Long Code & Short Code In CDMA
The long code is a PN sequence with period of 242-1chips
The functions of a long code:
- Scramble the forward CDMA channel
- Control the insertion of power control bit
- Spread the information on the reverse CDMA channel to identify the mobile stations
In a reverse direction, different long codes are used for the information sent by different users and these are known to the base station and these users. Thus, the base station can identify different mobile stations.
Short code is a PN sequence with period of 215 chips
- Sequence with different time offset is used to distinguish different sectors
- Minimum PN sequence offset used is 64 chips, that is, 512 PN offsets are available to identify the CDMA sectors (215/64=512).