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
| 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 |
WCDMA Stuff
What is WCDMA
FDMA vs TDMA vs CDMA
WCDMA MO CS call
WCDMA PS Call
CDMA vs GSM
WCDMA Compressed mode
Cell re-selection in GSM/WCDMA
IRAT handover GSM/WCDMA
Difference between TD-SCDMA,WCDMA,CDMA2000