两用户多天线协作通信传输方案的研究

发布时间：2018-09-08 21:47

【摘要】：多用户多输入多输出(Multiple-Input Multiple-Output, MIMO)无线通信网络允许多个用户在相同的时频资源下工作,能够有效提高系统容量,但用户间干扰问题限制了系统性能的提升。而协作通信技术能够更好地挖掘多用户MIMO系统内在的空间分集增益,扩大覆盖范围,改善系统整体性能。但结合两种技术的多用户协作通信方案往往存在网络结构复杂、编码及检测复杂度高等问题。为此,本文开展了如下研究工作。(1)研究了多用户MIMO系统的基本信道模型和干扰处理方法,重点研究了两种经典的干扰对齐方案。一种是基于Alamouti结构编码的干扰对齐方案,该方案利用Alamouti结构的正交性消除用户间的干扰；另一种方案在发射端未知信道状态信息的条件下,通过设计合理的空时编码传输方式,实现两用户MIMO干扰信道下的干扰对齐。(2)分析了协作通信的基本模型和协作中继传输的经典转发方式,深入研究了在多天线MIMO通信系统中采用循环延迟分集(Cyclic Delay Diversity, CDD)技术降低编码及检测复杂度的内在机理。研究结果表明,使用CDD技术可在获得分布式无线通信网络潜在分集增益的同时,简化整个通信系统的实现复杂度。(3)基于上述的研究成果,提出了一种低检测复杂度的两用户多天线协作通信传输方案。该传输方案中所有节点均配备多根天线,整个传输过程可分为两个阶段：第一阶段,两通信用户首先对待传输信号进行正交频分复用(Orthogonal Frequency Division Multiplex, OFDM)调制,然后采用基于干扰对齐思路设计的空时分组码对各个子载波上的调制信号进行编码,以在获得系统分集性能的同时,易于实现接收端的干扰分离,将编码后的信号广播发送给所有的中继节点；第二阶段,为降低检测复杂度,在中继转发过程中引入CDD方式。各个中继节点采用不同的循环延迟量对各自接收到的信号进行循环延迟操作后再放大转发给接收节点,在接收节点处基于发射端的空时编码原则设计合理的迫零消除矩阵去除用户间的干扰,获得期望信号。理论分析和仿真结果表明,本文提出的传输方案可在两用户多天线协作通信系统中实现简单的编码和检测,能够获得较大的空间分集增益和良好的误比特性能,中继节点数目的增加不会对接收端的检测复杂度产生影响,具有一定的实用性。
[Abstract]:Multi-user multiple-input multiple-output (Multiple-Input Multiple-Output, MIMO) wireless communication network allows multiple users to work under the same time-frequency resources, which can effectively improve the system capacity. However, inter-user interference problem limits the performance of the system. The cooperative communication technology can better mine the spatial diversity gain of the multi-user MIMO system, expand the coverage and improve the overall performance of the system. However, the multi-user cooperative communication scheme based on two technologies often has some problems, such as complex network structure, high complexity of coding and detection, and so on. In this paper, the following research work is carried out. (1) the basic channel model and interference processing methods of multi-user MIMO systems are studied, and two classical interference alignment schemes are studied. One is an interference alignment scheme based on Alamouti structure coding, which utilizes the orthogonality of Alamouti structure to eliminate interference between users, the other is to design a reasonable space-time coding transmission mode under the condition of unknown channel state information at the transmitter. The interference alignment of two user MIMO interference channels is realized. (2) the basic model of cooperative communication and the classical forwarding mode of cooperative relay transmission are analyzed. The inherent mechanism of using cyclic delay diversity (Cyclic Delay Diversity, CDD) to reduce the complexity of coding and detection in multi-antenna MIMO communication systems is studied. The results show that using CDD technology can simplify the complexity of the whole communication system while obtaining the potential diversity gain of the distributed wireless communication network. (3) based on the above research results, In this paper, a low detection complexity scheme for two user multi-antenna cooperative communication is proposed. In this transmission scheme, all nodes are equipped with multiple antennas, and the whole transmission process can be divided into two stages: in the first stage, the two communication users first perform orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplex, OFDM) modulation for the transmitted signal. Then the space-time block codes designed based on interference alignment are used to encode the modulation signals on each sub-carrier, so that the system diversity performance can be obtained and the interference separation at the receiver can be easily realized at the same time. The encoded signal broadcast is sent to all relay nodes. In the second stage, in order to reduce the detection complexity, the CDD mode is introduced in the relay forwarding process. Each relay node uses different cyclic delay to perform cyclic delay operation on each received signal, and then amplifies and forwards it to the receiving node. Based on the space-time coding principle of the transmitter at the receiving node, a reasonable zero-forcing elimination matrix is designed to remove the interference between users and obtain the desired signal. Theoretical analysis and simulation results show that the proposed transmission scheme can achieve simple coding and detection in a two-user multi-antenna cooperative communication system, and can achieve large spatial diversity gain and good bit error performance. The increase of the number of relay nodes will not affect the detection complexity of the receiver, and it is practical.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN919.3

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