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本文研究了认知无线电网络利用放大中继进行信息传输的中断和分集性能。当频谱感知表明授权信道空闲时，认知用户发送或转发信号。当频谱感知表明信道被授权用户占用时，中继节点放弃转发。本文给出了上述方案中断概率闭式表达形式，并推导出分集增益。研究结果表明上述方案无法获得满分集增益。为增加系统分集增益，进一步给出了基于重复的放大中继方案，该方案以引入系统延迟为代价，可以获得满分集增益。同时，研究给出了该方案所需的传输时间，并与前者方案进行了比较。为便于对比，同时给出了无中继情况下中断概率的表达式。最后利用数值结果验证了上述分析。“,”This paper investigates the outage and diversity performance in a cognitive radio (CR) network, in which data are transmitted through amplify-and-forward (AF) protocol. A fixed CR node is selected as relay to combat fading effect. The CR user transmits or relays data when the result of cooperative spectrum sensing indicates that primary user (PU) link is free and the relay node stops performing the protocol as soon as the PU link is detected to be active. A closed-form expression of outage probability for the CR network is calculated based on which diversity order is derived. The results show that the proposed scheme suffers a loss in diversity order. To compensate for this loss, a repetition-based scheme is proposed in a delay-insensitive system at the cost of the challenge in implementation. In this case, we evaluate the outage performance and the average transmit duration and then compare them with the ones in the delay-sensitive system. An asymptotic analysis is also presented to show the outage performance advantage of using a relay over the one without using it. The numerical results presented in the paper verify our analysis.