The Research On The Vertical Handoff Algorithms In Heterogeneous Wireless Networks

Handoff technology is one of the wireless network core technologies, and is the key to ensure seamless roaming of users. In the future heterogeneous wireless network environment, the there is not only the level handoff which occurs between the traditional homogeneous level of switching between two homogeneous network, but also the vertical handoff which is occurs between the heterogeneous networks. Vertical handoff is essentially different from horizontal handoff, and requires much higher performance, vertical handoff technology has been being the focus of the heterogeneous network research. Having the national major projects: " novel wireless resource management research and verification in IMT-Advanced " as the background, This paper focuses on the vertical handoff technique, designing a reasonable and efficient vertical handoff decision algorithm.Firstly, the paper expatiates on the vertical technology from the vertical handoff process, the vertical handoff performance requirements, vertical handoff algorithms and so on, while emphatically analyzes some typical vertical handoff algorithm: based on the received signal strength, based on the cost function, based on multi-objective decision making, based on fuzzy logic and neural networks, and based on context-aware.Secondly, for multi-service network selection, in this paper, an improved algorithm for multi-service network selection has been proposed, based on the collective session handoff algorithm and priority selection handoff algorithm, combining the advantages of these two algorithms, Application note: the improved multi-service network selection algorithm, without increasing the computational complexity, not only has met the user requirements of business priorities, but also has avoided the situation of a service dropping alone which occurs in the priority selection handoff algorithm successfully.Finally, for integration networks of LTE and WLAN, a new vertical handoff strategy based on the user speed has been proposed. Implementation of the strategy in two steps: first, make the initial handoff decision by the moving speed of the user; second, select the most appropriate destination network by the proposed improved multi-service network selection algorithm. Simulation results show that: the vertical handoff strategy based on the user speed meets the user speed and the requirements of service priorities, complements the advantages and disadvantages of LTE network and WLAN network, and gives users much more satisfaction.The research work, has an important theoretical significance for the realization smooth handoffing and seamless roaming of the user in the future heterogeneous network environment, and has some positive impact on improving the core competitiveness of the national telecommunications industry.