A Virtual Soft Handover Method Based on Base Station Cooperation with Fountain Codes

In this paper we propose a virtual soft handover method in uplink based on a coding scheme that combines BS cooperation with fountain codes to achieve the seamless handover. Two protocols are investigated and their performances of average throughput are compared: (I) conventional Automatic Repeat reQuest (ARQ) protocol with Threshold-Based Adaptive Modulation and Coding (TB-AMC) scheme, (II) BS Cooperation with Fountain Codes (BCFC) protocol with fixed Modulation and Coding (MC) mode. Theoretical analysis and numerical results show that, there exists a region near the cell edge, where Protocol II outperforms Protocol I by offering more stable QoS of throughput. Defining the beneficial region as Virtual Soft Handover (VSHO) region, we calculate the bound of VSHO region characterized by average received SINR. An algorithm is designed by switching the system to Protocol II once the users enter the VSHO region and switching back to Protocol I when they leave the region. The parameters which affect the performance improvement in VSHO region include average received SINR and MC modes characterized by error performance estimation parameters.