Cdma Tdd System, Dynamic Channel Allocation Techniques

With the rapid development of the wireless multimedia services, the traffic asymmetry between uplink and downlink is more and more obvious. TDD CDMA system has both the flexibility of timeslot allocation and good adaptability to the multimedia services. The research on the DCA (dynamic channel assignment) algorithm and its performance in the TDD CDMA system has been a hotspot in these years. The validity of DCA algorithm has been vital to utilize the advantages of TDD model and a lot of algorithms have been proposed to increase the system capability and decrease the interference in the system as possible.This paper discusses the DCA technique, which is one of the strategies in the wireless resources management. It is about how to arrange the channels among the uplink, downlink and cells effectively. In our CDMA/TDD system, different numbers of time slot are applied and they can be adjusted according to the traffic patterns.Our analysis is aiming at the slot allocation in the TDD CDMA system. We put the emphasis on the effects of different slot allocation on the capability of the system with the heterogeneous traffic such as voice and data. We also consider different assignment strategies in the single cell and multi-cells environment. The algorithms and simulation results of each strategy are provided.The selection of the channel assignment strategies is always aiming at achieving higher channel efficiency, better Qos, shorter channel search time and simpler application of the algorithm. There exits contradiction between the Qos guarantee and complexity of channel assignment algorithms. And the channel search time is correlated with the channel utilizing efficiency. So each solution plan is the compromise among these factors.To select a DCA strategy, we should consider whether it is feasible in the practical network construction.The conclusions in this paper will be valuable for the performance analysis and cells plan in the CDMA TDD system.