多输入多输出系统中的预编码技术研究

MIMO系统中的预编码技术,利用信道信息,使发射信号和空间信道相匹配,有效的对抗信道衰落,提高系统误码率和频谱利用效率,已成为无线通信技术的研究热点。本文首先对MIMO系统模型和容量进行了简单的介绍,然后分析了基于不同角度的预编码技术,其中主要针对基于信道预测的预编码技术的预测算法进行了研究。     

无线通信系统中的闭环MIMO技术

多入多出（MIMO）技术被认为是下一代无线通信的关键技术之一,本文主要讨论能够进一步提升多天线系统容量的闭环MIMO技术,即带有反馈的MIMO系统。反馈的信道信息既可以提高单链路的传输性能,也可以优化多用户之间的调度问题。本文给出了几种在未来无线通信系统中可能采用的闭环MIMO方案,包括基于SVD分解和基于码本的预编码技术,分析并比较了它们的性能。仿真结果表明,闭环MIMO技术将有效地提高通信系统的性能。     

LTE-A下行单用户MIMO增强技术研究

无线通信系统中,基站可以针对信道空间特性采用不同的下行传输模式获得空间复用增益和波束成形增益以提升系统性能。LTE-A中的下行单用户MIMO增强技术,采用了基于码本以及非码本的预编码技术优化性能,有必要分析其技术特点和增益来源以指导产品设计。分析了LTE-A中单用户MIMO技术演进的新特点,着重研究了新的双码本结构,在对信道属性匹配、码本搜索运算复杂度和UE上报载荷方面的改进。针对LTE-A预编码技术性能问题,通过计算机链路级仿真比较了LTE—A中基于码本以及非码本预编码技术的吞吐量性能,仿真结果表明码本技术较非码本技术具有一定优势。     

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。     

存在反馈延迟的短波MIMO预编码系统设计

利用基于码本的预编码MIMO技术去提升短波通信的空间分集增益,短波天波信道利用电离层的一次或多次反射进行远距离通信,信号传播延时较大,为了消除反馈延时对预编码MIMO系统性能的影响,文中基于Kalman滤波器提出一种信道估计与预测模型,自适应地跟踪短波时变信道,接着根据ITS短波时变信道模型提取信道时域特征,估计出预测模型参数,通过与传统无信道预测的预编码方案进行对比,方案能够有效降低反馈延迟对短波MIMO预编码系统性能的影响。     

MIMO通信系统中的信号检测技术

多输入多输出(MIMO)技术是近些年来通信系统领域中的重要突破,可极大的提升无线通信的传输可靠性与信道容量,是推动无线通信系统进步的关键技术,对其信号的检测是MIMO技术中需深入研究的而重要课题。本文从MIMO技术的概述出发,分析MIMO通信系统中的信号检测技术。     

人工噪声辅助MIMO系统下数据信号功率占比的误码率研究

针对多输入多输出（Multiple-Input Multiple-Output,MIMO）无线通信系统传输过程中的安全问题,提出了一种基于人工噪声辅助的安全传输方法。首先,建立人工噪声辅助MIMO系统的信道状态矩阵;其次,将信道状态矩阵进行奇异值分解,设计合理的预编码和人工噪声矩阵,从而显著提升MIMO系统的安全性。对于窃听节点的译码采用最大似然检测译码。仿真结果表明,利用MIMO系统信道信息的零空间矩阵,采用人工噪声进行信号加密,有效提高了潜在窃听节点的误码率,当合法信道质量降低时,通过降低分配数据信号功率系数来提高MIMO无线系统的窃听误码率。     

分层异构无线网络中基于预编码的干扰抑制技术

传统宏蜂窝(macro cell)与低功率小蜂窝(small cell)共存的分层异构组网方案能有效地提高无线通信系统的容量.但宏蜂窝与小蜂窝间的同频干扰严重影响了通信质量,并阻碍了系统容量的进一步提升.近年来,利用MIMO预编码及空域衰落特性进行干扰抑制的相关技术成为新的研究热点.本文着重介绍分层异构无线网络中基于MIMO预编码的干扰抑制技术的研究进展.以典型的双层异构下行网络为例,分析了利用多天线预编码进行干扰抑制的基本方法,并在此基础上介绍了多种基于MIMO预编码的新型干扰抑制方案,最后讨论了分层异构网络中干扰抑制技术的未来研究方向.     

