Research On Vertical Switching Method Of Heterogeneous Wireless Network

With the diversification of communication service demand and the rapid development of broadband wireless access technology, a variety of emerging wireless networks with different features have appeared continuously. A variety of different wireless access technology coexist and have complementary advantages, thus they formed overlapping coverage of heterogeneous wireless networks so as to provide diverse services demand to mobile users. The integration and interoperability of heterogeneous wireless networks could ensure seamless roaming and session continuity during user’s movement and it is the inevitable development trend of the next generation wireless communication system. Mobile management is the key technology to realize the integration of heterogeneous networks, while the vertical handover allows multi-mode terminals access to different wireless networks at different times in the mobile process, which is the core content of mobility management.This paper studies several mainstream vertical handover algorithms including based on a single element, the cost function method, simple additive weighting, technique for order preference by similarity to an ideal solution, analytic hierarchy process, grey relational analysis and fuzzy logic algorithm. The characteristics of different vertical handover algorithms are described and the performance of each algorithm in multi-attributes, validity, flexibility and algorithm complexity is analyzed.Based on the contradiction between the network discovery time and power consumption for the method of scanning wireless signal with fixed interval in the network discovery phase, this paper studied a vertical handover scheme based on periodic adaptive method. During the process of handover initiation, the mobile terminal always adjusts the interval for scanning signals according to the received signal strength so as to adaptively change the interval based on the quality of wireless signal. In the handover decision, firstly using precedence chart method to get the subjective weight for each network parameters. Afterwards, the objective weight can be obtained and then modify the subjective weight to get the final weight. Finally, multiple attribute decision algorithm is used to select the network which has the best performance to access. The simulation results show that the proposed scheme is able to reduce power consumption and discover new network timely so that reduce the delay of handover compared to the traditional scheme.In group vertical handover scenario, many users send handover requests to wireless networks simultaneously or during a short period of time, which may result in network congestion and thus increase handover blocking probability. This paper studied a new group vertical handover scheme based on maximum blocking probability in order to avoid network overload as well as utilize wireless resources reasonably. The permissible maximum number of users among total users that initiate handover at the same time is obtained according to the maximum blocking probability. Afterwards, the users select the networks using the criterion of minimizing average transmission delay or packet loss rate of the whole heterogeneous networks. Simulation results show that the scheme is able to reduce the congestion caused by the group vertical handover, average transmission delay and packet loss rate compared to random delay scheme.