY (CBQ) 2
B A
EXAMPLE OF CBQ SETTING
For some reasons, the traffic of Cells A and B is apparently higher
than that of other adjacent cells. To balance the traffic in the whole
area, you can set the priority of Cells A and B as low, and set the
priority of the rest cells as normal so that the traffic in the shade
area will be absorbed by adjacent cells. It must be noted that the
result of this setting is that the actual coverage of Cell A and Cell B
is narrowed. However, this is different from reducing the transmitting
power of Cell A and Cell B, the latter may cause blind areas of the
network coverage and the reduction of communication quality.
Content
Network identification parameters
System control parameters
Cell selection parameters
Network function parameters
LIMITn
According to GSM Specification 05.08, the BTS must
measure the interference levels of the upward links of all
the free channels for the purpose of providing basis for
managing and allocating radio resources.
Moreover, the BTS should analyze its measured results,
divide the interference levels into 5 grades and report them
to the BSC. The division of the 5 interference grades (i.e.
the so-called interference bands) is set by the operator
through the man-machine interface. The parameter
"Interference band border(LIMITn)” determines the borders
of the 5 interference bands.
Value Range Specified dBm Level
0 <-110 dBm
1 -110 dBm ~ -109 dBm
2 -109 dBm ~ -108 dBm
…
61 -50 dBm ~ -49 dBm
62 -49 dBm ~ -48 dBm
Default: LIMIT1:4 LIMIT2:8 LIMIT3:15 LIMIT4:25
LIMITn
The division of the interference bands should be favorable in
describing the interference in the system. Generally the default values
are recommended. In the ordinary situations, the free channel
interference level is smaller, so the LIMIT1~4 value should be
smaller. When apparently large interference appears in the system,
you can properly increase the LIMIT1~4 values in order to know the
exact interference.
INTAVE
Due to the randomness of the radio channel
interference, the BTS must average the measured
uplink interference levels within the specified
period, and this average cycle is determined by
the INTAVE parameter.
This parameter is a decimal number, in SACCH
multi-frames, within the range of 1 ~ 31.
New Cause Indication (NECI)
The NECI is a decimal number, within the range of
0 ~ 1, with the meaning described as below:
When the NECI is 0, it means that the cell does not
support the access of half-rate services.
When the NECI is 1, it means that the cell supports the
access of half-rate services.
RE-ESTABLISHMENT ENABLE (RE)
For the drop calls caused by the radio link fault, the MS can start the call reestablishment process to resume the conversation, but the network is entitled to determine whether the call reestablishment is allowed or not. “0”=Yes, “1”=No.
In some special circumstances, the drop call may occur when the MS goes through a blind area during the conversation. If the call reestablishment is allowed, the mean drop call rate will be reduced. However, the call reestablishment process will occupy a longer period of time, most of the subscribers have hung up before the reestablishment process is over, as a result, the call reestablishment failed to achieve its purpose and wasted many radio resources. We recommend that the call reestablishment be not allowed in the network except for some individual cells.
GSM Coverage problem & Solution
ZTE university
Objectives
To know different kinds of coverage problem, their
causes and solutions.
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Overview of coverage problem
Weak coverage
Over coverage
No-serving cell coverage
Too small coverage range will cause high
call drop rate and a large number of
customer complaints.
Too large coverage will result in frequent
handovers, and mutual interference as
well, if it’s rather serious, and network
indicators will also be affected.
When cell reselection parameters and
handover scenarios are similar, or there
are 2 or more cells with similar signal
strength ,Pingpong handover is easy to be
caused during calls.
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Main causes of weak coverage
Weak coverage
too small BTS power
too low antenna height
too small down-tilt
hardware problem
Obstruction of buildings
Main causes of over coverage
too high antenna height
inappropriate down-tilt
poor antenna performance
Causes of no-serving cell coverage unreasonable planning
of antenna parameters
inappropriate type of antenna
too large or too small
carrier transmission power
shrunk coverage caused
by equipment problem
influence of changes
in radio environment
unreasonable setting
of handover parameters
unreasonable setting of
cell reselection parameters
no-serving cell coverage
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Procedures of Handling Coverage Problem
Check setting of problem BTS’ radio parameters
Check if strong interference source exists
Check hardware
Check antenna system
Analyze the local geographical environment to
see if site location and type of site are appropriate
Contents
Overview of Coverage Problem
Main Causes of Coverage Problem & Solutions
Procedures of Handling Coverage Problem
Typical Cases
Poor coverage at cold storage warehouse
【Problem description 】
Subscribers complained about the poor coverage around a cold storage warehouse of animal foodstuff; it was difficult to detect signal even when they were not far from the warehouse.
【Problem analysis】
According to subscriber’s complaint, we confirmed there was problem with coverage around the warehouse. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality data distribution were normal. Hardware operated normally, as shown in OMCR warning report.
Hardware engineers went to the site and checked the system of the BTS, tested power amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.
Through DT on site, network engineers found that the signal strength of the antenna main lobe was weak, while that of the side lobes was stronger, so they tentatively confirmed the problem was due to antenna fault.
Poor coverage at cold storage warehouse
【Problem handling】
After the antenna was replaced with a new one, the coverage improved
greatly, so did the speech quality.
Poor coverage of a BTS
【Problem description 】 Subscribers complained about weak signal strength around a Food
Bureau (near a BTS).
【Problem analysis 】 According to subscriber’s complaint, we confirmed there was
problem with the BTS' coverage. We found all radio parameters of the site were set correct at OMCR. Statistical report showed that idle data of interference band and UL/DL quality distribution were normal. Hardware operated normally, as shown in OMCR warning report.
Hardware engineers went to the site and checked the system of the BTS, tested amplifier's power and VSWR, they were all shown normal. Connection between equipment was correct. Antenna azimuth and down-tilt were all set reasonable.
Through DT on site, network optimization engineers found that the BTS’ coverage was in normal condition. While the Food Bureau, where subscribers complained about the signal, was 4km away from the BTS, and only indoor signal was weak (covered by Cell2).
