Abstract: Random dynamic code allocation algorithm has a high blocking probability and too much overhead cost in searching for the minimum-cost branche in downlink of WCDMA（Wideband CodeDivision Multiple Access） systems, so we proposed an improved version of a dynamic code allocation algorithm. The algorithm uses the minimum-cost searching function to the code tree rearrangement based on the principles of neighbouring, and releases of a code at the same level with the greatest cost function in the value of the code strategy. The simulation results show that the probability of improved algorithm is less than the algorithm of random dynamic code allocationt algorithm. When the traffic load is 16 Erl, the improved version of a dynamic code allocationt algorithm can reduce the probability by 1837%. And the same time the improved algorithm can effectively reduce the complexity of the system.

Key words: code allocation, code blocking, wideband codedivision multiple access, radio resource management, orthogonal variable spreading factor