05-functions and performance
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User ManualM900/M1800 Base Transceiver Station (BTS30) Table of Contents
Table of Contents
Chapter 5 Functions and Performance ....................................................................................... 5-1
5.1 Networking Function.......................................................................................................... 5-1
5.1.1 E1 Networking......................................................................................................... 5-1
5.1.2 SDH Networking...................................................................................................... 5-3
5.1.3 Networking for Satellite Transmission..................................................................... 5-4
5.2 Main RF Function............................................................................................................... 5-6
5.3 Baseband Processing........................................................................................................ 5-8
5.3.1 Channel Types Supported ...................................................................................... 5-8
5.3.2 Channel Combinations Supported .......................................................................... 5-9
5.4 Signaling Processing ......................................................................................................... 5-9
5.5 Operation and Maintenance ............................................................................................5-12
5.5.1 Software Loading .................................................................................................. 5-13
5.5.2 Abis Interface Management .................................................................................. 5-13
5.5.3 Air Interface Management..................................................................................... 5-14
5.5.4 Testing Management ............................................................................................5-16
5.5.5 Status Management .............................................................................................. 5-16
5.5.6 Processing of Event Reports................................................................................. 5-17
5.5.7 Equipment Management....................................................................................... 5-18 5.5.8 Site Configuration.................................................................................................. 5-20
5.5.9 Tracing Operations................................................................................................ 5-20
5.5.10 Other Functions................................................................................................... 5-21
5.6 System Indices................................................................................................................. 5-21
5.7 Radio Interface Indices.................................................................................................... 5-23
5.7.1 Receivers .............................................................................................................. 5-23
5.7.2 Transmitters .......................................................................................................... 5-26
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User ManualM900/M1800 Base Transceiver Station (BTS30) Chapter 5 Functions and Performance
Chapter 5 Functions and Performance
The main functions of BTS30 will be introduced in the aspects listed: networking
function, baseband processing, signaling processing and operation and
maintenance.
5.1 Networking Function
The BTS30 allows for a flexible networking modes with many built-in transmission
functions. It supports transmission modes such as E1, SDH.
5.1.1 E1 Networking
With one site as a basic unit, M900/M1800 BTS30 supports star, tree, chain and ring
E1 networking topologies, which are illustrated in Figure 5-1.
BSC
BTS0
BTS1
BTS2
BSC BTS0
BTS1
BTS2
BTS3
BSC BTS0 BTS1 BSC BTS0 BTS1
star networking tree networking
ring networkingchain networking
Figure 5-1 The BTS30 E1 networking mode
Each TMU board provides 4 E1 interfaces and each cabinet can be configured with
2 TMU boards. If one interface is connected to the superior network, a maximum of
7 tributaries can be provided. A comparison between various connection modes is
made in the following.
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I. Star networking
Each site is connected directly to BSC by an E1 link, which brings very convenient
maintenance and simple network construction.
Signals pass through very few nodes, which means that no BTS depends on one
another. So in the case of the failure of one BTS, other BTSs will not be affected.
This networking mode is usually applied in densely populated urban areas to
facilitate easy expansion. But this type of networking requires a relatively large
number of transmission links.
II. Tree networking
Tree networking has a complicated network structure. Signals pass through many
nodes, i.e. any abnormality in the superior site will affect the subordinate sites,
which leads to low line reliability.
This type of networking is applicable in vast sparely-populated areas density. But in
such configuration, further expansion is quite difficult because it requires
reconstructing of the network.
Since a BTS usually chooses the phase locking mode for the clock of its superior
network and each time of choosing the phase locking will lead to the degeneration
of clock quality, the number of BSC signals pass through should be restricted (the
number of recommended serial connection layers is not more than five, i.e. thedepth of the tree should not exceed five layers).
III. Chain networking
Along highways and railway tracks where the population density is very low, the
most suitable networking is chain topology. But the problem lies in that in chain
networking the signals pass through many nodes, resulting in poor link reliability. But
for these areas, it has considerable advantages. It saves large quantity of
transmission equipment.
Similar to the tree networking, the number of serial connection layers should be
restricted and the number of the nodes that signals pass through should not exceed
5.
IV. Ring networking
Normally, the ring network is recommended because of its strong self-healing ability.
If the optical fiber in a certain area is damaged, the ring network can be self healed
into a chain network, without affecting services in any sense. The ring networking of
BTS30 should be supported by ABA and ABB.
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In practice a cellular network can have one or more than one network topology
according to the actual physical and geographical requirements. So, considerable
amount of transmission equipment investment can be saved and service quality can
be ensured if the networking modes are applied correctly.
5.1.2 SDH Networking
The BTS30 supports built-in transmission equipment. The ASU boards developed by
Huawei are inserted in the common resource frame of the BTS30. The E1 on the
BSC side can access the SDH network via Huawei’s OptiX155A transmission
equipment.
Huawei's transmission equipment is adaptable to complex network structures under
the support of its powerful cross-connect capability, abundant flexible interfaces, andadvanced software functions.
As alternative optical transmission equipment of an extremely high performance/
price ratio in OptiX155/622A networking, ASU in actual networking can interwork
with OptiX155/622A/B or Huawei's standard transmission equipment via the STM-1
optical interface. Besides, according to the transmission networking mode, it can
form both ring and chain topologies.
A chain or ring network topology can be implemented depending on the distribution
of the network routes. Normally, the ring network (as shown in Figure 5-2) is
recommended because of its strong self-healing ability. If the optical fiber in a
certain area is damaged, the ring network can be self healed into a chain network,
without affecting services in any sense.
