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Wideband DS-CDMA for Next-Generation Mobile Communications Systems

Reporter : Vincent Chen

Advisor : Prof. Li-Chun Wang

2000/8/13

Reference:IEEE Communication Magazine,1998.9

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Introduction:

Second-Generation cellular system:

•Adopted digital technology•Limited basic service•Low-bit-rate

Third-Generation cellular system:

•ITU:IMT-2000,2Mb/s• Wideband DS-CDMA•FDD,Air interface standard

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The difference between IS95 and WDS-CDMA

•IS95: Base on narrowband DS-CDMA

Optimized for basic service

The difference between second and third generation

•Isolated cell case

•Sectored cell: Overcome the interference program

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Content:

The important concepts:

•Intercell asynchronous operation

•Pilot channel associated with individual data

channels

1:Coherent Detection

2:Interference Cancellation

3:Adaptive antenna array

(can be viewed as Adaptive cell sectorization)

W-CDMA TechnologyW-CDMA Technology

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The technical features:

•Fast transmit power control

•Coherent spreading code tracking

•Coherent rake receiver

•Orthogonal multispreading factor forward link

•Variable-rate transmission with blind rate detection

Field experiment

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Enhanced Radio Transmission TechniquesEnhanced Radio Transmission Techniques

Multi-Stage Interference Canceller

An Adaptive Antenna Array Combined with A Rake Receiver

Matched Filter Rake Receiver

Turbo Codes

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Design Concept:Design Concept:

W-CDMA Technology

Channel Coding

Modulate10msData

Add Header QPSK

Spread2GHZ

MFRake

CombinerViterbi

Decoder

10msData

Transmiter

Receiver

SubtractHeader

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Fast Cell Search Under Intercell Asynchronous OperationFast Cell Search Under Intercell Asynchronous Operation

Cell search algorithm:

1: Detect scramble mask timing of best cell (least sum of propagation path loss plus shadowing)2: Identify the scramble code group

3: Search for the scramble code

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Fast TPCFast TPC

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Coherent spreading code trackingCoherent spreading code tracking

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Coherent Rake CombiningCoherent Rake Combining

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Orthogonal multi-spreading factor forward linkOrthogonal multi-spreading factor forward link

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Variable-rate transmission with blind rate detectionVariable-rate transmission with blind rate detection

Discontinuous:Keep same Symbol rate

Continuous:Keep same Chip rate

Cyclic Redundancy Check Decoding

Data rata=M Spreading code=01

Data rata=M/2 Spreading code=0011

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Field experimentField experiment

System set-up for 32kb/s data transmission

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Measurement course characterization

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The effect of spreading bandwidth

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High-speed(1.92 Mb/s) data transmission

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Enhanced Radio Transmission Techniques

Multi-Stage Interference CancellerMulti-Stage Interference Canceller

COMSIC: COherent Multi-Stage ICCEIGU:Channel Estimation-and-Interference Generation Unit

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An Adaptive antenna array combined with a Rake receiverAn Adaptive antenna array combined with a Rake receiver

CAAAR Receiver: Coherent Adaptive Antenna Array Rake Receiver

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Matched Filter Rake ReceiverMatched Filter Rake Receiver

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Turbo CodesTurbo Codes

The main difference between Turbo codes and Conventional code

•Concatenating two or more recursive systematic codes

•Using a pseudo-random interleaver

•Iterative decoding algorithm

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RSC:Recursive system convolutional encoder

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