Space-Time Correlated Mobile-to-Mobile Channels: Modelling and Simulation

A single- and double-bounced two-ring parametric reference model is proposed for multiple-input multiple-output (MIMO) mobile-to-mobile (M-to-M) Ricean fading channels. From this model, a closed-form joint space-time correlation function and a space-Doppler power spectrum are derived for a two-dimensional (2D) non-isotropic scattering environment. Also, space-time correlation functions for the in-phase and quadrature components of the complex faded envelope are derived, assuming a 2D isotropic scattering environment. Finally, two new sum-of-sinusoids based simulation models for MIMO M-to-M Ricean fading channels are proposed. The statistics of the simulation models are verified by simulation. The results show that the simulation models are a good approximation of the reference model and that they outperform existing simulation models.     

Wideband HAP-MIMO Channels: A 3-D Modeling and Simulation Approach

High-altitude platforms (HAPs) are considered as an alternative technology to provide future generation broadband wireless communications services. This paper proposes a three-dimensional (3-D) geometry-based reference model for wideband HAP multiple-input–multiple-output (MIMO) channels. The statistical properties of the channel are analytically studied in terms of the elevation angle of the platform, the antenna arrays configuration, and the angular, the Doppler and the delay spread. Specifically, the space-time-frequency correlation function (STFCF), the space-Doppler power spectrum, and the power space-delay spectrum are derived for a 3-D non-isotropic scattering environment. Finally, a sum-of-sinusoids statistical simulation model for wideband HAP-MIMO channels is proposed. The results show that the simulation model accurately and efficiently reproduces the STFCF of the reference model. The proposed models provide a convenient framework for the characterization, analysis, test, and design of wideband HAP-MIMO communications systems with line-of-sight and non-line-of-sight links.     

MIMO信道的GBDB模型及其信道容量分析

针对非频率选择性Rice衰落MIMO移动信道，建立GBDB模型，并推导出新的MIMO系统的GBDB模型的空时联合相关函数。新的GBDB模型统一现有的多种MIMO信道模型，新的空时联合相关函数综合考虑了无线衰落信道收发两端的多普勒扩展、非均匀角度扩展以及平均发射与到达方向，综合考虑了收发端天线阵的配置。最后基于新的空时联合相关函数，分析了非均匀散射参数以及Rice分布参数变化对MIMO信道统计容量的影响。     

Wideband MIMO Mobile-to-Mobile Channels: Geometry-Based Statistical Modeling With Experimental Verification

A 3-D reference model for wideband multiple-inputmultiple-output (MIMO) mobile-to-mobile (M-to-M) channels is reviewed along with its corresponding first- and second-order channel statistics. To validate the reference model, an experimental MIMO M-to-M channel-sounding campaign was conducted for M-to-M vehicular communication with vehicles that travel along surface streets and expressways in a metropolitan area. To compare the first- and second-order channel statistics that were obtained from the reference model with those obtained from the empirical measurements, a new maximum-likelihood-based stochastic estimator is derived to extract the relevant model parameters from the measured data. The measured data is processed and compared with the analytical results. The close agreement between the analytically and empirically obtained channel statistics confirms the utility of the proposed reference model and the method for estimating the model parameters.      

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     

A performance comparison of the SCM and the Onering channel modeling method for MIMO‐OFDMA systems

This paper compares two types of channel modeling methods, which are the spatial channel modeling (SCM) and the Onering channel modeling method. These two well‐known channel models are proposed for 4G wideband mobile communication networks. To compare the performance of these channel modeling methods, we analyze the properties of the spatial, temporal, frequency correlation functions simulated by using these methods. The correlation functions of the two channel models are compared in the same conditions of antenna arrangements. The simulation and calculation results show that the correlation functions of Onering and SCM channel models are very close to each other if the BS and the MS antenna arrays are parallel and perpendicular to the broadside of MS‐BS. In other cases, the correlation functions of the two models are slightly different; however, their shapes are similar. These differences can be explained that the Onering model hardly fully describes all the characteristics of 4G channels as the performance SCM model does. The performance of these channel modeling methods is compared in system simulation level—MIMO‐OFDMA systems. The combination SFBC‐MMSE is used for spatial channel coding and the signal detection. The simulation results show that the system performance obtained by using these two channel models are comparable, given that the both modeled channels have same parameters and antenna directions. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling, analysis, and simulation of MIMO mobile-to-mobile fading channels

