WCDMA Overview

GSM Vs WCDMA GSM Services : Voice & Data Speed : 9.6kbps (FR, HR, EFR) Modulation Scheme : GMSK Nodes : MSC, BSC, BTS, ME Air interfaces : Abis, A, Ater, Gb etc BW : 25 MHz with 200 KHz per carrier. Channels : BCCH, PCH, SDDCH,

FACCH, RACH, etc Access Method : TDMA Access Media : TDM Multipath Fading : Viterbi Equalizer. Coding scheme : CS1 (9.6kbps) To

CS4 (21.4 kbps) BSC to BSC no direct connectivity AUC : Triplets (SRES, Ki, RAND)

WCDMA Services : Voice, data, Video Speed : 12.8kbps-4.5 kbps (AMR) Modulation scheme : QPSK Nodes: SMSC, MGW, RNC, RBS, UE Air interfaces : Iu-CS, Iu-PS, Uu etc BW : 60 MHz, with 5 MHz spread BW. Channels: CPICH, PRACH, DPDCH,

DPCCH etc Access Method : Spread Spectrum

technique with wide bandwidth. Access Media : ATM, IP, TDM Multipath fading : Rake reciever Coding Scheme : MCS1(8.8kbps) to

MCS9 (59.2kbps) RNC to RNC connectivity via MGW. AUC : Vector-5 ( XRES, Ik, RAND, Ck,

AUTN) AUTN : MAC + SQN + Ak + AMF

3GPP Releases R99, R4, R5, R6 etc. Media gateway introduced in R99. IMS introduced in R4. HSDPA introduced in R5. EUL introduced in R6.

**** : Kindly refer 3GPP for further information.

Spreading and Dispreading

Spreading Factor and Data Symbol Rate

Carrier ARFCNDL Downlink Frequency (MHz) Uplink Frequency (MHz) ARFCNUL

  10550 2110 1920 9600

  10551 2110.2 1920.2 9601

  10552 2110.4 1920.4 9602

  10553 2110.6 1920.6 9603

  10554 2110.8 1920.8 9604

  10555 2111 1921 9605

  10556 2111.2 1921.2 9606

  10557 2111.4 1921.4 9607

  10558 2111.6 1921.6 9608

  10559 2111.8 1921.8 9609

  10560 2112 1922 9610

  10561 2112.2 1922.2 9611

1 10562 2112.4 1922.4 9612

  10563 2112.6 1922.6 9613

  10564 2112.8 1922.8 9614

  10565 2113 1923 9615

  10566 2113.2 1923.2 9616

  10567 2113.4 1923.4 9617

  10568 2113.6 1923.6 9618

  10569 2113.8 1923.8 9619

  10570 2114 1924 9620

  10571 2114.2 1924.2 9621

  10572 2114.4 1924.4 9622

  10573 2114.6 1924.6 9623

  10574 2114.8 1924.8 9624Microsoft Excel

Worksheet

GSM vs WCDMA

GSM

TCH (User payload)

BCH

AGCH

WCDMA

DCH : DPDCH (user + L3) & DPCCH (L1 ie Pilot bits, power control).

PCCPH (Broadcast Info)

SCPCCH ( FACH + PCH)

CPICH, PCCPCH are continuous.

S-CCPCH, PICH, AICH, DDCCH, DPCCH are on demands.

Basic frame structure

Frames Structure DPCCH

RACH

DPDCH & DPCCH

Control Channels vs SF

Note : AICH (Acquisition Indicator channel) uses 20 msec as it consist of 2 frames (means 30 slots).

Power Control Open Loop : When UE is IDLE, No air interface link.

In GSM, RACH is sent with max. power.

In WCDMA, RACH is sent with min. power. Inner Loop (fast power control): When UE connected.

SIR) target< SIR)estimat-----Reduce Power

SIR) target> SIR)estimat-----Increase Power

Frequency of commanding for power control:

GSM : 2 times/sec ; CDMA : 800 times/sec ; WCDMA : 1500 times/sec.

Outer loop (Slow power control) : RNC to control BLER.

BLER high------Quality low-----SIR) target increase.

BLER low------Quality high-----SIR) target reduce.

Handover Mechanism Softer Handover: Intra site handover (within two sector of same

site.

Soft Hanover: Handover between two sites.

Hard Handover:

Inter frequency (IF): WCDMA f1 and WCDMA f2.

Inter Radio Access technology (IRAT): WCDMA to GSM.

Rake reciever Deployed in UE to avoid Multipath fading. At least 4 rake receiver and 1 search finger is deployed. Inner loop power control is used to overcome the fast fading. Maximum ratio Combiner (MRC) is employed as combining

technique.

Search Finger is used when performing handovers, scans neighbor node B and estimated the channel parameters.