终端协同D2D多用户MIMO关键技术研究

发布时间：2018-11-07 11:01

【摘要】：MIMO(Multi-Input-Multi-Output)技术能够提供更多的空间自由度,在相同的时频资源上以空间复用的方式,利用多根天线同时传输多流数据,是一种增加系统容量的必要方法。MU-MIMO技术在同一时频资源服务多个用户,是传统SU-MIMO技术的多用户扩展。在下行数据传输时,如果基站已知下行信道状态信息,就可以通过预编码技术对发送信号进行预处理,将多用户干扰在发射端提前消除或者抑制,从而实现多用户通信,并充分发掘系统多用户分集增益,提高下行MU-MIMO系统的性能。预编码技术的重要前提是发射机知道当前时刻的信道状态信息,并且信道状态信息的准确程度,对蜂窝系统的性能有重要的影响。在FDD系统中,上下行信道使用的是不同的频点,因此不存在信道的互易性。发射机无法直接获取下行的信道状态信息,只能依靠来自接收机的信道反馈信息。D2D通信技术具有短距离通信和直接通信的特点,使得距离比较近的用户可以通过一定的方式共享本地信息。为MU-MIMO通信系统的进一步优化提供了一种新的思路。本文主要研究基于终端协同的MU-MIMO技术。将D2D通信技术引入现有MU-MIMO系统中,优化现有下行MU-MIMO系统中,因MU之间没有信息交互,各UE上行链路反馈能力有限,及下行预编码矢量的不完全正交性等因素引起的诸多问题。本文希望借助UE间的D2D链接,辅助MU-MIMO解决上述问题,形成MU-MIMO+D2D的具有竞争力的方案,提高现有蜂窝系统容量,推动MU-MIMO+D2D的标准化以及商用化。具体包括如下几个方面:首先,通过对传统的各种基于码本和基于非码本的预编码方案的分析,给出终端协同MU-MIMO新系统的潜在性能分析。其次,分析现有MU-MIMO系统存在的问题。如MU-MIMO配对概率低、CQI失配问题、多用户间干扰大、上行反馈量大等问题。第三,从联合信道估计的角度给出终端协同的新方案。基于Rank-2码本提出了一种基于广播模式的终端协同MU-MIMO增强方案。基于Rank-1码本提出了一种解决CQI失配问题的MU-MIMO增强方案。第四,从联合接收增强的角度给出终端协同的改进接收方案。分别基于检测数据和列范数交互提出终端协同干扰删除改进接收方案。第五,研究了基于终端协同的用户配对。分析了终端协同用户配对理论上限的计算方法,基于共享的本地CSI信息,提出了最大SU容量配对、最大奇异值配对及基于码本正交性配对等方案。最后,对上述新方案的吞吐性能等指标进行仿真比较。
[Abstract]:MIMO (Multi-Input-Multi-Output) technology can provide more spatial degrees of freedom, using multiple antennas to transmit multi-stream data simultaneously on the same time-frequency resources in a spatial multiplexing manner. MU-MIMO technology serves multiple users in the same time-frequency resource and is a multiuser extension of traditional SU-MIMO technology. When the downlink data is transmitted, if the base station knows the downlink channel state information, it can preprocess the transmitted signal by pre-coding technology, eliminate or suppress the multi-user interference in advance at the transmitter, and realize multi-user communication. And fully explore the system multi-user diversity gain, improve the performance of downlink MU-MIMO system. The important premise of precoding technology is that the transmitter knows the channel state information at the current time and the accuracy of the channel state information has an important effect on the performance of cellular system. In FDD systems, the uplink and downlink channels use different frequency points, so there is no channel reciprocity. The transmitter can not directly obtain the downlink channel state information, and can only rely on the channel feedback information from the receiver. D2D communication technology has the characteristics of short distance communication and direct communication. So that closer users can share local information in a certain way. It provides a new idea for the further optimization of MU-MIMO communication system. This paper mainly studies MU-MIMO technology based on terminal collaboration. The D2D communication technology is introduced into the existing MU-MIMO system, and the existing downlink MU-MIMO system is optimized. Because there is no information exchange between MU, the uplink feedback ability of each UE is limited. And some problems caused by the incomplete orthogonality of the downlink precoding vector. This paper hopes to use D2D links between UE to assist MU-MIMO to solve the above problems, to form a competitive solution of MU-MIMO D2D, to increase the capacity of existing cellular systems, and to promote the standardization and commercialization of MU-MIMO D2D. It includes the following aspects: firstly, the potential performance of the new cooperative MU-MIMO system is analyzed by analyzing the traditional precoding schemes based on codebook and non-codebook. Secondly, the existing problems of MU-MIMO system are analyzed. For example, the MU-MIMO pairing probability is low, the CQI mismatch problem, the multi-user interference is big, the uplink feedback quantity is large and so on. Thirdly, a new scheme of terminal collaboration is proposed from the point of view of joint channel estimation. A cooperative MU-MIMO enhancement scheme based on broadcast mode is proposed based on Rank-2 codebook. Based on Rank-1 codebook, a MU-MIMO enhancement scheme to solve CQI mismatch problem is proposed. Fourth, from the point of view of joint reception enhancement, the improved receiving scheme of terminal cooperation is given. Based on the interaction of detection data and column norm, the improved receiving scheme of terminal cooperative interference deletion is proposed. Fifth, user pairing based on terminal collaboration is studied. Based on the shared local CSI information, the maximum SU capacity pairing, maximum singular value pairing and code-based orthogonality pairing are proposed. Finally, the performance of the new scheme is simulated and compared.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3

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