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WCDMA Introduction Spreading Code - PowerPoint PPT Presentation


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WCDMA Introduction Spreading Code. Chia-Chi Yu 2004.8.13. Outline. WCDMA two layer Spreading Channelization code – OVSF code How to generate OVSF code? Scrambling code – Gold sequence Conclusions. Spreading. Two layer spreading. Define DL and UL.

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Presentation Transcript
outline
Outline
  • WCDMA two layer Spreading
  • Channelization code – OVSF code
  • How to generate OVSF code?
  • Scrambling code – Gold sequence
  • Conclusions
spreading
Spreading
  • Two layer spreading
define dl and ul
Define DL and UL
  • DL(downlink): Node B(BaseStation) to User Equipment(Mobile)
  • UL(uplink):UE to Node B
channelization code
Channelization Code
  • Usage◇Uplink: Separation of DPDCH and DPCCH from the same terminal◇Downlink: Separation of downlink connections to different users within one cell
  • Using OVSF code
  • Length◇Uplink: 4~256 chips same as SF ◇Downlink:4~512 chips same as SF
ovsf code
OVSF code
  • Orthogonal Variable Spreading Factor→The Spreading Factor can be changed (e.g.,for variable bit rate service)
  • Orthogonality preserved across the different symbol rates
scrambling code
Scrambling code
  • Usage◇Uplink: Separation of UE(Mobile) ◇Downlink: Separation of Base Station(cell)
  • Since WCDMA uses different scrambling codes to separate user from cells, it is not necessary to be synchronous between BS
  • Gold Sequence
scrambling code dl
Scrambling code(DL)
  • Length: 38400 chips(both UL and DL)
  • Use a 10msec radio frame of a 218-1 shortened Gold sequence
  • Total number of codes : 262,143
  • Use only 8,192 codes→ Broken into 512 sets of codes
      • Each set has 1 primary code with 15 secodary codes
      • Primary codes are further broken into 64 code groups, each with 8 primary codes
conclusions
Conclusions
  • Limited OVSF codes must be reused in every cell→Interference if two cells use the same code→Scrambling codes provide solutions
  • Asynchronous BS