Normally in areas along railways and highways, chain networking is the most
suitable solution (as shown in Figure 5-3). But even in such cases, if the distance
between the stations is not too far (usually, the maximum distance between 3
stations 80km), and there are enough optical fibers (4 fibers), ring networking is still
recommended.
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TMU
ASU
ASU
ASU TMU
TMU
155ABSC
BTS0
BTS2
BTS1
E1
E1
E1
E1
Optical fiber
Optical fiber Optical fiber
Optical fiber
Figure 5-2 SDH ring networking
BSC 155A ASU
TMU
ASU
TMU
BTS0 BTS1
E1E1
E1Optical
fiber
Opticalfiber
Figure 5-3 SDH chain networking
5.1.3 Networking for Satellite Transmission
In sparsely populated areas with poor transportation conditions, it is very hard and
expensive to deploy land transmission network since common transmission
technology and common BTS can hardly meet the requirements in such areas. So in
these areas, satellite transmission is really a cost-effective and efficient solution.
Figure 5-4 shows the networking for satellite transmission.
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SDH/PDH
or microwave/cable
E1
E1
MSCGround station
BTS
BTS
BTS
BTS
Ground receivestation
Ground receivestation
BSC
Figure 5-4 Networking for satellite transmission
Networking for satellite transmission is now faced with technological difficulties,
which is much related to some inherent features of satellite transmission, such as
long transmission delay and poor stability of transmission links. These difficulties
greatly constrains the promotion and application of satellite networking. To
overcome these problems, Huawei offers an effective and complete solution as
described in the following.
I. Solution to long transmission delay
Transmission delay at the Abis interface
During satellite transmission, there is a fixed delay of hundreds of milliseconds
during the signaling control process on the Abis interface. To avoid timeout release
of the activated call due to transmission delay, multiple timers are used for the
signaling between BTS and BSC.
Handover
Due to the delay, the handover command issued from the BSC arrives at the BTS in
hundreds of milliseconds, which leads to the degeneration of the voice quality of the
mobile phone during this period. But in M900/M1800 BTS30, the functions of
filtering, interleaving, PN judgement and prediction of the measurement report can
be adjusted by setting parameters, and a special handover algorithm can be used to
eliminate the impact of time delay.
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TRAU time adjustment
Satellite transmission delay affects the alignment of the TRAU frames. As the delay
in the common transmission modes is short, the TRAU frame adopts the simple
fixed cyclic frame alignment. While in satellite transmission, the CCU (channel coderunit) adopts the self-adaptive alignment, which ensures that data can be aligned in a
timely and correct manner in any delay amount, and that the transmission voice is of
high quality.
II. Solution to synchronization problems
The synchronization between BTS and BSC can be greatly affected by the
environmental factors which are stronger during satellite transmission, hence the
voice quality will also be affected.
To solve this problem, the clock source at the BTS side adopts clocks of high
accuracy and advanced APL algorithm. When BTS can synchronize with BSC, it will
work in the synchronous mode.
III. Solution to bit errors
Bit errors will affect system synchronization, voice quality, initiation of calls, call
connection and disconnection. So the reduction of bit errors must start with the
satellite equipment.
With measures implemented in both hardware and software design, Huawei'sE-Abis interface technology has greater error tolerance capability and demonstrates
excellent performance in error and jittery test, and in the actual running
environment.
5.2 Main RF Function
The BTS30 RF functions meet the GSM 05.05 specifications. It is characterized by
such advantages such as high sensitivity, flexible configuration, and convenient
operation and maintenance. A brief description of the main RF functions is given
below.
I. High receiving sensitivity
The receiving static sensitivity of the BTS30 is better than -109dBm (for 1800MHz),
and -110dBm (for 900MHz). High sensitivity ensures the high uplink performance of
the BS and it is also one of the preconditions for a better coverage of the BS.
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II. Flexible configuration
The BTS30 can support 1~18 TRXs in each sector. The omni or sector cell (over 3
sectors) can be configured according to specific circumstances or the requirements
of the operator. By adjusting the front end gain (such as the tower-top amplifier and
the low noise amplifier), a BTS can also compensate the loss of feeders of different
lengths, thus ensures the consistency in system receiving gain.
III. Convenient operation and maintenance
The RF unit of the BTS30 can be remotely controlled by the OMC to change
transmitting power and transmitting frequencies. Alarm signals generated at the RF
unit are reported to the OMC, so the operating personnel can observe and control
the operation of the RF unit.
IV. Diversity receiving
The BTS30 provides diversity receiving function that is implemented by two
independent receiving equipment, including antennas, tower top amplifier (optional),
feeders, dividers, and receivers.
Both receivers demodulate received signals, which are then sent to the baseband
processing unit for decoding by diversity algorithm. This diversity receiving function
can provide 3~5dB diversity gain.
The application of diversity receiving technology enhances the anti-fading abilities of
the base station receivers, so that the base station can maintain a good receiving
performance even in complex radio environments.
V. RF Hopping
Hopping is another important tool to enhance the performance of the base station. It
enhances not only the anti-fading ability of uplinks and downlinks, but also the
security of communication.
The BTS30 supports both frequency hopping and non-frequency hopping modes.
When frequency hopping is required, the transceiver controlled by BSC can change
its carrier frequency according to a hopping sequence which can be set through
OMC. In non-hopping mode, the transceiver is locked at a certain frequency.
