capacity planing
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Huawei ConfidentialHuawei Technologies Co., Ltd.
GSM Radio
Network
Capacity Planning
India NTS Technical Support
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Page 2Huawei Technologies Co., Ltd.
Basic Knowledge
Capacity Planing Strategy
BTS Configuration
Channel Configuration
Capacity Solution
Contents
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Page 3Huawei Technologies Co., Ltd.
Basic Knowledge
Traffic Load
BHCA: Busy Hour Call Attempt
GoS
Grade of Service
It is the probability of a call in a circuit group being blocked or delayed for
more than a specified interval.
For a Lost Call system, the GoS can be measured using such equation:
)(3600
TimeHoldingCallAvg.BHCABH@LoadTrafficAvg. Erlang
callsofferedofNumber
callslostofNumberServiceofGrade
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Page 4Huawei Technologies Co., Ltd.
Basic Knowledge
Erlang-B Table
Assumption: All traffic through the network is pure-chance traffic
i .e. al l call arr ivals and termin ations are independent random
events
There is statistical equilibrium
i .e., the average number of cal ls does not ch ange
Full availability of the network
i .e., every outlet from a switch is access ible from every inlet
Any call that encounters congestion is immediately lost.
Erlang-B equation of GoS
A = Expected traffic intensity in Erlangs; N = Number of circuits in group.
N
K
K
N
KA
NAerviceGrade of S
0
!
!
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Page 5Huawei Technologies Co., Ltd.
Basic Knowledge
Capacity Planning Strategy
BTS Configuration
Channel Configuration
Capacity Solution
Contents
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Page 6Huawei Technologies Co., Ltd.
Capacity Planning Strategy
Key point of RNP
Its always changing along with the network developing
Initial phase
Mainly pay attention to coverage, capacity is not the problem
Capacity planning is very easy:
Coverage
Dimension
Coverage
area per Site
Traffic model
Subscribers
Distribution
Traffic Load
pre Site
TRX/Channel/
.
Configuration
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Page 7Huawei Technologies Co., Ltd.
Capacity Planning Strategy
Developing phase
Pay attention to both coverage and capacity:
Coverage
Dimension
Coverage
area per Site
Traffic model
Subscribers
Distribution
Traffic Load
pre Site
TRX/Channel/
Configuration
LimitationJudgment
Figure out the
max. configuration
Frequency
Planning
Channel
Configuratio
n
END
Traffic Load
per Site
Coverage
area per Site
Coverage
limitation
BTS Quantity
Capacity
limitation
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Page 8Huawei Technologies Co., Ltd.
Capacity Planning Strategy
Mature phase
Pay more attention to capacity while coverage is good enough
Solve the congestion by
Cell sp l i t
Micro c el ls
Special In-Bu i ldin g Coverage system
Dual-band network
Capaci ty enhancement technolog y
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Page 9Huawei Technologies Co., Ltd.
Capacity Estimation
Capacity requirement contains
No. of subscribers
Population, distribution and increasing rate
Mobile penetration & market share
Roaming factor, active factor, events (festival),
Traffic model
Which relate to the actual situation such as society, economy, user habit
and so on.
Capacity estimation
Method
Short-term, Long-term; Analogy, Modeling,
Reference
Population, existing radio networks, PLMN, GDP,
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Page 10Huawei Technologies Co., Ltd.
Basic Knowledge
Capacity Planning Strategy
BTS Configuration
Channel Configuration
Capacity Solution
Contents
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Page 11Huawei Technologies Co., Ltd.
