Huawei RNC Huawei RNC Capacity dimensionCapacity dimension
2
Capacity dimension
Principle for capacity dimension
Input from operator( Total subscribers in network,
traffic model)RNC capacity limitation( Erl, Throughput,BHCA)
Number of WRBS
Subscribers per WRBS
Nodebs per WRBS
Subscribers per Nodeb If Nodebs per WRBS >100
Radio Network dimension
3
Traffic Model Parameters
Traffic Parameter Value
BHCA CS per sub 0.6
BHCA total per sub 0.9
CS Voice per sub/BH 16,2mErl
CS Data per sub/BH 1,1mErl
CS Video Telephony call duration/BH 135sec
CS call duration/BH 135sec
Rel.99 PS per sub/BH 580bps
Total PS per sub/BH 1160bps
Timer for CH switching (DCH/FACH) 600-800msec
Location update rate sub/BH 2.2
Ratio of soft/softer HO/BH 0.8:0.2
Proportion of HO/BH 30%
Handover times/call/BH (inter/intra RNC SHO)
7,0 times/call
PS CH switching 4.0 times/call
Cell update/PSCall 3 times/call
Ratio of UL : DL (Rel.99/HSDPA) 1:3.6
Traffic Model from Vodafone
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Limitation
Limiting factor : throughput capacity 60Mbps/ WRBS
Limiting factor : BHCA capacity 75,000/ WRBS
Limiting factor : NodeB capacity 100 NodeB/ WRBS
Limiting factor : Cell capacity 300 NodeB/ WRBS
120Mbps / 60Mbps = 2e.g. 2 WRBS
60,000 / 75,000 = 0.8e.g. 1 WRBS
150 / 100 = 1.5e.g. 2 WRBS
400 / 300 = 1.3e.g. 2 WRBS
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RNC Dimension
RNC types Configure Iub Mbps NodeB Cell STM-1 E1(ATM) E1(IP) FE Channelized STM-1
Small Capacity RNC 1WRSS+1WRBS 77 100 300 30 64 64 32 2Medium Capacity RNC 1WRSS+3WRBS 206 300 900 26 192 192 96 6High Capacity RNC 1WRSS+6WRBS 461 600 1800 20 384 384 192 12
Traffic capacityMax. Capacity for different RNC types
Interfaces
RNC Types Configure Subscribers BHCAIu
Mbit/s
Iu CS12.2
AMR ErlIu CS Data
Erl
Iu PS I/B64/128Mbit/s
IurMbit/s
SmallCapaticy RNC 1 WRSS+ 1 WRBS 95000 85500 50.19 923.4 52.25 28.50 7.654
MediaCapacity RNC 1 WRSS+ 3 WRBS 287000 258300 151.56 2789.64 157.85 86.07 20.623
HighCapacity RNC 1 WRSS+ 6 WRBS 574000 516600 303.10 5579.28 315.7 172.13 46.162
Traffic Capacity
2*63 channalized E1s
VF CALL PROFILE DATAS
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RNC Capacity Limitation
There define a relationship between CS Erlang and throughput as follows:
1 CS Erlang = 16kbps throughput.
The relation comes from the processing consuming in WFMRb board.
CS Erlang and CS Throughput
For each RNC subrack :
CS throughput + PS throughput <= 60Mbps;
CS throughput < = 40Mbps;
CS Throughput and PS Throughput
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RNC Capacity Limitation
Supposing each call duration is 120s. The maximum CS throughput is 40Mbps, equals to 2500Erl.
Erl = BHCA * Call duration /3600
It can derive that : BHCA = 2500/(120/3600) = 75,000
BHCA calculation from CS 40Mbps
1. This index is used to measure the signaling processing capability in WSPUb.
2. The equivalent BHCAconsiders the procedure not only the call procedure, but also other signalling procedure, including SMS, IMSI attachment, location update, handover, cell update, URA update, etc.
3. The equivalent BHCA comes from the test data where the WSPUb CPU load is up to 80%.
4. The maximum equivalent BHCA is 360k and the WSPUb CPU load is 80%.
Equivalent BHCA
Note: The actual signaling capacity is limited by Integrated BHCA
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RNC Capacity Limitation
Basic Signaling Equivalent BHCACS BHCA per BM per BH 1.00 PS BHCA per RNC per BH 1.00 Location Area Update per RNC per BH 0.46 Routing Area Update per RNC per BH 0.46 Soft Handover Addition per RNC (intra/inter RNC) 0.26 Soft Handover Deletion per RNC (intra/inter RNC) 0.13
Softer Handover Addition per RNC (intra/inter RNC) 0.18
Softer Handover Deletion per RNC (intra/inter RNC) 0.09 CS Inter-RAT handover per RNC 0.56 PS channel switching per RNC 0.41 SMS per RNC per BH 0.46 Paging per RNC per BH 0.01 RRC REJ 0.15
Equivalent BHCA
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RNC Capacity Limitation
The maximum number of subscriber depends on the Integrated BHCA, call model and maximum data throughput:
equivalent BHCA(# Subscriber, call model) < Maximum Equivalent BHCA
Total throughput ( #Subscriber, call model) < Maximum data throughput
Maximum Subscribers number
60M per subRack
Procedure multiplied per Cost 360k
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Board information
1. WFMRb board is user plane processing board, handling the user data of AAL2 cell for Iu/Iub/Iur interface.
2. One RNC subrack contains 10 WFMRb with the maximum capability of 60Mbps for PS throughput or 40Mbps for CS throughput
3. The maximum user plane capability of WFMRb board in RAN5.1 is 6Mbps for PS packet processing. (MAC layer 7.2M)
4. For CS voice processing, 4Mbps can be handle for each WFMRb board.
5. WFMRb board contributes to the RNC total PS throughput as well as the CS throughput.
WFMRb
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Board information
1. WSPUb board is signalling processing board which handle the RANAP/ RNSAP/SS7/QAAL2/RRC/NBAP signaling;
2. Each WSPUb board could handle 75,000 BHCA (for typical traffic model) which does not includes the location update, paging, handover, SMS, attaching/detaching, etc. procedure.
