减轻大规模MIMO系统中导频污染的研究

发布时间：2018-07-10 14:04

本文选题：大规模MIMO + 导频污染　；参考：《江苏科技大学》2016年硕士论文

【摘要】：伴随无线网络系统的稳步发展以及智能终端的不断推广,现代通信系统需要更高的传输速率和可靠性。然而移动通信业务的快速增长,使得无线频谱资源也日益紧张。第四代移动通信技术的日益成熟,让人们看到了多输入多输出(Multiple-Input Multiple-Output,MIMO)技术的性能潜力。它不仅可以带来频谱效率的大幅提升,而且还可以使得无线链路传输性能变得更加可靠。大规模MIMO(Massive MIMO)技术在现有MIMO技术的基础上进一步提高了系统性能,它可以有效的应对未来无线数据爆炸式增长的需求。相比较于传统的MIMO技术,大规模MIMO技术可通过直接增加基站处的天线数量(几十或上百根)来实现。该技术通过增加空间自由度的方式,在不需要额外带宽的情况下大幅度地提升系统容量。但是当应用到多小区蜂窝网络中,由于正交导频数量有限使得相邻小区之间导频存在复用,即造成导频污染问题。而导频污染问题严重影响了信道估计的准确性,限制了系统性能。因此,本文主要研究大规模MIMO系统中导频污染的问题。本文完成的工作如下:一、阐述了大规模MIMO系统的技术优势及研究热点,分析了大规模MIMO技术的性能特性,包括系统模型、信道空间衰落模型等等,并在此基础上着重探究比较了大规模MIMO系统中导频污染问题的解决方案;随后详细研究了大规模MIMO系统中的信道估计方法与预编码方案;二、在详细地分析研究了现有大规模MIMO蜂窝网络同步导频传输方案的基础上,探究了导频污染的产生原因;随后分析了改进后的基于偏移导频传输方案,该方案通过在时域上将目标小区导频帧与相邻小区数据帧相对应,从而到达减轻系统中导频污染的目的;最后通过仿真验证了导频污染对系统性能的影响及偏移导频传输方案的有效性;三、结合对系统信道估计均方误差的性能分析,在同步导频传输及偏移导频传输方案的基础上,提出一种时隙交错导频传输方案,该方案通过将小区分组,组内不同小区使用不同导频帧结构以达到减轻导频污染的目的,最后通过仿真实验验证了该方案的优越性。
[Abstract]:With the steady development of wireless network systems and the continuous promotion of intelligent terminals, modern communication systems need higher transmission rate and reliability. However, with the rapid growth of mobile communication services, wireless spectrum resources are increasingly tight. With the development of the fourth generation mobile communication technology, the performance potential of Multiple-Input Multiple-Output MIMO (MIMO) technology has been recognized. It not only improves spectrum efficiency significantly, but also makes wireless link transmission more reliable. Large-scale MIMO (massive MIMO) technology further improves the system performance based on the existing MIMO technology, and it can effectively meet the demand of the explosive growth of wireless data in the future. Compared with the traditional MIMO technology, the large-scale MIMO technology can be realized by directly increasing the number of antennas (tens or hundreds) at the base station. By increasing the degree of freedom of space, the system capacity can be greatly increased without the need of additional bandwidth. However, when it is applied to multi-cell cellular networks, due to the limited number of orthogonal pilots, there is multiplexing between adjacent cells, which leads to pilot pollution. Pilot pollution seriously affects the accuracy of channel estimation and limits the system performance. Therefore, this paper focuses on pilot pollution in large-scale MIMO systems. The work accomplished in this paper is as follows: firstly, the advantages and research focus of large-scale MIMO system are described, and the performance characteristics of large-scale MIMO system are analyzed, including system model, channel spatial fading model and so on. On the basis of this, the solutions of pilot pollution in large-scale MIMO systems are discussed and compared. Then, the channel estimation methods and precoding schemes in large-scale MIMO systems are studied in detail. Secondly, Based on the detailed analysis and study of the existing synchronous pilot transmission schemes in large-scale MIMO cellular networks, the causes of pilot pollution are explored, and then the improved scheme based on offset pilot transmission is analyzed. In this scheme, the pilot frame of the target cell is corresponding to the data frame of the adjacent cell in the time domain, so as to reduce the pilot pollution in the system. Finally, the effects of pilot pollution on system performance and the effectiveness of offset pilot transmission scheme are verified by simulation. Thirdly, combined with the performance analysis of channel estimation mean square error, based on synchronous pilot transmission and offset pilot transmission scheme, A time-slot interleaved pilot transmission scheme is proposed, in which different pilot frame structures are used in different cell groups to reduce pilot pollution. Finally, the superiority of this scheme is verified by simulation experiments.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN919.3

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