Investigation Of Fusion Technlogies Of Heterogeneous Wireless Networks

With the rapid development of various wireless access technologies, more and more new wireless networks for different application are springing up, but none of them can take the place of all others for their different characters. The fact that one hot spot is covered by more than two different types of networks has attracted the attention of the industry and the academy, and a lot of experts have researched fusion of heterogeneous wireless network (HWN).There are two key problems for HWN to be solved. The first problem is that there should be one access selection solution to maximize the use of the limited wireless bandwidth and grant the access priority based on the QoS of the service. The second one is that seamless handover should be supported to guarantee the QoS of the service in the diverse wireless network environments corresponding to the horizontal handoff during the MN's movement.Firstly, this thesis researches the centralized access selection to make use of the trunking gain and the multi-radio access diversity gain in the HWN. After introducing the solution algorithms with the abbreviation of ABR and RBR, one advanced algorithms ABRD has been proposed to minimize the overall bandwidth occupation and reduce the user blocking rate. For the different type of services which has different requirement in QoS, we introduce the weighted fair queue and price scheme to grant the different access priority. The simulation results show that the scheme proposed can grant access priority based on the QoS of the service.Secondly, this thesis focuses on the proactive handoff of the HWM which consists of WLAN and WiMAX. First, the flow diagram of vertical handoff with MIH service and mobile IP protocol has been analyzed and the difference between MIPv6 and FMIPv6 scheme has also been studied. To improve the performance of vertical handoff, we propose one proactive handoff scheme with adaptive threshold to trigger the handoff, which can avoid the shortage of fixed threshold. For the correct decision and execution of the scheme, accurate estimation of the required handoff time should be delivered in advance. Based on the flow of the handoff process, we estimate the required handoff time during the handoff process to implement the scheme. Simulation is carried out to validate the conclusion of theory estimation and the proactive handoff scheme proposed by us.Finally, the thesis is concluded and the future work is prospected.