Research On Vertical Handoff Of Heterogeneous Network Based-on Fuzzy Discrete Event System

The integration of heterogeneous wireless networks is the future trend of wireless communication networks, mobility management is a crucial part in it, and the vertical handoff is one of the key technologies of mobility management in the future communication network. In this paper, we focus on the application of fuzzy discrete event systems (FDES) to heterogeneous network vertical handoff. FDES theory is a method to study the system state diversification driven by event, it can be used to determine the uncertainity of certainity looking natured real world objects and also suitable to research the complexity of nonlinear systems related to human subjective judgments.In the paper, the basic concepts of the integration of heterogeneous wireless networks are described detailed, research achievement and development trend of mobility management and vertical handoff technologies are summarized, then the existing vertical handoff strategies are analyzed, their advantages and disadvantages are pointed out. On the basis of all these reserarchments, vertical handoff strategy for heterogeneous networks based fuzzy discrete event systems is proposd.For the investigation of FDES theory, we focus on FDES automata modeling, fuzzy state transition rules, automata composition and decision strategies. Based on the existing composition model of automaton, the simplified method of FDES automata composition on foundation of average tensor algorithm method is put forward, and the state transfer theorem with average tensor algorithm is proved. In addition, the theory of fuzzy discrete event systems is expanded, expansion FDES theory (EFDES) is proposed, to make the theory of fuzzy discrete event system more perfect, and applied more widely.This paper proposes a expansion composition of heterogenous networks FDES automata, the performance function of the network is given. FDES automaton is used in vertical handoff in heterogenous network, the vertical handoff is constructed, and FDES automaton model is established. According to the effectiveness function of vertical handoff, the quality of service (QoS) in heterogenous network in certain moment of time can be calculated, simultaneously handoff rules in according to individual choice and terminal speed can be formed; Based on the study of EFDES, we initially apply it in the heterogeneous network handover, the fuzzy memberships are defined with the new theory, and eventually do the the operation of state transition.Finally, we use NS-2 to simulate the vertical handoff for heterogeneous network. As NS-2 itself does not have the fuction that mobile node supports multiple network interface, first of all, we need to expand the multi-interface nodes. By means of performance function, the priority model of vertical handoff is observed, the handoff rules areformulated, and set an example to describe the implement rules of vertical handoff in heterogeneous networks. Through NS2, the process of vertical handoff can be simulated, some network indicators (TCP delay, throughput, etc.) are analyzed, and the results show that FDES automata methods can achieve the purpose of optimizing the network handoff.