Basic Knowledge of Frequency Planning
GSM frequency resource
GSM900
fUL(n) = 890 + n * 0.2 MHz
fDL(n) = fUL(n) + 45 MHz
DCS1800
fUL(n) = 1710 + (n 511) * 0.2 MHz
fDL(n) = fUL(n) + 95 MHz
C/I & CA
C/I request in GSM: 9dB (extra 3dB margin in the project)
Carrier/Interference, interference from the signal with same frequency
CA request in GSM: -9dB (extra 3dB margin in the project)
Interference from the signal with adjacent frequency, in GSM is 200KHz
890MHz 915MHz 935MHz 960MHz
1710MHz 1785MHz 1805MHz 1880MHz
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Page 12Huawei Technologies Co., Ltd.
loose
Frequency Reuse
Frequency reuse
{f1, fj, fk}
{f1, fj, fk} {f1, fj, fk}
Reuse Reuse
More and more mobile subscribersfnfn
fn
RD
fn
fn
fnfn
Frequency reuse factor
i .e. number of cel ls in a frequency reuse clusterTRX
ARFCN
reuse
N
Nf
0 12 20t igh t
High efficiency
Serious interference
Good quality, easy to plan
Low efficiency
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Page 13Huawei Technologies Co., Ltd.
Frequency Reuse
Frequency reuse pattern
Common frequency reuse pattern
4*3 (or 3/12)
A clu ster has 4 si tes
3 cel ls per site
General ly for BCCH frequency planning
Tight frequency reuse
MRP (Multiple frequency Reuse Pattern)
Grouping frequency
Use dif ferent reus e pattern for d if ferent TRX layer
Frequency Hopping (1*3, 1*1)
No. of ARFCNs in MA shou ld be at least 2 times more than no. of
TRXs
Usual ly BCCH layer doesnt adopt hopping for good q uali ty
IUO
Use tight reuse pattern for o verlay-cel ls
B3
A1
C1
B1
D1A2
A3B2
B3
C2
C3D2
D3
B1B2
B3
D3A1
C1
B1
D1A2
A3
B2
B3
C2
C3D2
D3
A1
C1
A2
A3
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Page 14Huawei Technologies Co., Ltd.
BTS Configuration
Frequency resource, Capacity and Quality
Max. BTS Configuration China Unicom has 6MHz GSM900 frequency (29 ARFCNs)
max. BTS configuration while 4*3 reuse?
max. BTS configuration while 1*3 hopping?
Capacity
Quality
Balance
AvailableFrequency
Frequency
Reuse Pattern
Interference
RxQual BER Range
MOS
Non-
Hop
Hop
0 12.8% E E
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Page 15Huawei Technologies Co., Ltd.
Basic Knowledge
Capacity Planning Strategy
BTS Configuration
Channel Configuration
Capacity Solution
Contents
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Page 16Huawei Technologies Co., Ltd.
Basic Knowledge of GSM Channels
Logical channel
Traffic CHannel and Control CHannel
4 kinds of CCH according to the function
BCH: Broadcast Channel
CCCH: Common Control Channel
DCCH: Dedicated Control Channel
CBCH: Cell Broadcast Channel
Channel combination types (GSM Phase 2)
TCH/F + FACCH/F + SACCH/TF
FCCH + SCH + BCCH + CCCH FCCH + SCH + BCCH + CCCH + SDCCH/4(0..3) + SACCH/C4(0..3)
SDCCH/8(0..7) + SACCH/C8(0..7)
CCH
BCH
CCCH
DCCH
CBCH
FCCH
SCH
BCCH
PCH
AGCH
RACH
SDCCH
SACCH
FACCH
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Page 17Huawei Technologies Co., Ltd.
Basic Knowledge of GSM Channels
BCCH
It carries very important information such as
list of frequencies used in cell, cell ID, location area ID, list of neighbor cells,
access control and DTX information, etc.
It transmit at a constant power all the time from the BTS.
Usually the BCCH TRX doesnt hopping, 4*3 reuse
SDCCH
SDCCH bears such traffic as following:
Mobility management such as location update;
Radio resource management such as call setup;
Point to point SMS, etc.
SDCCH/8 & SDCCH/4
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Page 18Huawei Technologies Co., Ltd.
Channel Configuration
BCCH Configuration
Only 1 BCCH per cell; TS0 of TRX0 Combined BCCH (considering SDCCH traffic)
TCH Configuration
8 channels (i.e. time slots) per TRX
n = No. of TRX
Consult Erlang-B table
Exercises
No.SDCCH-No.BCCH8TCHofNo. n
TRX No. TCH No. GoS Traffic (Erl)
2 ? 2% ?