Coverage shrinking after BTS starts operation
【Problem description 】
After Cell3 of a BTS started to operate, its coverage range was
found shrunk. On highway 3km away from the BTS, where the BTS
tower was visible, MS could not detect Cell3’s signal. MS could
receive signal when it’s around the BTS, and the signal level was
about -60dB.
【Problem analysis 】
We checked in radio resource management centre and found
Cell3’s static power class was set 2, which meant its static power
was reduced by 4dB, so we reset it to be 0. The next day, MS on
highway 3km away from the BTS could receive Cell3’s signal, and
its level was -60—70; and the signal level around the BTS was
strong, which was about -40dB.
we concluded that the cell’s coverage shrinking was caused by
wrong setting of static power control at OMCR.
High handover failure rate due to skip-zone
coverage 【Problem description 】
Configuration of a mountain site was S11, and the local network was single band GSM900. From indicator statistics of the past week, we found handover success rate of Cell2 under the BTS kept very low, which was around 80%, while TCH allocation failure rate was completely normal.
【Problem analysis 】 First, we could exclude the possibility of hardware problem and
interference, because there were no TCH assignment failures, which explained that MS could successfully occupy TCHs assigned to it by BSC; from DT analysis, we could see when signal level was above -90dbm, no call drops happened to MS, and speech quality was good, which could prove that no serious interference existed. Through further analysis, we found the target cell for handover was a bit far from Cell2; and probably adjacent cell relations were not set right during assignment planning, which resulted in isolated-island effect.
we could make area A and area B become adjacent cells to Cell2; while Cell2 coverage at A and B was already very weak, so Cell2 should not be adjacent cell to A and B .
After adjustment, handover success rate of Cell2 increased greatly, from 80% to 96%.
High handover failure rate due to skip-zone
coverage
Cell2
Cell1
Questions for thinking
Which parameters can be adjusted to improve
coverage?
GSM/GPRS/EDGE Basic Principles
ZTE University
Objective
At the end of this course, you will be able to:
Learn GSM development history
Learn and master network structure of GSM system and
functions & principles of different portions
Learn and be familiar with GSM wireless channel and
protocol
Learn and be familiar with main service call process for
GSM
Content
Chap.1: GSM Overview
Chap.2: GSM Network Structure
Chap.3: Interfaces and Protocols
Chap.4: GSM Radio Channel
Chap.5: Basic Service and Signaling Process
Chap.6: Voice Processing and Key Radio
Technology
Chap.7: GPRS and EDGE
GSM Overview
This chapter mainly introduces some basic
information for GSM, including GSM development
history, supported service type, specification, and
system features.
GSM Basic Concepts
Services Supported by GSM System
GSM Specification
GSM Overview
This section introduces network structure of GSM
system and basic functions of various NEs.
GSM Area Division Concepts
GSM composition
Mobile Switching System (MSS)
Base Station Subsystem (BSS)
Operation & Maintenance Subsystem (OMS)
Mobile Station (MS)
GSM System Number
GSM Area Division Concepts
Relationship between Areas in GSM
GSM System Composition
IBM
IBM
BSS MSS
MS
MS
PSTN
Other
PLMN
Um
Interfac
e
A
Interf
ace
GSM composition
Mobile Switching System (MSS)
The MSS consists of such entities as the mobile
switching center (MSC), home location register
(HLR), visitor location register (VLR), equipment
identity register (EIR), authentication center (AUC)
and short message center (SMC).
Base Station Subsystem (BSS)
BSS serves as a bridge between the NSS and MS.
It performs wireless channel management and
wireless transceiving. The BSS includes the Base
Station Controller (BSC) and Base Transceiver
Station (BTS).
Operation & Maintenance Subsystem (OMS)
The OMS consists of two parts: Operation &
Maintenance Center – System (OMC-S) and OMC-
Radio (OMC-R). The OMC-S serves the NSS, while
the OMC-R serves the BSS.
Mobile Station (MS)
The MS consists of mobile terminals and Subscriber
Identity Module (SIM) card.
GSM System Number
GSM system number contains:
Mobile Subscriber ISDN Number (MSISDN)
International Mobile Subscriber Identity (IMSI)
Mobile Subscriber Roaming Number (MSRN)
Handover Number
Temporary Mobile Subscriber Identification (TMSI)
Location Area Identification (LAI)
GERAN interfaces
This chapter introduces GERAN interfaces, User
plane/control plane protocol stack at PS and CS.
Interfaces
PS-Domain Protocol Stack
CS-Domain Protocol Stack
GSM interfaces
Interfaces
User plane protocol stack at PS domain
PS-Domain Protocol Stack
Control plane protocol stack at PS
domain
PS-Domain Protocol Stack
User plane protocol stack at CS domain
CS-Domain Protocol Stack
Control plane protocol stack at CS
domain
CS-Domain Protocol Stack
GSM Working Frequency Band
This section introduces GSM radio frame, channel
concept, division & function for different channels,
mapping combination mechanism between
channels.
GSM Working Frequency Band
Structure of GSM Radio Frame
Physical Channel and Logical Channel
System Messages
GSM Working Frequency Band
Currently, the GSM communication system works at
900MHz, extended 900MHz and 1800MHz.
1900MHz band is adopted in some countries.
1 hyper frame = 2048 super frames =2715648 TDMA frame
1 hyper frame = 1326 TDMA frame (6.12s)
(=51 (26 frames) multi-frames or 26 (51 frames) multi-frames
1 (26 frames) multi-frame = 26 TDMA frame (120ms) 1 (51 frames) multi-frame = 51 TDMA frame (3036/13 ms)
TDMA Frame
Hierarchical frame structure in GSM system
Structure of GSM Radio Frame
There are five layers for structure of GSM radio frame, that
is, timeslot, TDMA frame, multiframe, super frame, and
hyper frame.
GSM uses TDMA and FDMA technologies for physical
channel, as shown in the figure below.
