多天线系统中的天线选择技术

多天线系统可以改进无线通信的容量,提高可靠性。然而,使用多天线。就意味着多个射频链路会增加天线的体积、功率、硬件,从而增加成本。天线选择是一种低成本、低复杂度的有效方法。可以利用多天线系统的多数优点。通过对MIMO系统中的天线选择技术进行概述,指出了这个领域内的一些还未解决的问题。     

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。     

基于Kronecker法的MIMO信道模拟及硬件实现

针对多输入多输出（Multiple-Input Multiple-Output,MIMO）无线通信系统,在基于Kronecker 的MIMO信道模型中综合考虑了路径损耗、阴影衰落和多径衰落等因素,实现了基于现场可编程门阵列（Field Programmable Gate Array,FPGA）的MIMO信道模拟器,并分析了硬件设计方案以及MIMO信道模拟的实现方法。实测结果表明,设计的MIMO信道模拟器可以模拟瑞利衰落、莱斯衰落以及阴影衰落等常见的信道衰落类型,能够应用于3GPP、COST-207等标准信道模型的复现。该模拟器可作为无线通信系统研究的测试设备,辅助通信系统研究的算法验证、方案优化以及性能分析。     

嵌入式实时操作系统在MIMO无线通信中的应用

多输入多输出（Muhiple Input Muhiple Output，MIMO）无线传输技术可以在不增加带宽和天线发射功率的情况下，成倍地提高无线通信系统的信道容量。文中基于嵌入式实时操作系统，实现了MIMO传输系统中的协议处理、业务汇聚和高速数据传输。采用VxWorks操作系统为平台，以TCP／IP协议为基础，提出了实现MIMO系统中高层协议的总体方案。实验表明，采用的高层协议可以很好地支持话音、图像和数据传输，也可以为未来移动通信高速数据传输、无线资源管理、无线网络协议及规划提供良好的支持。     

MIMO OFDM短波无线通信的频率同步技术研究

多输入多输出(MIMO)技术是最近几年发展起来的无线通信技术。目前利用MIMO技术提高短波通信的传输速率和可靠性的研究已经开展。论文着重研究了MIMO OFDM短波无线通信的频率同步技术,利用频域正交的训练序列完成了系统各个发射/接收天线对之间频偏不同时的载波频偏估计。     

无线光通信中的空时编码研究进展(一)

MIMO技术在射频通信领域已被深入研究,使空间成为一种可以用于提高通信性能的资源。无线光通信与射频通信在调制/解调方法、信道特性诸方面有很大的差异。文中评述了国内外有关无线光MIMO技术的研究进展,对无线光MIMO的提出背景进行了详细分析,最后通过实验说明了MIMO对大气湍流的抑制效应。实验结果表明:无线光MIMO不但使空间成为一种资源,提高了无线光通信的信道容量,而且可以抑制大气湍流效应,扩大了无线光通信的应用场合。     

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。     

Optical wireless multiple-input multiple-output system based on avalanche photodiode receiver

With the rising demand for high data-transmission rates, optical wireless communication (OWC) is considered one of the particularly appropriate solutions. In this paper, an avalanche photodiode (APD)-based optical wireless configuration is used to approximate the receiver output. This paper also presents bit error rate (BER) evaluation statistics compared with the theoretical results for optical wireless multiple-input multiple-output (MIMO) communication systems. In particular, the simulated results show that the BER of a 4 × 4 MIMO system is significantly lower than that of other APD systems (over 10 times better when the mean energy is higher than − 165 dBJ). To summarize, the OWC-MIMO system shows enormous potential in the high-speed data-transmission field.     

Performance of Data-Rate Analysis of Massive MIMO System Using User Grouping

Wireless Personal Communications - The major challenges in massive MIMO networks are to increase the system throughput and capacity with low complexity and reliability of the wireless communication...     

Implementation of a MIMO OFDM-based wireless LAN system

The combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequency-selective fading environments. To realize this extension of OFDM with MIMO, a number of changes are required in the baseband signal processing. An overview is given of the necessary changes, including time and frequency synchronization, channel estimation, synchronization tracking, and MIMO detection. As a test case, the OFDM-based wireless local area network (WLAN) standard IEEE 802.11a is considered, but the results are applicable more generally. The complete MIMO OFDM processing is implemented in a system with three transmit and three receive antennas, and its performance is evaluated with both simulations and experimental test results. Results from measurements with this MIMO OFDM system in a typical office environment show, on average, a doubling of the system throughput, compared with a single antenna OFDM system. An average expected tripling of the throughput was most likely not achieved due to coupling between the transmitter and receiver branches.     

MIMO-OFDM系统功率分配研究

MIMO(多入多出系统)和OFDM(正交频分复用)技术是未来无线通信的关键技术.与单入单出系统相比,MIMO在不增加带宽的情况下增加了频谱的利用率,从而增大了无线通信系统的容量,改善了无线通信系统的性能.本文介绍了传统的自适应功率分配算法,提出了一种新的最大化SNR的调和平均值的MIMO-OFDM功率分配算法(HARM算法),仿真结果表明,该算法的性能比传统算法的性能有很大的改善.     

