多用户MIMO系统中的预编码技术研究

多用户MIMO系统的预编码技术是未来移动通信研究的关键技术之一。文章对常用的预编码算法——线性的与非线性的——实现流程进行了详细描述,根据研究现状提出了未来预编码研究的发展趋势。仿真结果表明,非线性预编码算法的性能要优于线性预编码算法。     

基于HousehoJder码本的三维预编码码本设计

在LTE系统中,基于码本的有限反馈预编码码本设计是非常关键的一部分,本文以3GPP协议为标准,设计了该部分技术性问题的解决方案。文章介绍了LTEMIMOth的预编码技术和基于码本的有限反馈预编码技术,给出73GPP的预编码方案。本文在现有的研究基础上,提出了一种适合三维波束赋形的三维预编码技术的码本设计,并进行了性能仿真和分析。     

一种联合迫零和独立信道预编码OFDM系统

提出了一种联合迫零和独立信道预编码OFDM系统。该系统用发送端迫零顸编码和哈达玛矩阵预编码对发送数据进行联合预处理,简化了接收端,提高了系统的分集增益,仿真结果表明该方法提高了系统的误码率性能。     

MIMO下行链路系统预编码技术

本文主要介绍了MIMO下行链路系统的几种非线性预编码算法,包括脏纸编码、THP预编码和矢量预编码,重点分析了矢量预编码算法中求解扰动矢量的格基规约算法,并对该算法进行了仿真分析.此外,本文也给出了对未来MIMO系统预编码研究的发展趋势.     

大规模MIMO下最优预编码选择策略研究

大规模多入多出(Massive MIMO)系统中,随着天线数的增加,线性预编码算法的性能逐渐趋于最优,选择合适的线性预编码对系统性能具有重要的意义.针对发射端信道状态信息(Channel State Information at Transmitter,CSIT)不完美的Massive MIMO系统,推导出了迫零(Zero-Forcing,ZF)和最大比传输(Maximum Ratio Transmission,MRT)这两种常见预编码方案在向量归一化方式下的下行可达和速率下界,并给出了证明.随后对两种下界进行了分析,提出了一个关于系统用户数的阈值,当系统用户数和阈值的大小关系不同时,两种预编码性能的优劣关系也不相同.根据分析结果,文章进一步提出了一种以系统中用户数为参量的预编码选择策略,可以保证不论用户数如何变化,系统都能选择出更优的那一个预编码算法来对信号进行预处理.分析的有效性和方案的可靠性通过仿真得到了验证.     

基于IT＋＋的MIMO—OFDM非线性预编码仿真研究

预编码技术能够有效的抑制MIMO信道中的多用户干扰,能显著提高系统容量,同时也能大大简化接收机的算法。主要对MIMO—OFDM系统的非线性预编码技术进行了深入研究,通过搭建出的MIM0-OFDM仿真平台对DPC（DirtyPaperCoding,脏纸编码）和THP（TomlinsonHarashimaPre—coding,模代数TH编码）两种非线性预编码算法进行了性能仿真,比较了这两种算法的BER（误码率）,同时也比较了它们与线性zv（ZeroForcing,迫零）预编码算法的BER差异,并指出了不同算法的适用性。     

预编码的反馈方式研究

本文主要对预编码的两种反馈方式进行研究.首先介绍了预编码技术,然后分别对1bit反馈法、随机矢量量化码本反馈法进行介绍和分析,比较不同反馈方式对于预编码性能的影响.1bit反馈法的系统性能可以接近完全信道信息反馈的系统性能,并能大大减少反馈数据量.     

大规模MIMO系统的预编码算法综述

相比于传统多输入多输出（MIMO）系统,大规模MIMO的天线数量大幅增加,使得系统的容量提升、误比特率下降,但也造成预编码矩阵维度升高,算法复杂度、系统成本及实现难度增大。将大规模MIMO系统主要采用的预编码技术分为线性和非线性两个部分,对两者进行了归纳和对比,并着重介绍了几种经过简化的线性预编码算法和几种比较典型的非线性预编码算法,指出因为非线性算法的复杂度很高,故未来大规模MIMO系统的预编码应当以线性算法为主。     

MIMO移动通信系统中的预编码技术研究

MIMO技术利用多根天线实现多发多收,能够在不增加传输带宽和发射功率的条件下,成倍地提高系统的数据速率;而预编码技术则可以利用接收端反馈回来的信道状态信息对信号进行预处理以改善信号的传输性能,从而达到消除干扰的目的,使得无线通信系统的可靠性得以提升。因此对MIMO系统预编码技术的研究,是解决如何提升无线通信系统性能的关键问题,具有重大的研究意义。     

