【作者】 郑雪云；

【导师】 朱近康；

【作者基本信息】 中国科学技术大学 ， 通信与信息系统， 2010， 硕士

【摘要】 近年来,认知无线电(CR: Cognitive Radio)技术作为一种有效解决频谱资源紧张与频谱利用率不高之间矛盾的途径,越来越受到人们的广泛关注。认知无线电技术中认知用户(也称CR用户)对周围无线频谱环境准确、快速的检测,即频谱感知,是提高其频谱利用率、保护授权用户免受干扰的重要前提和核心技术。频谱感知的两个重要衡量参数是:检测概率与虚警概率。检测概率越高,感知性能越好;虚警概率越低,认知用户接入频谱机率越大,可获得的吞吐量越大。本文基于此背景并结合中继协作技术研究了认知无线电系统中感知能力和可获得的吞吐量之间的折衷关系。本论文首先对认知无线系统的发展状况进行了综述。分析了认知无线电的各种频谱感知技术,其主要从接收端的角度考虑频谱感知的方法,并介绍了本文的研究主题,即频谱感知性能与系统吞吐量的关系,指出了该问题的研究是频谱感知性能研究的重要方面。总结了协作频谱感知的基本原理和融合准则,并给出了中继转发协作分集检测的简单分析。本论文随后给出了单个认知用户的感知性能和吞吐量折衷理论分析和仿真,并基于此研究了中继协作的两个认知用户认知无线电网络的感知性能与吞吐量折衷关系。基于两个认知用户之间的中继协作,即通过中继用户转发授权用户的信号实现认知用户之间的协作。仿真结果表明该方法在检测概率一定时,能够有效地降低认知用户感知授权用户的虚警概率,缩短“弱”认知用户获得最大吞吐量的最优感知时间,并提高其自身的最大吞吐量和认知系统的最大吞吐量。本文最后分析了基于中继协作的多用户认知无线电网络的感知性能与吞吐量折衷。多个认知用户按照两个一组进行分组,分别采用中继协作的方式,研究了多用户认知系统的感知性能与吞吐量。证明了中继协作方式在多用户认知背景下也是可以实现的,仿真验证了在多用户认知系统中,中继协作方式能够在保证不干扰授权用户的同时,有效地提高“弱”认知用户的吞吐量。更多还原

【Abstract】 Recently, as an effective way to solve the problem of spectrum scarcity and spectrum underutilization, Cognitive Radio (CR) has got more and more attention. CR technology can sense the around wireless environment accurately and rapidly. Spectrum sensing is the important precondition and key technology to improve CR users’spectrum utilization and protect primary users from interruption. Also, spectrum sensing is the key to improve spectrum utilization. There are two important parameters associated with spectrum sensing: probability of detection and probability of false alarm. The higher the probability of detection is, the better the primary users are protected. However, the lower the probability of false alarm is, the more chances the channel can be reused when it is available, thus the higher the achievable throughput for the second user. In this paper, we study the sensing-throughput tradeoff based on relay cooperation spectrum sensing.The thesis begins with the introduction to the development of cognitive radio system. Analyze several algorithms for spectrum sensing in the receiver’s opinion. The thesis’s study background, development status and importance of sensing-throughput tradeoff are pointed. The basic theory and fusion rules of cooperative spectrum sensing and spectrum sensing based on relay cooperation is summarized briefly.Then, the thesis introduces the sensing-throughput tradeoff for the single cognitive user and also studies the sensing-throughput tradeoff based on relay cooperation for two user cognitive radio system. Through relay retransmit of primary user’s signal between two cognitive users, the maximum throughput of cognitive system under the constraint that the primary users are sufficiently protected is studied. Simulation results show that the relay method reduces the probability of false alarm, shorts the optimal sensing time to maximize the throughput efficiently, and also improves the maximum throughput of the worse secondary and the secondary network under the constrain that primary users are protected sufficiently.Lastly, the thesis study the sensing-throughput tradeoff based on relay cooperation for multi-user cognitive radio system. Grouping the users into pairs, and if one user acts a relay for the other in each pair, can improve the performance and throughput of the multi-user cognitive radio system. Spectrum sensing based on relay cooperation is available when the number of cognitive users is more than two. Simulations confirm the point that relay cooperation can improve the throughput of the worse cognitive user under the constraint that the primary users are protected sufficiently.更多还原