S12 BR9 Dimensioning WI

Soc Classification level Presentation / Author / Date 1 © Nokia Siemens Networks

Nokia Siemens Networks S12 / BR9 Dimensioning Work Instruction


S12 / BR9 Dimensioning - Introduction

The purpose of this presentation is

• To show dimensioning example cases

• Compare Ex-Nokia and Ex-Siemens dimensioning (CS)

• To show dimensioning process

• Values are based on basic assumptions (traffic profile)

• This presentation is based on quick work instructions. Further information, please see dimensioning guidelines


S12 / BR9 Dimensioning – Traffic Profile used

In the example following traffic profile is used.

• Traffic per user 25mErl • Mean holding time 120s• Mobile originated calls (MO) 70%• Mobile terminated calls (MT) 30%• Handovers per call 1.5 handovers• Location updated per call 2 location updates• IMSI detach per call 0.1 detach• Paging response 63%• SMS (req(subs/1 hour) 1 SMS / subs• Terminated SMS 80%• Blocking 2%

• Traffic is assumed to be homogenous over BSC area. • Note! In real life Acell-BH > ALA-BH > ABSC-BH > AMSC-BH

• Note2! For example the number of BSC needed depends to a great extend on the traffic model per subscriber.


S12 / BR9 Dimensioning – Network layout

BSCMS

MS

BTS

TR

X

BTS

TR

XT

RX

BTS

TR

X

BTS

TR

XT

RX

TranscoderUnits

TranscoderUnitsE1/T1

E1/T1

TranscoderEQUIPMENT

E1/T1

E1/T1

MSC

SS7 links

Air Interface•CCCH

• TCH

•SDCCH

Abis Interface•Lapd links

•EDAP

•E1/T1

A Interface•E1/T1

Ater/Asub Interface•SS7 links

•E1/T1

•#ch,#E1


S12 / BR9 Dimensioning – Process +outputs

Air Interface Number of TRX’s

Start

Paging TRXsig Capacity

signaling Amount of SDCCH channels

Abis + Ater/Asub + A

interfacesNumber of PCM’s(#ch and #E1’s)

Transcoder Number of TC units

BSC

SS7

Number of BSC’s

Number and capacity of SS7 links

Finish

•Number of Subscribers

•Area size

•Coverage requirements

•Traffic profile

•=> traffic/ site


S12 / BR9 Dimensioning – Example Case

•1 500 000 subscriber•Area size 4776 km2

•Assumptions• 3 Cells / site• Assumption 25mErl /subscriber (based on reference model

of traffic)• Traffic is homogeneous over area => BTS/Cell

configurations are same• Site dominance area is 3 km2. Normally this depends on

– Site Location, Masts vs. Building roofs (dependent on authorities)– Area type, urban, suburban etc– Coverage thresholds

=>Planning tool with good propagation model must be used


S12 / BR9 Dimensioning – Air interface

• Dimensioning is based on Erlang B table (Blocking 2%)

1 500 000subs x 25mErl/ subs= 37500 Erl (Total traffic over area)

37500 Erl / 1592 sites = 23.56 Erl / Site => 7.85 Erl/Cell

ErlangB ( 2%Blocking, 7.85Erl) => 2 TRX / Site is enough

• 2 TRX = 16ch – 2 signaling – average 7.85Erl – mean free RTSL=> rest TSL’s are for data = 16-2-7.85-1.5 ~ 4.5 TSL’s for EGPRS

→ Site dominance area = 3km2 (only example) → 4776 km2 / 3km2 => 1592 sites (±0.5% = 8 sites) →3 cells per site = 4776 cells → 2 TRX / cell = 9552 TRX’s

Calculation method is same for Ex-Nokia and Ex-Siemens


S12 / BR9 Dimensioning – Air interface

• Note! Normally site area is calculated with planning tool

• RF specifications are effecting on amount of TRX’s How many sites are needed (better sensitivity, less sites) Combiners, power settings, MHA’s Configuration (UL or DL limited network)

• Capacity features HR/FR BSC capacity features Soft blocking is not considered in this document

• Capacity tools can be used for dimensioning


S12 / BR9 Dimensioning – Paging

• TRXsig link (LAPD link) is on a TRX basis and it can be configured for example to one of the following link speed: 16 kbit/s, 32 kbit/s or 64 kbit/s etc. In BR9 there are more options.