The frequency hopping of the BTS30 is realized through the real-time switchover
between two frequency synthesizers. This implementation mode has two
advantages, one is that the requirement about the rate of the frequency synthesizer
can be reduced, the other is that one of the two frequency synthesizers can function
as a backup to enhance the system reliability in non-frequency hopping mode.
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Besides the traditional frame hopping, the BTS30 supports timeslot (TS) hopping,
which further enhances the anti-fading ability.
VI. Power control
The BTS30 provides both static and dynamic power controls.
Static power control is used to adjust the service coverage range of BTS, i.e. it
defines the coverage area of the cell. It has 0~10 power levels in step of 2dB.
When a mobile station moves and the distance to BTS changes, BSC can adjust
BTS transmitting power according to the distances automatically. This process is
called dynamic power control. It has 0~15 different power levels in steps of 2dB.
The power control at each level adopts automatic power closed-loop control (APC),
which ensures a minimum power deviation.
When a timeslot is idle, as there are no downlink signals, BSC will send a command
to BTS to shut down the transmitting power of this timeslot.
These power control functions can enhance the efficiency of transmitters, the
reliability of power amplifier, and can also cut the interference of transmitters to the
minimum.
5.3 Baseband Processing
The baseband processing unit mainly fulfills the functions of the physical layer on
the Um interface, and processes all the full-duplex channel baseband data on a
TDMA frame.
At the transmitting end, it performs rate adaptation, channel encoding and
interleaving, encryption, and the generation of TDMA bursts. At the receiving end, it
is responsible for digital demodulation, decryption, de-interleaving, channel
decoding and rate adaptation.
5.3.1 Channel Types Supported
The baseband processing unit supports the following channel types:
TCH/EFS: Enhanced Full-rate Speech Traffic Channel
TCH/FS: Full-rate Speech Traffic Channel
TCH/F9.6: Full-rate Data Traffic Channel (9.6kbits)
TCH/F4.8: Full-rate Data Traffic Channel (4.8kbit/s)
TCH/F2.4: Full-rate Data Traffic Channel ( 2.4kbit/s)
FCCH: Frequency-Correction Channel
SCH: Synchronization Channel
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BCCH: Broadcast Control Channel
PCH: Paging Channel
RACH: Random Access Channel
AGCH: Access Grant Channel SDCCH/8: Standalone Dedicated Control Channel
SACCH/C8: Slow Associated Control Channel/SDCCH/8
SACCH/TF: Slow Associated Control Channel/TCH/F
FACCH/F: Fast Associated Control Channel/Full Rate
SDCCH/4: Standalone Dedicated Control Channel/BCCH/CCCH
SACCH/C4: Slow Associated Control Channel/SDCCH/4
CBCH: Cell Broadcast Channel
5.3.2 Channel Combinations Supported
The baseband processing unit supports the following types of channel
combinations:
TCH/F+FACCH/F+SACCH/TF
FCCH+SCH+BCCH+CCCH
FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/C4
BCCH+CCCH
SDCCH/8+SACCH/8
SDCCH/8+SACCH/8+CBCH
FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/C4+CBCH Here CCCH=PCH+RACH+AGCH
5.4 Signaling Processing
The BTS30 signaling processing mainly fulfills:
The interworking between MS and BSS/NSS on the Um interface.
Management function of the radio resources under the control of the BSC.
The BTS30 signaling processing includes radio link management, dedicated
channel management, common channel management and TRX management.
I. Radio link layer management procedures
Link establishment indication procedure: Through this procedure BTS indicates
to the BSC that a multiframe data link has been established at the initiative of an MS.
BSC can use this indication to set up an SCCP connection to MSC.
Link establishment request procedure: Through this procedure BSC request the
setup of a multiframe data link on the radio channel.
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Link release indication procedure: Through this procedure BTS indicates to BSC
that a radio link has been released at the initiative of an MS.
Link release request procedure: Through this procedure BSC requests the BTS to
release a radio link.
Transfer procedure of a transparent L3-message in acknowledged mode:
Through this procedure BSC requests the BTS to send a transparent Um interface
RIL3 message in acknowledged mode.
Receive procedure of a transparent L3-message in acknowledged mode:
Through this procedure BTS indicates the BSC to receive a transparent Um
interface RIL3 message in acknowledged mode.
Transfer procedure of a transparent L3-message in unacknowledged mode:
Through this procedure BSC requests the BTS to send a transparent Um interface
RIL3 message in non-acknowledged mode.
Receive procedure of a transparent L3-message in unacknowledged mode:
Through this procedure BTS indicates the BSC to receive a transparent Um
interface RIL3 message in non-acknowledged mode.
Link error indication procedure: Through this procedure BTS indicates BSC
incase of any abnormality in the radio link layer.
II. Dedicated channel management procedures
Channel activation procedure: Through which the BSC sends commands to BTS
to activate a dedicated channel for a certain MS. After the activation, BSC assigns
the channel to the MS through commands such as Immediate Assign, Assign
Command, Additional Assignment or Handover commands.
Channel mode modify procedure: This procedure is used by BSC to request BTS
to change the mode of the activated channel.
Handover detection procedure: This procedure is used between the target BTS
and target BSC to detect the handover access of MS.
Start ciphering procedure: Used for starting the ciphering procedure defined in TS
GSM 04.08.
Measurement reporting procedure: It includes the necessary basic measurement
reporting procedure and optional measurement reporting procedure with
preprocessing. BTS reports all parameters related to handover decision to the BSC
through it.
