Research On A Vertical Handoff Algorithm Based On Handoff Necessity Estimation And TOPSIS

The next generation of wireless communication network is a heterogeneous wirelessenvironment where a variety of wireless network technologies coexist and complement each other,seamlessly integrated in, mobile terminal equipped with multiple wireless interfaces can access todifferent networks. In such a heterogeneous wireless environment, it becomes an important issue todesign an efficient and intelligent vertical handoff algorithm that maintain mobile user access to thebest network and make the radio resources of the whole network used effectively.The vertical handoff decision can be divided into handoff initiation and target network selection.Handoff initiation mainly finishes the task that estimates the necessity of handoff and chooses theright time to initiate the handoff. Target network selection ranks the candidate networks by theirperformance to select the best network. Most of the research work focus on dealing with the targetnetwork selection, ignoring the handoff initiation and necessity estimation, and some schemes lackin taking into account some important parameters to select the target network. Hence, addressingthese issues, this paper does some researches from the following two aspects.Firstly, the paper studies an algorithm to estimate the necessity of vertical handover based onfuzzy logic, the algorithm establish several parallel fuzzy logic controllers based on the theory offuzzy logic control to form a handoff necessity estimation module determining whether a handoff isnecessary. This module inputs the terminal velocity, the RSS and QoS of the current network to thefuzzy inference system, outputting a VHO-Factor that is a comprehensive evaluation of thecondition of the user and network, and comparing with the handoff threshold value to determiningwhether a handoff is necessary. Simulation results show that the algorithm can effectively reflect thecondition of the user and the network, choose the right time to initiate a handover.Then, this paper studies a vertical handoff algorithm based on handoff necessity estimation andTOPSIS. The algorithm combines handoff necessity estimation algorithm with TOPSIS，providinga complete framework to perform vertical handoff from handoff initiation to target networkselection. The handoff necessity estimation algorithm determines whether a handoff is necessary tocomplete handoff initiation, TOPSIS takes various decision criteria into account to select theoptimal network for the user. Since adding handoff necessity estimation module and taking morecomprehensive decision criteria into account, the subsequent simulation results show that the algorithm can select the most appropriate network for the user, and effectively reduce the number ofhandoff and the failure probabilities of handoff, improve the end-user’s satisfaction.