多用户Massive MIMO系统中的导频污染抑制技术研究

发布时间：2018-04-01 08:18

本文选题：Massive　切入点：MIMO　出处：《山东大学》2017年硕士论文

【摘要】：随着移动通信传输需求的增长,MassiveMIMO技术由于其具有数倍提升系统能量效率和频谱效率的能力成为第五代移动通信(5G)的关键技术之一。多用户Massive MIMO通信网络也相应地成为未来5G的典型通信网络。多用户Massive MIMO通信系统的性能与系统内用于信道估计的正交训练导频的数量有关,由于系统内正交训练导频的数量受信道相干时间的限制不能满足于庞大的用户数的需求,因此在系统内会不可避免地出现用户复用训练导频的情况从而导致小区间用户的相互干扰,这种干扰被称为导频污染。研究表明导频污染不能够通过增加基站端的天线数目来消除,因此成为限制Massive MIMO系统性能提升的主要问题。论文针对导频污染问题,主要研究了两种抑制多用户Massive MIMO系统中导频污染问题的技术——导频分配技术和导频污染预编码技术。论文的主要工作及创新点总结如下:(1)提出一种兼顾系统整体性能和系统内公平性的导频分配技术方案。现有关于导频分配技术的研究大致分为两类,一类是提升系统整体性能的导频分配技术;另一类是实现系统内公平性的导频分配技术。这两类导频分配技术的研究都存在着不足:提升系统整体性能的导频分配方案以最大化系统和速率为优化目标,在提高系统整体性能时忽略了系统内的公平性;而关注于系统中最小用户速率提升的导频分配方案因过分注重系统内的公平性,大大削弱了系统的整体性能。在现有导频分配技术的研究中,几乎没有一种导频分配技术方案能够实现系统整体性能和系统内公平性的有效兼顾。针对这种不足,论文提出了一种在最大化系统整体性能的同时有效兼顾系统内公平性的导频分配方案。该方案以最大化系统内用户速率乘积的优化准则为基础构建关于导频分配的优化问题,通过基于贪婪策略的用户交换方法(UEBG)以及最小泄露方法(Min Leakage),可以在抑制导频污染的同时实现系统整体性能和系统内公平性的有效兼顾。(2)提出一种基于基站端有限天线情况下最大化系统整体性能的导频污染预编码方案。在实际应用场景中,受天线尺寸和配置难度的限制,基站端不可能实现无穷多的天线配置,在这种情况下,信道中的噪声、信道估计误差、信道间的非正交性以及由于统计信道引发的不确定性等因素相对于导频污染来说都是不可被忽视的因素。现有的基于无穷多天线情况下得到的导频污染预编码在基站天线有限的情况下并不适用,为使导频污染预编码技术更加实用化,论文综合考虑了导频污染及以上所有因素的影响,提出了一种适用于基站端天线数有限情况下,最大化系统整体性能的导频污染预编码方案。该方案可以在有限天线的情况下以有限的复杂度实现系统性能的有效提升,当导频污染比较严重时该方案尤为有效。
[Abstract]:With the increasing demand for mobile communication transmission, MassiveMIMO technology has become one of the key technologies of the fifth generation mobile communication due to its ability to increase the energy efficiency and spectrum efficiency of the system by several times. The multi-user Massive MIMO communication network is correspondingly also one of the key technologies in the fifth generation mobile communication. The performance of a multiuser Massive MIMO communication system is related to the number of orthogonal training pilots used for channel estimation in the system. Because the number of orthogonal training pilots in the system is limited by the channel coherence time, it can not meet the needs of a large number of users. Therefore, it is inevitable that user multiplexing training pilots will occur in the system, which will lead to inter-interference of inter-cell users. This kind of interference is called pilot pollution. The study shows that pilot pollution can not be eliminated by increasing the number of antennas at base station, so it becomes the main problem to limit the performance improvement of Massive MIMO system. This paper mainly studies two kinds of technologies to suppress pilot frequency pollution in multi-user Massive MIMO system-pilot allocation technology and pilot pollution precoding technique. The main work and innovation of this paper are summarized as follows: 1) A new scheme is proposed to take into account the whole system. Pilot assignment schemes for performance and fairness in the system. One is pilot allocation technology to improve the overall performance of the system. The other is pilot allocation technology to achieve fairness in the system. There are some shortcomings in the research of these two kinds of pilot allocation techniques: the optimization goal of pilot allocation scheme to improve the overall performance of the system is to maximize the system and speed. In order to improve the overall performance of the system, the fairness in the system is neglected, and the pilot allocation scheme, which focuses on the minimum user rate increase in the system, pays too much attention to the fairness in the system. The overall performance of the system is greatly weakened. In the research of the existing pilot allocation technology, almost none of the pilot allocation schemes can effectively balance the overall performance of the system and the fairness within the system. This paper presents a pilot allocation scheme which maximizes the overall performance of the system while taking into account the fairness of the system effectively. The pilot allocation optimization problem is constructed based on the optimization criterion of maximizing the user rate product in the system. By using UEBG (user switching method based on greedy strategy) and Min LeakagePen (a minimum leak method), we can reduce pilot pollution and realize the overall performance of the system and the fairness within the system effectively. 2) A new method based on the limited base station end is proposed. Pilot pollution precoding scheme that maximizes the overall performance of the system in the case of antennas. Because of the limitation of antenna size and configuration difficulty, it is impossible for the base station to realize infinite antenna configuration. In this case, the noise in the channel, the channel estimation error, The non-orthogonality between channels and the uncertainty caused by statistical channels are all important factors relative to pilot pollution. Where the base station antenna is limited, In order to make pilot pollution precoding technology more practical, this paper comprehensively considers the influence of pilot pollution and all the above factors, and proposes a new method which is suitable for the limited antenna number of base station. The pilot pollution precoding scheme, which maximizes the overall performance of the system, can effectively improve the system performance with limited complexity in the case of limited antennas, especially when the pilot pollution is serious.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3

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