This paper' deals with the modeling, analysis, and simulation of multiple-input multiple-output (MIMO) narrowband fading channels for mobile-to-mobile communications. A stochastic MIMO mobile-to-mobile reference channel model is derived from the geometrical two-ring scattering model under the assumption that both the transmitter and the receiver are surrounded by an infinite number of local scatterers. Using a wave propagation model, the complex channel gains are derived and their statistical properties are studied. General analytical solutions are provided for the three-dimensional (3-D) space-time cross-correlation function (CCF). We show that this function can be expressed as the product of two 2D space-time cross-correlation function (CFs), called the transmit and receive CF. From the non-realizable reference model, a stochastic and a deterministic simulation model are derived using a double sum of complex exponential functions. It is shown how the parameters of the simulation model can be determined for any given distribution of the angle of departure (AOD) and angle of arrival (AOA). In case of isotropic scattering, we present a closed-form solution for the parameter computation problem and illustrate some numerical results concerning the transmit CF. The proposed procedure provides an important framework for designers of future mobile-to-mobile communication systems to verify new transmission concepts employing MIMO techniques under realistic propagation conditions.     

频率选择性衰落MIMO信道的GBDB模型及其性能分析

针对频率选择性MIMO信道建立GBDB模型。综合考虑了无线衰落信道收发两端的多普勒扩展、非均匀角度扩展以及平均发射与到达方向,综合考虑了收发端天线阵的配置,推导出频率选择性MIMO信道的联合空时频相关函数,给出该模型的时延扩展的概率密度函数、时延谱与角度谱,并且与实测数据进行对比分析,验证了该模型的准确性。     

三维MIMO信道物理模型的统计特征

提出以散射矩阵来概括并简化电波传播过程中散射体对电磁波的影响,并对传统的距离分集和极化分集多入多出（MIMO）信道模型进行扩展,建立了一种可以应用于各种分集情况的三维通用MIMO物理信道模型。再以此模型为基础,对三维环境中的MIMO信道统计特征进行了研究,推导出任意情况下交叉极化鉴别度（XPD）和子信道间相关性的计算方法,并进行了仿真验证。仿真结果表明从文中所提出信道模型提取得到的统计特征与理论分析的结果是相符的。     

Geometrical Modeling of Scattering Environment for Highways in Umbrella Cell Based MIMO Communication Systems

In this paper, we develop a three-dimensional (3D) eccentricity-based cylindrical geometrical channel model for nonisotropic multiple-input-multiple-output (MIMO) communication systems under umbrella macrocellular environment. We use elliptic cylindrical geometry to model the scattering phenomenon in streets, canyons and highways. The scattering objects like, high-rise building, trees and vegetation that lie along the roadside premises are modeled by the height of an elliptical cylinder. The proposed channel model targets fast moving vehicles on the highways in an umbrella-cell of cellular communication networks. We assume that both ends of the communication link are equipped with multiple antenna arrays, where, mobile-station antenna height is lower than base-station antenna. Utilizing the proposed MIMO communication channel model, we obtain closed-form expressions for the space–time correlation function among the MIMO antenna elements. The obtained theoretical expressions are plotted and analyzed for different values of channel parameters. Finally, we compare the proposed model with the existing models in the literature and prove that our model can be deduced to the existing two-dimensional and 3D channel models.     

分布式MIMO雷达目标散射模型研究

针对当前分布式多输入多输出(MIMO)雷达目标散射模型的不足,提出了一种三维特体目标模型;在考虑点散射体电磁散射的方向性、遮蔽及收发天线方位角、俯仰角等因素的条件下,推导了目标静态雷达截面积(RCS)的计算公式和MIMO雷达信道的相关函数;同时,仿真分析了目标动态RCS的统计模型及其与收发天线双基地角的关系,以及MIMO雷达信道空间去相关的条件。仿真分析结果与RCS的经典统计模型、双基地RCS的经验结论以及单基地雷达回波信号去相关角度的经验值是吻合的,证实了模型的科学性和合理性。研究结果对分布式MIMO雷达的检测、跟踪和系统配置等研究具有参考价值。     