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SACCH deactivation procedure: According to the requirements of channel release
procedure specified in TS GSM 04.08, BSC uses this procedure to deactivate TRX
related SACCH channel.
Radio channel release procedure: BSC uses this procedure to instruct BTS to
release a radio channel, which is not in use state.
MS power control procedure: BSS uses this procedure to control the transmitting
power of the MS related to a specific activated channel. MS power control decision
must be implemented in BSC, and as an optional procedure in BTS.
Base station transmission power control procedure: BSS uses this procedure to
control the transmission power of the activated channel in TRX. The base station
transmitting power control decision should be implemented in BSC, or in BTS.
Connection failure procedure: BTS uses this procedure to indicate to BSC that an
activated dedicated channel is already disconnected.
Physical environment content request procedure: BSC uses this procedure to
obtain the physical parameters of a specific channel. This usually occurs before a
channel change. This is an optional procedure.
SACCH information change procedure: BSC uses this procedure to instruct BTS
to change the information (system information) filled in a specific SACCH channel.
III. Common channel management procedures
MS channel request procedure: This procedure is triggered when TRX detects
random access ("channel request" message) from the mobile station.
Paging procedure: It is used to page information on a specific paging sub-channel.
It is initiated by MSC and paged through BSC. BSC determines the paging group to
be used according to the IMSI of the called MS. The value of this paging group
together with the identity of the mobile station is sent to BTS.
Immediate assignment procedure: When a mobile station accesses BTS, BSC
uses this procedure to assign a dedicated channel for the mobile stationimmediately.
Deletion indication procedure: BTS uses this procedure to indicate to BSC that a
RIL3-RR immediate assignment message is deleted (i.e., not put in the AGCH array)
due to overloading of the AGCH channel.
CCCH load indication procedure: BTS uses this procedure to indicate to BSC the
load on a specific CCCH channel.
Broadcast information change procedure: BSC uses this procedure to instruct
the BTS to broadcast new system messages on the BCCH channel.
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Short message cell broadcast procedure: BSC uses this procedure to request
BTS to issue cell broadcast short messages.
IV. TRX management procedures
SACCH filling information change procedure: BSC uses this procedure to
indicate BTS to use new system information on all downlink SACCH channels.
Radio resources indication procedure: BTS uses this procedure to indicate the
interference level on each idle dedicated channel of TRX to BSC.
Traffic control procedure: FUC uses this procedure to indicate the overload
condition of TRX to BSC, the cause may be CCCH overload, ACCH overload or
processor overload.
Error reporting procedure: BTS uses this procedure to report the BSC about
detected downlink message errors that can not be reported by other protocols.
5.5 Operation and Maintenance The BTS30 also provides powerful operation and maintenance functions. It has four
major functional modules, including the software loading, the configuration of object
attributes of the base station, the equipment management and the operational status
monitoring.
Software loading: BSC stores copies of software of all BTS boards. So when BTS
operates for the first time after the installation, BTS successfully resets or BTS
software is upgraded, the BSC will performs software loading to BTS.
Configuration management: including attributes configuration of such managed
objects as sites, cells, radio carriers, and channels, as well as the management of
Abis interface and transmission equipment.
Equipment management: including the detection of equipment switchover,
resetting, and faults, performance testing, statistics measurement and status event
reporting.
Running status monitoring: including the monitoring and recording of various
message flows, status conversion processes, and change of environment
parameters during the operation of the base stations.
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5.5.1 Software Loading
I. TMU software loading
After the power on or manual/auto restart of the TMU, it will request the BSC for the
software version confirmation to ensure that the version acknowledged by the BSC
is in operation. If the version number is incorrect, the BSC will load the correct
version to the TMU.
All software loaded from the BSC to the TMU is stored in the Flash RAM of the TMU.
When the BSC requests the activation, the TMU will execute the operation of the
new software version.
II. Software loading from TMU to boards
After the manual/auto resetting, the board will send the software version
confirmation request to TMU. TMU checks whether its version number is identical to
that stored in the FLASH MEMORY. If it is, TMU will directly activate the version of
this software. If it is not, TMU will load the version previously saved to the board, so
as to ensure that the proper version is loaded and operating in this board. In
addition, the BSC can also update the software version of the board through TMU.
The validity of the software is of great importance, therefore, both layer 2 and layer 3
have the checking and reloading system to guarantee high reliability.
III. Centralized management of software versions
To facilitate software updating, this function is provided to load software from BSC or
MMI to the boards of BTS. As mentioned before, this function is implemented
through the TMU. A TMU stores two versions of the software for the boards TMU,
TBU (including SCP, CHDSP and EQDSP) and STU (including SCP and DSP), etc.,
and their version number is recorded respectively. The BSC or MMI can activate
either of the two software versions to run or load new versions. The BSC or MMI can
get the software version information of all the boards from the TMU, and display the
information at the graphical interface.
5.5.2 Abis Interface Management
I. Abis interface management
Abis interface is a standard interface between BTS and BSC, which takes the TS
switching equipment as the main object of its management. It also involves the
management of part of the data link layers.
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The Abis interface management covers two aspects: the connection management of
layer 1 and management of part of the signaling link layer. The Abis interface TS
switching equipment of the BTS30 fulfills the switching between the E1 line and HW
line inside the rack to accomplish the layer 1 connection of the link.
Signaling link connections should also be established on layer 2.
