Research On Handover Algrithom In TD-SCDMA System

With the rapid development and popularity of mobile communication technology, mobile users and multimedia communication services grow rapidly, wireless cells distribute more and more densely, and the handoff business traffic between cells becomes more frequent, which make contradictions between growth in demand for radio resources and wireless resources limitation increasingly conspicuous. Baton handover technology, as one of the key technologies in the TD-SCDMA system and an important part of radio resource management, is closely related with the system service quality and system capacity. Therefore, it has been concerned by people.In this paper, the basic principles and algorithms of baton handover in TD-SCDMA system is discussed, the shortcomings of current baton handover technology is analyzed and the improvement program of handoff process is discussed accordant with the technical features of TD-SCDMA. In order to avoid the ping-pong handovers and balance the cell load more effectively, fuzzy control theory in the target cell selection process is presented, which overcomes the shortcomings of single criterion in traditional selection process. In the new strategy of target cells selection, factors reflecting the communications environment are considered, such as signal strength, bandwidth utilization and the number of users online, which makes the target cell selection more reasonable.Current mobile communication business is diverse and complex, and in view of shortcomings of current handoff algorithm in business acceptance process, a baton handover strategy which applies integrated services (voice/data) into TD-SCDMA mobile communication system is proposed in this paper. This strategy reserves channels for voice handover calls, defines different handover priorities according to voice user attribution, provides voice handover calls and new voice calls with preemptive priority over channels serving for data calls. Simulation results show that, while the system voice traffic is heavy, this strategy reduces blocking probabilities of VIP voice handover calls and high-speed handover calls by at least 50%. Furthermore, while the system has heavy voice traffic, this strategy reduces the data call blocking probability and queue length. Besides, data call transmission delay decreases by nearly 0.01s. Performance evaluation parameter GoS of the channel reservation scheme is proposed, which provides a channel reservation scheme selection guide for practical application.