• It is recommended to use 32 kbits/s for BCCH TRX when high paging load in the LAC, location update area

• A bottleneck could occur, as in some cases BTS/BCSU processors can handle more messages than the Abis link can transfer.

• To be safe, the system should be running below 30%.

• Table below can be used for rule of thumb for both Ex-Nokia and Ex-Siemens

TRXSIG comments

16 kbit/s Can be used if 32k is not possible to use

32 kbit/s Default Value. Must be used if HR or high SMS is used

64 kbit/s Must be used if HR and high SMS are used


S12 / BR9 Dimensioning – SDCCH

• SDCCH channels, logical channel on the radio interface that is used for sending short messages, and during connection set-up used for identification and authentication procedures, and for starting the ciphering

• Capacity of SDCCH in the cell is depending on the amount of TRX’s in the cell

• Capacity of SDCCH in the cell is also depending heavily on Traffic profile, for example amount of SMS’s

– (SDCCH traffic Assumptions in the table below: authentication+ciphering: 7s, SMS:4s, location update:7s)

• For example – 2 TRX, 1 SMS/subs/hour => 1 bcch + 1 sdcch are needed– 2 TRX, 5 SMS/subs/hour => 1 bcch + 2 sdcch are needed

Erl mErl/subs subs 1 sms/subs/hour 5 sms/subs/hour 10 sms/subs/hour 1 sms/subs/hour 5 sms/subs/hour 10 sms/subs/hour1 2.2 25 88 0.4 0.8 1.3 1 1 12 8.2 25 328 1.6 3.1 4.9 1 2 23 14.9 25 596 3.0 5.6 8.9 1 2 34 21 25 840 4.2 7.9 12.6 2 2 35 27 25 1080 5.4 10.2 16.2 2 3 4

SDCCH Traffic (Erl)Number of TRX in the cell

Number of SDCCH in the cell


S12 / BR9 Dimensioning – Abis interface

• Pulse code modulation (PCM)

• ITU Standard G.703

• “2 Mbit/s” - line• 8 bit per sample

• 8000 signal samples per second

• 31 (+1) timeslots per frame

• Europe: “E1-trunk”

32 channels = 2048 kb/s

• USA : “T1- trunk”

24 channels = 1536 kb/s

BIT-> 1 2 3 4 5 6 7 8TS-> 0 LINK MANAGEMENT

1 TCH.1

2 TCH.2

3 TCH.3

4 TCH.4

5 TCH.5

6 TCH.6

7 TCH.7

8 TCH.8

9 TCH.9

10 TCH.10

11 TCH.11

12 TCH.12

13 TCH.13

14 TCH.14

15 TCH.15

16 #7 SIGNALLING17 TCH.16

18 TCH.17

19 TCH.18

20 TCH.19

21 TCH.20

22 TCH.21

23 TCH.22

24 TCH.23

25 TCH.24

26 TCH.25

27 TCH.26

28 TCH.27

29 TCH.28

30 TCH.29

31 TCH.30

= 1

/80

00 se

c.

Principle of E1/T1 frame structure

• “2Mbit/sec” line

• 8 bit per sample

• 8000 signal samples per second

• 31 (+1) timeslots per frame

-> 32 x 64kbit/s = “2 Mbit/s”

• Europe: “E1 Trunk”

• 32 channels = 2048 kbit/s

• USA: “T1 Trunk”

• 24 channels = 1536 kbit/s


S12 / BR9 Dimensioning – Abis interface

• In voice static resources can be used

• One Radio timeslot corresponds one 16 kbit/s abis-TSL

• GPRS and EDGE provide a variable bitrate therefore the resources are assigned dynamically.

• Dynamic Abis in Ex-Nokia

• FAAS (Flexible Abis Allocation Strategy) in Ex-Siemens

• Amount of data services are increasing all the time => Abis dimensioning is more important

1 E1, 32 channels

0 MCB LCB1 TCH0 TCH1 TCH2 TCH3 1 TRX2 TCH4 TCH5 TCH6 TCH7

3 TCH0 TCH1 TCH2 TCH3 2 TRX4 TCH4 TCH5 TCH6 TCH7





This Space (TSL's 13 -31) can be used as follow:

- TRXsig + OMU + sync

- Additional sites

-TSL's for data( static or dynamic abis TSL's)

-Q1 management


S12 / BR9 Dimensioning – Abis, EDAP

• Table below can be used as rule of thumb for Abis E1 Allocation for both Ex-Siemens and Ex-Nokia. T1’s are calculated for 24 channels

• Site Configuration 2+2+2 – 1 E1 (32chs) or 1 T1 (24ch) is enough

• With 32 kbps TRX signalling. The required Abis capacity is 2.5 Abis TSL per TRX + OMUsig + DAP


S12 / BR9 Dimensioning – Ater/Asub interface

BSCTranscoderEQUIPMENT

TC Circuit type

Different codecs separately, for example

EFR, FR HR, AMR etc.

