wcdmaoverviewpresentation-12836235753565-phpapp01

8/12/2019 wcdmaoverviewpresentation-12836235753565-phpapp01

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WCDMA Overview


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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) ToCS4 (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 Spectrumtechnique 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


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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.


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Spreading Factor and Data Symbol Rate


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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 9624


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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.


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Basic frame structure


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Frames Structure

DPCCH

RACH

DPDCH & DPCCH


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Control Channels vs SF

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


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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.


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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.

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