MIMO无线通信系统的关键技术和应用前景

简单地描述了在平坦消失的无线信道中多输入多输出(MIMO)系统的基本工作原理;讨论了MIMO系统的三 大关键核心技术:MIMO无线信道建模、多天线空时编码和接收机设计;分析了MIMO技术的四大优点:阵列 增益、空间分集、空间复用和干扰减少。未来的第二代无线局域网和第四代移动通信系统等采用MIMO技术 将是大势所趋。     

射频接收机非线性对分集与复用影响分析

分别从分单输入单输出系统(single-input single-output, SISO)与多输入多输出系统(multiple-input multiple-output, MIMO)研究了多天线系统中射频接收机非线性对通信系统性能的影响规律,发现原有对非线性分集与复用折中的定义不再适用于考虑射频接收机非线性情况,并给出了适用于考虑射频接收机非线性情况的新定义. 通过复合信道建模推导了非理想情况下分集增益的定义和中断概率表达式,仿真了考虑射频接收机非线性时多天线系统分集增益与复用增益关系曲线,得出了考虑分集与复用折中时目标速率的增长规律. 理论和仿真表明,传统的分集增益和复用增益的定义并不适用于考虑接收机非线性的实际情况,SISO系统中射频接收机非线性对分集与复用的折中影响与理想情况一样,MIMO系统中需要对原有的分集增益和复用增益进行修正才能得到分集与复用的最优折中.     

基于MIMO的无线认知传感器网络研究

作为现代无线通信的核心技术,MIMO(多输入多输出)利用发射端和接收端的多副天线,来改善无线通信性能,而无需额外的无线带宽。MIMO中的空间分集、空间复用、波束形成、智能天线等可以帮助WCSN(无线认知传感器网络)接入有价值的频谱,提高链路质量和频谱效率。文章分析MIMO在阵列增益、分集增益和复用增益等方面的优势,介绍空时分组编码、空时网格编码和分层空时编码的工作原理,给出MIMO无线认知传感器网络的基本中继策略。     

MIMO系统中简单的扩展空时块编码分集技术研究

本文提出一种多输入多输出（MIMO）天线系统中简单的扩展空时块编码（SSTBC）分集技术，采用沃尔什码来区分各天线发送数据子流。采用这种方法，在系统带宽一定时，不降低发送信息速率，同时接收机简单。不同天线的发送信息经过了所有收一发天线对之间的空间子信道，获得了所有路径的部分空间分集增益，仿真结果表明，这种增益的获得不受限于接收分集阶数，并且随发射天线的增加以一定的线性关系增加。     

TD-SCDMA HSPA+中的单双流MIMO技术的研究

多输入多输出(MIMO)技术是近年来移动通信的热门研究领域,它的特征在于无线发射机和接收机都引入了多根天线.MIMO技术除了通过空间分集方式获得容量的提升外,还可以通过空间复用方式,利用不同天线信道的独立性建立多个空间子信道来提高容量.但是,无论是基于空间分集的单流模式还是基于空间复用的双流模式,单独在TD-SCDMA...     

一种基于分布式空时码的协作MIMO分集复用折衷新方案

协作MIMO通过多个单天线节点的相互协作构造多发射天线,以此形成一种虚拟MIMO多天线阵列获得空间分集增益。考虑到协作MIMO特点,天线间采用分布式空时编码进行编码协作。文章研究了协作MIMO中基于分布式空时码(DSTC)的分集复用折衷(DMT)新方案,该方案通过推导两种DSTC的中断概率与分集增益表达式,结合两类DSTC的DMT策略,根据改变复用增益阈值自适应获得最佳DMT与中断性能。数值仿真表明,所提的DMT策略可以逼近协作MIMO的DMT上限,协作节点采用该策略的中断性能仅次于上限的中断性能。在多节点构成协作MIMO网络分布式空时编码协作中,提出的DMT新方案可使系统高效地获得协作分集增益与中断性能。     

自适应STBC-VBLAST系统的QRD-M检测

综合考虑多输入多输出(MIMO)系统的分集和复用增益,将STBC和VBLAST2种编码方案结合起来组成STBC-VBLAST混合系统,实现了数据传输速率和可靠性之间的折衷?根据无线信道的时变特性,自适应地调整发射天线,提高了系统的灵活性,并在接收端引入新的QRD-M译码算法?仿真结果表明,该算法进一步降低了系统误码率,提高了系统性能?     

