全双工认知中继系统功率分配方法研究

发布时间：2018-02-12 08:46

本文关键词： 认知中继功率分配全双工认知容量中断概率　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：认知无线电技术作为提高频谱资源利用率的有效手段近年来得到了广泛地关注和研究。在认知系统中,认知用户能够利用合法授权主用户的频谱资源进行通信,前提是其发射功率不能过高进而影响到主用户的通信质量,这一使用前提使得认知网络中发射节点的功率很受限制,造成其信号的覆盖范围较小,特别是长距离通信会变得很困难,系统通信速率较低,限制了频谱利用率的提升空间。而中继技术作为提高信号覆盖、提升系统容量、和抗击衰落的有效手段被深入研究,因此中继技术与认知无线电结合进一步提升频谱效率就成为了研究的热点。现有的大量关于认知中继系统的研究都是集中在半双工认知中继系统上面,然而关于中继的研究表明,全双工中继相对半双工中继因其全双工增益特性可能提供更好的系统性能,因此为更进一步提高频谱利用率考虑,本文对全双工认知中继系统进行的研究就变得很有必要。文中首先在第一章对频谱资源日益紧张的状况和认知无线电作为提高频谱利用率有效手段的基本原理分别进行了介绍,并对认知中继的研究现状做了详细描述。第二章针对半双工认知中继系统可能有一个时隙会产生浪费这一问题,为充分利用时隙资源,本章研究了一个既含有直接链路又含有中继辅助链路的认知中继系统,并分别从瞬时干扰信道和统计干扰信道两个角度分析了该认知中继系统的功率优化问题,分别得到了在这两种情况下的最优功率分配方法。第三章介绍分析了全双工DF(Decode-and-Forward)认知中继系统的功率分配及中断概率。在瞬时干扰信道下,提出了一种基于无协作情况的干扰平均分配的功率分配方法,并得到了该方法下的中断概率表达式;然后分析了有协作下认知系统的最优功率分配问题,得到了最优的功率分配方法,并从噪声主导和干扰主导两个角度分析了最优功率分配下认知系统的中断概率。另外,从更实际的角度出发,文中分析了在主用户中断概率限制下的最优功率分配问题,由于问题直接解决十分困难,文中分别分析了其在噪声主导和干扰主导下的功率分配方法。由于第三章中关于全双工DF认知中继系统得到的结果不能简单的直接套用到全双工AF(Amplify-and-Forward)认知中继系统中,且全双工AF认知中继相较全双工DF认知中继更为简单实用,所以第四章研究了全双工AF认知中继系统的功率分配问题。本章基于实际的干扰信道获取情况从三个方面对全双工AF认知中继系统的功率分配问题进行了研究,即瞬时干扰信道下、统计干扰信道下、和未知干扰信道下,分别得到了闭合的最优功率分配表达式、一种迭代搜索的功率分配方法、和一种基于感知的迭代搜索方法。第五章对全文进行了总结,并指出以后可行的研究方向。
[Abstract]:As an effective means to improve the efficiency of spectrum resources, cognitive radio technology has been widely studied in recent years. In cognitive systems, cognitive users can use the spectrum resources of legitimate authorized primary users to communicate. The premise is that the transmission power should not be too high and thus affect the communication quality of the primary user. This premise makes the power of the transmitting node in the cognitive network very limited, resulting in the smaller coverage of the signal. In particular, long distance communication will become very difficult, and the system communication rate will be low, which limits the spectrum efficiency, and relay technology as an effective means to improve signal coverage, enhance system capacity, and combat fading has been deeply studied. Therefore, the combination of relay technology and cognitive radio to further improve spectral efficiency has become a hot topic. Many existing researches on cognitive relay systems are focused on half-duplex cognitive relay systems. However, researches on relay show that full-duplex relay may provide better system performance than half-duplex relay because of its full-duplex gain characteristics. It is necessary to study full duplex cognitive relay system in this paper. In the first chapter, we introduce the situation of spectrum resource becoming increasingly tight and the basic principle of cognitive radio as an effective means to improve spectrum efficiency. The second chapter aims at the problem that there may be a time slot waste in the half-duplex cognitive relay system, in order to make full use of the time slot resources. In this chapter, a cognitive relay system with both direct link and relay auxiliary link is studied, and the power optimization problem of the cognitive relay system is analyzed from the perspective of instantaneous interference channel and statistical interference channel, respectively. In chapter 3, the power allocation and interrupt probability of fully duplex DFO Decode-and-Forward-based cognitive relay system are analyzed. In this paper, a power allocation method based on interference average allocation without collaboration is proposed, and the expression of interruption probability is obtained, and then the optimal power allocation problem for cognitive systems with collaboration is analyzed. The optimal power allocation method is obtained, and the outage probability of the cognitive system under the optimal power allocation is analyzed from the point of view of noise dominance and interference dominance. In addition, from a more practical point of view, In this paper, the optimal power allocation problem under the limit of primary user interrupt probability is analyzed. It is very difficult to solve the problem directly. In this paper, the power allocation methods under noise and interference are analyzed, respectively. Since the results obtained from the full-duplex DF cognitive relay system in Chapter 3 can not be applied directly to the full-duplex AFA Amplify-and-Forward-based cognitive relay system, And full duplex AF cognitive relay is more simple and practical than full duplex DF cognitive relay. Therefore, in Chapter 4th, the power allocation problem of full-duplex AF cognitive relay system is studied. Based on the actual interference channel acquisition, the power allocation problem of full-duplex AF cognitive relay system is studied from three aspects. That is, the closed optimal power allocation expression is obtained for instantaneous interference channel, statistical interference channel and unknown interference channel, and an iterative search power allocation method is proposed. Chapter 5th summarizes the full text and points out the possible research directions in the future.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN925

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