Time
Frequency
Frequency
Time
Physical Channel and Logical Channel
System Messages
System message falls into 12 types: type1, 2, 2bis,
2ter, 3, 4, 5, 5bis, 5ter, 6, 7, 8.
Basic Service and Signaling Process
This section introduces GSM terminal start,
position register / update, service call and
handover service implementation and signaling
interaction process.
Mobile subscriber state
Location Update
Typical Call and Handover Process
Basic Signaling Process
Mobile subscriber state
The mobile subscriber has three states as follows:
MS starts, network does "Attach" marks on it
MS shutdowns, separated from network
MS Busy
Location Update at Same MSC Office
BSC
(2)
(1)
(3) (4)
MSC/VLR
LAI
1
LAI
2
M
S
M
S
Location update between different MSCs
(5)
(2)
(3) (1)
(4)
HLR
MSC/VLR1
MSC/VLR2
M
S
M
S
Location Update
Call process
Typical Call and Handover Process
Handover process
Typical Call and Handover Process
Location Update Process of MS
RLC
RLSD
DT1:CIPH MODE CMD
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:LOC UPD REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:LOC UPD ACCEPT
Basic Signaling Process
IMSI Detach Process
RF CH REL ACK
RF CH REL
REL IND UA
DISC DEACT SACCH
DR:CH REL CH REL
CREF
CR:IMSI DETACH EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
Basic Signaling Process
Mobile-Originated Call and Called
Party On-hook Process
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:CM SERV REQ EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
MS BTS BSC MSC
DTAP:SETUP
DTAP:CALL PROC
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
DTAP:CM SERV ACCP
Basic Signaling Process
Mobile-Terminated Call and Calling
Party On-hook Process
UDT:PAG PAG CMD PAG REQ
RF CH REL ACK
RF CH REL
RLC
RLSD
CH REL
DISC
UA RF CH REL
RF CH REL ACK
REL IND
DEACT SACCH
DR:CH REL
EST IND
ASS COM DT1:ASS COM
DT1:ASS REQ
DT1:CIPH MODE CMD
CH ACT ACK
CH ACT
PHY CONT CONF
UA
SABM
PHY CONT REQ
DR:ASS CMD ASS CMD
DT1:Clear COM
DT1:Clear CMD
DT1:CIPH MODE COM DI:CIPH MODE COM
CIPH MODE COM
CIPH MODE CMD ENCRY CMD
CC
CR:PAG RES EST IND
UA
SABM
IMM ASS IMM ASS CMD
CH ACT ACK
CH ACT
CH RQD CH REQ
DTAP:SETUP
DTAP:CALL CONF
DI:ASS COM
DTAP:Alerting
DTAP:Connect
DTAP:Connect ACK
数据流
DTAP:Disconnect
DTAP:Release
DTAP:Release COM
BSC MSC BTS MS
Basic Signaling Process
Inter-cell Handover Process
DT1:HO PERF
HO CMD
CH ACT
MEAS REP
RF CH REL ACK
RF CH REL
DI:HO COM
EST IND
HO DET
CH ACT ACK
MS BTS1 BTS2 BSC MSC
MEAS RES
DR:HO CMD
HO ACCESS
PHY INFO
SABM
UA
HO COM
Basic Signaling Process
key radio enhanced technologies
This section describes basic voice processing for
GSM, and several key radio enhanced
technologies.
Voice Processing
Frequency multiplexing
Adaptive equalizing
Diversity Receiving
Discontinuous Transmission (DTX)
Power Control
Timing Advance
Frequency Hopping Technology
Voice Processing
Voice Processing in the GSM System
Frequency multiplexing
Frequency multiplexing is the core concept of the cellular
mobile radio system. In a frequency multiplexing system,
users at different geographical locations (different cells)
can use channels of the same frequency at the same time
(see the figure above).
Adaptive equalizing
Equalizer can do equalizing at frequency domain
and time domain. GSM uses time domain
equalizing, enabling the better performance in
whole system.
Diversity Receiving
Diversity reception technology is commonly used in GSM.
Diversity consists of different forms: Space diversity,
frequency diversity, time diversity and polarity diversity.
Discontinuous Transmission (DTX)
The DTX mode accomplishes two objectives: Lower the total
interference level in the air and save the transmitter power.
Speech Frame Transmission in DTX Mode
Power Control
Power control means to control the actual transmitting power (keep it
as low as possible) of MS or BS in radio propagation, so as to reduce
the power consumption of MS/BS and the interference of the entire
GSM network.
Power Control Process
Timing Advance
In the GSM, the MS requires three intervals between timeslots when
receiving or transmitting signals. See the figure below.
Uplink and Downlink Offset of TCH
Frequency Hopping Technology
Frequency hopping (FH) refers to hopping of the carrier frequency
within a wide frequency band according to a certain sequence.
Basic Structure of FH
section describes evolution of GSM
technologies
This section describes evolution of GSM
technologies: basic concept, network structure,
radio channel, and basic application of GPRS and
EDGE.
Definition and Feature
Inheritance and Evolution
GPRS Radio Channel
Radio Link and Media Access Control Flow
Terminal and Application
Definition and Feature
The General Packet Radio Service (GPRS) is the
packet data service introduced in GSM Phase2+.
The GPRS has the following features:
Seamless connection with IP network
High rate
Always online and flow charging
Mature technology
Definition and Feature
Enhanced Data Rate for GSM Evolution (EDGE) is a kind
of technology for transition of GSM to 3G.
The EDGE has the following features:
EDGE neither changes GSM or GPRS network structure nor
introduces new network element, but only upgrades the BSS.
EDGE does not change the GSM channel structure, multiframe
structure and coding structure.
EDGE supports two data transmission modes: packet service (non-
real time service) and circuit switching service (real time service).
EDGE adopts octal 8PSK modulation technology, supports 303%
of GMSK payload, and provides higher bit rate and spectral
efficiency.
Compared with GPRS, EDGE adopts new coding mode.
GPRS Radio Channel
This section introduces GPRS physical channel,
GPRS logic channel, mapping of logical channel
combination in the physical channel, and GPRS
channel coding.