The Abis interface management has the following functions:
TEI set up (for both OML and RSL)
Signaling channel connection set up
Signaling channel disconnection
Traffic channel connection set up
Traffic channel disconnection
II. Transmission management
Transmission here refers to the cascade transmission of E1 signals. As both the
BTS30 E1 transmission and the Abis timeslot switching are carried out by BIU,
implementation of this function is similar to that of Abis interface management. Link
connection on layer 1 is set up by changing the timeslot switching configurations
between BIU and E1 lines.
One BSC normally can carry multiple SITEs. Between BSC and SITEs, multiple
connection modes are supported, such as star, chain, tree, ring and hybrid
networking. Except star networking, all other modes involve the cascademanagement of E1 signals, i.e., forwarding traffic and signaling to subsequent sites.
The ring connection mode also involves loop management.
Transmission management has the following functions:
Multi-point connection set up
Multi-point connection deletion
Ring connection set up
Ring connection deletion
5.5.3 Air Interface Management
The air interface management mainly involves the parameter configuration that
determine the physical channel and the logical channel of the air interface, including
the configuration of the attributes of the cell, carrier frequency and transmission
channels.
The physical channel parameters of the air interface mainly include the carrier and
the timeslot parameters, which are configured according to the carrier attributes.
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The logical channel parameters mainly include the channel types, and the
messages appeared on them, especially the system message, which are
determined by the attributes of both the channel and the cell.
I. BTS attributes setting
BTS attributes refer to the parameters applicable to the whole cell, but not related to
specific carriers and channels, including:
1) Interference level limit
2) Interference average value
3) Connection failure decision threshold: the BER or the receiving level threshold.
4) T200, including the T200 timing values of the following channels:
SDCCH
FACCH (full rate) FACCH (half rate)
SACCH (relevant to TCH, SAPI=0)
SACCH (relevant to SDCCH)
SDCCH (SAPI=3)
SACCH (relevant to TCH, SAPI=3)
5) Maximum timing advance
6) Overload indication period
7) CCCH load threshold
8) CCCH load indication period
9) RACH busy decision threshold
10) RACH load average TS number
11) BTS air timer
12) Maximum number of physical channel message retransmissions (Ny1)
13) BCCH absolute RF number
14) Base station identification code (BSIC)
15) Configuration start time
II. Carrier frequency attributes setting
The carrier frequency attributes are the parameters relevant to the specific carrier
frequency, which include:
Maximal power descending of the RF
RF absolute channel numbers table
III. Channel attributes setting
The channel attributes refer to the parameters related to the specific channel,
including:
Channel combination mode
Frequency hopping serial number
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Mobile allocation index offset (MAIO)
RF absolute channel numbers table
Configuration start time
Training sequence number
IV. Air interface management extension
The operation and maintenance protocol of the base stations is mainly stipulated in
GSM 12.21 standards. This protocol is not yet perfect, and should be extended in
actual applications.
The BTS30 protocol extension includes two aspects: the setting of BTS extended
attributes (frequency hopping modes etc.), and the setting of sites extended
attributes, including environment parameters and clock hardware parameters (phase
locking reference source, DAC values). 5.5.4 Testing Management
Testing management is an important function of the base station maintenance. With
the help of this function, the user can determine and locate the fault in BTS. During
the normal operation of a base station, periodic tests should also be carried out over
certain items to trace the performance of the base stations and to predict the
possible faults of base stations.
It must be noted that with the increasing of base station maintenance functions,demands for testing functions become more stringent, which constitutes one of the
most extendable parts of operation and maintenance functions.
The BTS30 provides powerful testing functions with a large variety of test items
provided, mainly including:
1) TRX Abis link testing
2) Free burst testing
3) E1 self-loop testing
4) Functional object self-test, including:
Site self-test
Cell self-test
TRX self-test
Board self-test
5.5.5 Status Management
The status of various logical objects and physical objects of the base station is
stored in 3 entities, i.e., BSC, TMU, and boards. The correctness and consistency of
states stored in these 3 entities is one of the basic conditions for the normal
operation of the base station.
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The base station status management mainly involves 3 kinds of status:
management status, operation status, and availability status. Management status is
required to remain consistent from top to bottom, i.e., from BSC, TMU to boards,
while operation status is required to remain consistent from bottom to top. Availability status is the specific explanation of operation status.
Consistency of these 3 kinds of states is vitally important, for inconsistency will
result in resources waste as some available channels might not be distributed, or
abnormal service provision occurs due to possible distribution of damaged
channels.
TMU monitors the setup and disconnection of various communication links, and
checks the status of the boards in realtime. If any change occurs, it will immediately
report the change to BSC and MMI, and display it through the OMC.
5.5.6 Processing of Event Reports
Event report mainly refers to the report of internal base station errors, or fault reports
generated during alarming.
Considering the importance of such reports, it must be ensured that each command
and report reaches the destination and is correctly explained, i.e., there must be a
response mechanism. The response mechanism from top to bottom is stipulated in
GSM protocol 12.21, but the response mechanism from bottom to top is not yet
specified in the protocol. For the sake of simplicity and to save command codes, the
upward reports are directly returned as responses.
A base station can be managed through BSC and MMI. For inquiry operations, both
can perform the operations simultaneously. For operations that may change the
running status of the base station (e.g., parameters setting), only the one with the
management authority can perform such operations. By default, BSC enjoys the
management authority.
To obtain the management authority, MMI must first send to BSC a management
status changing request. After BSC confirms the request, it will issue a managementstatus changing command, so as to shift the management authority to MMI. When
MMI operation ends, it must request BSC to take back its management authority.
The BTS30 may involve two kinds of alarms: board alarms and environment alarms.