一种新的MIMO无线通信系统链路自适应算法

提出并分析了一种适用于MIMO系统的新的链路自适应算法。通过接收端估计信噪比,并利用各种编码调制方式的特性,该算法在接收端采用递归的方法确定了每一个发射端子信道所采用的编码调制方式,使反向链路仅传输少量的控制信息,实现了链路的自适应。仿真结果表明,文章所提出的算法大大提高了MIMO系统的吞吐量,且可靠性也显著增加。     

空时码性能分析

空时码（STC）技术是移动通信系统中提高频谱利用率的关键技术之一,是当前的研究热点。使用空时编码是达到或接近多输入多输出（MIMO）无线信道容量的一种可行、有效的方法。通过对空时编码MIMO-OFDM系统进行译码性能仿真,得出相关结论。     

Joint detection and combining schemes in MIMO-HARQ systems

This article mainly investigates the combining schemes for hybrid automatic retransmission request (HARQ) protocols in multiple-input multiple-output (MIMO) wireless communication systems. A novel scheme, which joins MIMO detection and HARQ combining, called mid-combining, is presented in this article. Based on the position of HARQ combining, we classify the HARQ combining schemes into three types, named pre-combining, mid-combining, and post-combining. The simulation results show that mid- combining can increase the system throughput for all SNRs.     

基于DMT/QAM和STBC的室内MIMO光无线通信

针对室内漫射光无线通信问题,提出一种采用离散多音/正交幅度调制和空时块编码的多输入多输出(MIMO)光无线通信技术.基于离散多音/正交幅度调制技术,并通过考虑室内全光无线信道的脉冲响应和其噪声特性,建立起室内红外光无线链路的信道模型;再采用空时块编码技术,提出一种实现室内漫射光无线通信的MIMO无线通信系统,并通过分析...     

Multiple antenna systems: their role and impact in future wireless access

Multiple antennas play an important role in improving radio communications. In view of this role, the area of multiple antenna communication systems is in the forefront of wireless research. This article reviews two key related aspects of multiple antenna communication systems: multiple access interference mitigation at the receiver via multi-user beamforming; and space-time modulation and coding for MIMO systems. It is shown that both multi-user and MIMO receivers share similar signal processing and complexity tradeoffs.. Following that, a general unified framework for assessing different types of space-time modulation for MIMO systems is introduced. These space-time modulation methods are then compared in terms of Shannon capacity over multipath channels. Key MIMO system performance and implementation issues are also highlighted.     

协作通信技术的研究进展

首先,介绍协作通信技术产生于MIMO技术在无线通信领域的运用。分析协作通信技术原理,概括出当前协作通信技术研究主要集中于信道容量、协作方式、协作中继可靠性以及协作功率等方面。其次,指出当前协作通信研究中存在中继节点带来干扰、安全保密性以及信道问题,重点分析协作通信中继节点及其带来的干扰。最后,提出协作通信技术研究中有待解决的问题,即如何减少干扰、优化功率分配、提高网络性能等。     

Field Measurements with a 5.25 GHz Broadband MIMO-OFDM Communication System

Theoretical capacity calculations and corresponding simulations show significant capacity/throughput gains from MIMO systems. Whether these gains are achievable in a real system, deployed in a practical environment, depends on a variety of factors, such as the choice of the communication algorithms, analog impairments and the "quality" of the wireless channel to sustain MEMO communications. In this paper, a 5.25 GHz broadband MIMO-OFDM testbed is described along with field measurements conducted with it. The MIMO-OFDM communication algorithms and also the impact of analog impairments on the performance of the system are described. Detailed system calibration results are described which serve as a baseline for results of field measurements. The results of wireless measurements are compared with the theoretical capacity, computed with the channel estimates obtained during the demodulation process. The average achievable capacity in the indoor wireless environment is shown to be 9.97 bps/Hz (bits per sec per Hz) while the capacity loss due to analog impairments and the choice of algorithms is about 2.33 bps/Hz. Also, field measurements conducted with the system in various environments are presented comparing the average throughput/capacity achieved in each of these environments.     

几种接收机在MIMO信道下的性能比较

多入多出（MIMO）无线信道具有空间复用增益和分集增益特性,因此MIMO系统和单入单出（SISO）无线系统相比能够获得更高的频谱效率。本文在不同天线组合下分析了几种MIMO空时信号处理算法的性能,仿真结果和理论分析表明：空间复用增益和分集增益不能同时获得最大,因此在设计MIMO通信系统时可根据实际情况选择天线数,即不仅考虑系统抵抗信道衰落的分集增益,还要考虑能够提供更高的数据传输速率,通过折衷考虑空间复杂增益和分集增益,从更全面的观点评估系统的性能。     

MIMO无线设备的空间辐射性能测试

随着人们对高速数据服务需求的日益增长,多入多出（MIMO）技术被认为是未来移动通信中的关键技术。相对传统单天线空间辐射性能测试而言,MIMO设备的空间辐射性能测试存在较大区别。空间多径衰落信道环境会直接影响MIMO的空间辐射性能,故研究空间信道模型是MIMO空间辐射性能测试的基础。目前MIMO空间辐射性能测试的方案还在探讨之中,但基本系统框架已经确立．