Radio Link and Media Access Control Flow
This section introduces paging flow, TBF setup
flow, GPRS suspend/resume flow, and TBF
release flow.
Terminal and Application
The GPRS MSs fall into three categories: Type A,
B, and C.
GSM Handover Problems & Solutions
ZTE university
Objectives
To master different types of handover and their
signaling flows;
To master handover statistical signaling point and MR
tasks;
To know common handover problems and the handling
procedures.
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Aims of handovers
Why there are handovers?
To keep calls going on during movement;
To improve network service quality;
To decrease call drop rate;
To decrease congestion rate.
Handover classification
Inter-MSC
Inter-BSC
Intra-BSC
Intra-cell
Handover
classification
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Intra-cell handover
Air A
TCBTS
BSC
New Channel
Old Channel
Signaling flow of intra-cell handover
MS BTS BSC MSC
1、Measurement Report(SACCH)
2、Measurement Report
3、Channel Activation
4、Channel Activation Ack
5、Assigment Command (FACCH)
6、SABM(FACCH)
8、UA(FACCH)
7、Establish Indication
9、Assigment Complete(FACCH)
10、Receiver Ready(FACCH)11、HO Performed
12、RF Channel Release
13、RF Channel Release Ack
Air A
TCBTS
BTS
BSC
Old Cell / BTS New Cell / BTS
Inter-cell handover within one BSC
Signaling flow of inter-cell handover within one BSC
MS Old BTS BSC MSC
1、Measurement Report(SACCH)2、Measurement Report
5、HO Command
7、HO Access(FACCH)
12、UA(FACCH)
13、HO Complete(FACCH)
14、Receiver Ready(FACCH)
16、HO Performed17、RF Channel Release
18、RF Channel Release Ack
New BTS
3、Channel Activation
4、Channel Activation Ack
6、HO Command(FACCH)
8、HO Detect
9、Physical info(FACCH)
10、SABM(FACCH)
11、Establish Indication
15、HO Complete
Air A
BTS
Old Cell / BTS
New Cell / BTS
BTS
BSC TC
BSC TC
VLRMSC
Inter-BSC handover
Signaling flow of inter-BSC handover
MS Old BTS Old BSC MSC
14、HO ommand
6、HO Command
13、UA(FACCH)
New BTS
3、Channel Activation
4、Channel Activation Ack
10、HO Detect
11、Physical info(FACCH)
12、SABM(FACCH)
New BSC
1、HO_REQ
2、HO_REQ
5、HO_REQ_ACK
7、HO Command8、HO Command
9、HO Access(FACCH)
15、HO Command16、HO Command
17、HO Command
Air A
BTS
Old Cell / BTS
New Cell / BTS
BTS
BSC TC
BSC TC
VLRMSC
VLRMSC
Inter-MSC handover
Basic signaling flow of Inter-MSC handover
MS/BSS-A
MSC-A MSC-B
MAP-Prep-Handover req. MAP-Allocate-Handover-Number req.
A-HO-REQUEST
A-HO-REQUIRED
BSS-B/MS
VLR-B
A-HO-REQUEST-ACK
MAP-Send-Handover-Report req.
MAP-Prep-Handover resp.
IAM
MAP-Send-Handover-Report resp.
ACM A-HO-COMMAND
A-HO-DETECT
A-HO-COMPLETE
MAP-Process-Access-Sig req.
MAP-Send-End-Signal req. A-CLR-CMD/COM
ANSWER
RELEASE End of call
MAP-Send-End-Signal resp.
MS/BSS-B
MSC-A MSC-B
MAP-Prep-Sub-Handover req. A-HO-REQUIRED
BSS-A/MS
VLR-B
A-HO-COMMAND MAP-Prep-Sub-Handover resp.
A-HO-REQUEST-ACK
A-HO-DETECT
A-HO-COMPLETE MAP-Send-End-Signal resp. A-CLR-CMD/COM
A-HO-REQUEST
Release
Signaling flow of inter-MSC back-handover
MSC-B
A-HO-REQUIRED
VLR-B
A-HO-COMMAND
MAP-Prep-Sub-Handover req.
A-HO-DETECT
A-HO-COMPLETE
MSC-A
MS/BSS
MSC-B’ VLR-B’
MAP-Prepare-Handover req.
MAP-Prepare-Handover resp.
MAP-Allocate-Handover-Number req.
MAP-Send-Handover-Report req.
IAM
MAP-Send-Handover-Rep. resp. (1)
MAP-Prep-Sub-Ho resp.
MAP-Process-Access-Signalling req.
MAP-Send-End-Signal req.
ACM
Answer
Release
MAP-Send-End-Signal resp.
MAP-Send-End-Signal resp.
Release
(end of call)
A-CLR-CMD/COM
Signaling flow of inter-MSC handover to a third MSC
Basic flow of handover signaling
Inter-cell handover
within BSC
There is no “HO-Request” message for intra-BSC handover; all
information is analyzed within BSC; Once a target cell in the
BSC fulfilling handover conditions is found, send “Channel
activation” message directly;
Inter-BSC handover
within MSC
BSC reports CGI and handover cause of original cell and target
cell to MSC through “HO-Request”;
After MSC finds target cell LAC, it sends “HO-Request” to the
BSC which the target cell belongs to;
Target BSC activates channel in target cell, and executes the
following flow.
Basic flow of handover signaling
Inter-MSC handover
MSC inquires “REMOTLAC sheet” (including LAC and
route address of adjacent MSC);
MSC sends (Prepare-HO) message to the target
MSC-B according to the route address;
According to the (Prepare-HO) message, target
MSC-B requests for Handover number from VLR-B,
then sends “HO-Request” message to BSC-B;
After the target BSC-B receives “HO-Request ACK”, it
sends (Prepare-HO ACK)message to the original
MSC, and executes the following flow.”
