PERFORMANCE IMPROVEMENT IN OVSF BASED CDMA NETWORKS USING FLEXIBLE ASSIGNMENT OF DATA CALLS

Orthogonal variable spreading factor (OVSF) codes are used to support multimedia calls in CDMA wireless networks. The inefficient use of OVSF code tree reduces the system throughput. The paper discusses a novel code assignment design to provide flexibility of rate variation in data calls maximizing channel utilization. The ongoing call uses different codes at different times depending on the code tree status and instantaneous traffic load. For low traffic loads, the high rate codes can be utilized. For medium to high instantaneous load conditions, the vacant codes with capacity less than the call rate can be utilized. For same call reassignments are done to assign different codes at different times. The utilization of the code tree can reach close to 100%. Simulation results are given to verify the superiority of the proposed design.