Research On Handoff Algorithms In Heterogeneous Wireless Networks

With the rapid development of mobile communication technologies, along with the great increasing of mobile users and business needs, the heterogeneous wireless networks has drawn the most attention since it is the tendency of future communication technologies. When the users mobile are working in the integrated heterogeneous wireless networks, handoff technology plays an important role to improve the quality of network service and system capacity. Therefore, related handoff algorithms of heterogeneous wireless networks have become the key to research for the multi-integrated networks.Based on the acknowledgement of baton handoff control mechanism and the analysis of existing baton handoff algorithms, an advanced scheme which could optimize the system performance had been proposed with the use of channel reservation and preemptive priority baton handoff strategy. In this scheme, maximum number of occupied channels of new voice calls was adjusted by the use of fuzzy control theory, thus the blocking rates of different attributes business could satisfy the system requirements to achieve the best overall performance. The simulation results showed that, with the increasing business volume, the blocking rates of different attributes business in this scheme were controlled within the acceptable range by adjusting maximum number of occupied channels of new voice calls. At the same time, superior and stability system performance was ensured with significantly better effect.In this paper, by researching the vertical handoff control mechanism in the heterogeneous networks, the pre-handoff technology in the handoff process was focused on. Existing pre-handoff mechanisms usually include a fixed threshold method or an adaptive threshold method, but both of them have serious problems, for example, the utilization of network resources can’t be fully used, and quality of signal may decline sharply. To improve the shortages mentioned above, a pre-handoff mechanism with adaptive threshold based on mobile prediction had been presented in this paper. This mechanism determined the mobile terminal’s coordinates by predicting the speed when it was switching to other network, and reasonably calculated the pre-handoff threshold to improve the performance. The simulation results showed that, in this mechanism, the packet loss rate was reduced by reasonably setting the threshold, meanwhile the current network resources were fully used, therefore the system with superior performance was guaranteed in the vertical handoff process.