MSC participates
or not
CGI is carried
or not
Inter-
BSC
handover
Intra-
BSC
handover
MSC transmits “HO-REQ” message,
and CGI of original cell and target cell
is carried in the message;
As for inter-BSC handover, MSC
participates in it since “HO-Request”;
As for intra-BSC handover, “HO-
Performed” message is sent to MSC
only after the handover is
completed; MSC doesn’t participate
before that;
For intra-BSC handover, CGI isn’t
carried in any message, it’s handled
within BSC.
Main differences between intra-BSC handover
and inter-BSC handover
MS BTS BSC MSC
BCCH
frequency
point, BSIC
and level
values of
the six
adjacent
cells (with
strongest
level) and
serving cell;
UL MR
Process of MR
Confirmation of
adjacent cell CGI
Execution of
handover decision
Selection of
target cell
Channel activation
External cell?
HO
req
uest
Intra-MSC
handover
Target MSC Target BSC
BA2 sheet
List of cells
under one LAC
HO
req
uest
HO
req
uest
No
Yes
Flow of handover algorithm
Common timers at BSC
T3107
Suitable for: intra-cell handover
Start-up: BSC sends “assignment command”
Stop counting: when “assignment completed” or
“assignment failure” is received;
A1
BSCBTS:TRXMS
ASSIGNMENT COMMAND
CHANNEL ACTIVATE
A2
CHANNEL ACTIVATE ACK
SET T3107
T3107
Timeout
Common timers at BSC
T3103
Suitable for: inter-cell handover
Start-up: BSC sends “handover command”
Stop counting: when “handover completed” or “handover failure” is
received;
A1
BSCOld BTS:MS
HANDOVER COMMAND
CHANNEL ACT
A2
CHANNEL ACT ACK
New BTS
HANDOVER COMMANDSET T3103
T3103
Timeout
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
MR cycle
MR is sent to BTS in SACCH UL direction;
When MS is in SDCCH, MR cycle is 470ms/time;
When MS is in TCH, MR cycle is 480ms/time.
12TCH 12TCH 1SACCH 1 idle
480ms 26 multi-
frames of 4
TCHs
Indicator definition of handover success rate
KPI name Handover success rate
Indicator
definition
( busy hour number of handover success times /busy hour total
number of handover request times)*100%
V6.20 (C900060098+C900060102+C900060120+C900060094
+C900060096)*100/(C900060097+C900060213+C9000
60214+C900060215+C900060099+C900060100+C900
060101+C900060216+C900060119+C900060093+C900
060095)
Signaling statistical point of handover success
C900060098 C900060102
C900060120
A
BTSBSC
HO_ COM
BSC-controlled inter-cell incoming handover success
A
BSCMSC BTS
HO_COM
HO_COM
MSC-controlled incoming handover success
A
BSC BTS
ASS_COM
ASS_CMD
Intra-cell handover success
C900060096
A
MSCBSC
CLEAR_CMD
No. of MSC-controlled outgoing handover success times
Signaling statistical point of handover success
C900060094
MS
HO_CMD
BTS(Src)
CHL_ACT
BSC
HO_CMD
MEAS_RESMEAS_RES
SABM
UA
HO_COM
MSC
HO_COM
EST_IND
HO_PERFORM
HO_ACCESS
BTS(Target)
CHL_ACT_ACK
HO DETECT
Phy Info
A
BSC-controlled inter-cell outgoing handover success
Signaling statistical point of handover request
C900060097
A
BTSBSC
CHL_ACTIV_ACK
BSC-controlled inter-cell incoming handover execution
C900060213
C900060214
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Forced release attempt
,Resource Available
Execution of forced release
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Cell queuing
,Resource Available
Execution of cell queuing
C900060215
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Force handover attempt
,Resource Available
Execution of force handover
Signaling statistical point of handover request
C900060099 C900060100
C900060101
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACK
CHL_ACTIV_ACK
CHL_ACTIV
MSC BSC-controlled incoming handover execution
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACKCHL_ACTIV_ACK
CHL_ACTIV
Forced release attempt,
resource available
Execution of forced release
A
BSC
HO_REQ
MSC BTS
HO_REQ_ACKCHL_ACTIV_ACK
CHL_ACTIV
Cell queuing, resource available
Execution of queuing
A
BSCBTS
ASSIGN_ CMD
CHL_ ACTIV_ACK
Execution of intra-cell handover
C900060119
Signaling statistical point of handover request
C900060216 C900060095
C900060093
BTS
A
MSC
HO_CMD
BSC
HO_CMD
No. of MSC-controlled outgoing handover execution times
A
BTS( Target) BSC
CHANNEL ACT
CHANNEL ACT ACK
Force handover attempt
,Resource available
Execution of force handover
MS
HO_CMD
BTS(Src)
CHL_ACT
A
BSC
HO_CMD
MEAS_RESMEAS_RES
SABM
UA
HO_COM
MSC
HO_COM
EST_IND
HO_PERFORM
HO_ACCESS
BTS(Target)
CHL_ACT_ACK
HO DETECT
Phy Info
No. of BSC-controlled inter-cell outgoing handover execution times
Handover-related measurement tasks
Handover
causes
measurement
Measure the frequency of MS handovers caused by various kinds of
reasons, so as to examine radio environment of a cell;
Common
handover
measurement
Measure the process of MS handover to inspect handover success or
failure and abnormal situations causing failures, so as to improve the
cell’s radio configuration and observe traffic dispersion, etc.;
Measurement
of adjacent
cell handover
Measure the number of times of incoming/outgoing handover
attempt/success/failure from/to certain cells, and number of times of
handover caused by different reasons, so as to get the handover
situations of the serving cell and its adjacent cells and to optimize their
radio configurations correspondingly;
Sub cell
statistical
measurement
Focus on traffic load of the second subcell.
