Research On Vertical Handoff Algorithm In Heterogeneous Wireless Networks

The goal of future communication technology is to achieve any person in anyplace, at any time, with anyone in any way for any form of communication. Presentsituation is any single network can not meet the future communications’ needs, eitherbecause the coverage is not wide enough, or the network can not provide higherbandwidth for some communications, making different networks which with differentcoverage areas and the ability of business provide to mutual integration become aninevitable trend of the network development. Mobility management technology as a keytechnology integration for heterogeneous networks has become the focus of domesticand foreign institutions, mobility management technology is no longer limited tohomogeneous network switching, but more involved the switching between thenetworks with different structures. Therefore the study of reasonably and efficientvertical handover algorithms between heterogeneous networks has important theoreticaland practical significance.The study of vertical handoff algorithms in heterogeneous wireless networksmostly based on the value of the signal strength of each network, such algorithm, whilesimple, but do not consider the enormous differences existed in heterogeneous networks,such as the network structure and coverage areas, making judgments accuracy is nothigh; some algorithms draw on fuzzy logic and neural network theories, whichimproved the accuracy of the judgment, but the complexity of these algorithms is toohigh, making these algorithms do not apply to general communication terminals. Thispaper based on the summarize the existing vertical handoff algorithms in heterogeneousnetworks, making users get the best communications experience and always access themost suitable network as the target, considering features of UMTS and WLAN whichare largely erecting in our country and different communication needs in our real life,proposed three different vertical handoff algorithms, as follows.(1) For an increasing of user’s business types, and different communicationservices requires different quality of service, we proposed a traffic differentiation-basednetwork selection scheme in wireless heterogeneous networks. The algorithm uses the Analytic Hierarchy Process to calculate network judgment factors in the various typesof communication services and utilizes cost function to determine the performance ofeach of the alternative network. We made use of the scenario simulation method toverify the algorithm can enable users access to the most effective appropriate networkbased on different user business type.(2) With the accelerated pace of life, the communication terminal’s standby stategrowing impact on the choice of the network, so we proposed an vertical handoverdecision algorithm based on the terminal’s standby state, in the algorithm we definesthree types of terminal standby mode and defined a network gravitation judgment whichused to measure network performance, we formulated different network switch triggerstrategies depending on different standby mode. OPNET simulation validated that thealgorithm allows the user to quickly and efficiently access the best network, and canextend the standby time of the terminal, so as to protect the user’s communicationexperience.(3) In order to further improve the accuracy of network switching, we proposed alocation information auxiliary network switching algorithm, in some place where caneasily obtain user’s location information, the algorithm makes use of the network andthe user’s location information auxiliary network switch selection which can improvenetwork switching efficiency, enabling the user to obtain the optimal communicationsexperience. In connection with the key requirements for this algorithm, an RSSI-basedlocation system is designed and implemented.