Research On Downlink Resource Scheduling In Relay-enhanced TD-LTE-Advanced System

In recent years, people get closer relations to mobile communications for they have high data rates, high quality, and variation of traffic. To satisfy the trend, the 3rd Generation Partnership Project(short for 3GPP) provides the LTE-Advanced systems based on Long Term Evolution(short for LTE). The most obvious difference between LTE-Advance system and LTE system is that the former one has introduced some enabling technologies including relay, which extends the network coverage, improves the cell-edge performance and enhance the fairness among the users. The relay technology has been the hot spot for researching, since relay nodes also can be set up conveniently and they are cost-efficient. The resource partitioning strategy of relay-enhanced system is really important so as to enhance the function of relaying.Nowadays, there have been two general standards of LTE, and the standard of TD-LTE made by China has been developed to TD-LTE-A standard. In this thesis, we focus on TD-LTE-Advanced system and study the resource scheduling algorithm of relay-enhanced cellular system. Firstly, relay classification, its architecture and theoretical knowledge of physical layer related technologies are introduced. Downlink resource scheduling procedure is described as well. And we study the effects on system performance that relay technology brings. We compare with the scenario without relay on the simulation platform. Simulation results show the introduction of relay technology can improve the performance of cell-edge users and the overall system.Then, Qo S-guaranteed downlink resource scheduling algorithm in TD-LTE-Advanced relay-enhanced system is studied. We deploy downlink communication scenario with traffic with different Qo S applicable to the relay system based on summary of Qo S in TD-LTE-A standards. Focusing on the above scenario, we propose a Qo S-guaranteed downlink resource scheduling algorithm including: scheduling in the backhaul subframe and scheduling in the access subframe. And we compare the proposed algorithm with the exiting algorithms on the built system level simulation platform of TD-LTE-A relay-enhanced system. Simulation results show that the proposed algorithm can distinguish traffic priorities, achieve low loss rate, meet the needs of GBR better, balance the performance of both relay users and direct users, and achieve high system throughput and good user fairness.Finally, in this thesis, based on the architecture of MIMO relay-enhanced TD-LTE-Advanced system, we study and determine transmission modes and pre-coding and detection algorithms in each link. Then, the gain brought by the combination of multi-antenna technology is verified on TD-LTE-A multi-antenna simulation platform. In order to further improve system performance, a fairness-aware resource allocation algorithm is proposed. In the proposed algorithm, resource allocation is divided into 3 phases: a frequency resource partition scheme is firstly proposed to realize the tradeoff between fairness among UEs served by various Relay nodes and system throughput; and then, a backhaul allocation algorithm is presented to match the e NB to Relay transmission with the Relay to UE transmission with reduced feedback overhead; finally, a resource allocation algorithm from e NB and Relay to UEs is given to maximize the proportional fair utility so that user fairness can be guaranteed. Simulation results show that the both system throughput and user fairness can be improved with the proposed resource allocation algorithm with limited feedback overhead.