中文摘要：

分析了认知中继系统中双向的频谱共享干扰。一方面，依据主用户的QoS（qualityofservice，服务质量）需求，限制认知用户对主用户的干扰；另一方面，在瑞利干扰信道条件下，建模主用户对认知用户的干扰。在此基础上，进行基于信干噪比的认知中继选择和性能分析，推导出认知中继系统中断概率的闭式表达式，并通过理论分析和仿真结果证明，随着主用户发射信噪比的增大，频谱共享干扰会导致认知系统中断饱和现象的发生，而在特定的主用户信噪比条件下，认知系统仍可获得完全的分集增益。

英文摘要：

The mutual spectrum-sharing interference in cognitive relay systems was considered. On the one hand, the interference from the secondary users （SU） to the primary user （PU） was limited in order to guarantee the QoS of primary transmissions; and on the other hand, Rayleigh-faded interference from the PU to the SU was modeled. Based on these considerations, the closed-form expression of the outage probability of cognitive relay systems was derived. Theoretical solutions and simulation results show that spectrum-sharing interference leads to the outage saturation of cognitive relay systems as the SNR of the PU increases and the full diversity gain is able to be achieved with a certain SNR of the PU.