Optimized Soft Handoff Technology For Multi-Traffic CDMA Systems

Mobile communications satisfy the demand of human beings in the modern society on communication technology, due to their flexibility and convenience. In CDMA mobile communication systems, soft handoff technology has become the key technology which can pursue the largest system capacity and improve the quality of communications. When the mobile station makes soft handoff, it connects with the new base stations before breaking the connection of the old base station. Soft handoff could achieve seamless mobile communication, reduce call blocking rate, get gain of diversity, increase system capacity, and so on.This thesis focuses on soft handoff algorithm optimization for CDMA system. In the past, the research on soft handoff algorithm focuses on parameter setting and resource allocation. The research on soft handoff criteria is little, and is only for single traffic.In the traditional soft handoff algorithm, when the link quality deteriorates and needs to be handed off, the mobile station could communicate with networks with many wireless links and select the strongest signal pilot as a goal. The base station whose pilot signal is the strongest has the smallest path loss. The traditional soft handoff algorithm just considers path loss without considering the balance of realistic traffic. The load balance of the base stations, utilization of system resources and system performance are very important during handoff when the handoff request happens.Future wireless communication system is required to provide many kinds of communication services for different users. Different services have different requirements of service quality. In order to make better use of wireless networking features, all kinds of resources of wireless systems need to be managed and distributed reasonably. We could guarantee data's transmission quality as far as possible while making full use of the limited bandwidth of wireless systems. So in the choice of the cell target to be handed off, path loss and load should both be considered.In this thesis, optimized soft handoff algorithm for multi-traffic is proposed and used in hierarchical cellular systems. This algorithm could achieve load balance and reasonable use of resources, rather than adding the base station whose pilot signal is the strongest. When the load of each cell is same, this algorithm is just as the traditional algorithm. The simulation results indicate that the optimized algorithm could reduce the transition interruption and improve system performance significantly. The algorithm has some theoretical value and significance of engineering practice.Finally, full thesis is summarized.