Ater

interface• All traffic from BSC must be transferred to transcoders. Number of E1’s in Ater / Asub interface is depending on:

• TCH Traffic from all abis IF’s

• CCS7 traffics

• O&M links

• Utilization rate

• 1 PCM timeslot in Ater/Asub interface:

• 64Kbit/s

• 1 PCM timeslot in Abis interface :

• FR= 16 kbit/s

• HR = 8 kbit/s

=> 4 or 8 PCM timeslots in abis = 1 PCM timeslot in Ater

• Number of E1’s in Ater/Asub interface depends on codec used

Abis

interfaces

Transcoderunits



Number of Ater E1’s (E1’s = 32 channels)• Ex- Nokia

– #PCM = ErlangB(BSC_traffic,0.1%) = ErlB(7500,0.1%) 30 x 4 120

=> = 64 E1’s/ BSC

• Ex-Siemens– #PCM = ErlangB(BSC_traffic,0.1%)/4 + CCS7+O&M+GPRS+LCS

30 x utilization

=>ErlB(7500,0.1%)/4+ 40 / 30 = (1913 +40)/ 30 = =65.1=66 E1’s / BSC

=> Note!results are different due to different calculation method. Ex-Siemens method is more general. In practice, the results would be same.

In Ex-Nokia this part is calculated separately, for example data in Gb .



• Formulas are “same” for both Ex-Nokia and Ex-Siemens– ErlangB(BSC_traffic,0.1%) is most dominating factor

• Utilization rates are effecting to amount of E1’s

• Total amount of E1’s (T1’s) can be calculated– E1’s(T1’s) per BSC x number of BSC’s


S12 / BR9 Dimensioning – Transcoder units

• In Ex-Nokia number of transcoder units are based on table

• In Ex-Siemens number of transcoder units are based on table

1000

URNNN Asubmax,PCMS,TCHBSC,PCMS

TRAU,MSB

Number of PCMS= asub PCM’s can be calculated as in previous slide


S12 / BR9 Dimensioning – Transcoder units

• Based on formulas on previous page, following table can be calculated

– Ex-Nokia values are from table in previous page

– Ex_siemens values are calculated• Assumption, utilization Ur is 100%

960 1 11920 2 22880 3 33840 4 44800 5 55760 6 66720 7 77680 8 88640 9 99600 10 10

10560 11 1111520 12 12

ETSI channels Ex-Nokia Ex_siemensIn example case:

7500 Erl / BSC

ErlangB (7500,0.1%) = 7654 channels

• Ex-Nokia

•7654 channels => 8 units (Table)

=> 5 BSC’s = 40 units

• Ex Siemens

• 66 x 120 / 1000 = 8 units

=> 5 BSC’s = 40 units


S12 / BR9 Dimensioning – A interface

• Transcoder • converts the A interface 64

kbit/s traffic channels arriving from the (MSC) into channels of 16 kbit/s time slots

• multiplexes these channels in a ratio of 4:1 to fit into time slots of one 2 Mbit/s Ater /Asub PCM line towards the BSC and vice versa.

• Number of A interface PCM’s• ~ 4 x Ater/Asub PCM’s for

both Ex-Nokia and Ex-Siemens

=> 4 x 64 = 256 PCMs/BSC Ex-Nokia

=> 4 x 66 = 264 PCMs/BSC Ex-Siemens

BSC

MSCTC Circuit type

Ater

interface

A

interfaces

TC


S12 / BR9 Dimensioning – Number of BSCs

Ex-Nokia (BSC312000) Ex-Siemens (BR9)

Max CS Traffic 11880 Erl 10800 ErlTRX/BSC 2000 2000Max Cells 2000 1000Max Sites 2000 500Max E1/T1 800 540Max number of PCUs 100 logical PCUs 256

• The parameters being related to minimum number of BSC have to determined for the area to be planned, e. g.

