协作中继转发策略优化及编码协作研究

发布时间：2018-05-04 09:26

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

【摘要】：当前,无线协作通信由于传输可靠、有效和覆盖范围广而成为研究热点,但仍存在复杂度高和性能未能接近理论值等缺陷。为协助解决上述问题,本学位论文主要开展了中继转发策略优化及编码协作的改进研究。首先,简介了协作通信背景、发展和现状。然后,重点分析了现有无线协作通信模型、合并技术和中继协议,并引入了链路自适应再生(LAR)转发协议。最后,重点探讨了优化LAR转发协议、量化转发(QF)及Raptor编码协作等创新改进。全文内容和贡献主要如下:1.针对译码转发(DF)中继系统不能获得分集增益的问题,引入了LAR理论分析研究。首先,研究了LAR协议的实现过程及低复杂度单中继选择方案。然后,针对单中继系统,推导了高信噪比(SNR)下误码率(BER)和中断概率的近似表达式。仿真表明:LAR较放大转发(AF)、DF和选择译码转发(SDF)在BER方面有更大优势。当BER=10-3时,分别有约3.5dB、7dB和7dB的SNR增益,且LAR中继系统的中断概率随中继个数的增加而不断提高;2.针对现有QF复杂度较高的缺陷,提出了低复杂度QF方案。其采用了低阶量化和调制,使复杂度有较大降低。在目的节点,其将量化信息和直传信息最大比合并(MRC),可降低系统BER。同时,利用中继选择和功率分配技术进一步优化该方案。最后,仿真分析了1-bit、2-bit和3-bit QF的BER性能。结果表明:当BER=10-2,3-bit QF方案较1-bit、2-bit QF分别有约4.5~7.5dB和1~2.5dB的SNR增益;当中继距离目的节点较近时,所提QF协议具有较好BER性能。在等功率分配方案下,对于2-bit QF,在BER为10-3处,当源-中继链路归一化距离为0.9时,较0.7、0.5、0.3和0.1情况分别有约5dB、7.5dB、9dB和15dB的SNR增益。另外,相对于等功率分配方案,优化功率分配系统平均有约2.5dB功率增益;3.针对无线协作通信系统的信道状态信息(CSI)难以准确估算问题,利用喷泉码的无码率特性,提出了Raptor编码协作(CC)方案。在该方案中,源和中继节点使用不同Raptor编码,目的节点接收不同来源独立消息后,根据码字间关系联合译码,可在高SNR下获得较大编码增益和满分集效果。为了降低复杂度,Raptor预编码采用了整数序列构造的准循环低密度奇偶校验(QC-LDPC)码,获得了较低的线性预编码复杂度。仿真表明:在BER为10-4时,所提Raptor编码协作方案较传统DF协议Raptor方案、Raptor与分布式空时分组码(DSTBC)结合方案,分别有约2dB和1dB的SNR增益。而且,当中断概率为10-2时,其SNR增益较CC、DF提高了约2dB和7dB。本文通过对协作中继转发策略和编码协作的优化改进,可较好地改善协作通信系统性能。所提改进点也均以低复杂度模式实现,便于工程实践,具备较高实用价值。
[Abstract]:At present, wireless cooperative communication has become a research hotspot because of its reliable transmission, effective and wide coverage, but there are still high complexity and failure to approach the theoretical value. In order to help solve the above problems, this dissertation mainly carried out the research on the optimization of relay forwarding strategy and coding cooperation. First, the collaborative communication back was briefly introduced. The current wireless cooperative communication model, merging technology and relay protocol are analyzed, and link adaptive regeneration (LAR) forwarding protocol is introduced. Finally, the optimization of LAR forwarding protocol, quantitative forwarding (QF) and Raptor coding cooperation are discussed. The content and contribution of the full text are as follows: 1. The DF relay system can not obtain diversity gain, and introduces the LAR theoretical analysis. First, the realization process of the LAR protocol and the single relay selection scheme with low complexity are studied. Then, the approximate expression of the bit error rate (BER) and the interrupt probability under the high signal to noise ratio (SNR) is derived for the single relay system. The simulation shows that LAR is more magnified. AF, DF and selective decoding forward (SDF) have a greater advantage in BER. When BER=10-3, there are SNR gains of about 3.5dB, 7dB and 7dB, and the interrupt probability of the LAR relay system increases with the increase of the number of relay. 2., a low complexity QF scheme is proposed for the existing QF complexity. Low order quantization and modulation are adopted. The complexity is greatly reduced. In the destination node, it combines the maximum ratio of quantized information and direct transmission information (MRC), reduces system BER. and optimizes the scheme by using relay selection and power allocation technology. Finally, the simulation analysis of the BER properties of 1-bit, 2-bit and 3-bit QF shows that BER=10-2,3-bit QF scheme is more than 1-bit, 2-bit QF has a SNR gain of about 4.5~7.5dB and 1~2.5dB respectively; when the relay distance is closer, the proposed QF protocol has a better BER performance. In the equal power allocation scheme, the 2-bit QF is 10-3 at BER, and when the source relay link normalization distance is 0.9, the 0.7,0.5,0.3 and 0.1 are about 5dB, 7.5dB, and gain gain. In addition, the optimal power allocation system has an average 2.5dB power gain relative to the equal power allocation scheme, and 3. is difficult to accurately estimate the channel state information (CSI) for the wireless cooperative communication system. The Raptor coding cooperation (CC) scheme is proposed by using the fountain code's non bit rate characteristics. In this scheme, the source and relay nodes use different Raptor compacts. In order to reduce the complexity, the Raptor precoding uses an integer sequence constructed quasi cyclic low density parity check (QC-LDPC) code to reduce the complexity. In order to reduce the complexity, the complexity of the Linear Precoding is obtained. The complexity of the low Linear Precoding is obtained. It is true that when BER is 10-4, the proposed Raptor coding scheme has a SNR gain of about 2dB and 1dB, compared with the traditional DF protocol Raptor scheme, Raptor and distributed space time block code (DSTBC). Moreover, when the interrupt probability is 10-2, the SNR gain of the SNR is CC. The optimization and improvement of cooperation can better improve the performance of the cooperative communication system. The proposed improvement points are also implemented in a low complexity mode, which is convenient for engineering practice and has high practical value.

【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

【参考文献】