Contents
Overview of handover
Flow of handover signaling
Handover statistics
Handover problem analysis
Analysis handover problems
Analysis of handover problems
Location method of handover problems
Common handover problems
Common handover problems
Possible influences
Handover nonoccurrence
• Result in call drop;
Handover failure • Affect call quality and result in call
drop;
Frequent handover • Affect call quality, and increase
system load;
Handover hysteresis • Affect call quality and result in
call drop;
Discovery of handover problems
Meters at A interface
Traffic statistics analysis
Customer complaints
DT/CQT tests
TOPN analysis
Abnormal number of handover times
Call drop
Poor speech quality
Bad coverage
Handover problem Slow handover
Handover to best cell inhibited
No handover
Handover failure
Frequent handover
Flow of handover problem checking Too high TCH
handover failure rate
of a cell
Complete
Any antenna
problems?
Solve
antenna
problems
Eliminate
equipment
faults
Check &
eliminate
interference
Is radio
parameter setting
reasonable?
Interference
exists?
Any equipment
faults?
No
Yes
Adjust
parameters
Yes
Yes
Coverage
problem exists?
Improve
coverage
Yes
Location methods of handover problems
Analyze traffic statistics Conduct handover statistics measurement, identify
problem range: If just some cells fail to make handovers to the cell, check
handover data, check if co-channel and co-BSIC exist;
If the cell fails to take handovers from all other cells, check its data.
Check warnings: single board malfunction, transmission and clock malfunctions, etc.;
Check if radio parameters are set reasonably If co-channel or co-BSIC exist among adjacent cells;
If handover parameters are set reasonably;
If data configuration of external cells is correct.
Location methods of handover problems
Interference checking
DT analysis
Signaling analysis: Um interface、Abis interface 、 A interface;
Hardware checking: like DCU, transceiver, clock generator, RF
connection lines between boards;
Antenna system checking
Analysis of handover problems
Coverage & interference
Antenna system
BTS software & hardware
transmission
BSC software & hardware
A interface malfunction
Busy target cell
Connection & adaptation to equipment from different suppliers
Coverage & interference
Coverage:
Poor coverage: due to influence from forest, complex
landforms, houses, indoor coverage, etc.;
Isolated site: no adjacent cells around;
Skip-zone coverage: no adjacent cells available due to
isolated-island effect;
Interference:
It makes MS unable to access in UL, or DL signal
receiving problem will be resulted.
Handover nonoccurance due to isolated-
island effect
Adjacent cell N3
adjacent cell N2
adjacent cell N1
Non-adjacent
cell
Non-adjacent
cell
Non-adjacent
cell
Serving cell
Handover can’t happen due to lack of adjacent cells.
Skip-zone
coverage leads to
isolated island.
Antenna system problems
Too large VSWR
Reversed installation of antenna
Non-standard antenna installation
Unreasonable azimuth, down-tilt
Below-standard antenna insulation
Twisted cables, loosened connectors and wrong
connections;
BTS software/hardware
Problems about :
Single board
Clock generator malfunction
Internal communication cable malfunction
BTS software malfunction
Transmission and BSC problems
Transmission fault
Unstable transmission
Too high transmission error rate
BSC hardware/software malfunctions
Clock generator malfunction: unconformity among clocks in
different BTSs due to clock generator malfunction;
Problem about single board
Wrong data configuration
Unreasonable setting of handover threshold
CGI, BCCH and BSIC values in “external cell data sheet” do not
match up to those in the corresponding BSC;
Wrong BSC signaling point in “list of cell under a LAC” in MSC; co-
channel& co-BSIC adjacent cells exist.
A interface malfunction
A interface malfunction
Abnormal handover due to lack of link resource, abnormal calls;
Busy target cell
Abnormal handover due to lack of link resource, abnormal calls;
handover between equipment from different suppliers
Difference in signaling at interface A and interface E between ZTE
and other suppliers’ equipment, causing non-recognition or non-
support problem, including speech version, handover code and
addressing mode (CGI or LAI) etc., which will result in handover
failure.
Typical case 1- frequency interference
Problem description:
The data in performance report shows that Cell 1 under
a BTS suffers from low handover success rate.
Problem analysis
Examine the problem cell, discover that 2 cells under a
BTS co-channel and co-BSIC, and close to each other,
which results in low handover success rate in the cell.
Problem handling
After adjustment of frequency point, handover success
rate obviously increases, and number of handover times
reduces.
Typical case 1- frequency interference
Changes of HO indicators before & after Frequency point adjustment
0
30
60
90
120
150
180
9-4 9-5 9-6 9-7 9-8 9-9 9-10 9-11
Number of HO Req./number of HO success
0%
20%
40%
60%
80%
100%
120%
HO success rate
切换请求总次数 切换成功总次数 切换成功率(%)No. of HOReq. HO success
rate
No. of HOsuccess
Typical case 2- clock malfunction
Problem description For a newly-commissioned BTS, handover nonoccurrence appears
during DT: the MS occupies a channel in cell A; during DT from cell A to cell B, cell B can’t be observed in the adjacent cell list, and it doesn’t start normal handovers.
Problem analysis It’s a common network problem that handover nonoccurrence
appears in many cells;
It’s a newly-commissioned BTS; handover parameters are as default in the system;
Check adjacent cells relation, no problem found;
Observe from test MS, find out that adjacent cell frequency appears in the adjacent cell, but BSIC can’t be decoded. Since adjacent cell is searched through BA2 table during a call, and
BA2 relies on BCCH and BSIC to confirm an adjacent cell, when the adjacent cell’s BSIC is unobtainable, BSC is unable to locate it, thus handover won’t be started.
Typical case 2- clock malfunction
Problem analysis
Process of MS decodeing on DL channel
decode FCCH decode SCH(SCH comprises MS frame
synchronous information and BSIC.
MS can show adjacent cell frequency point, but not BSIC. It’s
suspected that adjacent cell’s SCH information can’t be decoded
by MS due to clock or transmission fault.
Check clock and transmission
BTS adopts network clock
BSC traces superior clock
MSC traces superior GPS clock through long-distance satellite link
The long-distance satellite link is found unstable, which leads to
high error rate on the meter, and warning of clock deterioration
appears on MSC.
Typical case 2- clock malfunction
Problem handling
Decide that it’s handover problem
caused by poor clock quality.
