Fuzzy-Logic Based Vertical Handoff Algorithm Research

With the rapid development of wireless communication technology in the past twenty years, the service of wireless communication networks is upgrading extremely fast. Though there are currently several deployed wireless networks, none of these can provide high bandwidth, low latency, low pawer consumption and wide area data service to large numbers of mobile users. Wireless communications networks in the future are a combination of these different wireless networks. Vertical handoff is crucial for seamless roaming in heterogeneous wireless networks.First, this paper introduces the history of wireless communication and the future trends.then the characters of the future heterogeneous wireless networks is simply discribled.Severval key technologies such as IMS,IPv6have been researched. Especially, the existing vertical handoff algorithms have been reviewed and researched.Second, to minimum unnecessary handoff number, a fuzzy logic based vertical handoff algorithm is researched. It uses the fuzzy logic method to evaluate the performance of the available networks. The algorithm considers received signal strength(RSS)、delay、bandwidth and preference as the vertical handoff criterias.After the original inputs have been processed by fuzzy logic, It makes the network selection by MADM mothod. The simulation results demonstrate that this vertical handoff algorithm can reduce the number of handoffs and improve the system performance.During the vertical handoff progress, many criterias should be taken into consideration. Among these criterias, some of them are QoS correlative. In roder to improve the QoS, an other vertical handoff algorithm which is based on fuzzy logic and AHP algorithm is proposed, In this algorithm the weights of different criteria is calculated by AHP algorithm accordding to the current service type and its characters. The simulation demonstrates that this vertical handoff algorithm can improve the system throughtout.