大规模MIMO无线通信关键技术

MIMO（多输入多输出）无线通信系统是通信领域中一项重要的技术突破,MIMO在不增加功率与带宽的情况下能够在很大程度上提高无线通信系统的频谱效率,因此MIMO迅速成为了无线通信系统中的一项关键技术,也是近年来无线通信系统工作者的研究热点之一。笔者将根据相关工作经验,综合分析MIMO系统的基本工作原理,分析MIMO系统的关键技术：①接收机设计;②MIMO无线信道建模;③多天线空时编码。简而言之,大规模地利用MIMO技术传输能够显著提高无线通信系统的功率与效率。     

大规模MIMO无线通信关键技术

基于大规模MIMO基本架构,探讨了信道建模和系统性能分析、信道状态信息获取技术、多用户上下行无线传输技术等大规模MIMO传输关键技术;认为利用大规模阵列天线的多用户多输入多输出(MIMO)传输,将显著提升无线通信系统的频谱效率及功率效率。     

Optimization of the spectral efficiency in MIMO cellular wireless communications

Expressions are derived that make it possible to calculate and optimize the spectral efficiency (SE) of multiple-input-multiple-output (MIMO) cellular wireless communication systems (WCSs) with allowance for the interaction of radiators in the receiving and transmitting antennas of the MIMO systems, the properties of the deterministic radio channel, and the presence of directionally concentrated interference. The effect of the interaction of radiators on the SE of the MIMO systems is studied, and the efficiency of the MIMO technology is analyzed on the basis of the model example of two receiving and two transmitting antennas with a conducting screen placed in between them. It is demonstrated that, in comparison to single-channel-transmission technology, MIMO technology allows an increase the WCS SE only at relatively high values of the signal-to-interference-plus-noise ratio at the receiver input and in the case of nearly equal channel gains. It is shown that the relative positions of the transmitter and receiver at which the MIMO-WCS SE can be significantly increased are dependent on the channel energy and are substantially limited at real powers transmitted under urban conditions.     

4×6 MIMO信道解码器的FPGA设计与实现

多输入多输出(MIMO)技术在现代无线移动通信系统中应用广泛,FPGA实现MIMO信道估计和解码是其实用化的关键。为保证系统性能,设计了一种OFDM-MIMO系统的并行流水浮点4×6 MIMO信道解码器,并在单片Xilinx Vertix6 FPGA芯片上进行了实现。实验结果表明,系统处理速率可以达到120 MHz,可以用于速率为1.485 Gbit/s的HDI高清视频的实时传输。     

Silicon complexity for maximum likelihood MIMO detection using spherical decoding

Multiple-input multiple-output (MIMO) wireless systems increase spectral efficiency by transmitting independent signals on multiple transmit antennas in the same channel bandwidth. The key to using MIMO is in building a receiver that can decorrelate the spatial signatures on the receiver antenna array. Original MIMO detection schemes such as the vertical Bell Labs layered space-time (VBLAST) detector use a ing and cancellation process for detection that is sub-optimal as compared to constrained maximum likelihood (ML) techniques. This paper presents a silicon complexity analysis of ML search techniques for MIMO as applied to the HSDPA extension of UMTS. For MIMO constellations of 4/spl times/4 QPSK or lower, it is possible to perform an exhaustive ML search in today's silicon technologies. When the search complexity exceeds technology limits for high complexity MIMO constellations, it is possible to apply spherical decoding techniques to achieve near-ML performance. The paper presents an architecture for a 4/spl times/4 16QAM MIMO spherical decoder with soft outputs that achieves 38.8 Mb/s over a 5-MHz channel using only approximately 10 mm/sup 2/ in a 0.18-/spl mu/m CMOS process.     

Cooperative MIMO channel models: A survey

Cooperative multiple-input multiple-output technology allows a wireless network to coordinate among distributed antennas and achieve considerable performance gains similar to those provided by conventional MIMO systems. It promises significant improvements in spectral efficiency and network coverage and is a major candidate technology in various standard proposals for the fourth-generation wireless communication systems. For the design and accurate performance assessment of cooperative MIMO systems, realistic cooperative MIMO channel models are indispensable. This article provides an overview of the state of the art in cooperative MIMO channel modeling. We show that although the existing standardized point-to-point MIMO channel models can be applied to a certain extent to model cooperative MIMO channels, many new challenges remain in cooperative MIMO channel modeling, such as how to model mobile-to-mobile channels, and how to characterize the heterogeneity and correlation of multiple links at the system level appropriately.     

