【作者】 谢映海；

【导师】 杨维；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2012， 博士

【摘要】 数字通信系统的物理层关注的是发送节点到接收节点之间数据流的传输问题,如信道编码、信号调制及解调等。为进一步提高无线多天线系统的传输性能,本文在物理层上对发送端和接收端的若干技术环节进行一定的改进,具体如下：1)发送端的新型信号设计：传统调制方式的信号波形是通过幅度,相位或频率,或者两个或多个信号参数的组合的差异来携带一定量的数字信息。而本文引入一种新的波形差别方式一功率差异,其核心思想是往传统调制方式生成的能量信号波形中的不同位置按照一定映射关系插入连续零信号区间。理论计算表明,安装有多根接收天线的接收机可以得到多个信号副本,利用信号功率之间的差异,接收机可以以很低的错误概率在一段接收信号中区分出其中的受噪声污染的能量信号和纯噪声信号。基于上述结果,本文针对相干SIMO系统和非相干MIMO系统,提出了多种新型空时信号的设计方案,理论分析和仿真结果都表明,新编码方案的传输性能明显优于传统方案。2)接收端的信号预处理：解调前利用离散空间上的最小能量小波框架数列对接收信号进行预处理来提高信号的解调性能。本文首次给出离散信号空间上的最小能量框架的定义,并证明了它所具备的一些优良性质；接着利用这些性质针对受加性高斯噪声污染的矩形和升余弦脉冲信号展开接收信号预处理算法的相关研究。仿真结果表明,如果在接收机上增加这样一个信号预处理环节,由于充分利用了信号的先验信息,预处理算法可以降低脉冲信号在信道传输时受到的各种不利影响,有效提高了信号解调器的输出信噪比,获得了较大性能增益。3)基于双向传输的网络编码理论研究：一个网络通信系统可以视作是一些试图互相通信的节点以及它们之间的信道组成的集合体。目前关于无线网络通信的研究大部分仅考虑信息流的单向流动,即认为在一次通信过程中,信源节点集合与信宿节点集合之间的交集为空集。但受无线信道广播特性的影响,这种划分事实上会造成很大的网络资源浪费。由于下一代的移动通信系统将采用新的扁平网络架构,因此本文引入‘网络编码’和‘协作通信’的思想,从信息流的双向传输的角度出发,对一些基本网络拓扑结构,包括信息交换通信模型和协作中继通信模型,开展一些基础编码理论的研究。具体包括：针对交换节点的多维网络纠错码及性能的研究、多维网络线性分组码和网络卷积码的设计、多维空时码和双星座空时码的设计；针对协作中继节点的二维和三维网络纠错码的设计、以及二维和三维网络空时码的设计。理论分析和仿真结果表明,比起传统的基于单向信息流的编码理论,新型编码方案可以更好地利用无线信道的广播特性和无线的网络的空间资源,有效提高发射能量的利用率,从而获得更多的编码增益。在物理层上,源节点和中继节点都需要编码和信号处理算法,而目的节点则需要信号处理和解码算法。本文把发送信号设计、接收信号的预处理、基于‘网络编码’和‘协作通信’思想的纠错编码及空时编码等技术综合在一起进行设计和优化,贯穿于通信过程的始终,给无线网络带来协同的涌现增益。比起传统信号传输方式,这些新技术的使用将使得无线多天线系统在频谱效率、能耗、编译码复杂度、误码率性能和系统吞吐量等许多方面都获得了较大的性能增益。图61幅,表2个,参考文献187篇。更多还原

【Abstract】 The physical layer of digital communication system is of concern of the information flow transmission problem between the sending nodes and receiving nodes, such as channel coding, signal modulation and demodulation. To further improve the transmission performance of wireless MIMO system, some physical layer technical improvements are proposed for the sending end and receiving end, as follows:1) The new transmission signal design:In order to carry digital information, the traditional modulation methods utilize the waveform difference of amplitude, phase or frequency, or two or more different combinations of signal parameters. But we introduce power difference as a new waveform different way, its core idea is to insert certain continuous zero signal intervals into the energy signal waveform according to some mapping relationship. Theoretical calculation indicates that the receiver with multiple antennas can get many copies of signal, and then distinguish the noise pollution signals and the pure noise signals by the signal power difference with a very low error probability. Based on these results, some novel space-time signal designs are proposed for various systems, such as coherent SIMO and non-coherent MIMO. Analysis and simulation results all show that the new encoding schemes are superior to traditional programs.2) Receive signal preprocessing:using the minimum-energy wavelet frame in the discrete space to pre-process the receive signal before demodulation. We first give the definition of minimum energy frame in discrete signal space, and prove some good characteristics of it. Then the denoising pre-processing algorithms are proposed for the polluted rectangular and raised cosine pulse signal by additive Gaussian noise using these characteristics. Simulation results show that, if adding a signal pre-processing part in the receiver, due to take full advantage of a priori information of signal, the signal pre-processing algorithms can reduce some adverse effects from transmission for the receive signal and improve the output signal-to-noise-rate of signal demodulation, and then obtain greater performance gain.3) Network coding theory based on two-way transmission:a network communication system can be regarded as the collection of the nodes which try to communicate with each other and their channels between them. Currently, most of the researches on wireless network communications are considering one-way information flow, namely, in a communication process, the intersection set between the source nodes and destination nodes is empty. In fact, with the broadcast characteristics of wireless channel, this division will cause great waste of network resources. Because of the new flat network architecture of next generation mobile communication systems, based on two-way flow of information transmitted, this paper introduces the network code and collaborative communication ideas, and carry out some basic coding theory research for some basic network topology. These include:multi-dimensional network error-correcting codes, multi-dimensional network linear block codes and convolutional codes, multi-dimensional space-time code and dual-constellation space-time code design for the exchange node; two-dimensional and three-dimensional network error-correcting code design, as well as two-dimensional and three-dimensional network of space-time code design for cooperative relay node. Theoretical analysis and simulation results show that, compared to the traditional coding theory based on one-way information flow, the novel coding schemes can make better use of the broadcast nature of wireless channel and wireless networking space resources, and effectively improve the utilization of energy emission and obtain more coding gain.In the physical layer, the source nodes and relay nodes need encoding and signal processing algorithms, while the destination nodes will need signal processing and decoding algorithm. the design of transmission signals, the pre-processing algorithm for the received signal, the error correction coding and space-time coding based on the network coding and collaborative communication are put together to carry out the optimization of communication. They are throughout all communication process and bring great gain for the wireless network. Compared to traditional methods, these novel technologies will obtain many gains on the performance of spectral efficiency energy consumption, encoding and decoding complexity, bit error rate and system throughput.更多还原