An efficient multi code design for code blocking reduction in 3G wireless networks

Orthogonal Variable Spreading Factor (OVSF) channelization codes limit the performance of third generation (3G) mobile communication systems employing Wideband Code Division Multiple Access (WCDMA). The codes must be assigned to incoming call requests with different data rate requirements, in such a way that the codes are mutually orthogonal. The single code assignment and reassignment schemes usually lead to the internal and external fragmentation problems in the traditional OVSF code tree which can be efficiently improved by using the multi code assignment and reassignment schemes. In this paper multi code design is proposed for optimum use of rake combiners (rake fingers) by the use of OVSF code tree. The work addresses three multi code assignment schemes with improved code blocking performance. Extensive simulations are conducted to illustrate that our code assignment reduce the code blocking problem as compared to the existing coding schemes.