一种提高部分反馈预编码MIMO系统安全性能方案

MIMO(Mutiple-In Mutiple-Out,多输入多输出)技术是无线移动通信领域智能天线技术的重大突破。无线通信的广播特性容易引起信息泄露,开展研究提高无线通信网络安全性能的课题十分必要。目前,MIMO系统中的预编码技术已成为无线通信领域的研究热点。本文将介绍一种加密技术控制下通过旋转码本提高预编码系统安全性能的方案。通过仿真,验证了该方案可以使无线通信可靠性接近1,并且该方案的设计思想可以推广到其他预编码系统中。     

高速移动环境下基于动态CSI的MIMO系统改进模代数预编码

针对高速移动场景下信道快时变特性给多输入多输出（Multiple Input Multiple Output,MIMO）系统预编码带来的技术挑战,提出基于动态信道状态信息（Channel State Information,CSI）的MIMO系统改进模代数预编码（Tomlinson-Harashima Precoding,THP）算法.该算法利用信道统计量信息以及相关性构建动态CSI模型,更准确实时地体现当前信道状况;进一步地,提出一种基于循环遍历搜索的多用户调度算法,以最大化信干噪比为目标进行用户调度,且将多用户调度算法应用到THP中,提高了预编码精度.仿真结果表明,所提算法相比传统预编码算法具有更优的误码率性能和信道容量,验证了所提算法能有效地适应高速移动场景.     

基于协作多点下行传输的非线性鲁棒预编码

对于协作多点系统,下行信道信息误差会大幅降低联合传输的性能。为了避免下行信道信息误差对联合传输的影响,本文利用其二阶统计特性,设计了非线性鲁棒预编码算法。由于协作多点系统的特点和非线性鲁棒预编码的结构会导致用户间的性能差异,本文通过优化非线性鲁棒预编码算法的连续干扰消除先后顺序,从而改善性能最差用户的误码率,降低非线性鲁棒预编码算法的平均误码率。仿真结果表明当下行信道信息误差存在时,本文所提出的非线性鲁棒预编码性能优于传统的线性和非线性预编码性能。仿真结果还表明优化排序能提高非线性鲁棒预编码的性能增益。     

A Novel Nonlinear Precoding Algorithm for the Downlink of Multiple Antenna Multi-User Systems

By pre-equalizing inter-stream interference at the transmitter, Tomlinson–Harashima precoding (THP) algorithm provides a solution for the downlink of multiple antenna multi-user systems, in which the decentralized structure of the receivers makes the receiver-processing impossible. However, for the zero-forcing (ZF) THP algorithm available in the literature there are significant performance differences between specific mobile stations. In this paper, a novel version of the THP algorithm is proposed. It greatly improves the worst mobile's performance and ensures balanced performance of all the mobiles. For the new THP algorithm, better performance can be obtained by suitably ordering the rows of the channel matrix. We show that the “best-first” ordering method achieves optimal order for BER performance in systems with two mobile stations and achieves near optimal order in systems with more than two mobile stations. Simulation is used to show the advantages of the new THP algorithm and the “best-first” ordering method. Jia Liu received the B.E. and M.Sc. degrees in electrical engineering from Beijing University of Posts and Telecommunications, Beijing, China, in 1998 and 2001, respectively. Between 2001 and 2002, she worked as a system engineer in Siemens Ltd. (China), ICM N R&D, TD-SCDMA. She is currently pursuing a Ph.D. degree at the Department of Electrical and Computer Engineering, University of Alberta, and at TRLabs in Edmonton, Alberta, Canada. Her current research interests include broadband wireless communications, multiple input multiple output (MIMO) antenna systems, precoding for multi-user MIMO, signal detection, and multi-user interference cancellation. Witold A. Krzymień received his M.Sc. (Eng.) and Ph.D. degrees (both in Electrical Engineering) in 1970 and 1978, respectively, from the Poznań University of Technology in Poznań, Poland. He received a Polish national award of excellence for his PhD thesis. Since April 1986 he has been with the Department of Electrical & Computer Engineering at the University of Alberta, Edmonton, Alberta, Canada, where he currently holds the endowed Rohit Sharma Professorship in Communications & Signal Processing. In 1986, he was one of the key research program architects of the newly launched TRLabs, Canada's largest industry-university-government pre-competitive research consortium in the Information & Communication Technology area, headquartered in Edmonton. His research activity has been closely tied to the consortium ever since. Over the years Dr. Krzymień has also done collaborative research work with Nortel Networks, Ericsson Wireless Communications, German Aerospace Centre (DLR -Oberpfaffenhofen), Telus Mobility and the University of Padova (Italy). He has held visiting research appointments at Twente University of Technology (Enschede, The Netherlands; 1980-1982), Bell-Northern Research (Montréal, Canada; 1993-1994), Ericsson Wireless Communications (San Diego, USA; 2000), Nortel Networks Harlow Laboratories (Harlow, UK; 2001), and the Department of Information Engineering at the University of Padova (2005). His research is currently focused on broadband high throughput packet data access for mobile and nomadic users, employing multi-carrier signalling, multiple antenna techniques and link adaptation, as well as on the related MAC and network layer issues of hybrid ARQ, packet scheduling and relaying. Dr. Krzymień is a Fellow of the Engineering Institute of Canada, and a licensed Professional Engineer in the Provinces of Alberta and Ontario, Canada. From 1999 to 2005 he was the Chairman of Commission C (Radio Communication Systems and Signal Processing) of the Canadian National Committee of URSI (Union Radio Scientifique Internationale). He received the 1991/1992 A.H. Reeves Premium Award from the Institution of Electrical Engineers (U.K.) for a paper published in the IEE Proceedings, Part I.     

