协作通信系统中的中继选择方案及其优化的研究

发布时间：2019-01-08 09:42

【摘要】：协作通信技术由于能够抵抗信道衰落的影响,提供分集增益,因此成为无线通信领域研究的热点。为了能够有效地提升系统性能和降低资源消耗,协作中继的选择、中继协作的方式和引入中继的时机等问题已经成为重要的研究内容。本文将深入研究协作通信系统中的中继选择及其优化问题。首先,对协作通信的研究背景、研究现状以及实际应用做了简单的介绍。其次简要分析和归纳了典型的中继转发策略和中继选择方案的优缺点。最后对中继选择方案及其优化问题展开研究。本文的主要内容和创新点如下:(1)为了提高中继选择方案的灵活性和降低系统开销,引入自动请求重传技术,结合混合译码放大转发(HDAF)中继策略,提出了一种基于接收信噪比最大化的改进HDAF单中继选择方案。通过目的节点发送的三种反馈信息来决定信息传输的方式。信息传输方式包括:直接传输、源节点重传和引入中继。通过理论和仿真分析得出:改进HDAF的中继选择方案不仅能够有效地降低中断概率,而且大大提高了频谱效率,从而提高了信息传输的可靠性和灵活性。在中断概率为-210时,与基于HDAF的中继选择方案相比,改进方案能够获得1dB的信噪比增益。另外,随着候选中继个数的增加,中断概率性能的改善更加明显。(2)为了降低能量消耗以及方案运算复杂度,以误码率最小化为目标,提出了一种在HDAF中继策略下的最优中继集合的快速选择方案。首先,采用矩量母函数原理推导得出基于放大转发(AF)、译码转发(DF)和HDAF中继策略的多中继系统的误码率近似表达式。然后以此为中继选择的依据,巧妙地定义了HDAF等效信道增益,快速选择出最优中继集合。接着,针对选择单个最优中继的情况,为使误码率达到实际的需求值,求解了最优功率分配问题。结果表明:首先,误码率性能能够得到有效的提升;其次,与穷举算法相比,误码率性能相近但运算复杂度大大降低;最后,最优功率分配能够降低系统总功耗。在相同误码率限定值下,与AF、DF方案相比,所提方案能够降低1dB-1.5dB的总功率消耗。此外,与等功率分配相比,所提方案能够节约0.2dB左右的总功率,从而在降低误码率和系统总功耗的问题上达到折中,使中继选择更具有实际意义。
[Abstract]:Cooperative communication technology has become a hotspot in wireless communication field because it can resist the influence of channel fading and provide diversity gain. In order to effectively improve system performance and reduce resource consumption, the selection of cooperative relay, the mode of relay cooperation and the timing of introducing relay have become important research contents. This paper will study the relay selection and its optimization in cooperative communication systems. Firstly, the research background, research status and practical application of cooperative communication are briefly introduced. Secondly, the advantages and disadvantages of typical relay forwarding strategies and relay selection schemes are briefly analyzed and summarized. Finally, the relay selection scheme and its optimization are studied. The main contents and innovations of this paper are as follows: (1) in order to improve the flexibility of relay selection scheme and reduce system overhead, automatic request retransmission technology is introduced, combined with hybrid decoding, amplifying and forwarding (HDAF) relay strategy. In this paper, an improved HDAF single relay selection scheme based on maximization of reception signal-to-noise ratio (SNR) is proposed. The mode of information transmission is determined by three kinds of feedback information sent by the destination node. The modes of information transmission include direct transmission, retransmission of source node and introduction of relay. Through theoretical and simulation analysis, it is concluded that the improved relay selection scheme of HDAF can not only effectively reduce the interrupt probability, but also greatly improve the spectral efficiency, thus improving the reliability and flexibility of information transmission. When the outage probability is -210, compared with the relay selection scheme based on HDAF, the improved scheme can obtain the SNR gain of 1dB. In addition, with the increase of the number of candidate relays, the improvement of outage probability performance is more obvious. (2) in order to reduce the energy consumption and the computational complexity of the scheme, the goal is to minimize the bit error rate (BER). A fast selection scheme for optimal relay set under HDAF relay strategy is proposed. Firstly, an approximate expression of BER for multi-relay systems based on amplifying and forwarding (AF), decoding and forwarding (DF) and HDAF relay strategies is derived by using the principle of mother moment function. Based on this, the equivalent channel gain of HDAF is defined skillfully, and the optimal relay set is quickly selected. Then, the optimal power allocation problem is solved for the case of selecting a single optimal relay in order to make the BER reach the actual requirement value. The results show that: first, the BER performance can be effectively improved; secondly, compared with exhaustive algorithm, the BER performance is similar but the computational complexity is greatly reduced; finally, the optimal power allocation can reduce the total power consumption of the system. Under the same BER limit, compared with the AF,DF scheme, the proposed scheme can reduce the total power consumption of 1dB-1.5dB. In addition, compared with the equal-power allocation, the proposed scheme can save the total power of the 0.2dB, thus achieving a compromise between reducing the bit error rate and the total power consumption of the system, and making the relay selection more meaningful.
【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】：TN914

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