衰落信道下提高协作频谱感知能力的方法

Robust cooperative spectrum sensing schemes for fading channels in cognitive radio networks

由于协作频谱感知能够更准确地确定主用户的存在与否,因此,它被认为是认知无线电技术中的一个重要研究分支.在协作频谱感知中,各认知用户需要通过报告信道发送其本地判决结果(0或1)到融合中心(FC).然而,在实际中,报告信道通常受衰落的影响,这将降低频谱感知的检测性能.针对这个问题,首先,文中提出一种基于认知用户选择的协作频谱感知算法.该算法通过减小由衰落信道引入的误码概率来提高协作频谱感知的检测性能.其基本思想为:只有具有较好瞬时信道增益报告信道的认知用户才将其本地二进制判决结果发送到FC,否则,该认知用户不发送其本地检测结果到FC.其次,提出一种基于空时编码的协作频谱感知方法.通过在CR网络中,利用空间分集增益来降低由衰落型报告信道引入的误码概率,从而提高检测性能.最后,对提出的这两种协作频谱感知方法的检测性能进行理论分析研究,并对其进行数值仿真.仿真结果表明:相比于传统的协作频谱感知,本文提出的这两种协作频谱感知算法都能提高对主用户的检测性能.

In cognitive radio systems,cooperative spectrum sensing can detect the presence of the primary user accurately.In practice,however,since the sensing observations are forwarded to a data collector through fading channels,the sensing performance is severely degraded.To deal with this problem,in this paper,we first propose a secondary user selection based cooperative spectrum sensing method to improve sensing performance by decreasing the reporting errors introduced by the fading channels.More specifically,only the secondary users with better signal-to-noise ratio（SNR） for reporting channels are allowed to send their local binary decisions（0 or 1） to the data collector while the others will send nothing.Additionally,we further propose a diversity based cooperative spectrum sensing method which applies existing space-time coding.By exploiting space diversity in CR network,the reporting errors introduced by the fading channel can be decreased and then the sensing performance is improved significantly.For either proposed cooperative spectrum sensing method,the sensing performance is derived and the analytical performance results are given.Our analysis and numerical results verify that proposed methods outperform the conventional cooperative spectrum sensing with OR-rule by taking into account the error e？ect on the reporting channels.