I. Board alarms When any board alarm occurs or disappears, the board reports it to TMU, and TMU
will report it to BSC or MMI immediately. According to the cause, an alarm may be
classified into one of the following categories:
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Transmission and communication alarms: This mainly refers to an
out-of-synchronization alarm of either the local end or remote end of E1 port, or loop
interruption alarm.
Clock alarms: various kinds of clock source alarms and TBPU clock alarms.
Power supply alarm: over/under voltage alarms of power supply of the carrier part
and power supply fault alarms.
General alarms: hardware faults of various boards, internal bus alarms, and
software running errors.
After receiving alarm messages from a board, TMU will take the corresponding
measures according to the alarm severity. For a critical alarm, immediate measures
will be taken to reduce any possible damage, such as resetting the board or
switching off the carrier power supply, etc.
TMU reports all the alarms to BSC and MMI to display them at the graphic interface.
II. Environment alarms
Environment alarms (including fire, smog, intruder, water, temperature and humidity
etc.) are collected by the environment monitoring instrument. On receipt of an alarm,
TMU will activate the attached device(s) through the alarm box, such as
air-conditioner, fire-extinguisher, smoke-removing devices, and dehumidifier. Also, it
will report it to BSC and MMI for it to be displayed at the graphic interface.
5.5.7 Equipment Management
I. Equipment switchover
To guarantee the system reliability, the BTS30 provides active/standby configuration
for important components. In case of any abnormality in the active boards, the
system can shift the service to the standby boards automatically or manually.
In addition, the BSC can send a switchover command to perform switchover on theobject desired. When a board receives a switchover command from BSC, activated
by this command, it directly receives commands from the TMU to initiate switchover.
Otherwise, the switchover is initiated by the board itself, and will be directly reported
after the switchover.
II. Operation starting
The operation of the equipment involves the steps and synchronization during the
starting. The operation starting function is used to start the equipment at the proper
time.
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III. Re-initialization
In some cases, the running object may require re-initialization, which is mostly
caused by the failure of the equipment or the need to reconfigure large quantity of
data. And it can be initiated by the command from BSC via TMU.
IV. Configuration of site output (external devices)
There may be some external devices for each BTS, such as air-conditioner,
dehumidifier, humidifier, and controllable camera etc. The controlling over these
devices can be regarded as output variables.
V. Power supply management commands
When some critical faults occur to carrier equipment, such as too high temperatureor standing wave ratio exceeding the threshold, make the equipment quit serving
any more or power off the carrier part (including the power amplifier) so as to
prevent it from being completely damaged. In case of mains power supply failure,
the base station can turn off some TRXs, and keep only the BCCH carrier working to
handle the necessary data so as to reduce the voice services and prolong the
service of standby power supply.
VI. Software and hardware version's query
During the maintenance, for example, when the software is being updated, usually
the software and hardware version number shall be checked. After TMU is started,
the software and hardware version number shall be read so as to upgrade the
database for future query, and to judge whether the version number is identical with
the configuration or not.
VII. Board re-initialization after resetting
After being reset, boards will request for re-initialization. The re-initialization process
is to configure the required parameters first, and then restart the board.
VIII. Processing of board and environment alarms
Base station alarms mainly includes two types: board alarms and environment
alarms. When there is any abnormality in board itself or its resources, a board
running failure alarm will be reported to TMU. Environment alarms are collected by
TMU and alarm box. TMU reports all alarm messages timely to BSC and take
necessary emergency processing measures.
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5.5.8 Site Configuration
I. Configuration of logical parameters
The configuration of site logical parameters is to determine such basic site
configuration parameters as the number of sectors, baseband processing units and
carrier units etc. Logical units can be added or deleted during future network
expansion or network optimization.
II. Configuration of physical boards
Site physical board configuration is to configure, add or delete given boards for sites
in configuration tables.
5.5.9 Tracing Operations
I. Interface tracing
It is usually necessary to trace various interface messages during operation, for the
sake of convenient debugging, detecting and locating of faults occurred during
normal operation.
The interfaces now available for tracing include various interfaces between the TMU
layer 3 and its lower levels, and the air interface (Um interface). What's more, otherinterfaces can be added to the tracing list for the sake of convenient debugging.
II. Resource tracing
The resource utilization conditions are the important parameters for analyzing the
program efficiency and status, and important indexes for testing whether the system
meets the requirements or not. Resource tracing can be started or stopped
according to the actual need to adjust the traffic flow.
III. System logs
To keep system operation process records is one of the best way to trace the errors.
The TMU software log mainly keeps two types of information: one is the interface
message mentioned above, and the other is the program running errors. The board
log is reported to the TMU, from which it is transferred transparently to the BSC or
saved in the log buffer area.
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5.5.10 Other Functions
I. Attributes query
Most of the attributes of managed objects are configured by the BSC during base
station initialization, and part of them may be modified during the operation. Any of
the attributes can be queried during maintenance, which is helpful to decide the
operation status of the base station.
II. Alarm threshold setting
Different threshold values can be set through OMC for the protection of different
objects so as to avoid system down. For example, alarm limits can be set on the RF
working power and the standing-wave ratio etc.
III. OML link test
In order to guarantee the proper operation of OML link and to supervise its status,
the BSC transmits some routine messages to the TMU to supervise this link. In
addition, the BSC realtime clock is also transmitted, which is used as the TMU
superior level clock reference.
IV. Transparent commands
For debugging convenience and adding of new functions, transparent commands
can be used to flexibly transfer some customized commands or debugging
commands to some designated boards.