MIMO-OFDM广义空间信道频率响应间的相关性分析

多输入多输出-正交频分复用(MIMO-OFDM)技术被普遍认为是宽带无线通信的一种最具前景的技术。以往的研究重点放在如何利用收发天线间的多路空间信道,该文首次提出混合天线信道与波束信道的广义空间信道这一新概念。在不增加天线数目的前提下,广义空间信道能够增加空间信道的数量。当独立多径数远大于阵元数时,广义空间信道频率响应间的相关性较小,因此能够使空频码(SFC)的分集、编码及复用增益得到提高,从而提高MIMO-OFDM系统的性能。     

一种空间相关MIMO信道下的空时预编码方案

在实际的多输入多输出（MIMO：Muhiple Input Multiple Output）移动通信系统中，信道的空间相关性通常会使得现有的空时编码方案难以获得最佳的误码性能。为了解决该问题，本文提出了一种适用于MIMO空间相关信道的空时预编码方案。该方案在完成对发射信号的空时编码后，针对发射天线的空间相关矩阵设计了合理的预编码矩阵，进而能够在保证分集增益的前提下克服相关信道的不利影响。仿真结果证实，该方案能够在一定程度上有效提高整个系统的误码性能。     

基于复杂系统自组织MIMO无线传输分集和编码技术研究现状及其技术路线

空间分集与编码调制技术相结合的空时编码技术,可以获得分集和编码增益,具有优异的抗衰落性能。传统空时编码和多输入多输出(MIMO)技术是通过多天线来实现空间分集的,但是由于移动台的尺寸和载频的限制,使多天线技术很难实现。基于复杂系统自组织MIMO无线传输分集和编码技术成为解决这一问题的可选方案,并且无需通过信道反馈信息,动态分配资源,提高了端到端的通信服务质量(QoS)和信道容量。     

On the Diversity Order of Spatial Multiplexing Systems With Transmit Antenna Selection: A Geometrical Approach

In recent years, the remarkable ability of multiple-input-multiple-output (MIMO) wireless communication systems to provide spatial diversity or multiplexing gains has been clearly demonstrated. For MIMO diversity schemes, it is well known that antenna selection methods that optimize the postprocessing signal-to-noise ratio (SNR) can preserve the diversity order of the original full-size MIMO system. On the other hand, the diversity order achieved by antenna selection in spatial multiplexing systems, especially those exploiting practical coding and decoding schemes, has not thus far been rigorously analyzed. In this paper, a geometrical framework is proposed to theoretically analyze the diversity order achieved by transmit antenna selection for separately encoded spatial multiplexing systems with linear and decision-feedback receivers. When two antennas are selected from the transmitter, the exact achievable diversity order is rigorously derived, which previously only appears as conjectures based on numerical results in the literature. If more than two antennas are selected, we give lower and upper bounds on the achievable diversity order. Furthermore, the same geometrical approach is used to evaluate the diversity-multiplexing tradeoff in spatial multiplexing systems with transmit antenna selection     

MIMO无线传输技术综述

MIMO无线传输技术是通信领域的一项重要技术突破,它能在不增加带宽与功率的情况下成倍地提高无线通信系统的容量和频谱效率,堪称新一代无线通信系统中的关键技术之一,近年来引起了人们的广泛关注与研究兴趣。回顾无线移动通信的发展历程,概述天线分集技术与智能天线技术,剖析MIMO无线传输技术的原理与国内外研究现状:传统单天线系统向多天线系统演进、智能天线向多天线系统演进、MIMO无线传输技术的原理、MIMO系统中的分集与复用、MIMO无线信道建模、MIMO系统中的多天线设计等,为深入认识与进一步研究MIMO无线传输技术奠定基础。     

Multiple-antenna techniques for wireless communications - a comprehensive literature survey

The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. With an enormous amount of yearly publications, the field of multiple-antenna systems, often called multiple-input multiple-output (MIMO) systems, has evolved rapidly. To date, there are numerous papers on the performance limits of MIMO systems, and an abundance of transmitter and receiver concepts has been proposed. The objective of this literature survey is to provide non-specialists working in the general area of digital communications with a comprehensive overview of this exciting research field. To this end, the last ten years of research efforts are recapitulated, with focus on spatial multiplexing and spatial diversity techniques. In particular, topics such as transmitter and receiver structures, channel coding, MIMO techniques for frequency-selective fading channels, diversity reception and space-time coding techniques, differential and non-coherent schemes, beamforming techniques and closedloop MIMO techniques, cooperative diversity schemes, as well as practical aspects influencing the performance of multiple-antenna systems are addressed. Although the list of references is certainly not intended to be exhaustive, the publications cited will serve as a good starting point for further reading.     

Joint pre-processing co-channel interference cancellation for single user MIMO

In general, multiplexing and diversity gains of single user MIMO systems are restricted by min(M,N) where M, N denote the number of antenna elements at a transmitter and receiver, respectively. In order to increase the multiplexing/diversity gains and improve the performance of single user MIMO systems, a joint pre-processing co-channel interference cancellation (JPCIC) method is proposed. The JPCIC is analyzed in both the perfect and the imperfect channel state information. The dependence of channel capacity on the number of antenna elements in every subset, the number of subsets, transmit powers and channel estimation errors is discussed. As theoretical calculation result, the channel capacity increases when the multiplexing/diversity gains and/or the transmit power increase in a certain channel model whether the channel estimation error is absent or present. Compared to the conventional zero-forcing method, the channel capacity of JPCIC is considerably higher because of higher multiplexing/diversity gains, however, it is less robust and decreased more rapidly due to incomplete cancellation of interference terms when the channel estimation error increases. There is a trade-off between the channel capacity and the complexity of system, however, according to quick development in circuit techniques and miniaturization of devices, the JPCIC is expected to be an attractive technology for MIMO system.     

