Dynamic Future Code Allocation Scheme for Dsch in Wcdma Systems

-Third generation wireless system is based on the WCDMA (Wide band Code Division Multiple Access) access technique. In this technique all the users share the same bandwidth simultaneously but with different codes. System transmits from base station to multiple user terminals or from user terminal to base station. WCDMA uses Orthogonal Variable Spreading Factor (OVSF) codes. Each user terminal data is being spread by different code chosen from the set of orthogonal codes. Each receiver in the user terminal or base station correlate for its intended data by de-spreading the signal using its particular one of the orthogonal codes. The paper describes a method of selecting spreading codes for multiple users at a particular scheduled time in future. According to the proposal, dynamic future code allocation is done for DSCH which keeps the transmission power as constant as possible and number of user terminals can share the same code tree and gain from statistical multiplexing.