CDMA System Basis

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CDMA System Basis
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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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Classification of Wireless Telecomm
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(No Transcript)
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Frequency Reuse
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Evolution of Wireless Telecomm
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Makeup of Wireless Telecomm
MS Mobile Station BSS Base Station System BTS
Base-station Transceiver System BSC Base_Station
Controller MSCMobile-service Switching
Center VLRVisiting Location Register HLRHome
Location Register PSTN ISDN

BSS
MS
BSC
BTS
VLR
BTS
BTS
MS
HLR
MSC
PSTN
MS
ISDN
BTS
BSC
BTS
BTS
MS
Um
Abis
A
MSC
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Spectrum Spreading Technique

• Theoretical Basis is Shanon equationCBlog2(1S/
  N)
• DSSS applied in CDMA
• Used in military communication in 1950s and
  1960s
• Qualcomm company successfully put it into
  commercially cellular wireless telecommunication
  by the end of 1980s

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Signal processing by DSSS
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Features of CDMA System(1)

• Large capacity
• 810 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

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Features of CDMA System (2)

• Soft capacity
• MSs 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

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Key techniques of CDMA (1)

• Diversity receiving
• Time diversityinterleaving, error-detection
  and correction
• Frequency diversityinherent feature of
  wideband communication
• Space diversitymultiple antenna receiving,
  RAKE receiving, soft handoff

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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

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Key techniques of CDMA (3)

• Rate variable codec (QCELP)
• VOICE Detection (VOD)
• Synchronization
• Mobile assisted soft handoff

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Key techniques of CDMA (4)

• Blossoming Wilting
• Low Eb/No and high redundant error correction
  encoding
• Multiple accesslong PN code, short PN code and
  WALSH orthogonal code

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Channel structure

• Forward Channels
• Piloting channel
• Synchronizing channel
• Paging channel
• Traffic channel
• Reverse Channels
• Access channel
• Traffic channel

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IS-95A Channel Modulation--Forward Link
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Procedure of MSs COMMUNICATION

• Searching base stations pilot channel
• Demodulating synchronizing channel
• MS requests on access channel
• BS responds on paging channel
• Traffic channel is assigned for communication

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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
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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
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ZXC10_BSS System Specification-BSC

• Maximal BTS supported 512
• Vocoder7200
• Maximal Channels (including payoff and soft
  handoff)512 X 32 16384
• Maximal traffic channels 512 X 20 10240
• Maximal subscribers 102,500
• BTS side traffic2,930 Erl
• BHCA125,000
• Traffic1.28BHCA/subscriber

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ZXC-10 BSS-transition to 3G

• Capacity increased
• Non-symmetrical data service provided
• For64Kb/s
• Rev14.4Kb/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