Research On Handoff Technology In Heterogeneous Wireless Networks Environment

Under the context of amalgamation of networks, operation and terminal, how to provide the users and terminal with mobile administer in order to ensure the seamless communication and the QoS is becoming the pressing question of the generation heterogeneous networks. The handoff technology, especially the vertical handoff technology influence on the mobile administer greatly.This paper summarizes the actuality and current of the wireless heterogeneous networks. It studies and overcomes some questions of handoff technology, including the design of the heterogeneous network framework structure based on MIH, the judging method of handoff among bases, the vertical handoff method and the building of the handoff model based on MIH and controlled by network.Aiming at flaw of traditional multi-mode network framework, this paper introduced a framework model of multi-mode terminal framework structure, analyzed and depicted the components of the framework structure and their function, and designed the realizing method of handoff choosing function of heterogeneous networks.In order to solve the problem of too many ping-pong handoffs and judging lagging due to handoff delay existing in the traditional methods, this paper introduced an improved RSS handoff judging method based on estimation and forecast. This method estimated the velocity and distance and forecasted the RSS after the handoff delay based on wireless freedom radiating model, and improved the traditional judging method based on RSS. At last, the result of simulation shows, this method reduce the times of whole handoff by 58%, the times of false handoff by 20%, and the times of ping-pong handoff by 92%.The another advantage of this method is that, it need not additional equipment or strict condition.Aiming at the difficulty of setting the attribute weighs by the user, this paper introduced the concept of connection numbers, introduced a new method of setting attribute weighs, and improved the traditional TOPSIS vertical handoff method. Then a simulation and comparison is introduced and made to testify the improved TOPSIS method, and the results show that the new method can improve the effect of vertical handoff.At last, a network handoff model based on MIH and controlled by network is built. Especially, the processes of the network choosing and network handoff are designed in detail.