Vertical Handoff Methods For Heterogeneous Wireless Networks

As the rapid development of wireless networks, there are more and more types of network technologies, and the wireless networks of next generation is heterogeneous wireless networks, where multiple wireless access technologies coexist, with the integration of heterogeneous wireless networks getting more complex. Nowadays, the field of heterogeneous wireless networks has become the research hotspot and many research organizations and institutions have carried out the research on the related key technology of heterogeneous wireless networks. Vertical handoff is one of the key technologies of mobility management in heterogeneous wireless networks, to ensure the continuity of the session when users roaming in the heterogeneous network. The current study still lacks a reliable and efficient handoff algorithm. Meanwhile, how to improve the utilization rate of the network resource should be considered when making the handoff decision.On account of the insufficiency of the current handoff algorithm, the dissertation focuses on the aspects of meeting users’ needs, transmission mode and improving the authentication protocol, to enhance the performance of the handoff algorithm and the utilization rate of the network resource. The main work of this dissertation includes the following three parts:(1)The research on vertical handoff decision method based on user demand and application properties in heterogeneous wireless networks. A handoff algorithm based on user demand is proposed in this dissertation. In network perception stage, firstly distinguish the type of users, and then get rid of the inappropriate candidate network according to the type of users. The mobile nodes cannot send and receive packets in the state of perceiving the candidate access point, therefore, this method can improve the network performance to a certain extent, also, mobile nodes switching to the obvious improper network will cause unnecessary handoff, for example, the high-speed mobile nodes should avoid switching to WLAN, as the mobile nodes will quickly get away from the coverage area of WLAN within very short time. Based on the different needs for network properties of the entire current application program when handoff decision making, comprehensive weight is calculated, and finally the optimal candidate network is calculated by using multi-attribute decision making method. (2) The research on the trusted handoff algorithm in multihop-enabled heterogeneous wireless networks. A multihop-enabled trusted handoff algorithm is proposed in this dissertation, and the current research has proved that multihop and cooperative communication can improve the overall performance of the network. Taking the two typical network technology WiMAX and WLAN (The two kinds of network technology characteristics are complementary, WiMAX has larger coverage area and smaller bandwidth, while WLAN has smaller coverage area and larger bandwidth) in heterogeneous wireless networks for example, multihop is used to improve the overall performance of network and the coverage area of WLAN, furthermore, a trust model based on vertex similarity is designed to improve the safety of the algorithm. This algorithm can effectively alleviate the resource reservation demand, and decrease the access blocking probability while preserving high spectral efficiency. Also, when finding the relay forwarding nodes, mobile nodes can prevent the malicious nodes from joining the forwarding table, and prevent the malicious links from joining the setup procedure of links, at the same time, the end-to-end delay and throughput has greatly improved.(3) The research on the fast handoff authentication of heterogeneous network. A fast handoff authentication method of WLAN is proposed in this dissertation. The nodes can no sooner start to communicate or finish the handoff process than completing the authentication, while the existing research has proved that the delay caused by node authentication accounts for a large proportion of the handoff delay. EAP-AKA is a kind of EAP authentication framework, which uses the obtained five tuple (aka) from the mobile network to get the MAC for certification and the key for encryption, being the typical authentication protocols for WLAN. However, EAP-AKA protocol lacks the fast re-authentication method. The delay is mainly due to the transmission of the authentication information between mobile nodes (MN), WLAN and HAAA/HSS. Therefore, EAP-AKA is modified, handoff authentication process of WLAN is redesigned, and the handoff authentication of WLAN is divided into three types:initial authentication, fast inter-domain authentication and fast intra-domain authentication. A modified authentication protocol can reduce the communication with HAAA/HSS on the Internet, lessen the delay caused by the transmission of the authentication information, and improve the handoff performance.In summary, the handoff technique in heterogeneous wireless networks is studied in this dissertation, and the research results can be a good theoretical guidance in the work of heterogeneous networks integration and mobility management in heterogeneous networks.