基于协作多点传输的非线性顽健预编码

A nonlinear robust precoding algorithm was proposed,which redesigned the feedback matrix,the forward matrix and the scaling matrix of the traditional tomlinson-harashima precoding algorithm based on the statistical characteristics of the downlink channel state information errors.Simulation results show that the nonlinear robust precoding algorithm can achieve better performance than the traditional linear and nonlinear precoding algorithms when the downlink channel state information errors exist.Due to the different downlink channel state information errors between user equipments in the coordinated multi-point transmission,the traditional “best-first” ordering algorithm was invalid.So an improved ordering algorithm was proposed to reduce the average bit error rate of the nonlinear robust precoding algorithm.     

大规模MIMO时分双工系统的鲁棒预编码设计

对于采用大规模MIMO技术的时分双工系统,天线互易误差会破坏上下行信道互易特性,大幅降低预编码算法下行传输性能。由于实际系统难以完全消除天线互易误差,该文以最大化各用户平均信泄噪比为目标,根据天线互易误差的统计特性,设计了对该误差具有鲁棒性的线性预编码算法。同时为了进一步降低用户接收端的等效噪声功率,该文还将该线性鲁棒预编码算法扩展为基于矢量扰动的非线性鲁棒预编码算法,并通过减格辅助技术降低其扰动矢量求解复杂度,使其更适用于大规模MIMO系统应用。计算机仿真结果表明在存在基站天线互易误差条件下,该文所提出的线性与非线性鲁棒性预编码算法的性能均优于传统预编码算法的性能。     

自适应调制的预编码SM-MIMO性能分析

SM-MIMO系统可以极大的提高系统容量,在下一代移动通信系统中有着广阔的应用前景;但SM-MIMO系统对信道病态矩阵非常敏感。作为一种优化手段,有限速率反馈预编码技术可以大大提高MIMO系统对衰落信道的鲁棒性,另外,自适应调制编码技术也可以使系统性能和吞吐量得到很好改善。预编码技术和自适应调制编码技术的应用都是建立在对信道信息的获取上,因此,文中在SM-MIMO系统融合了这两种技术,仿真结果表明SM-MIMO系统性能得以明显提高。     

MMSE based joint Tomlinson-Harashima source and linear relay precoder design in non-regenerative MIMO relay system

This paper proposes a joint nonlinear transceiver design scheme based on minimum mean square error(MMSE) criterion for non-regenerative multiple input multiple output(MIMO) relay system.The proposed scheme decomposes the error covariance matrix,reformulates the original joint design problem as two separate optimization problems,and then provides a closed-form solution with only local channel state information(CSI) available at the source and destination.Performance evaluation shows that the proposed scheme significantly outperforms linear schemes,and has a competitive performance compared with existing global CSI based nonlinear schemes,both iterative and non-iterative.     

Robust Tomlinson–Harashima Precoding for the Wireless Broadcast Channel

Previous designs of Tomlinson-Harashima precoding (THP) for the broadcast channel with multiple (cooperative) transmitters and noncooperative (decentralized) scalar receivers assume complete channel state information (CSI) at the transmitter. Due to its nonlinearity, THP is more sensitive to errors in CSI at the transmitter than linear precoding, which may be large in wireless communications. Thus, THP performance degrades severely-and it is even outperformed by corresponding linear precoders. We propose a novel robust optimization for THP with partial CSI based on mean-square error (MSE), which performs a conditional mean (CM) estimate of the cost function including a novel model of the receivers. This enables a smooth transition of robust THP from complete, via partial, to statistical CSI. The performance is now always superior or in the worst case equal to corresponding linear precoding techniques. With these features, the proposed robust THP is very attractive for application in the wireless broadcast channel