• Number of TRX’s

• Number of Cells

• Number of Sites

• Total amount of traffic

• Minumum number of BSC can be caluculated

...max

.;max

.;max

;max

;max

;max

max

min

1/1

1/1

PCU

PCU

TE

TE

BSC

region

Sites

Sites

TRXC

TRXCell

BSC

N

N

N

N

Erl

Erl

N

N

N

N

NCell

N

N


S12 / BR9 Dimensioning – Number of BSCs

• Number of BSC’s are depending heavily on:– Traffic profile used

Mean holding times are varying very much in different countries (30s…90s)

– Utilization rates used Different utilizations can be operator specific values. If these are different

than NSN recommended values, dimensiong should be made based on these utilization rates

• Before dimensioning project all parameters, traffic profiles used etc should be check– Inaccurate values can lead to can lead to very big commercial risks.


S12 / BR9 Dimensioning – Number of SS7 links

subscribers 1500000 mean holding time 120

Erlangs / user 0.025Utilization

20%

BSCs 5

BH call attemst / BSC 225000

Procedure Bytes # in Busy Hour Kbps

Mobile Originated Call 290 157500 101.5 Mobile originated calls 70%

Mobile Terminated Call 267 67500 40.05 Mobile terminated calls 30%

Handover 145 337500 108.8 Handovers per call 1.5

Location Update 160 450000 160 Location updated per call 2

Security 120 225000 60 IMSI detach per call 0.1

SMS 218 225000 109 SMS (req(subs/1 hour) 1

579.3

per BSC total

Number of 64Kbit/s SS7 links 45 225

Total (kbit/s)

• Number of SS7 link can be calculated as below for both Ex-Nokia and Ex-Siemens

•1 E1 = 31 x 64kbps

•1 T1 = 24 x 64kbps


S12 / BR9 Dimensioning – Number of SS7 links

• Number of SS7 links are heavily depending on parameter used (in calculations)

• In Ex-Nokia and Ex-Siemens dimensioning material following differences can be found

• This is the reason why number of SS7 links are different in Ex-Nokia and Ex-Siemens document

• For example Hanover, intra, BSC controlled, MSC controlled, different amount of bytes are needed

EX-Nokia Ex-SiemensProcedure Bytes BytesMobile Originated Call 290 274.5Mobile Terminated Call 267 305Handover 145 61Location Update 160 91.5Security 120 135SMS 218 183


S12 / BR9 Dimensioning – Case - Summary

Subscribers 1 500 000

Area size 4776km2

*1)*1)

*1) Results are different due to different calculation method. In-Ex-Siemens calculation formula is more general. In Ex-Nokia for example dat is calculated in Gb. If calculation method would be same (like in practice), the results would be totally same.

*2) Result are different due to different procedure profile.

*2)

Dimensioning target Ex-Nokia Ex-Siemens1: Number of Sites 1592 Sites 1592 Sites2: Number of Cells 4776 Cells 4776 Cells3: Number of TRXs 9552 TRX s 9552 TRX s4: Amount of TRX / cell 2 TRX / cell 2 TRX / cell5: Air interface for EGPRS 4.7 RTSL 4.7 RTSL6: Paging (TRXSIG) Default 32kbps Default 32kbps7: Capacity of SDCCH per site 1 TSL for BCCH and 1

TSL for SDCCH1 TSL for BCCH and 1 TSL

for SDCCH8: Number of E1s for Abis 1 E1 per site = 1592 E1s 1 E1 per site = 1592 E1s9: Number of BSCs 5 BSC (BSC3i2000) 5 BSCNumber of A interface PCMs 1280 PCMs 1320 PCMsNumber of Ater/Asub interface PCMs 5x 64= 320 PCMs 5 x 66 = 330 PCM'sNumber of Transcoder units 40 units 40 TRAUsNumber of SS7 links 225 SS7 links (64kbps) 175 CCS7 links (64kbit/s)


Dimensioning - Impact on S13

This document is related to S12, but in S13 following features related to capacity are under development

• BSS20872 Robust AMR Signalling (FACCH/SACCH)– Improves coverage, allows the network to operate in very low C/I

conditions.

• BSS20900 Combined BSC3i/TCSM3i Capacity Evolution– More capacity. BSC3i 1000 installed together with 1, 2 and 3 TCSM3i

cabinets

• BSS20094 Extended Cell for GPRS/EDGE– Extended Cell Range increases the cell radius up to about 70 km

Documents

S12 BR9 Dimensioning WI