中文摘要：

针对协作通信系统中源到中继及中继到目的两阶段的瞬时信道状态信息（CSI）影响系统整体误码率（BER）的问题,提出一种综合衡量两阶段信道系数的中继选择方案。首先,根据每个候选中继的CSI,比较源到中继及中继到目的的两阶段信道系数,选出两者中较差的信道状态;然后,按照较差的信道状态对候选中继排序,得到近似较优的中继节点集合;最后,从中选择两阶段信道系数之和最大者作为被选中继参与协作传输。仿真结果表明,当候选中继节点数为100及5,BER下降到10-4及10-5时,所提的中继选择方案与基于最优较差信道的中继选择方案、基于最近邻关系的中继选择方案相比,所需信噪比（SNR）分别降低了0.4 d B和0.2 d B。所提方案能够增加无线中继网络的信息传输范围,提高信息传输的可靠性。

英文摘要：

As the instantaneous Channel State Information（ CSI） of source to relay and relay to destination affects the overall Bit Error Rate（ BER） of the cooperative communication system, a relay selection scheme which evaluated the two-stage channel coefficients was proposed. Firstly, the channel coefficients of source-relay channel and the channel coefficients of relay-destination channel were compared according to the CSI of each candidate relay, and the worse one was found out.Moreover, a node set containing the approximate optimal relays was obtained by sorting the candidate relays based on their worse channel coefficients. Finally, the relay with the highest summation of the two-stage channel coefficients in the set was selected as the one which participated in the cooperative transmission. The simulation results reveal that the Signal-to-Noise Ratio（ SNR） of the proposed relay selection scheme respectively decreases by 0. 4 d B and 0. 2 d B compared with the best worse channel selection scheme and the delay selection scheme based on the nearest neighbor relation, when the number of candidate relay nodes is 100 and 5, and the BER decreases to 10- 4and 10- 5. In general, the proposed scheme can expend the information transmission range and improve the reliability in the wireless relay network.