双向中继系统的中继选择方案与波束成形向量设计

发布时间：2018-04-30 10:26

本文选题：双向中继 + 中继选择　；参考：《北京交通大学》2014年博士论文

【摘要】：协作通信系统通过多个单天线节点共享彼此的天线以形成一个虚拟的多天线系统。在双向多中继系统中应用协作通信技术可以提高系统的容量、安全性、鲁棒性,降低系统的误码率和中断概率,已经成为了当前的一个研究热点。放大转发(AF)和解码转发(DF)是中继对信息的两种主要处理方式。本文首先分析了DF双向单中继系统的误符号率(SER)性能,并以此为基础研究了DF双向多中继系统的中继选择方案。接着分别以提高系统和速率与提高系统安全性为目标,设计了AF双向多中继系统的中继波束成形向量。本文的主要研究内容为：首先,扩展了传统最近邻近似方案,且应用该方法对DF双向单中继系统的中继端SER进行讨论,得到了加性高斯白噪声(AWGN)信道下BPSK调制、QPSK调制、8PSK调制的SER闭式表达式和衰落信道下BPSK调制、QPSK调制的瞬时SER与平均SER的表达式。研究发现,在AWGN信道下采用8PSK调制的DF双向中继系统中,固定其中一个源节点的发送功率,另一个源节点的功率从0增大到与其功率相等的过程中,中继节点的SER并不是单调递减的。其次,在DF双向单中继系统SER性能分析的基础上,将场景扩展到双向多中继系统,提出了一种基于最小SER的DF双向多中继系统中继选择方案。考虑到最小SER中继选择方案的复杂度较高以及中继星座图中最近邻星座点之间的距离在端到端SER中的重要作用,进一步提出了基于星座图最小距离最大化的中继选择方案,并推导出在BPSK、QPSK和8PSK调制时,该方案能达到满分集增益。然后,研究了AF双向中继系统的信息传输和能量收集问题。即在中继功率约束以及源节点能量收集约束下,通过设计中继的波束成形向量从而最大化系统的和速率。本文分别提出了一种理想情况设计方案、三种实际设计方案和一种鲁棒设计方案,并对这些方案建立了最优化模型,且通过半正定松弛以及连续凸近似技术对它们进行求解,还证明了所提出的求解算法至少可收敛到一个局部最优解。最后,研究了有窃听节点存在时AF双向中继系统物理层安全性问题。提出了一种中继波束成形设计方案以及一种中继波束成形与人工噪声的联合设计方案,从而在保证双向中继系统的通信质量和安全性的前提下最小化中继的功率和,并为这两个方案建立了最优化模型,且应用半正定松弛技术对这两个非凸的优化问题进行了求解。证明了在所提出的两种方案中,应用人工噪声方案的性能更优。
[Abstract]:Cooperative communication systems share each other's antennas through multiple single antenna nodes to form a virtual multi-antenna system. The application of cooperative communication technology in bidirectional multi-relay systems can improve the capacity, security, robustness and reduce the bit error rate and interrupt probability of the system, which has become a hot research topic at present. Amplifier forwarding (AFA) and decoded forwarding (DFF) are the two main processing methods of information in relay. In this paper, the performance of symbol error rate (SERR) of DF bidirectional single relay system is analyzed, and the relay selection scheme of DF bidirectional multi-relay system is studied. Then the beamforming vector of AF bidirectional multi-relay system is designed to improve the system speed and system security respectively. The main contents of this paper are as follows: Firstly, the traditional nearest proximity scheme is extended, and the relay end SER of DF bidirectional single relay system is discussed by using this method. The SER closed expression of BPSK modulation / 8PSK modulation over additive Gao Si white noise channel and the expressions of instantaneous SER and average SER of BPSK modulation QPSK modulation over fading channel are obtained. It is found that in DF bidirectional relay system with 8PSK modulation in AWGN channel, the transmission power of one of the source nodes is fixed, and the power of the other source node increases from 0 to the same power. The SER of relay nodes is not monotone decrement. Secondly, based on the performance analysis of DF bidirectional single relay system (SER), the scene is extended to bidirectional multi-relay system, and a relay selection scheme based on minimum SER is proposed for DF bidirectional multi-relay system. Considering the high complexity of the minimum SER relay selection scheme and the importance of distance between nearest neighbor constellation points in the constellation diagram in end-to-end SER, a relay selection scheme based on maximum minimum distance of constellation diagram is proposed. It is also deduced that the scheme can achieve full diversity gain in BPSK QPSK and 8PSK modulation. Then, the problem of information transmission and energy collection in AF bidirectional relay system is studied. In the case of relay power constraints and source node energy collection constraints, the sum rate of the system is maximized by designing the beamforming vector of the relay. In this paper, an ideal design scheme, three practical design schemes and a robust design scheme are proposed, and the optimization models of these schemes are established, and they are solved by positive semidefinite relaxation and continuous convex approximation techniques. It is also proved that the proposed algorithm can converge to at least one local optimal solution. Finally, the physical layer security of AF bidirectional relay system with eavesdropping nodes is studied. A relay beamforming design scheme and a joint design scheme of relay beamforming and artificial noise are proposed to minimize the relay power sum while ensuring the communication quality and security of the two-way relay system. The optimization models for the two schemes are established and the two non-convex optimization problems are solved by using the positive semidefinite relaxation technique. It is proved that the performance of artificial noise scheme is better than that of artificial noise scheme.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN929.5

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