Bring new GPS clock device and
adopt the local one, thoroughly
solve clock malfunction.
Problem of handover
nonoccurrence is solved.
Experience conclusion
If no high accuracy clock
available, clock in BTS can be
used; calibration of each BTS
must be made by using
frequency meter and LMT to
ensure that frequency deviation
meets precision requirement.
Typical case 3-HO parameter setting problem
Problem description
During DT at a BTS, we find slow handover problem is
common (>10S), which affects speech quality and even
causes call drops.
Problem: level of cell 2 is higher than that of cell 3 by
20dB, total handover time is 15s.
Typical case 3-HO parameter setting problem
Problem analysis and handling
Slow handover seriously affects network quality. Make adjustment of handover parameters accordingly:
Change adjacent cell handover threshold to improve timeliness of handover trigger;
Adjust the whole network’s handover window to be 2, so as to accelerate handover speed;
Adjust the whole network’s handover preprocess to 2, so as to accelerate handover speed.
Parameter Before
adjustment
After adjustment
Level threshold
(HOMARGINRXLEV)
30 28
Quality threshold
(HOMARGINRXQUAL)
30 26
Result
Test after adjustment shows that handover time is reduced to 5s; the slow
handover problem is solved and speech quality is improve.
Questions for thinking
Please simply illustrate effects on handover due to
changing T3103、T3107.
Suggestions on parameter settings of handovers on
highway.
GSM Network Interference &
Solutions
ZTE university
Training goals
To know the classification of interference;
To master the analytical methods of interference
problem;
To master the flow of handling interference problem;
To know the analytical tool of interference problem;
To be able to handle common interference problems.
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
GSM Frequency Allocation
Frequenc
y band
UL
frequency
DL
frequency
Duplex
interval
Band
width
Carrier
frequenc
y interval
EGSM+G
SM900
880MHz
~915MHz
925MHz~9
60MHz 45MHz 35MHz 200kHz
DCS1800 1710MHz~1
785MHz
1805MHz~
1880MHz 95MHz 75MHz 200kHz
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Phenomena of Interference
Call drop
Unable to
establish calls Metallic noise
On-and-off
speech
Poor
speech
quality
Phenomena
Classification of Interference
Internal interference
Internal interference refers to unreasonable frequency planning
and equipment hardware faults, which could lead to decrease in
network service quality.
External interference
External interference refers to unknown signal source out of the
network, whose existence could seriously disturb the network’s
signals and lead to decrease in service quality.
UL interference
DL interference
Internal Interference _Causes
Unreasonable frequency planning
Equipment faults
Skip-zone coverage
Internal
interference
Internal Interference
_due to unreasonable frequency planning
Unreasonable frequency planning :
Frequency and adjacent cell relation may be set
unreasonable in network planning because of planning
tools or human mistakes .
Interference will be reflected in too large DL_RxQuality,
MS unable to access into network, poor speech quality,
and call drop.
Internal Interference
_due to unreasonable frequency planning
Check and confirm problem: Use planning tool to check if co-channel exists; co-
channel is easy to be detected if it does exist.
As for cells in boundary areas, we can block co-
channel cells in the network; meanwhile, make tracing
test with DT devices at areas with emergence of large
DL_RxQuality. If co-channel interference does exist, the
DL_RxQuality value shall become smaller after the
blocking of co-channel cells, thus we can adjust the
cell’s frequencies to eliminate the interference.
Internal Interference _due to skip-zone
coverage
Interference caused by skip-zone coverage
If the actual cell coverage greatly exceeds requirement,
interference will be increased.
Incorrect setting of engineering and network
parameters may lead to skip-zone coverage.
Internal Interference _due to skip-zone
coverage
Unreasonable setting of engineering parameters:
Wrong antenna type, down-tilt and azimuth may result
in over large cell coverage, which exceeds actual
coverage need;
Unreasonable setting of network parameters:
Network parameters include: minimum access level,
BTS transmission power, MS max transmission power,
handover thresholds, etc..Improper setting of these
parameters will result in skip-zone coverage problem
and interference as well.
Internal Interference _ due to equipment
fault
Interference caused by equipment fault:
Radio fault of BTS is mainly caused by defective UL
unit parts.
External Interference
Definition: External interference refers to other interferences caused by
external factors, but not due to equipment fault or unreasonable
frequency planning.
Common external interferences:
due to wide-band repeater;
due to CDMA system (trailing signal);
due to signal jammer;
Characteristic:
It’s hard to detect this kind of interference without
specific devices.
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Flow of Handling Interference Problem
Confirm
interference
range
Check
frequency,
change
frequency
points
Complete
Poor speech
quality due
to
interference
Check and
change
TRX
Check
external
interference
Check
VSWR/antenna/divider/dupl
exer
One cell
Interference
exists
One
TRX
Interference
exists
Interference
exists
Any new sites? If thorough change
of frequency parameters taken
recently?
Several
cells
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Analytical Methods of Interference
Problem
Analytical
Methods of
Interference
Problem
Statistical
analysis of
network
performance
indicators
Analysis of
parameter
checking
Investigation
of hardware
fault
Drive Test
and Dialing
Test
External
interference
test
Analytical Methods of Interference Problem - Statistical analysis of network performance
indicators
Statistical analysis of network performance indicators
Statistics of interference band : When TCHs are in idle status, UL noise/interference is constantly being measured BTS, and the measurement result will be analyzed, and interference level will be sent to BSC in 6 levels. 。
Statistics of handover due to UL/DL interference : We can judge whether interference exists through statistics of handover caused by UL/DL interference.
Collection of UL/DL RQ samples during speeches : RxQual is an indicator to reflect speech quality, which is based on error rate and falls into 8 grades (0~7).
