Abstract: Relay selection can validly mitigate performance degradation caused by channel fading and increase diversity level, however all-time cooperation decreases bandwidth efficiency. This paper investigates performance of threshold-based relay selection in amplify-and-
forward cooperative networks over Rayleigh fading channels. SER closed-form expression and bandwidth efficiency formula are derived when M-PSK signal is given. This paper also provides numeric simulation to verify the analysis. It shows that, with low-SNR or few relay-nodes, raising threshold can improve bandwidth efficiency and, with high-SNR or lots of relay-nodes, decreasing threshold can dramatically improve SER performance.

Key words: amplify-and-forward protocol, selection relaying, threshold-based relaying, symbol error rate

摘要： 中继选择能有效地克服信道衰弱影响，提高分集效果，但全天候协作降低了系统的带宽效率。研究了Rayleigh信道条件下一种新的基于门限决策的多中继选择系统并分析了系统性能，推导了M-PSK信号多中继选择系统的SER闭式表达式和系统带宽效率表达式。实验结果显示，在低信噪比和较少候选中继场景，提高协作门限，可提高系统带宽利用率；高信噪比和较多候选中继场景，适度降低协作门限，可有效提高系统平均SER性能。

关键词: 放大前传协议, 选择中继, 门限决策中继, 码元错误概率