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CDMA System Basis

CDMA System Basis. Features of Wireless Telecomm. Individually Bad propagation environment Co-channel, Adjacent channel interference and near-far effect. Contradiction between limited frequency resource and vast numbers of subscribers. Complicated network and control equipment are required.

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CDMA System Basis

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  1. CDMA System Basis

  2. Features of Wireless Telecomm • Individually • Bad propagation environment • Co-channel, Adjacent channel interference and near-far effect. • Contradiction between limited frequency resource and vast numbers of subscribers. • Complicated network and control equipment are required.

  3. Classification of Wireless Telecomm

  4. Frequency Reuse

  5. Evolution of Wireless Telecomm

  6. Makeup of Wireless Telecomm MS: Mobile Station BSS: Base Station System BTS: Base-station Transceiver System BSC: Base_Station Controller MSC:Mobile-service Switching Center VLR:Visiting Location Register HLR:Home Location Register PSTN: ISDN: BSS MS BSC BTS VLR BTS BTS MS HLR MSC PSTN MS ISDN BTS BSC BTS BTS MS Um A Abis MSC

  7. Spectrum Spreading Technique • Theoretical Basis is Shanon equationC=B*log2(1+S/N) • DSSS applied in CDMA • Used in military communication in 1950’s and 1960’s • Qualcomm company successfully put it into commercially cellular wireless telecommunication by the end of 1980’s

  8. Signal processing by DSSS

  9. Features of CDMA System（1） • Large capacity 8~10 times of analog system • High-quality service 8Kb/s QCELP EQUALS 13Kb/s of GSM; 13Kb/s QCELP EQUALS 64kb/s of wireline • Soft handoff lowers call drop rate • RAKE receiving overcomes multi-path fading • Good secrecy

  10. Features of CDMA System （2） • Soft capacity • MS’s averaging transmission power is lowered, decreasing radiation to human body and environment . Be named as “Green Handset” • Easy to realize dual-mode operation • System complexity increased

  11. Key techniques of CDMA （1） • Diversity receiving Time diversity——interleaving, error-detection and correction Frequency diversity——inherent feature of wideband communication Space diversity——multiple antenna receiving, RAKE receiving, soft handoff

  12. Key techniques of CDMA （2） • Precise power control Open loop power control on reverse link Closed loop power control on reverse link Outer loop power control on reverse link Power control on forward link

  13. Key techniques of CDMA （3） • Rate variable codec (QCELP) • VOICE Detection (VOD) • Synchronization • Mobile assisted soft handoff

  14. Key techniques of CDMA （4） • Blossoming & Wilting • Low Eb/No and high redundant error correction encoding • Multiple access：long PN code, short PN code and WALSH orthogonal code

  15. Channel structure • Forward Channels Piloting channel Synchronizing channel Paging channel Traffic channel • Reverse Channels Access channel Traffic channel

  16. IS-95A Channel Modulation--Forward Link

  17. Procedure of MS’s COMMUNICATION • Searching base station’s pilot channel • Demodulating synchronizing channel • MS requests on access channel • BS responds on paging channel • Traffic channel is assigned for communication

  18. Power On Task Initialization Start analog mode MS Initial Status End analog mode MS idle changeover when NGHBR_CONFIG is”011” MS fully catches System timing MS idle status MS paged, originating or registering Access channel confirmation System access status End traffic channel Indication of traffic channel MS in traffic Channel status Notes：not all are listed out

  19. ZXC10-BSS System structure-BSC BSC: Base_Station Controller BTS: Base-station Transceiver System NCM: Network Control Module HIRS: High-speed Interconnect Router Subsystem CDSU: Channel/Digital Service Unit TCM: Timing Control Module SVM: Selector Vocoder Module SVICM: Selector Vocoder Interface Control Module CPM: Call Process Module OMC: Operation & Maintenance Center

  20. ZXC10-BSS System structure-BTS BTS: Base-station Transceiver System CHM: Channel Processing Module CCM: Communication Control Module HIRS: High-speed Interconnect Router Subsystem TCM: Timing Control Module RFIM: RF Interface Module TRx: Transceiver HPA: High Power Amplifier RFE: RF Front End CDSU: Channel/Digital Service Unit BTM: Base-station Test Module BSC: Base-station Controller

  21. ZXC10_BSS System Specification-BSC • Maximal BTS supported: 512 • Vocoder：7200 • Maximal Channels (including payoff and soft handoff):512 X 32 = 16384 • Maximal traffic channels: 512 X 20 = 10240 • Maximal subscribers: 102,500* • BTS side traffic：2,930 Erl* • BHCA：125,000* • Traffic：1.28BHCA/subscriber

  22. ZXC-10 BSS-transition to 3G • Capacity increased • Non-symmetrical data service provided • For:64Kb/s • Rev:14.4Kb/s • Backward compatible with 95A • Capacity doubled (relative to 95A) • Data service • 144Kb/s • 307.2Kb/s(max) • Backward compatible with 95A/B • Data service • 384Kb/s • 2Mb/s(max) • Backward compatible with 95A/B/1X Features:

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