Analytical Methods of Interference Problem - Statistical analysis of network performance
indicators
Corresponding relation between RxQual and Ber
Analytical Methods of Interference Problem
- Analysis of parameter checking
Check
parameters
related to
transmitting
power
Check antenna
engineering
parameters
Check frequency
planning
parameters
Check
parameters
related to skip-
zone coverage
Parameter
checking
Analytical Methods of Interference Problem
- Checking hardware fault
Checking hardware fault
OMCR warning analysis
Checking latent equipment fault
Analytical Methods of Interference Problem
- Checking latent equipment fault
Block the two
input ways of
TRX, observe
UL
interference
band; if it’s 0,
it’s proved
that TRX
hasn’t
brought UL
interference.
Input the two
stimulations
of TRX
without
connecting
them to
power
amplifier,
observe UL
interference
band; if it’s
0, it means
external
interference
doesn’t exist.
If serious UL
interference exists
even though there
is no stimulation
imposed on
power amplifier,
disconnect rack
top feeder cables,
if the interference
disappears, we
can infer that the
problem is caused
by external
factors.
Disconnect the
rack top feeder
cables, and
observe UL
interference
band; if the
interference
isn’t fading at
all, then we can
conclude that
the problem is
with the divider
unit.
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test
Drive Test and Call Quality Test
Drive test can effectively detect the location
and degree of interference, which is
convenient for analyzing the cause of
interference.
In CQT, we can actually feel the speech
quality at areas being interfered, and we can
see call quality class on the test phone.
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test
DT parameters:
C/I: co-channel carrier-to-interference ratio
RxQual 0 1 2 3 4 5 6 7
C/I[dB] 23 19 17 15 13 11 8 4
0
5
10
15
20
25
0 1 2 3 4 5 6 7
C/I[dB]
Analytical Methods of Interference Problem
- Drive Test and Call Quality Test DT parameters:
SQI:SPEECH QUALITY INDEX is the comprehensive description of BER, FER and HANDOVER EVENT by TEMS.
Analytical Methods of Interference Problem
- Test of external interference Confirm external interference with
SITEMASTER : Test of UL interference;
Connect the input port of frequency-sweep generator to the output port of divider to increase the degree of sensitivity, as shown in the figure.
Analytical Methods of Interference Problem
- Test of external interference
Confirm external interference with SITEMASTER :
persistent strong level exists within the bandwidth of 20MHz, we can conclude that serious UL interference exists.
Analytical Methods of Interference Problem
- Test of external interference
Confirm external interference with YBT250:
Make UL interference analysis of GSM 900M UL frequency band with frequency scanning meter-NetTek Analyzer(TEK company). The model we usually use is YBT250.
Connection method of YBT250:
One is to use its own test antenna ;
One is to obtain interference information through connection to
the output port of divider.
Analytical Methods of Interference Problem
- Test of external interference
Connection method using YBT250 to test UL
interference:
Antenna
CDU
YBT 250
Feeder
Analytical Methods of Interference Problem
- Test of external interference
Wave graph of UL interference tested by YBT250: This output is the average value of the test results of
one minute, which shows the frequency and strength of interference. Persistent observation is needed to confirm if the interference continues.
Analytical Methods of Interference Problem
- Test of external interference Time scatter graph of UL interference tested by YBT250:
TEK frequency scanning meter features in three dimensional recording of time, frequency and signal.The vertical bold red lines in the graph represent the time duration, signal level strength and frequency .
vertical
axis=time
Colour
spectrum
=strengt
h
horizontal
axis=frequency
Contents
GSM Frequency Allocation
Phenomena & Classification of Interference
Flow of Handling Interference Problem
Analytical Methods of Interference Problem
Typical Cases
Typical case 1: Problem description
Since March 2005, an operator has received a lot of
complaints about poor speech quality; sometimes calls
even couldn’t be setup; the caller could hear the
counterpart, but could not be heard.
Typical case 1: Problem analysis
At the
beginning we
thought it was
caused by
poor signal.
After on-site
test, we found
it wasn’t
coverage
problem.
When the level
tested by MS was
-85dbm, UL call
problem
occurred, which
was displayed as
on-and-off
speech, silence,
metallic noise
and current noise,
so we concluded
that the problem
was caused by
interference.
Performanc
e statistics
at OMCR
showed that
the rank of
idle channel
interference
band was
high.
Confirmed the
problem was
caused by
interference
Typical case 1: Problem handling process—
STEP1 Test UL interference with YBT250 connected to CDU. CDMA wave
form was strong when wave filter wasn’t used, the peak value reached
about -35dbm (average about -60dbm), which was close to GSM UL
wave band and could cause UL interference to GSM network.
Typical case 1: Problem handling process—
STEP1 In the three dimensional graph of interference tested by YBT250, the
CDMA wave form was strong and the wave form of GSM background
noise on the right was high in a long period of time.
Typical case 1: Problem handling process—
STEP2
Use CDMA wave filter to eliminate CDMA
interference.
Antenna Common
CDU
YBT 250
Feeder
CDMA wave
filter
Typical case 1: Problem handling process—
STEP2 When CDMA wave filter was adopted, CDMA wave
form was obviously weakened, but it was still strong at
some certain point; the background noise in GSM
frequency band was also reduced.
Typical case 1: Problem handling process—
STEP2
Because of CDMA wave filter, the UL interference in GSM
frequency band reduced greatly.
Typical case 1: Problem handling process—
STEP3
With the aim to eliminate CDMA interference, adopt IRCDU
+CDMA wave filter.
Antenna CDMA wave
filter
YBT 250
IR CDU
Typical case 1: Problem handling process—
STEP3 Adoption of IRCDU+CDMA wave filter can effectively
filter CDMA waves to below -104dbm. This kind of filtering
effect can help completely avoid CDMA network interfering
GSM UL network.
Typical case 1: Problem handling process—
STEP3 Adoption of IRCDU+CDMA wave filter can eliminate
CDMA wave form to a great extent; during the test period,
CDMA interference was almost eliminated.
Typical case 1: Summary
The interference source was from CDMA system.
Through comparisons of tests above, we can see after
IRCDU+CDMA wave filter was used, call quality
obviously improved.
Questions for thinking
How is interference resulted from wrong setting of transmitting power-related parameters?
What is the flow of checking external interference?