Cdma System, Soft-switching Technology Research And Improvement

Mobile communication matches the demand of modern society in communicationtechnique with its flexibility and convenient, soft handoff is the key technique with which topursue the capacity maximum and to improve the quality of service in CDMA mobilecommunication system. Soft handoff make the channel of mobile station can be switched toanother base station with new link before breaking the old link, this tactic makes handoffsmoothly and without interruption. Soft handoff technique makes system have a great numberof advantages such as lower outage probability, high diversity gain and larger system capacity.This paper focuses on the soft handoff of CDMA system. Firstly, the principle of CDMAand the process of soft handoffare briefly introduced, also Markov chain is applied to analyzefour typical handoff schemes, such as non-priority, FIFO queuing, channel reserved, integratedchannel reserved/FIFO queuing. Secondly, make the analysis and research of the mutualrelationship among capacity, load and outage probability of the system. Soft handoff will havea direct impact on the quality of services, as well as on the overall performance of the system.After studying the traditional soft handoff algorithm, putting forward an improved algorithm,and the new algorithm adopt the strategy of call admission control which is based on residualcapacity, it not only consider path loss of mobile business but also residual capacity of system.Compared to the traditional algorithm, the improved algorithm selects the better target basestation in the process of soft handoff, so that make the allocation and utilization of channelresources more reasonable. Finally, make the simulation by the means of Matlab tool, adoptedhexagon soft handoff model, and the simulation results show that the performance indicatorssuch as outage probability, blocking probability and successful probability of soft handoffcanbe improved in the new algorithm as well as quality of service.