分布式天线系统MIMO信道容量分析

结合了分布式天线系统和MIMO信道特点的分布式MIMO系统可以改善覆盖特性,提高系统容量。提出了包含路径损耗、快衰落和阴影衰落的两层分集分布式MIMO系统。对MIMO信道容量的分析表明,分布式MIMO系统具有良好的信道容量均匀覆盖特性。与传统集中式天线系统相比,分布式MIMO系统可以获得更好的小区平均信道容量。对下行信道容量的数值分析表明,由于“充水”方式功率分配可以充分利用MIMO信道信息,此时的分布式MIMO系统可以比等功率分配条件下的分布式天线系统多获得0.25bit/(s·Hz)每发送天线的信道容量增量。     

室内MIMO无线信道:模型和性能预测

提出了一种包含小尺度衰落、相对路径衰落和阴影衰落的室内MIMO信道模型,考虑到室内人员的流动性,并对模型的性能进行了预测,拓展了室内MIMO无线衰落信道模型的研究.实验结果验证了提出模型的性能.得到有用的结论:在低秩的信道,信道容量减少,能合理解释针孔信道容量,在高秩的信道,不考虑相对的路径衰落和阴影衰落的情况下,信道的容量随天线的数目增加和信号相关性的减少而增大.考虑相对的路径衰落和阴影衰落,在LOS传播环境中,若存在丰富的散射传播,信道容量要高得多.     

基于分布式MIMO矿井无线通信系统的研究

针对矿井巷道的特殊环境以及无线通信问题,通过MIMO系统和分布式天线系统,建立了井下分布式MIMO信道模型。仿真结果表明,分布式MIMO系统具有更高的信道容量。基于分布式天线的灵活设置,分布式MIMO系统既提高了频谱利用率又减少了信号盲区,最终扩大了井下信号覆盖范围,提高了整个系统的信道容量。     

基于分布式MIMO矿井无线通信系统的研究

针对矿井巷道的特殊环境以及无线通信问题,通过MIMO系统和分布式天线系统,建立了井下分布式MIMO信道模型。仿真结果表明,分布式MIMO系统具有更高的信道容量。基于分布式天线的灵活设置,分布式MIMO系统既提高了频谱利用率又减少了信号盲区,最终扩大了井下信号覆盖范围,提高了整个系统的信道容量。     

相关Rician衰落信道下紧凑MIMO系统的容量分析

研究了Rician衰落信道下采用紧凑型双偶极子阵列的MIMO系统容量,建立了相关Rician衰落信道下紧凑MIMO系统的模型,深入分析了天线互耦、空间相关性、功率分配方案以及信道衰落环境对信道容量的影响。数值结果表明天线间距较小时,互耦和相关性会导致信道容量的损失,而在某些情况下互耦和相关性的影响会使信道容量有所增加。     

多输入多输出系统信道容量研究

该文研究接收端采用均圆阵天线阵放置空间有限的条件下,存在相关衰落时MIMO系统的信道容量。建立了衰落相关模型,分析了散射角大小及天线数对信道容量的影响,采用随机理论推导了MN的MIMO系统信道容量的闭式解。分析结果表明,MIMO系统信道容量主要由衰落相关矩阵的特征值决定。仿真结果表明,在接收端空间有限的情况下,天线数增大到一定程度时,信道容量达到饱和,再增加天线数,对信道容量的影响很小。     

MIMO—OFDM加性信道容量仿真实现

OFDM技术能将频率选择性信道转变为平坦衰落信道,而MIMO技术在平坦衰落信道上可显著提高信道容量,从而大幅度提高频谱效率。本文分析了MIMO—OFDM系统中加性高斯自噪声（AWGN）信道的信道容量。     

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。     

复合衰落信道下分布式MIMO系统下行中断概率分析

针对复合衰落信道模型下分布式MIMO系统下行中断概率问题,首先建立了一个综合考虑Nakagami-m衰落、路径损耗和阴影衰落的复合衰落信道模型;然后针对存在中心基站的分布式MIMO系统,提出了一种更符合实际应用环境的准均匀小区移动台分布模型;接着利用矩生成函数、Gauss-Hermite积分公式和Simpson积分公式等数学手段推导了任意移动台分布下、单小区内系统平均下行中断概率闭合表达式;最后将准均匀移动台分布模型应用到该中断概率闭合表达式,并通过MATLAB仿真证明了所推导得到的闭合表达式及小区分布模型的合理性。     

