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中继选择协议下的认知无线电系统性能研究
来源:电子技术应用2012年第10期
唐菁敏, 龙 华, 邵玉斌, 彭 艺
昆明理工大学 信息工程与自动化学院, 云南 昆明650500
摘要: 在保证授权用户服务质量(QoS)和认知用户峰值功率限制的前提下,推导出高信噪比时放大转发中继选择(SAF)协议、解码转发中继选择(SDF)协议和混合中继选择协议(HPRS)下认知中继系统中断概率的近似表达式。Monte Carlo仿真验证了三种协议下中断概率近似表达式的合理性,理论和仿真结果表明,三种协议的中断概率与干扰限制条件和认知用户峰值功率密切相关,且HPRS中断性能要优于SAF和SDF。
中图分类号: TN929.53
文献标识码: A
文章编号: 0258-7998(2012)10-0096-03
Research the outage performance of cognitive radio system based on protocols of relay selection
Tang Jingmin, Long Hua, Shao Yubin, Peng Yi
Faculty of Information Engineering and Automation, Kunming University of Science and Technology, Kunming 650500, China
Abstract: An approximate outage probability formulation were derived for amplify-and-forward with relay selection(SAF), decode-and-forward with relay selection(SDF) protocol and hybrid protocol with relay selection(HPRS) on the premise of guarantee primary user quality of service(QoS) and limit of maximal power in cognitive user. By Monte Carlo simulation, the rationality of the approximate outage probability formulation is validated. Theoretical analysis and simulation results show that the outage probability of three cooperative protocols is closely related to interference limit and maximal power in cognitive user. Meanwhile, the three protocols can achieve the full space diversity and the HPRS outperforms both the SAF and SDF in outage performance.
Key words : cognitive radio; relay selection; power constrained; outage probability; cooperative diversity

    认知无线电技术能提高对频谱资源的有效利用率,但不能克服无线环境中的信道衰落等问题,而协同通信恰恰能有效地解决这方面的问题。因此,融合认知无线电技术与协同通信技术,能有效解决无线信道的衰落和频谱资源有限这两大问题[1-7]。参考文献[3]研究了在重叠共享(US)方式下的认知系统信道容量,指出通过波束成形和中继选择协作可有效改善系统性能。参考文献[4]推导了US方式下认知中继系统的中断性能上界。

    本文主要研究了在US方式下认知系统通过采用不同中继选择协议的中断性能,分别推导了高信噪比时基于SAF、SDF和HPRS协议的中断概率近似表达式。仿真结果表明,中断概率与干扰限制条件和认知用户峰值功率密切相关,HPRS性能要优于SAF和SDF的。
1 系统模型
    认知系统传输模型如图1所示,考虑一个认知网络包括一个授权用户PU(Primary User)节点,一个认知用户SU(Secondary User)源节点,一个SU目的节点和M个SU中继节点。认知系统的通信过程分两个时隙完成:第一时隙,源节点广播信息, 中继i(i=1,…,M)和目的节点的接收信号yi和yd,1分别为:



 

 

     

    本文理论推导了SAF、SDF和HPRS在高信噪比时认知系统中断概率近似表达式,并且对其中断概率进行了Monte Carlo仿真,结果表明,近似曲线与仿真曲线较接近,因此验证了近似表达式的正确性,同时对比了三种协议的性能,发现HPRS中断性能始终最优。由于认知用户发射节点同时需要满足干扰限制及峰值功率限制,因此最终的中断概率与这两个限制条件密切相关。
参考文献
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