3. The maximum equivalent BHCA is 360k and the WSPUb CPU load is 80%.
1. WOSEc board is Iub interface board.
2. Each WOSEc board can process 60Mbps throughput.
WSPUb
WOSEc
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Board Information
1. WFMRb and WSPUb are the main boards contributing to RNC capacity;
2. WOSEc board is the Iub interface board which is not the limitation for the RNC capacity;
3. WMUXb board is the switching board in each sub-rack and is not the limitation for the RNC capacity;
Summary
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Some analysis for New Year’s eve
1. Between 00:00-00:15, Altogether 21000 CS call attempts processed by RNC 121, but only 13000 RAB assigned by CN, so somewhere in CN must be overload.
2. Between 00:00-00:59, Altogether 51055 RRC connect rejected, among them 49683 belong to SMS, only 1372 belong to voice call.
Conclusion:
Between 00:00-00:15, both RNC and CN are overloaded.
RNC is overloaded (RRC rejection) with only 600 Erlangs because abnormal high number of SMS and Core network lack of reply.
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RRC EVOLUTION NEW YEAR CHARTSRRC.FailConnEstab.Cong
0100002000030000400005000060000
2006
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31 2
1:00
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2006
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2:00
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2007
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0:00
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RRC Attemps New year
0
20000
40000
60000
80000
100000
120000
140000
160000
2006
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7:00
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SumaDeRRCAttConnEstabUnknow n
SumaDeRRCAttConnEstabTmStrCall
SumaDeRRCAttConnEstabTmLw PrSig
SumaDeRRCAttConnEstabTmInterCall
SumaDeRRCAttConnEstabTmHhPrSig
SumaDeRRCAttConnEstabTmConvCall
SumaDeRRCAttConnEstabTmBkgCall
SumaDeRRCAttConnEstabReg
SumaDeRRCAttConnEstabOrgStrCall
SumaDeRRCAttConnEstabOrgInterCall
SumaDeRRCAttConnEstabOrgConvCall
SumaDeRRCAttConnEstabOrgBkgCall
SumaDeRRCAttConnEstabOgSubCall
SumaDeRRCAttConnEstabOgLw PrSig
SumaDeRRCAttConnEstabOgHhPrSig
SumaDeRRCAttConnEstabIRATCelRes
SumaDeRRCAttConnEstabIRATCCO
SumaDeRRCAttConnEstabEmgCall
SumaDeRRCAttConnEstabDetach
SumaDeRRCAttConnEstabCallReEst
SMS locUpdate
interRAT
CS call orig
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Mapping nodeb to SubRack40 nodeb on SubRack1 Half of NodeB on Cpu1
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SPU load evolutionCPU on WSPU:1:0
0%
20%
40%
60%
80%
100%
VS.MeanCPUUtil.SPU
VS.MaxCPUUtil.SPU
CPU WSPU1:1
0%
20%
40%
60%
80%
100%
30/1
2/20
06 0
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30/1
2/20
06 4
:00
30/1
2/20
06 8
:00
30/1
2/20
06 1
2:00
30/1
2/20
06 1
6:00
30/1
2/20
06 2
0:00
31/1
2/20
06 1
:00
31/1
2/20
06 5
:00
31/1
2/20
06 9
:00
31/1
2/20
06 1
3:00
31/1
2/20
06 1
7:00
31/1
2/20
06 2
1:00
01/0
1/20
07 2
:00
01/0
1/20
07 6
:00
01/0
1/20
07 1
0:00
01/0
1/20
07 1
4:00
01/0
1/20
07 1
8:00
01/0
1/20
07 2
2:00
VS.MeanCPUUtil.SPU
VS.MaxCPUUtil.SPU
WFMRName Time(As hour) VS.MeanCPUUtil.FMRVS.MaxCPUUtil.FMRWFMR:1:1 01/01/2007 0:00 26% 31%WFMR:1:12 01/01/2007 0:00 29% 34%WFMR:1:13 01/01/2007 0:00 26% 30%WFMR:1:14 01/01/2007 0:00 26% 31%WFMR:1:2 01/01/2007 0:00 27% 33%WFMR:1:3 01/01/2007 0:00 26% 31%WFMR:1:4 01/01/2007 0:00 29% 34%WFMR:1:5 01/01/2007 0:00 24% 29%WFMR:1:6 01/01/2007 0:00 27% 33%WFMR:1:9 01/01/2007 0:00 25% 30%
More space on User plane than Signalling plane
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SPU Dimension using current CPU load
• Total nber of subcribers in network: 1000k
• Erlangs_RNC121/TotalErlangs=2% =>20k Subs in RNC121
• Erlangs for each Nodeb from counters
• Nodeb to SPU map( worse SPU 40 nodeb among 87)
• The cpu load is 8% for common task if the traffic load is 0
• Cpu load with 275 Erlangs=40% at BH and limit is 80% => the SPU can handle 275*(80-8)/(40-8)=618 Erlangs => If 618/87=7 Erlangs per nodeB => a SPU can handle 550/7=78Nodeb
Erlangs per SPU=600*40/87=275 Erl
600Erl