Research On Vertical Handover Decision Scheme In Heterogrnrous Networks

With the development of computer technology and the increasing demands for mobile communication, the next generation wireless network will be composed of various wireless networks (e.g.,WiMAX and WLAN). In heterogeneous networks, users will enjoy more services and access to communication services anywhere and anytime. But in this environment, it is difficult for users with seamless communication. So scholars proposed vertical handover technology to solve this problem. One of the most important problems of handover is handover decision, which includes handover trigger and network selection. Handover trigger solves the problem of triggering time, and network selection solves the problem of which network is the most suitable to access. In this paper, we proposed a vertical handover trigger algorithm based on ARMA prediction model and a network selection mechanism based on utility theory.The handover trigger algorithm we propose aims to improve the performance of vertical handover and reduce unnecessary handover, which based on the current received signal strength and the previous received signal strength to predict the next receiving signal strength using ARMA model. And then according to the predicted signal strength to determine whether to trigger the link layer triggering event and complete vertical handover. The simulation results indicate that the proposed algorithm outperforms the RSS-based approach with the threshold in the performance of handover and the number of handover.Some studies based on utility theory to solve the problem of resource allocation, we use this method to solve the problem of network selection. In this paper, the different QoS indicators which should be considered in the process of network selection are expressed by different utility function, mobile node can calculate the value of the utility by the utility function, to indicate its satisfaction with the candidate network. This mechanism makes the indicators which should be considered in the process of network selection can be compared with unified criterion, and this mechanism does not involve matrix operations so it has smaller computing than most existed mechanisms. In the NS-2 simulation environment, we simulate the data application and voice application in the process of network selection. The result shows that the QoS of the selected network is accord for the requirements of the application.