Research And Implementation Of The Integration And Handoff Algorithm Of Heterogeneous Network

The next generation wireless communication system will consist of various kinds of radio technologies. These technologies have respective characteristics in terms of coverage, bandwidth, latency, security and cost, etc. Meanwhile, there is an increasing demand to support seamless roaming among heterogeneous networks for better user experience and resource utility. Therefore, handoff algorithms have attracted much research attention in relative fields. This thesis uses the IEEE 802.21 protocol to integrate the heterogeneous networks. After the integration of the heterogeneous networks, this thesis proposes a speed sensitive vertical handoff algorithm based on fuzzy control.First, this thesis gives a general introduction of the heterogeneous networks and the top three most popular radio networks in China:TD-SCDMA, WLAN and WiMAX. Then handoff technologies are described. In the third part of the thesis, IEEE 802.21 media independent handover protocol is introduced. The thesis also reveals the way of how to implement these functions in NS-2 simulator. In the fourth part, a novel speed sensitive vertical handoff algorithm based on fuzzy control is proposed. Based on the collected information on received signal strength (RSS), load conditions of candidate networks, velocity of mobile terminals and user preference, the vertical handover decision is then made by fuzzy logic process. This algorithm focuses on the handoff efficiency and user experiences when users are moving at high speed and the network situation is complex. Simulations are done with NS-2 simulator. The Simulation results show that the proposed algorithm can reduce unnecessary vertical handoffs caused by high speed. Simulations are also carried out to show that the vertical handoff algorithm can benefit the efficiency of the resource usage in the heterogeneous network.Finally, the thesis makes a conclusion of the proposed vertical handoff algorithm. And further researches are focused on the load balance and traffic scheduling by means of making vertical handoffs.