MIMO系统中基于有限反馈的预编码及天线合并技术研究

发布时间：2018-05-23 12:07

本文选题：多输入多输出 + 有限反馈　；参考：《电子科技大学》2014年博士论文

【摘要】：随着无线信息服务需求的不断增长,为了高效地利用稀缺的频谱资源,以多输入多输出(MIMO)为系统架构的信号传输技术近十几年来受到广泛关注。理论证明MIMO系统较传统的单输入单输出(SISO)系统能够在不占用额外信道资源的前提下成倍提高系统容量,因此MIMO技术被认为是未来移动通信系统的关键技术之一。本论文分别对多用户MIMO系统的预编码算法和天线合并算法进行了研究。特别是针对实际商用无线通信系统中上行信道速率较低的特性,本论文研究的是基于有限反馈的闭环MIMO系统。本论文主要研究内容概括如下:考虑到在有限反馈MIMO系统中用户的码字搜索需要较大的运算量,本论文第二章提出了一种简化的码字搜索方案。码字搜索的复杂度分为两个部分,一个部分是对于每个码字量化误差的计算,另一个部分是对码本搜索路径的选择。码本搜索路径的选择取决于当前码本的设计,不同的码本的优化方法各不相同,而当前通用的方法是在所有码字中进行遍历搜索。本论文提出的码字搜索方案对码字量化误差的计算进行了简化,这种简化的计算方法可以适用于各种类型的码本。为了保证能获得满复用增益,现有的线性预编码算法需要相当大的反馈量。降低反馈量的一种有效方法是针对不同的场景设计特定的预编码方案。在实际的MIMO系统中,1个基站同时向2个用户发射数据是一种常见的应用场景。本论文第三章基于一个2用户的多用户MIMO场景,提出了一种运算复杂度低、性能较现有线性预编码算法均有提升的有限反馈预编码方案。每用户酉速率控制(PU2RC)是基于机会通信的多用户MIMO系统中最具有代表性的线性预编码方案,在实际中也得到广泛应用。本论文第四章针对PU2RC系统的固有缺陷提出了一种多模传输(MMT)方案并给出了使用该方案的量化码本设计算法,该方案使用双参数反馈使基站可以设计最优的用户调度方案,在保证反馈量不变的前提下增强了系统的鲁棒性。本章还分析给出了PU2RC系统中每个用户的调度前信干噪比(SINR)的概率密度函数(pdf)表达式。这个结果可以广泛应用于PU2RC系统中的MMT方案以及反馈方案的设计,并且在分析过程中提出的一种降维分析算法可广泛应用于MIMO系统预编码算法的性能分析以及波束成型设计。在有限反馈多用户MIMO系统中,天线合并算法是一种的重要信号检测方案。现有最优的天线合并算法是基于大量用户反馈后调度设计的,而最近研究证明,将有限的反馈资源分配给少量用户是最优的反馈资源分配策略。第五章基于这个反馈资源分配策略,提出了统计最优的天线合并算法并给出了该算法的性能下界表达式,而且这种分析方法可以很容易推广其他的MIMO应用场景中。最后一章对全文进行了简要总结,并对未来继续研究的方向进行了展望。
[Abstract]:With the increasing demand for wireless information services, in order to efficiently utilize the scarce spectrum resources, the signal transmission technology based on multi-input and multi-output MIMOs has been paid more and more attention in the past ten years. It is proved theoretically that the MIMO system can increase the system capacity exponentially compared with the traditional single input single output (SISO) system without taking up additional channel resources. Therefore, MIMO technology is considered as one of the key technologies in the future mobile communication system. In this paper, precoding algorithm and antenna merging algorithm for multi-user MIMO systems are studied. Especially in view of the low uplink channel rate in commercial wireless communication systems, a closed-loop MIMO system based on finite feedback is studied in this paper. The main research contents of this thesis are summarized as follows: considering that the codeword search of users in a limited feedback MIMO system requires a large amount of computation, a simplified codeword search scheme is proposed in the second chapter of this paper. The complexity of codeword search is divided into two parts, one is the calculation of quantization error for each codeword, the other is the choice of codebook search path. The choice of codebook search path depends on the current codebook design. Different codebook optimization methods are different, while the current common method is to traverse all codewords. The codeword search scheme proposed in this paper simplifies the calculation of quantization error of codewords, and this simplified method can be applied to all kinds of codebooks. In order to obtain full multiplexing gain, the existing linear precoding algorithms need a large amount of feedback. One effective way to reduce feedback is to design specific precoding schemes for different scenarios. In a practical MIMO system, it is a common application scenario that one base station transmits data to two users simultaneously. In the third chapter, based on a two-user multi-user MIMO scenario, a finite feedback precoding scheme with lower computational complexity and better performance than existing linear precoding algorithms is proposed. Unitary rate control per user (PU2RC) is the most representative linear precoding scheme for multi-user MIMO systems based on opportunistic communication. It is also widely used in practice. In the fourth chapter of this paper, we propose a multi-mode transmission scheme and a quantization codebook design algorithm based on this scheme, which makes the base station design the optimal user scheduling scheme by using two-parameter feedback. The robustness of the system is enhanced on the premise that the feedback quantity is invariant. In this chapter, the expression of probability density function (PDF) for each user before scheduling in PU2RC system is also analyzed. This result can be widely used in the design of MMT scheme and feedback scheme in PU2RC system, and a reduced dimension analysis algorithm proposed in the process of analysis can be widely used in the performance analysis and beamforming design of MIMO system precoding algorithm. Antenna merging is an important signal detection scheme in finite feedback multiuser MIMO systems. The existing optimal antenna merging algorithms are based on a large number of users' feedback post-scheduling. Recent studies have proved that allocating limited feedback resources to a small number of users is the optimal feedback resource allocation strategy. In chapter 5, based on this feedback resource allocation strategy, a statistically optimal antenna merging algorithm is proposed and the performance lower bound expression of the algorithm is given. Moreover, this analysis method can be easily extended to other MIMO application scenarios. In the last chapter, a brief summary of the whole paper is given, and the future research direction is prospected.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN919.3

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