An Efficient Dynamic Orthogonal Variable Spreading Factor Code Allocation Approach in WCDMA through Swarm Intelligence Technique

摘要

CDMA is the access technique adopted in the third generation wireless system. In this technique, all users share the same bandwidth simultaneously but with different codes. This sharing generates interferences that can reduce the overall throughput of the WCDMA network when using a weak code allocation algorithm. On the other hand, shared channels are made for the transmission of bursty data as they allow a single OVSF channelization code to be shared among several users. In WCDMA, effective utilization of OVSF codes has become an active area of research as the number of codes is very limited. It is a fact that the successor and predecessor codes of OVSF cannot be used simultaneously when a specific code is used in OVSF as their encoded sequences become indistinguishable. Consequently, OVSF code tree has inadequate number of available codes. Thus, this research work uses a Swarm Intelligence Technique called Artificial Bee Colony (ABC) approach for dynamic OVSF code assignment in WCDMA networks. The simulation results show that the ABC especially with diploid structure provides reduced code blocking probability and improved spectral efficiency in the system when compared to the CCA and DCA schemes.