无线局域网中的多用户MIMO预编码技术研究

发布时间：2018-02-11 08:53

本文关键词： 无线局域网多用户MIMO 预编码格基约减信道状态信息反馈结合　出处：《西南交通大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来,随着无线通信技术的飞速发展以及无线终端的迅速普及,无线局域网作为一种重要的网络接入方式以其独特的优势广泛应用于企业、校园、家庭等热点区域,无线通信业务以及用户数的爆炸式增长使得人们对无线局域网的系统容量和用户体验度提出了更高的要求。将多用户MIMO技术应用于无线局域网中能大大提升系统容量和增加同时接入的用户数,但是多个用户在相同的时频资源内与AP通信势必会带来严重的多用户干扰。在上行多用户MIMO系统中AP可以采用多用户检测技术来区分不同用户的信息,而下行多用户MIMO系统中用户间无协作,因此多用户间干扰只能在AP端采用预编码技术来抑制。本文首先概述了无线局域网的发展历程、物理层关键技术以及下行链路多用户数据处理流程。接着分析了下行多用户MIMO系统模型和MIMO-OFDM系统的预编码方式,研究了常用的线性预编码,包括迫零预编码、最小均方误差预编码以及块对角化预编码,并在WLAN平台上做了性能仿真。然后研究了非线性预编码,包括脏纸编码和TH预编码,重点分析了ZF准则和MMSE准则下的TH预编码,并结合格基约减技术对TH预编码进行了优化,提升了误比特率性能,并在WLAN平台上做了仿真验证；最后重点研究了WLAN场景下的预编码应用,分析了造成非完美信道状态信息的因素,包括信道估计误差和频率偏移,介绍了目前无线局域网中的信道状态信息反馈机制和减小信道状态信息反馈开销的方法,以提高反馈效率为目的给出了多用户并行反馈方案,通过仿真分析了采用不同的量化比特数和子载波分组大小来反馈信道状态信息对预编码性能的影响,并给出了一种较优的用于子载波分组中的共用子载波信道状态矩阵选取方法,根据线性预编码和TH预编码的特点提出了结合两者的思路并给出了相应的多用户帧结构改变和自适应选择方案。
[Abstract]:In recent years, with the rapid development of wireless communication technology and the rapid popularity of wireless terminals, WLAN, as an important network access mode, has been widely used in enterprises, campuses, homes and other hot areas with its unique advantages. The explosive growth of wireless communication service and the number of users make people request higher system capacity and user experience of WLAN. The application of multi-user MIMO technology in WLAN can greatly enhance the system. Capacity and increase in the number of users accessing at the same time, However, communication between multiple users and AP in the same time-frequency resources will inevitably bring serious multi-user interference. In uplink multi-user MIMO systems, AP can use multi-user detection technology to distinguish different users' information. However, there is no cooperation among users in the downlink multi-user MIMO system, so multi-user interference can only be suppressed by pre-coding technology at the AP end. This paper first summarizes the development of WLAN. The key technologies of the physical layer and the downlink multiuser data processing flow are analyzed. Then the downlink multiuser MIMO system model and the precoding method of the MIMO-OFDM system are analyzed and the commonly used linear precoding including zero forcing precoding is studied. The minimum mean square error precoding and block diagonalization precoding are simulated on WLAN platform. The nonlinear precoding, including dirty paper coding and th precoding, is studied, and the th precoding based on ZF criterion and MMSE criterion is analyzed. Combined with trellis reduction technique, th precoding is optimized, the performance of bit error rate is improved, and the simulation is done on WLAN platform. Finally, the precoding application in WLAN scenario is studied emphatically. The factors causing imperfect channel state information, including channel estimation error and frequency offset, are analyzed. The channel state information feedback mechanism in WLAN and the method to reduce the channel state information feedback overhead are introduced. In order to improve the feedback efficiency, a multi-user parallel feedback scheme is proposed. The effects of different quantization bits and sub-carrier packet sizes on the precoding performance are analyzed by simulation. A better method of selecting common subcarrier channel state matrix for subcarrier packet is also presented. According to the characteristics of linear precoding and th precoding, the idea of combining them is proposed, and the corresponding multi-user frame structure change and adaptive selection scheme are given.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN925.93

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