V. Query on-site board
The on-site board refers to the board which has been installed in the slot and hasn’t
been configured on the data configuration console. This kind of boards can be
queried on the board maintenance panel and are differentiated by color.
5.6 System Indices
I. Power consumption
Test conditions: temperature: 25®C; relative humidity: 80%; power amplifier power
output: 40W. Measured at the inlet of the cabinet power supply (the output of the
primary power supply) 30 minutes after the power-on and normal working of the
system.
The power consumption of the cabinet in different configurations are listed in
Table 5-1.
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Table 5-1 Power consumption of the BTS30 in different configurations
Number of TRXs Voltage (V) Current (A) Power consumption (W)
6 26.8 44.3 1187
5 26.8 37.8 1013
4 26.8 31.2 836
3 26.8 24.7 662
2 26.8 17.2 461
1 26.8 10.7 287
II. Clock
Frequency: 1.3×107 Hz, with the precision upon leaving the factory better than 0.1
Hz.
Frequency deviation varied with temperature changes: < ± 0.05 ppm (temperature
from 0®C to 70®C). Annual aging rate: < ± 0.1 ppm.
III. Environmental conditions
Since the BTS30 is an indoor base station, the automatic air-conditioning system is
required in the room.
It can work smoothly within the temperature range -5®C~+45®C under 15-85%
relative humidity.
The environmental alarm box is available to supervises the environmental
parameters and report the alarms.
IV. System reliability
Table 5-2 The mean time between failures (MTBF) of BTS30
No. Cell confi guration Failure rate accumulated (10-6h) MTBF(h)
1 O(1) 37.452 35000
2 O(2) 33.996 30000
3 S(2/2/2) 56.560 18000
4 S(4/4/4) 75.414 15000
5 S(6/6/6) 97.834 11000
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V. Physical characteristics
Dimensions: 1600 mm (H) × 600 mm (W) × 450 mm (D). Weight: Empty cabinet 85 kg.
Fully configured cabinet 180kg. 5.7 Radio Interface Indices
I. The functional frequencies of M900 BTS30
Uplink (MHz) Downlink (MHz)
Primary band 890-915 935-960
II. The functional frequencies of M1800 BTS30
Up Link (MHz) Down Link (MHz)
Primary band 1710-1785 1805-1880
5.7.1 Receivers
I. Receiving sensitivity
Testing conditions: FCH/FS channel, no frequency hopping, BER and frame deletion
rate meet the requirements of Table 1 of GSM 05.05 standards.
1) M900 BTS
Static sensitivity: better than -110dBm.
Multipath sensitivity: better than -104dBm under TU3, TU50, RA250 and HT100
transmission conditions.
2) M1800 BTS
Static sensitivity: better than -109dBm.
Multipath sensitivity: better than -104dBm under TU3, TU50, RA250 and HT100transmission conditions.
II. Receiver input level range
1) M900 BTS
In the static transmission condition, the relationship between the input levels and the
M900 BTS Type II BER measured on the TCH/FS channel is given in Table 5-3:
Table 5-3 Relationship between the M900 BTS Type II BER and input levels
Input level range Static sensitivity level~-84dBm -84dBm~-40dBm -40dBm~-15dBm
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Type II BER <2 % <10-4 <10-3
2) M1800 BTS
In the static transmission condition, the relationship between input levels and M1800
BTS Type II BER measured on the TCH/FS channel is given in Table 5-4:
Table 5-4 Relationship between the M1800 BTS Type II BER and input levels
Input level range Static sensitivity level~-84dBm -84dBm~-40dBm -40dBm~-23dBm
Type II BER <2 % <10-4 <10-3
III. Blocking features
1) M900 BTS
When the sine wave interference signals with frequency and level as shown in
Table 5-5 are input together with the -101dBm useful signals into the M900 BTS
receiver, the BER still meets the requirements.
Table 5-5 Frequency and level of M900 BTS sine wave interference signals
Frequency (inband) 600kHz |f-f 0|<800kHz 800kHz |f-f 0|<3.0MHz 3.0MHz |f-f 0|
Level (dBm) -26 -16 -13
Frequency (outband) 0.1MHz f<870MHz 925MHz f<12750MHz
Level (dBm) 0 0
Where f 0 is the useful signal frequency, and f is the interference signal frequency. 2) M1800 BTS
When the sine wave interference signals with frequency and voltage level as shown
in Table 5-6 are input together with the -101dBm useful signals into the M1800 BTS
receiver, the BER still meets requirements
Table 5-6 Frequency and level of M1800 BTS sine wave interference signals
Frequency (inband) 600kHz |f-f 0|<800kHz 800kHz |f-f 0|<3.0MHz 3.0MHz |f-f 0|
Level (dBm) -35 -25 -25
Frequency (outband) 0.1MHz f<1690MHz 1805MHz f<12750MHz
Level (dBm) 0 0
Where f 0 is the useful signal frequency, and f is the interference signal frequency.
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IV. C/I and bit error code rate
When the useful signal is -84dBm, relationship between the TCH/FS channel TYPE
II BER and C/I measured under the non-hopping multipath condition is shown as in
Table 5-7. This relationship in M900 is the same as that in M1800.
Table 5-7 Relationship between the BTS TYPE II BER and C/I
Interf erence frequency C/I(dB) TCH/FS TYPE II BER
f = f 0 9 TU1.5 RBER<4.0%
| f - f 0| = 200kHz -9 TU50 RBER<8.1%
| f - f 0| = 400kHz -41 TU50 RBER< 8.1%
f is the random continuous GSM modulated interference signal frequency, and f 0 is
the useful signal frequency.
