Research On The Fuzzy Logic-based Vertical Handover Algorithms In Heterogeneous Wireless Networks

With the rapid development of mobile communication system in recent years,a variety of wireless access technologies have been produced.Heterogeneous wireless networks are formed in the area where these different access technologies cover and integrate each other.One kind of network can’t satisfy the user’s all requirements for the reason that there are great differences in bandwith and coverage of these access networks,so the most important characteristics of the next generation wireless networks are that all kinds of access networks cooperate with each other to provide users with ubiquitous network environment.In the integrated heterogenous wireless networks,how to design a kind of efficient and reasonable vertical handover mechanism to meet the quality of service(QoS)requirements of terminals is the focus of the study in academia.For the purpose of meeting QoS requirments of different application classes and improving timeliness of handover decision of vehicle terminals,this papper studied the vertical handover algorithms in heterogenous wireless networks.Firstly,considering the differences in QoS requirements of different application classes in heterogeneous wireless networks,this paper proposes an individualization service oriented type-1 fuzzy vertical handover algorithm.The handover performance is improved from two aspects: In the network discovery phase,the candidate networks are sifted by predicting the network loads in handover execution.Moreover,in the handover decision phase,different type-1 membership functions are designed according to the different QoS requirements of each application classes.The simulation results show that the proposed algorithm can reduce the blocking probability,improve the system throughput,select the target network reasonably,and meet the QoS requirements of terminal individualization service.Secondly,in order to solve the vertical handover problems which are caused by short sojurn time of vehicle terminals after handover and the fuzziness and randomness of decision parameters in handover decision phase in vehicle heterogeneous network,this paper proposes a sojurn time prediction based type-2 fuzzy vertical handover algorithm.The sojurn time in all candidate networks are predicted based on the movement trend of vehicle terminals.Moreover,type-2 fuzzy membership functions of sojurn time,available bandwith and usage cost are designed on the basis of their fuzziness and randomness to build type-2 fuzzy inference system,and the optimal network is selected according to the output of the fuzzy system.The simulation results show that the proposed algorithm can reduce the handover failure rate,the ping-pong handover numbers and the average handover numbers significantly,improve the system throughput,thus improving the QoS of vehicle terminals.