? ? 2% 15
? ? 5% 15
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Page 19Huawei Technologies Co., Ltd.
SDCCH Configuration
SDCCH capacity requirement
Which relate to
Traffic model, user habit, network structure, etc.
Default value:
~5mErl/user @ BH
20%~25% of voice traffic load
Event Normal
Cell
Inner Cell Edge Cell Notes
Location update 0.4 0 1.2 1, Unit:
mErl/user
2, TCH traffic
load
assumption:
25mErl/user
Periodic location update 1.8 1.8 1.8
IMSI attach/detach 0.8 0.8 0.8
Call setup 0.9 0.9 0.9
Point to point SMS 1.0 1.0 1.0
Other applications 0.2 0.2 0.2
SUM 5.1 4.7 5.9
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Page 20Huawei Technologies Co., Ltd.
SDCCH Configuration (cont.)
GoS of SDCCH
SDCCH/8, of TCHs GoS
SDCCH/4, of TCHs GoS
For instance, TCH GoS = 2%, and then
GoS of SDCCH/8 = 0.5%
GoS of SDCCH/4 = 1%
SDCCH type
SDCCH/4, combine with BCCH (TS0); 4 sub-channels
SDCCH/4 + CBCH, 3 sub-channels
SDCCH/8, on any time slot except for BCCH time slot, 8 sub-
channels
SDCCH/8 + CBCH, 7 sub-channels
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Page 21Huawei Technologies Co., Ltd.
SDCCH Configuration (cont.)
SDCCH configuration suggestion
TRX
No.
Without CBCH With CBCH
Normal cell Inner cell Edge cell Normal cell Inner cell Edge cell
1 SDCCH/4 SDCCH/8
2 SDCCH/8 SD/8 + SD/4
3 SDCCH/8 + SDCCH/4
4 2*SDCCH/8 SD/8 + SD/4 2*SDCCH/8
5 2*SDCCH/82*SDCCH/8
+ SDCCH/4
62*SDCCH/8
+ SDCCH/42*SDCCH/8 2*SDCCH/8 + SDCCH/4
7 2*SDCCH/8 + SDCCH/4 3*SDCCH/82*SDCCH/8
+ SDCCH/43*SDCCH/8
8 3*SDCCH/83*SDCCH/8
+ SDCCH/4
Simply calculating: 1 SDCCH/8 per 2 TRXs
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Page 22Huawei Technologies Co., Ltd.
Basic Knowledge
Capacity Planning Strategy
BTS Configuration
Channel Configuration
Capacity Solution
Contents
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Page 23Huawei Technologies Co., Ltd.
Half Rate Solution
Half Rate theory
Half Rate is a speech encoding system for GSM
Since the codec, operating at 5.6 kbit/s, requires half the
bandwidth of the Full Rate codec, network capacity for voice
traffic is doubled
HR Channel Allocation Principle
Be used in area with little interference
HR dynamic allocation
When network busy: HR > FR, for more capacity
When network idle: FR > HR, for better quality
Others
Priority ofSingle > Couple
Allocate channels on the TRX which cannot adjust rate firstly
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Page 24Huawei Technologies Co., Ltd.
Half Rate Solution
Capacity enhancement by HR
A S6 cell, 42 traffic time slots; GoS = 2%
Half rate ratio
By TRX: = HR_TRX_No. / Total_TRX_No.
By time slot: = HR_TS_No. / Total_TS_No.
By channel: = 2*HR_TS_No. / (2*HR_TS_No. + FR_TS_No.)
Ratio of Full
Rate Call
Required
TCHF No.
Capacity
(Erl)
Capacity of
all FR (Erl)
Capacity
Enhancemen
t
20% 14 59.1332.84
80%30% 20 53.43 62.7%
40% 24 49.64 51.2%
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Thank youwww.huawei.com
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