V. Inter-modulation response suppression
1) M900 BTS
For M900 BTS, when the useful signals with a sensitivity 3dB higher than the
reference sensitivity are input to the receiver simultaneously with two -43dBm
interference signals, the TYPE II BER measured on the TCH/FS channel is better
than 2%, and the carrier relationship and modulation forms of interference signalssatisfy GSM 11.21 specifications.
2) M1800 BTS
For M1800 BTS, when the useful signals with a sensitivity 3dB higher than the
reference sensitivity are input to the receiver simultaneously with two -49dBm
interference signals, the TYPE II BER measured on the TCH/FS channel is better
than 2%, and the carrier relationship and modulation forms of interference signals
meet GSM 11.20 specifications.
VI. Stray radiation The testing result is the same for both M900 BTS and M1800 BTS:
Radiation within 9kHz~1GHz: <-57dBm
Radiation within 1GHz~12.75GHz: <-47dBm
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5.7.2 Transmitters
I. Average carrier frequency power
For M900 BTS and M1800 BTS, the average carrier frequency power of the
transmitter measured at the combiner input end is 46dBm with a tolerance of
±1dBm.
II. Power Control
1) Static power control
Both the M900 BTS and M1800 BTS transmitters have 10 levels for static power
adjustment, with a step length of 2±1dB. On each static power level, the absolute
precision is better than ±3dB.2) Dynamic power control
Both the M900 BTS and M1800 BTS transmitters have 15 levels for dynamic power
adjustment, with a step length of 2±1.5dB. On each dynamic power level, the
absolute precision is better than ±3dB.
III. Carrier frequency envelope
Power flatness of the 147 bit useful part: <±1dB.
Cutoff timeslot power: <-30dBc.
The ramping up and down of the power bursts is in accordance with the
power-versus-time template (Figure 5-5).
+4+1-1-6
-30
10 8 10 10 8 10542.8t(us)
dB
Figure 5-5 Power-versus-time template
Note: Testing results are the same for both M900 and M1800 BTSs.
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IV. Transmission spectrum
1) Modulated spectrum
Power of various deviating frequency points of M900 and M1800 BTSs are shown in
Table 5-8 and Table 5-9 respectively.
Table 5-8 Power of various deviating frequency points of M900 BTS
Frequencydeviation
100kHz 200kHz 250kHz 400kHz600kHz~1.2MHz
1.2MHz~1.8MHz
1.8MHz~6MHz
ƒ 6MHz
Max. powerlevel (dBc)at relativecarrier
0.5 -30 -33 -60 -70 -73 -75 -80
Table 5-9 Power of various deviating frequency points of M1800 BTS
Frequencydeviation
100kHz 200kHz 250kHz 400kHz600kHz~1.2MHz
1.2MHz~1.8MHz
1.8MHz~6MHz
ƒ 6MHz
Max. powerlevel (dBc)at relativecarrier
0.5 -30 -33 -60 -70 -73 -75 -80
2) Transient spectrum
For M900 and M1800 BTSs, the power levels caused by handover at the various
deviating frequency points are shown in Table 5-10 and Table 5-11 respectively.
Table 5-10 Power levels of M900 BTS caused by handover at various deviating frequency points
Frequency deviat ion 400kHz 600kHz 1.2MHz 1.8MHz
Maximum power level (dBc) ofrelative carrier
-57 -67 -74 -74
Table 5-11 Power levels of M1800 BTS caused by handover at various deviating frequency points
Frequency deviat ion 400kHz 600kHz 1.2MHz 1.8MHz
Maximum power level (dBc) ofrelative carrier
-50 -58 -66 -66
V. Intermodulation suppression
1) M900 BTS
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For interference signals coming from the antenna into the transmitter, the
intermodulation signal suppression of the transmitter is over 70dBc (or under
-36dBm), and the levels of the 3rd order and 5th order intermodulation signals falling
within the 890~915MHz frequency band are under -98dBm.
The suppression of the intermodulated signal after multi-carrier combination is over
70dBc (or under -36dBm) when it falls within the 935MHz~960MHz frequency band,
and that falling within the 890MHz~915MHz frequency band has an output level
under -98dBm.
2) M1800 BTS
For interference signals coming from the antenna into the transmitter, the
intermodulation signal suppression of the transmitter is over 70dBc (or under
-36dBm), and the levels of the 3rd order and 5th order intermodulation signals falling
within the 1710~1785MHz frequency band are under -98dBm.
The suppression of the intermodulated signal after multi-carrier combination is over
70dBc (or under -36dBm) when it falls within the 1805MHz~1880MHz frequency
band, and that falling within the 1710MHz~1785MHz frequency band has an output
level under -98dBm.
VI. Spurious emission
Conductive stray radiation measured at antenna connection points meets the
following requirements:1) M900 BTS
9kHz~1GHz: <-36dBm
890MHz~915MHz: <-98dBm
1GHz~12.75GHz: <-30dBm
2) M1800 BTS
9kHz~1GHz: <-36dBm
1710MHz~1785MHz: <-98dBm
1GHz~12.75GHz: <-30dBm
VII. Frequency deviation and phase deviation
Transmitting signal frequency deviation: <0.05ppm
Transmitting signal phase deviation: <5°(rms)
<20°(peak)
Note: For M900 BTS and M1800 BTS, the testing results are same.