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What is WCDMA/UMTS OVSF Code


This tutorial section on WCDMA (UMTS) basics covers following sub topics:
UMTS Tutorial  UMTS channels  measurements  PHY layer  TDD vs FDD PHY  RRC States  Security  Cell search  Bands  UARFCN  Frame 


•  OVSF stands for Orthogonal Variable Spreading Factor. They are also referred as channelization codes. They are used to separate data and control channels from same UE

•  It preserves orthogonality between these control and data channels. Following are useful features of OVSF codes used in WCDMA system.

•  The use of OVSF codes allows the spreading factor to be changed and orthogonality between different spreading codes of different lengths to be maintained

•  The codes are picked from the code tree, based on the data rate and channel numbers requirement

OVSF code
code OVSF(channelisation code)
Property Orthogonal property helps to reduce interference. Do not have good correlation properties. Needs additional long codes. Walsh code is an example.
Usage Uplink- separation of DPDCH and DPCCH from same UE. Downlink- separation of DL connections to different users within one cells.
Length Uplink- 4-256 Downlink- 4-512
Number of codes Number of codes under one scrambling code = spreading factor
Spreading Increases bandwidth

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WCDMA Compressed mode
Cell re-selection in GSM/WCDMA
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Difference between TD-SCDMA,WCDMA,CDMA2000

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