协作中继选择及优化功率分配策略研究

发布时间：2018-04-20 16:21

本文选题：协作通信 + 中继选择　；参考：《杭州电子科技大学》2017年硕士论文

【摘要】：为了更好满足日益增长的现代多媒体通信业务等需求,迫切需要研制更快和更高频谱效率的无线网络。多输入多输出(MIMO)通过收发两端配备多天线来抑制信道衰落,可获较高传输速率和可靠性。但受限于尺寸等因素,其无法实现微小型化应用。协作通信利用相邻用户天线协作,组成虚拟天线阵,获得了类似MIMO优势,可克服其因传输复杂、不易小型化等难题。但目前协作通信还存在传输效率低和复杂度过高等难点,较难实现高速可靠的传输。针对这些问题,本文主要开展了单、双向中继协作通信系统中的中继选择和功率分配优化研究。全文内容和创新点主要如下:(1)第一部分为协作通信概述。首先,简介了空间分集中三种主要的分集合并准则,分别推导了其信噪比输出公式,并验证了最大比合并方案在所有线性合并方案中获得了最大信噪比。然后,重点讨论在固定中继模型下的放大转发(AF)和译码转发(DF)两种协议,并分析了它们的中断概率、误符号率及瞬时信道容量上界,并对此实验仿真,验证了采用中继转发协议的系统性能比无中继传输方式有了明显的改善。最后,还简介了编码协作(CC)和压缩转发(CF)协议以及各协议间的差异。(2)第二部分主要研究了单向中继模式下的中继选择算法和功率分配优化方案。为了弥补全部中继都参与放大转发(AAF)的低资源利用率和单中继参与放大转发(SAF)的低协作分集增益,并改进系统复杂度和中断性能,提出了多中继选择策略的删余改进算法。此外,还提出了针对该算法的次优功率分配(NOPA)方案。仿真表明:所提出的删余改进算法的中断概率相对其他中继数目参与转发的情况是最小的;其中断性能在任何信噪比(SNR)时,都优于AAF和SAF算法;且在中断概率为10-4时,该算法相对AAF和SAF方案分别有近0.3dB和5.2dB信噪比增益;在功率分配优化上,相比于等功率分配(EPA)方案,基于该算法的NOPA方案能获得了更好的中断概率性能。(3)第三部分主要研究了双向中继模式下的中继选择算法和功率分配优化方案。针对Max-min算法和双向中继选择算法在可达速率性能上的不足,提出了双向中继选择策略的门限信噪比乘积算法。对此,还结合SNR平衡,提出了一种最优功率分配(OPA)方案,并与现有的凸优化和等功率这两个分配方案比较。仿真表明:相比于Max-min和双向中继选择算法,所提出的门限信噪比乘积算法能提升系统速率性能,且实现复杂度代价增加较小;在功率分配优化上,所提出的运用SNR平衡的OPA方案,在系统的速率和中断性能上较凸优化和等功率方案都有明显的改善。通过对协作通信中继选择和功率优化的研究,可有效改善系统的可靠传输问题。且全文中的改进点均以低复杂度实现,故可方便的应用于多中继场景,以获得更优系统性能。
[Abstract]:In order to better meet the increasing demand of modern multimedia communication services, it is urgent to develop faster and more spectral efficient wireless networks. Multiple input and multiple output (Mimo) channel fading can be suppressed by multiple antennas at both ends of the transmitter and receiver, and high transmission rate and reliability can be achieved. However, limited by the size and other factors, it can not achieve micro-miniaturization applications. Cooperative communication uses adjacent user antennas to form a virtual antenna array, which has similar advantages as MIMO, and can overcome the difficulties of complex transmission and difficult miniaturization. However, there are still some difficulties in cooperative communication, such as low transmission efficiency and high complexity, so it is difficult to achieve high-speed and reliable transmission. To solve these problems, this paper focuses on relay selection and power allocation optimization in single and bidirectional relay cooperative communication systems. The first part is an overview of cooperative communication. Firstly, three main diversity combining criteria are introduced, and the output formulas of SNR are derived, respectively, and the maximum signal-to-noise ratio (SNR) of the maximum ratio combination scheme is verified in all linear combination schemes. Then, two kinds of protocols, Amplifier forwarding (AFA) and Decoding forwarding (DFF) in fixed relay model, are discussed, and their interrupt probability, symbol error rate and upper bound of instantaneous channel capacity are analyzed, and the simulation results are given. It is verified that the performance of relay forwarding protocol is better than that of non-relay transmission. Finally, the CCS and CFC protocols and the differences between them are briefly introduced. In the second part, the relay selection algorithm and the power allocation optimization scheme in unidirectional relay mode are studied. In order to compensate for the low resource utilization of all relays participating in AAFs and the low cooperative diversity gain of single relay participating in amplification forwarding (SAF), and to improve the system complexity and interrupt performance, an improved censored algorithm for multi-relay selection strategy is proposed. In addition, a suboptimal power allocation scheme for this algorithm is proposed. The simulation results show that the outage probability of the improved censored algorithm is minimum than that of other relays, where the outage performance is superior to that of AAF and SAF algorithms at any SNR / SNR, and when the outage probability is 10 ~ (-4), the outage performance of the improved algorithm is better than that of AAF and SAF when the outage probability is 10 ~ (-4). Compared with AAF and SAF schemes, the proposed algorithm has near 0.3dB and 5.2dB signal-to-noise ratio gain, compared with the equal-power allocation scheme in power allocation optimization. The NOPA scheme based on this algorithm can achieve better outage probability performance. In the third part, relay selection algorithm and power allocation optimization scheme in bidirectional relay mode are studied. Aiming at the shortcomings of Max-min algorithm and bidirectional relay selection algorithm in the performance of reachable rate, a threshold SNR product algorithm of bidirectional relay selection strategy is proposed. Based on the SNR equilibrium, an optimal power allocation scheme is proposed and compared with the existing convex optimization and equal power allocation schemes. Simulation results show that compared with Max-min and bidirectional relay selection algorithm, the proposed threshold signal-to-noise ratio product algorithm can improve the system rate performance and increase the complexity cost less. The proposed OPA scheme with SNR balance has obvious improvement in system speed and interrupt performance, as well as in the convex optimization scheme and the equal power scheme. By studying the relay selection and power optimization of cooperative communication, the reliable transmission problem of the system can be effectively improved. The improvement points in this paper are all implemented with low complexity, so they can be easily applied to multi-relay scenarios to obtain better system performance.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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