Research Of Relay Selection In Cooperative Communication System

In the case of jointly using MIMO and OFDM technology still can't meet therequirement; distributed Relay Assisted communication is an important technology thatcan meet the QoS requirement of terminal users. The main purpose of Relay Assistedcommunication can be summarized as extending the user coverage and increasing thesystem capacity. The distributed virtual MIMO system relies on the leakprooffit amongthe independent relay nodes which randomly located nodes in space, which inducing therelay selection problem. This thesis will focus on the following points, including:1) Investigate the exsting problem for relay coordination schemes in fixedrelay enhanced network, propose a more praticable relay coordination scheme based onopportunistic relay selection which eliniminates the synchronization among relaystations, and design its signaling procedure in the LTE A scenario. For the relaycoordination scheme based on opportunistic relay selection, simulation results showsthat CSI report overhead is related to the number of candidate relays, at most four bitsare needed to gain a moderate system performance; to solve the sysyem overheadproblem caused by transmitting quantized channel state information in centralized relayselection, propose an improved relay selection scheme based on threshold quantizationwhich can increase the bit utilization rate. For the adaptively relay selection schemebased on threshold quantization, camparison research demonstrate that by settingappropriate threshold at relay nodes, it can increase the bit utilization rate, meanwhilehas no significant effect in the BER performance.2) Investigate the random relay selection and location relay selection scheme for acooperative MAC protocol named ALLIANCES; propose a new relay selection shemebased on received SNR which can choose the best relays more accurately. Applicatingthe improved relay selection rule base on received SNR, and comparing with randomrelay selection and location relay selection rule, results indicates that the new relayselection rule can lead to better performance.