Downlink Scheduling Algorithm Research In TD-LTE-A Relay System

In the TD-LTE-A (Long Term Evolution Advanced) system, users who are on the edge of the cell have relatively poor channel conditions. If edge users are allocated more resources to improve throughput, then central users couldn’t get enough resources, leading to the cell throughput falling sharply. If we increase the power of edge users, it couldn’t make the throughput of edge users larger because of increasing the ICIC (Inter-Cell Interference Coordination) and reducing the users’ SINR (Signal to Interference and Noise Ratio).Relays are placed on the edge of the cell to solve the problem in TD-LTE-A system and the data transmission need two jump. First, the BS(base station) sends the data to the relay which the edge user belong to. Second, the relay then sends the data to edge users. Relay not only can strengthen the channel conditions of edge users, but also can increase number of available resources in the sector through resource reuse. It could improve the throughput of cell edge user and thus improve the cell throughput.The TD-LTE-A system solved the problem of the poor throughput of edge users well, but it brings new challenge for downlink scheduling and resource allocation. Because of the addition of relay, the TD-LTE-A system has the backhaul link and access link on the basis of direct link. The frame structure of the configuration is the important thing, different frame structure configurations influence the transfer time of three link ratio, which affects the throughput of three links. Secondly, the BS allocates the resource to relays and macro users per a backhaul subframes. Finally, the BS schedules the macro users and the relay schedules edge users per a access subframe. So the resource allocation is conducted. The concrete problems will be elaborated and the technical stauts will be introduced.In this paper, a novel packet scheduling algorithm is proposed. It can provide a higher fairness for users’throughput and a small delay for more users. It also provides a resource allocation algorithm which takes throughput and fairness into account. The simulation results show that the proposed scheme has higher fairness and smaller delay while the cell throughput is stable.