认知无线电中合作频谱感知的性能分析

【作者】 纪莎莎；

【导师】 王中训； 刘云学；

【作者基本信息】 烟台大学 ， 信号与信息处理， 2010， 硕士

【摘要】 随着无线通信的迅速发展,频谱资源的稀缺成为提供新的通信服务的瓶颈。认知无线电的出现与发展是无线通信的一个重大转折,它提供了一种新的方式来共享频谱资源。认知无线电解决了在许多频段中的频谱低利用率的问题。频谱感知技术能够尽可能的增加利用频谱的机会,因此成为认知无线电的关键技术之一。本文的主要内容是研究认知无线电中的频谱感知技术,主要研究以平均功率为统计量的基于中继合作方案的增益点和2-bit软化硬合并方案的性能。1.我们研究了以平均功率为统计量的基于中继合作的频谱感知方案,认知无线电用户U1采用认知无线电用户U2作为其中继,从而获得性能改善。在这个方案下怎样为U1找到一个合适的中继U2是非常重要的,而且发现要使U1在合作方案受益,U2的归一化功率必须大于一个定值(增益点)。结果表明,当两个认知无线电用户的发送功率相等时,非功率限制和功率限制方案的增益点相同。若两个认知无线电用户的发送功率不相等时,我们改变非功率限制方案下的比例因子后使得两种方案的增益点相同。2.在合作频谱感知中,2-bit软化硬合并方案可以获得检测性能与复杂性的折中。本文研究了考虑了报告信道衰落对2-bit软化硬合并方案的影响,通过仿真分析得出2-bit软化硬合并方案性能受到非完美报告信道的影响,且性能下降与报告信道中的信噪比有关。并且得到了在非完美报告信道下,2比特合并方案比1比特合并方案优势更为明显的结论更多还原

【Abstract】 With the rapid development of wireless communication, the scarcity of spectrum resources becomes the bottleneck to providing new communication services. A major shift in wireless communications is now emerging with the development of cognitive radios, which attempt to share spectrum in a fundamentally new way. Cognitive radios address the problem of poor spectrum utilization exhibited in many frequency bands. Spectrum sensing technique through primary user detection can obtain as many available transmission opportunities as possible, which thus is identified as a key enabling functionality of cognitive radios.The goals of this dissertation are study the cooperative spectrum sensing and propose methods for obtaining the good performance of cooperative spectrum sensing.1. The sensing performance of a cognitive user U1 by allowing another cognitive user U2 to act as its relay is studied. We take the average power rather than the instantaneous power as the decision statistic. Then we pay much attention to studying how to find a proper relay U2 for U1 so that the detection capability of U1 can be improved. Results show that, the normalized received power of U2 should be larger than a certain value which is called gain point if U1 can benefit from the cooperation. We find that, by varying the scaling factors of the unconstrained scheme, the gain point of the constrained scheme equals that of the unconstrained scheme when the transmission powers of U1 and U2 are equal. Next, by varying the scaling factors of the unconstrained scheme, the gain point of the constrained scheme equals that of the unconstrained scheme when the transmission powers of U1 and U2 are unequal.2. In cooperative spectrum sensing, softened hard combination scheme with two-bit overhead for each cognitive radio (CR) user can achieves a good tradeoff between detection performance and complexity. In this paper, we study the performance of two-bit hard combination scheme under imperfect reporting channel. Also the comparison of performances between two-bit hard combination scheme and one-bit hard combination scheme in imperfect reporting channel is exhibited. Numerical results will show that the performance is affected by the SNR of reporting channel and much better than convention hard combination scheme.更多还原