Research On Scheduling For VoIP In The LTE-Advanced Relaying System

With the developing and maturing of LTE project,3GPP starts evolution to LTE-Advanced (LTE-A), the target of LTE-A is to become a candidate system for ITU IMT-Advanced. As a key technique of LTE-A, relay can effectively increase cell throughput, expand cell coverage, and improve system fairness. Meanwhile, the future mobile communication system will create a fully IP based access network and core network, means there will be pure packet switched. Thus, VoIP service will instead of circuit switched to become the only carrier of voice traffic in LTE and LTE-A system. During the progress of LTE standardization, many companies in 3 GPP have done extensive studies on supporting VoIP service in LTE. However, the correlative research in the LTE-A relaying system is only on the beginning. Therefore, proposing scheduling schemes and evaluating system performance for VoIP service in the LTE-A relaying system will have a high value of research and application.On the basis of statement above, this thesis focuses on VoIP scheduling techniques in the LTE-A relaying system. The first chapter briefly introduces about LTE and LTE-A project, gives research backgrounds and main contributions of the thesis. Next, the second chapter describes several types of relay technologies, and shows the challenges in relaying system. The third chapter descripes two traditional VoIP scheduling algorithms in LTE system:dynamic scheduling and semi-persistent scheduling. Based on the two algorithms above, this chapter proposes VoIP scheduling algorithms which are appropriate to LTE-A relaying system. A system layer simulation platform is built to evaluate the VoIP performance of LTE-A relaying system with different parameter settings. Results show that through deployment of relay node, VoIP capacity can be effectively improved. In the fourth chapter, optimized VoIP scheduling schemes were proposed for backhaul link and access link respectively. Simulation results show that the proposed scheduling schemes can effectively reduce packet delay of relay users, and finally increase the VoIP capacity. In the fifth chapter, an inter cell interference coordination scheme for relay system is proposed to mitigate the interference caused by deployment of relay node, VoIP system performance under the proposed scheme is aslo evaluated in this chapter.The final chapter gives the summary of this thesis and emphasizes the valuable research directions in the future.