Vertical Handover Technologies Of Heterogeneous Networks: Research And Implementation

The Research is supported by Huawei Technology Foundation "Resource Allocation and Interference Coordination Mechanism in Multi-hop OFDMA Cellular System" and "Research on Multi-Cell Joint Resource Allocation and Schedule Algorithm in OFDM-OFDMA System".With the progress of communication technology, computer technology, integrated circuit technology, as well as the expansion of mankind's communication needs, users have increasingly demands for mobility. Future wireless communication system will contain all kinds of wireless access networks that may have different transmition rates, different coverages, different system capacities and different service levels. Mobility management is one of the most challenging technologies in the future ubiquitous and heterogeneous network environments. As one of the key control functions of the future mobility management technology, vertical handoff is used to provide session continuity across heterogeneous networks. Vertical handover algorithms become the key factor of seamless coverage and seamlessly handover in heterogeneous networks.LTE and WiMAX are two popular technologies in nowadays radio access networks. It is a trend that these two networks will be integrated. This paper is focus on the vertical handover between LTE and WiMAX. Firstly, there is a comprehensive introduction to mobility management in heterogeneous networks, and on this basis a systematic summary of the vertical handover algorithm and its related technology development and research is showed. Then, a system level simulation based on LTE and WiMAX heterogeneous networks is introduced, and a system level simulation platform is set up. The article gives a more detailed simulation design idea, gives the summary of the simulation platform for process control module, the base station module, the user module, wireless channel modules, wireless environment module (initialization module), business and statistical module and the specified design methods. Finally, focused on handover trigger and handover decision, a Difference Threshold based Fuzzy Handover (DTFH) algorithm for LTE and WiMAX is proposed in this paper. Channel quality indicator (CQI) of current network and target networks is measured by user equipment (UE), while the difference of two kinds of CQI is used to trigger the handover; and then, based on fuzzy logic method, the UE makes the judgment on the difference between the fuzzy decision value of the target network and service network, and compare to a threshold, deciding whether or not to handover. Simulation and comparison results showed that, in both of the two scenarios, the DTFH algorithm can effectively reduce the "Ping Pong Effect" in overlapping coverage areas and lower the overhead of system, as well as, in some extent, guarantee the throughput of UE to improve the performance of the vertical handover.