非同步物理层网络编码的误符号率分析方案

发布时间：2018-03-25 05:02

本文选题：双向中继网络　切入点：非同步物理层网络编码　出处：《东北大学》2014年硕士论文

【摘要】：物理层网络编码(Physical-layer network coding, PNC)是一种新的无线中继方式,它利用电磁波叠加原理和无线信道的广播特性,在两个时隙内就可以完成双向中继系统的数据交换。相比较于网络编码的三个时隙和传统中继方式的四个时隙,它进一步缩短了数据交换的时间,提高了网络吞吐量,因此受到广泛的关注。由于无线终端的时钟不同步以及信道环境的不同,在PNC的信号叠加阶段,会出现相位偏移和码元偏移等不同步情况,这严重地影响中继节点解码(解码,即先解调叠加信号,然后再进行编码映射)叠加信号的误符号率。因此,分析非同步情况下解码误符号率将对物理层网络编码的实现具有理论指导意义。本文提出了非同步物理层网络编码的误符号率分析方案,基于BPSK和QPSK调制方式,得出误符号率上界和下界的数学表达式。本文的误符号率分析基于两种解码方案,基于多用户检测(Multiuser Detection, MUD)的异或(XOR)编码映射方案(MUD-XOR)和基于置信传播(Belief Propagation, BP)的最大后验概率(Maximum a Posteriori, MAP)解码方案(BP-MAP).本文证明了BP-MAP方案的误符号率性能优于MUD-XOR方案,但是二者误符号率性能相差很小。基于BP-MAP方案,假设中继节点已知部分叠加信息,从而得出误符号率的下界表达式;而基于MUD-XOR方案,我们引入了差错向量和差错向量可分解的概念,证明出误符号率上界只与不可分差错向量有关,从而得出误符号率的上界表达式。因此,本文求出的误符号率上下界对于两种解码方案都适用。通过仿真验证证明利用本文提出的误符号率分析方案和推导出的误符号率表达式能够得出比较准确的误符号率上下界。
[Abstract]:Physical-layer network coding (PNCC) is a new wireless relay mode, which utilizes the principle of electromagnetic wave superposition and the broadcast characteristics of wireless channel. The data exchange of bidirectional relay system can be completed in two time slots. Compared with three time slots encoded by network and four slots in traditional relay mode, it can further shorten the time of data exchange and improve the throughput of network. Because the clock of wireless terminal is out of sync and the channel environment is different, the phase offset and symbol offset will appear in the signal superposition phase of PNC, which seriously affects the decoding (decoding) of relay node. That is, demodulating the superposition signal first, then coding mapping) the symbol error rate of the superposition signal. The analysis of symbol error rate in asynchronous decoding will be of theoretical significance to the realization of physical layer network coding. In this paper, a scheme of symbol error rate analysis for asynchronous physical layer network coding is proposed, which is based on BPSK and QPSK modulation. The mathematical expressions of upper bound and lower bound of symbol error rate are obtained. The analysis of symbol error rate in this paper is based on two decoding schemes. Based on Multiuser Detection (mud) and confidence Propagation (BP), the maximum posterior probability Maximum a Posteriori (MAPP) decoding scheme based on multiuser detection (mud) is proposed. It is proved in this paper that the performance of BP-MAP scheme is better than that of MUD-XOR scheme. However, the performance of symbol error rate is very small. Based on BP-MAP scheme, the lower bound expression of symbol error rate is obtained by assuming that the relay node has known superposition information, while based on MUD-XOR scheme, the lower bound expression of symbol error rate is obtained. In this paper, we introduce the concepts of error vector and decomposable error vector, and prove that the upper bound of symbol error rate is only related to the indistinguishable error vector, thus the upper bound expression of symbol error rate is obtained. The upper and lower bounds of symbol error rate obtained in this paper are applicable to both decoding schemes. The simulation results show that more accurate upper and lower bounds of symbol error rate can be obtained by using the analysis scheme of symbol error rate proposed in this paper and the derived expression of symbol error rate.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN915.0

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