Compact polarisation and spatial multiplexing antenna for MIMO applications

A compact size, polarisation and spatial multiplexing slot antenna utilising the Spatial Multiplexing of Local Elements (SMILE) technique, is proposed. The antenna is used to explore diversity gain with a single RF channel in the applications of a multiple-input multiple-output (MIMO) wireless communication system.     

MIMO systems with full and reduced hardware complexity

MIMO (multiple-input-multiple-output) systems propose enormous gains in the capacity of wireless systems without requiring more spectral resources. This paper first gives an overview of the use of MIMO for diversity and spatial multiplexing, and the use of channel state information in MIMO systems. It then explores the use of antenna selection as a means for the reduction of the hardware complexity. It is shown that the performance in a spatial-multiplexing application is almost as good as that of full-complexity systems as long as the number of RF chains is at least as large as the number of data streams.     

An efficient resource-allocation scheme for spatial multiuser access in MIMO/OFDM systems

Fast adaptive transmission has been recently identified as a key technology for exploiting potential system diversity and improving power-spectral efficiency in wireless communication systems. An adaptive resource-allocation approach, which jointly adapts subcarrier allocation, power distribution, and bit distribution according to instantaneous channel conditions, is proposed for multiuser multiple-input multiple-output (MIMO)/orthogonal frequency-division multiplexing systems. The resultant scheme is able to: 1) optimize the power efficiency; 2) guarantee each user's quality of service requirements, including bit-error rate and data rate; 3) ensure fairness to all the active users; and 4) be applied to systems with various types of multiuser-detection schemes at the receiver. For practical implementation, a reduced-complexity allocation algorithm is developed. This algorithm decouples the complex multiuser joint resource-allocation problem into simple single-user optimization problems by controlling the subcarrier sharing according to the users' spatial separability. Numerical results show that significant power and diversity gains are achievable, compared with nonadaptive systems. It is also demonstrated that the MIMO system is able to multiplex several users without sacrificing antenna diversity by using the proposed algorithm.     

相关瑞利信道下的分集与复用折衷

多天线可以用来增加通信系统的分集增益或者复用增益，二者之间存在着基本的折衷关系。相关瑞利信道的折衷性能差于i．i．d瑞利衰落信道，并且相关矩阵降秩时，折衷性能进一步下降。本文给出了相关瑞利信道下分集增益和复用增益的最优折衷关系。     

分布式多天线技术研究

在基于多输入多输出-正交频分复用(MIMO-OFDM)技术的下一代宽频无线通信系统中,为了提高频谱利用率,一般采用同频组网,这就在小区边缘引入了同频干扰,影响了系统覆盖范围、容量以及边缘用户的切换体验。分布式多天线系统可以有效地解决上述问题,它通过拉远天线的距离,充分利用多输入多输出(MIMO)技术的空间分集和宏分集优势,通过集中式的预编码、用户调度、功率控制等策略较好地控制基站内不同小区间的干扰,尤其适合于增强数据热点地区的覆盖,减少用户的切换次数,提升小区边缘用户的服务质量。     

Performance of multiantenna signaling techniques in the presence of polarization diversity

Multiple-input multiple-output (MIMO) antenna systems employ spatial multiplexing to increase spectral efficiency or transmit diversity to improve link reliability. The performance of these signaling strategies is highly dependent on MIMO channel characteristics, which, in turn, depend on antenna height and spacing and richness of scattering. In practice, large antenna spacings are often required to achieve significant multiplexing or diversity gain. The use of dual-polarized antennas (polarization diversity) is a promising cost- and space-effective alternative, where two spatially separated uni-polarized antennas are replaced by a single antenna structure employing orthogonal polarizations. This paper investigates the performance of spatial multiplexing and transmit diversity (Alamouti (see IEEE J. Select. Areas Commun., vol.16, p.1451-58, Oct. 1998) scheme) in MIMO wireless systems employing dual-polarized antennas. In particular, we derive estimates for the uncoded average symbol error rate of spatial multiplexing and transmit diversity and identify channel conditions where the use of polarization diversity yields performance improvements. We show that while improvements in terms of symbol error rate of up to an order of magnitude are possible in the case of spatial multiplexing, the presence of polarization diversity generally incurs a performance loss for transmit diversity techniques. Finally, we provide simulation results to demonstrate that our estimates closely match the actual symbol error rates.