空时相关复合衰落多输入多输出信道模型研究

针对多输入多输出(Multiple-Input Multiple-Output,MIMO)无线传播环境,综合考虑路径损耗、阴影衰落和多径衰落影响,提出一种基于Nakagami-Lognormal分布的相关复合衰落MIMO信道模型,推导并获得各信道自相关和互相关系数的理论表达式;提出一种基于谐波叠加思想的复合衰落MIMO信道仿真方法,并分析了该方法输出信道衰落的空时相关特性.数值仿真结果表明:仿真模型输出统计特性均与理论模型吻合;各子信道之间存在互相关性且随阴影衰落方差减小而下降,而自相关性则呈现快速起伏并缓慢下降的特性.     

Characteristic‐Function‐Based Analysis of MIMO Systems Applying Macroscopic Selection Diversity in Mobile Communications

Multiple‐input multiple‐output (MIMO) systems can provide significant increments in capacity; however, the capacity of MIMO systems degrades severely when spatial correlation among multipath channels is present. This paper demonstrates that the influence of shadowing on the channel capacity is more substantial than that of multipath fading; therefore, the shadowing effect is actually the dominant impairment. To overcome the composite fading effects, we propose combining macroscopic selection diversity (MSD) schemes with MIMO technology. To analyze the system performance, the capacity outage expression of MIMO‐based MSD (MSD‐MIMO) systems using a characteristic function is applied. The analytic results show that there are significant improvements when MSD schemes are applied, even for the two‐base‐station diversity case. It is also observed that the effect of spatial correlation due to multipath fading is almost negligible when multiple base stations cooperatively participate in the mobile communication topology.     

3×3多天线系统衰落相关与信道容量研究

为分析天线间距和散射角等信道物理参数对多输入多输出系统信道容量的影响,提出了一种相关衰落环境中信道容量的分析方法。该方法基于接收均匀圆阵构建了蕴含信道物理参数的衰落相关矩阵。并由此详细推导了3×3多天线系统信道容量的闭式表达。结果表明,相关矩阵特征值的个数和大小决定了系统信道容量的大小。该方法回避了已有算法需求取相关衰落信道特征值概率密度函数的问题,降低了运算量,可以被推广到任意收发天线数的多输入多输出和多输入多输出-频分复用系统。仿真结果表明,天线间距增大,信道容量随之增大。但是当天线间距增大到衰落相关的第一个过零点时,信道容量达到最大值,再增大天线间距对信道容量影响很小。散射角越大,信道容量收敛到最大值速率越快。     

分布式MIMO系统小区平均遍历容量分析

针对分布式MIMO系统的圆形小区平均遍历容量展开研究.文章首先建立了包含快衰落、阴影衰落和路径损耗的复合衰落信道模型;然后,对分布式天线采用覆盖式（BT）传输策略,并在高信噪比条件下,导出给定移动台位置时,区上、下行点对点链路遍历容量表达式.最后,考虑移动台在小区内任意分布特点,进一步推导出小区平均遍历容量闭合近似表达式.仿真结果表明,所推导的近似表达式可很好的反应系统的实际性能.导的近似表达式可很好的反应系统的实际性能.     

On the capacity of OFDM-based spatial multiplexing systems

This paper deals with the capacity behavior of wireless orthogonal frequency-division multiplexing (OFDM)-based spatial multiplexing systems in broad-band fading environments for the case where the channel is unknown at the transmitter and perfectly known at the receiver. Introducing a physically motivated multiple-input multiple-output (MIMO) broad-band fading channel model, we study the influence of physical parameters such as the amount of delay spread, cluster angle spread, and total angle spread, and system parameters such as the number of antennas and antenna spacing on ergodic capacity and outage capacity. We find that, in the MIMO case, unlike the single-input single-output (SISO) case, delay spread channels may provide advantages over flat fading channels not only in terms of outage capacity but also in terms of ergodic capacity. Therefore, MIMO delay spread channels will in general provide both higher diversity gain and higher multiplexing gain than MIMO flat fading channels     

Performance analysis of multi‐input multi‐output systems with maximum likelihood detection over shadowed fading channels