Receiver Algorithms for Multi-stream Data Transmission in WLAN 802.11n Networks

Multiple Input Multiple Output (MIMO) systems employ multiple antennas to provide high spectral efficiency and wireless link reliability thanks to multipath diversity and space multiplexing. This technology is now being implemented into wireless standards such as 802.11n, as well as the 4th generation cellular networks. In this paper we present results of an extensive simulation research in which we compare three receiver models for MIMO WLAN 802.11n system. We investigate maximum-likelihood, zero-forcing and Vertical Bell Laboratories Layered Space Time receivers. Performance of these receivers for a range of 802.11n environments, i.e. for several channel models and different number of transmitter and receiver antennas is evaluated. The results of the comparison highlight the benefits of MIMO technology and show to what extent it is possible to improve the MIMO 802.11n system performance increasing the receiver complexity.     

应用软件无线电（SDR）实现MIMO通信实验研究

移动通信系统通过四代的发展变革,在5G的大规模商用下,多输入多输出(MIMO)技术凭借本身的特殊优点已经成为了5G的核心技术,MIMO具备着可在不用增加功耗的条件下提升无线系统性能的优点。它在应用多个天线时,传输的信号以信道分集的方式得到容量增益,凭借不同无线信道传输至接收天线。主要工作及创新点如下:(1)基于USRP平台设计了MIMO系统。(2)提出了解决设备相位同步的方案。     

On the MAC-BC duality of multiuser non-regenerative MIMO relay systems

Multiple input multiple output(MIMO) relaying techniques can greatly improve the spectral efficiency and extend network coverage for future wireless systems.This article investigates a multiuser MIMO relay channel,where a base station(BS) with multiple antennas communicates with multiple mobile stations(MS) via a relay station(RS) with multiple antennas.The RS applies linear processing to the received signal and then forwards the processed signal.The dual channel conditions between MIMO relay multiple access channel(MAC) and broadcast channel(BC) are first developed for single-relay scenario with white Gaussian noise.Then the MAC-BC duality for MIMO relay systems is established by proving that the capacity region of MIMO relay MAC is equal to that of dual MIMO relay BC under the same total network transmit power constraint.In addition,the duality is also extended to multi-relay scenario with arbitrary noise.Finally,several simple general numerical examples are provided to better illustrate the effectiveness of the MIMO relay MAC-BC duality.     

A performance bound for prediction of MIMO channels

Knowledge of future channel conditions can increase the performance of many types of wireless systems. This is especially true for radio channels with multiple transmit and receive antennas, i.e., multiple-input multiple-output (MIMO) systems. This paper derives a performance bound for MIMO channel prediction. It is assumed that prediction is based upon estimating a model for the channel and then extrapolating that model to predict future values of the channel. A vector formulation of the Crame/spl acute/r-Rao bound for functions of parameters is used to find a lower bound on the prediction error. Numerical evaluation of this bound shows that substantially longer prediction lengths are possible for MIMO channels than for single antenna channels. An intuitive interpretation of this result is that more of the channel structure is revealed when using multiple antennas at both ends. Finally, the longer prediction lengths for MIMO channels are confirmed by numerical results obtained by implementing a MIMO extension of a single-antenna prediction scheme.     

Energy efficiency of massive MIMO wireless communication systems with antenna selection

Massive multiple-input multiple-output (MIMO) requires a large number (tens or hundreds) of base station antennas serving for much smaller number of terminals, with large gains in energy efficiency and spectral efficiency compared with traditional MIMO technology. Large scale antennas mean large scale radio frequency (RF) chains. Considering the plenty of power consumption and high cost of RF chains, antenna selection is necessary for Massive MIMO wireless communication systems in both transmitting end and receiving end. An energy efficient antenna selection algorithm based on convex optimization was proposed for Massive MIMO wireless communication systems. On the condition that the channel capacity of the cell is larger than a certain threshold, the number of transmit antenna, the subset of transmit antenna and servable mobile terminals (MTs) were jointly optimized to maximize energy efficiency. The joint optimization problem was proved in detail. The proposed algorithm is verified by analysis and numerical simulations. Good performance gain of energy efficiency is obtained comparing with no antenna selection.     

基于MIMO系统的天线选择

多天线MIMO（Multiple Input Multiple Output）系统利用多个收、发天线有效地改善无线通信系统性能，提高系统容量，增强系统可靠性。然而，由于使用多天线同时收发，这要求发射机和接收机使用与天线一样多的射频链路，增加了系统成本和复杂度。使用天线选择技术可以降低系统成本和复杂度，同时保留MIMO系统的优越性能。文中首先介绍了MIMO系统的实现方式，然后讨论天线选择的方法及性能，最后提出天线选择技术还存在的问题，并得出相关的结论。