Research On Vertical Handoff Technologies Of Wireless Heterogeneous Networks

With the rapid development of mobile communication and wireless network, a variety of wireless access technologies which can provide different type of service have been put into practice. In order to make full use of the network resources, provide users with support for a various of service needs and ensure the quality of service, the integration of networks becomes the direction of network development. Therefore, the future communication network which can provide different data rates, coverages and support of different service levels will be a heterogeneous network, containing multiple access technologies.As a key technology for mobility management in heterogeneous networks, vertical handoff is used to switch users between different access technologies. Thus, in heterogeneous network, the performance of vertical handoff algorithm is a key factor in the efficient allocation of network resources and the seamless switch of users.Based on the description of the development in mobility management of heterogeneous network and the vertical handoff technologies firstly, the paper summarized the related algorithms and the current research in the three stages of the vertical handoff. Then, a simulation platform which was used to perform system-level simulation for WCDMA and WLAN based heterogeneous network was built in the paper and the design ideas and simulation methods of the platform was described. Finally, in view of the deficiencies in current algorithms, this paper proposed a new vertical handoff algorithm-Predictive network information based vertical handoff algorithm[2]. In the algorithm, the bandwith of each access network is considered as multiple channels[3]and the channel usage situation of each access network is presented based on birth-death theory. Based on the information mentioned above, the algorithm predicts the available bandwidth of each access network and the blocking probability of user accession. Then, based on the fact that the network available bandwidth is described as a value function and the blocking probability is expressed as a cost function, a decision function is defined as the combination of the two functions being weighted. Finally, the best access network is chose by substituting various parameters of each access network into the decision function. Simulation results show that the proposed vertical handoff algorithm can improve the system throughput effectively and lower the blocking probability of handoffs with consideration of guaranteeing the QoS of users which avoids the waste of network resources.