Multiple‐input multiple‐output (MIMO) transmission techniques constitute an important technology in modern wireless communication. Hence, performance analysis methods for such systems are of considerable interest. This paper considers first the average pairwise error probability for uncoded MIMO systems employing maximum likelihood detection over a composite Rayleigh‐Lognormal fading channel with spatial correlation. It provides general results, applicable also to a wider class of shadowing models, concerning asymptotical diversity gains and shows that they are not changed by such shadowing. Then, analytical evaluation techniques for bit‐error‐rate (BER) over composite Rayleigh‐Lognormal fading channels, based on the truncated union bound and the transfer function, are considered. Furthermore, these techniques are modified for applications over spatially correlated channels. This paper shows that such performance evaluation techniques provide good approximations to BER of spatially uncorrelated MIMO systems and also in the presence of moderate spatial correlation, over Rayleigh‐Lognormal fading channels. Copyright © 2013 John Wiley & Sons, Ltd.     

Capacity of MIMO Rician channels

This paper presents exact results on the capacity of multiple-input-multiple-output (MIMO) Rician channels when perfect channel state information (CSI) is assumed at the receiver but the transmitter has neither instantaneous nor statistical CSI. It first derives the exact expression for the average mutual information (MI) rate of MIMO Rician fading channels when the fading coefficients are independent but not necessarily identically distributed. The results for the independent and identically distributed (i.i.d.) MIMO Rician and Rayleigh fading channels are also obtained as special cases. These results are derived using a different approach than the one used by Telatar for the i.i.d. Rayleigh case. The complementary cumulative distribution function (CCDF) of the MI is also obtained using a Gaussian approximation. The CDF of MI can serve as an upper bound to the outage probability of nonergodic MIMO Rician channels. Numerical results confirm that for a fixed channel gain, a strong tine-of-sight component decreases the channel capacity due to the lack of scattering.     

Outdoor MIMO wireless channels: models and performance prediction

We present a new model for multiple-input-multiple-output (MIMO) outdoor wireless fading channels and their capacity performance. The proposed model is more general and realistic than the usual independent and identically distributed (i.i.d.) model, and allows us to investigate the behavior of channel capacity as a function of the scattering radii at transmitter and receiver, distance between the transmit and receive arrays, and antenna beamwidths and spacing. We show how the MIMO capacity is governed by spatial fading correlation and the condition number of the channel matrix through specific sets of propagation parameters. The proposed model explains the existence of "pinhole" channels which exhibit low spatial fading correlation at both ends of the link but still have poor rank properties, and hence, low ergodic capacity. In fact, the model suggests the existence of a more general family of channels spanning continuously from full rank i.i.d. to low-rank pinhole cases. We suggest guidelines for predicting high rank (and hence, high ergodic capacity) in MIMO channels, and show that even at long ranges, high channel rank can easily be sustained under mild scattering conditions. Finally, we validate our results by simulations using ray tracing techniques. Connections with basic antenna theory are made.     

The Capacity Performance of ASTC-MIMO-OFDM System in a Correlated Rayleigh Frequency-Selective Channel

Algebraic Space-Time Codes (ASTC) for Multiple Input Multiple Output (MIMO) systems are based on quaternion algebras. Thanks to their algebraic construction, the ASTC codes are full-rank, full-rate and have the non-vanishing determinant property. These codes have been proposed for MIMO flat fading channels in order to increase the spectral efficiency and to maximize the coding gain. The purpose of this work is to analyze the performance of the ASTC in a frequency selective Rayleigh channel. To deal with the frequency selectivity, we use the OFDM modulation. The capacity performances of an ASTC-MIMO-OFDM system, under correlated Rayleigh frequency-selective channel, have been evaluated.     

A space-time correlation model for multielement antenna systems inmobile fading channels

Analysis and design of multielement antenna systems in mobile fading channels require a model for the space-time cross correlation among the links of the underlying multiple-input multiple-output (MIMO) channel. In this paper, we propose a general space-time cross-correlation function for mobile frequency nonselective Rice fading MIMO channels, in which various parameters of interest such as the angle spreads at the base station and the user, the distance between the base station and the user, mean directions of the signal arrivals, array configurations, and Doppler spread are all taken into account. The new space-time cross-correlation function includes all the relevant parameters of the MIMO fading channel in a clean compact form, suitable for both mathematical analysis and numerical calculations/simulations. It also covers many known correlation models as special cases. We demonstrate the utility of the new space-time correlation model by clarifying the limitations of a widely accepted correlation model for MIMO fading channels. As another application, we quantify the impact of nonisotropic scattering around the user, on the capacity of a MIMO fading channel