Abstract: This paper proposes an analytical model for cognitive radio networks with imperfect spectrum sensing.In cognitive networks，secondary users utilize spectrum sensing technology to avoid interference to primary users.However，collisions may occur between primary and secondary traffic when secondary users misdetect primary signals；moreover，secondary users may abandon to access an idle channel if it is mistakenly sensed to be busy.All these events may degrade the system Quality-of-Service（QoS）.To evaluate the performance，the cognitive network is investigated by a two-dimensional Markov model，and analytical results are derived based on this model.The results show that the spectrum utilization can be significantly improved in cognitive networks；and a certain primary QoS requirement may be guaranteed by limiting secondary traffic intensity.

Key words: Markov chain, dynamic spectrum access, false alarm, misdetection, spectrum management, Quality-of-Service（QoS）

摘要： 通过对非理想频谱感知下的认知无线电网络（Cognitive Radio Network，CRN）建模，分析了认知网络的主要性能参数。由于漏检的存在，可能造成主次级用户业务之间的碰撞，从而引起用户业务的中断或阻塞；另一方面，由于虚警，认知用户将放弃接入可用的空闲频段，从而降低了频谱资源的利用率，无论哪种情形都将导致系统的QoS性能降低。通过将认知网络建模成一个二维马氏链，推导了系统的主要QoS参数。结果表明，尽管误检的存在，认知网络仍能显著提高频谱资源利用率；而主用户的QoS需求也可以通过控制认知业务的接入量来得到保证。

关键词: 马尔科夫链, 动态频谱接入, 虚警, 漏检, 频谱管理, 服务质量