A Coverage-Based Handover Algorithm For High-Speed Data Service

4G supports various types of services. Different services have different coverage. The coverage of high-speed data service is smaller than that of low-speed data service, which can not guarantee continuous coverage and usually makes the high-speed data service users occur dropping before reaching the handover area.OFDMA is typical 4G system. First, this paper introduces OFDMA system theory, multiple access schemes and radio resource management (RRM) technologies; High-speed data service usually occupies more system resource in 4G system, which will bring greatly impact on dynamic characteristics of system, cause system performance to decline during and after handover process. Existing handover algorithms for multiple services are mainly concerned on classification of services of different QoS and handover with queuing, ignoring the problem of handover failure caused by the discontinuous coverage of high-speed data service in the condition of the coexistence of multiple services and QoS classes.Second, considering the disadvantages of present handover algorithms, this paper proposes a new OFDMA handover algorithm: A Coverage-based Handover Algorithm for High-speed Data Service. The new handover algorithm reduces source rate and adopts FSES (Faint Sub-carrier Elimination Strategy) to adjust the sub-carrier allocation and make the resource allocation more flexible, which extends the coverage of high-speed data service and makes users acquire "transient coverage". Meanwhile, the new algorithm utilizes the "transient handover QoS" to reduce the handover effect to target cell for high-speed data service users and make these users acquire smooth handover. Last, this paper designs and completes the OFDMA system level simulation platform. Based on the platform, the new handover algorithm performance is evaluated by simulation analysis. The simulation results shows that the new algorithm can improve the whole system performance, reduce the handover dropping probability and new call blocking probability, enhance the resource utilization ratio.