Efficient OVSF code assignment and reassignment strategies in UMTS

This paper presents an integrated solution for code management, assignment, and reassignment problems. We propose a new architecture for code management, and based upon this new architecture, a new code assignment strategy, referred to as ‘crowded-group first strategy’. Our system architecture and code assignment strategy represent significant improvements in the time complexity and in the complexity of the storage operation. Moreover, the code blocking probability of the crowded-group first strategy can be as good as that of the crowded-first strategy. In this paper, we also propose a new code reassignment strategy, called the ‘inner-group code reassignment’. The main objective of this reassignment strategy is to provide fast codes change under our maintenance structure, and to reduce the amount of code reassignments. In order to systematically analyze the performance of the code assignment strategy, we implement a simulator to analyze the code selection behavior of each strategy, and the performance of the code blocking can be anticipated based on the analysis. Moreover, we propose a new performance metric, named ‘weighted code blocking’, in order to precisely measure the performance obtained by different strategies. From the simulation results, we show that our integrated solution efficiently utilizes the OVSF codes with the low computation overhead.