一种MIMO智能天线融合方法研究

提出一种采用波束调度策略的MIMO与智能天线融合设计方案,用以解决MIMO传输中空域相关性问题。融合方案在天线结构上以智能天线单元组建MIMO阵列,智能天线单元之间协同工作。分析了采用波束调度时的MIMO矩阵构成及其合并接收方式,给出一种波束间空域相关性的计算方法。仿真结果表明,在小角度扩展条件下,同指向的波束相关性与全向阵元相关性相似,而波束调度策略具有良好的去相关性,能有效提高MIMO信道容量。     

基于天线子集选择算法的DSTBC优化

为进一步提高空时码性能,在信道模型为瑞丽和莱斯慢衰落信道的情况下,文中提出了一种优化差分空时分组码的＂天线子集选择算法＂——假设发射信号为特定的Alamouti正交空时分组码,通过最大化信道参数矩阵F范数的方法,优化了MIMO系统的天线集。仿真结果表明：此方法可降低码元的比特错误率,并且可获得相当客观的分集增益和能量增益。此外,还讨论了该优化方法的适用范围。     

Spatially and temporally correlated MIMO channels: modeling and capacity analysis

Wireless communication systems employing multiple antennas at both the transmitter and receiver have been shown to offer significant gains over single-antenna systems. Recent studies on the capacity of multiple-input-multiple-output (MIMO) channels have focused on the effect of spatial correlation. The joint effect of spatial and temporal correlation has not been well studied. In this paper, a geometric MIMO channel model is presented, which considers motion of the receiver and nonisotropic scattering at both ends of the radio link. A joint space-time cross-correlation function is derived from this model and variates with this joint correlation are generated by using the vector autoregressive stochastic model. The outage capacity of this channel is considered where the effects of antenna spacing, antenna array angle, degree of nonisotropic scattering, and receiver motion are investigated. When n transmit and n receive antennas are employed, it is shown that the outage capacity still increases linearly with respect to n, despite the presence of spatial and temporal correlation. Furthermore, analytical expressions are derived for the ergodic capacity of a MIMO channel for the cases of spatial correlation at one end and at both ends of the radio link. The latter case does not lend itself to numerical evaluation, but the former case is shown to be accurate by comparison with simulation results. The proposed analysis is very general, as it is based on the transmit and receive antenna correlations matrices.     

用于快时变MIMO衰落信道的一种差分空时调制技术

针对快时变多输入多输出(MIMO)平坦衰落信道,利用时变信道的基扩展模型(BEM),提出了一种差分空时调制方案。差分编码按块进行,发射信号矩阵为对角酉矩阵。通过设计发射端的交织及接收端的解交织,判决反馈差分检测不需要信道状态信息。理论分析和仿真表明,该方案能同时实现最大的天线分集和信道时变性所提供的Doppler分集。     

Genetic Algorithm Based MIMO Capacity Enhancement in Spatially Correlated Channels Including Mutual Coupling

Higher system capacities can be achieved if multiple antennas are used on both sides of the wireless link, thus creating a multiple-input-multiple-output (MIMO) system. In this work, the maximization of MIMO system capacity in Rayleigh fading, spatially correlated channels involving practical antenna arrays is challenged through inter-element spacing optimization. The system capacity is evaluated using a proposed formula that takes into account both antenna mutual coupling and signal correlation. Capacity values turn out to outperform the ones obtained considering the conventional antenna array geometries.     

A novel wideband space‐time channel simulator based on the geometrical one‐ring model with applications in MIMO‐OFDM systems

In this paper, we extend the geometrical one‐ring multiple‐input multiple‐output (MIMO) channel model with respect to frequency selectivity. Our approach enables the design of efficient and accurate simulation models for wideband space‐time MIMO channels under isotropic scattering conditions. Two methods will be provided to compute the parameters of the simulation model. Especially, the temporal, frequency and spatial correlation properties of the proposed wideband space‐time MIMO channel simulator are studied analytically. It is shown that any given specified or measured discrete power delay profile (PDP) can be incorporated into the simulation model. The high accuracy of the simulation model is demonstrated by comparing its statistical properties with those of the underlying reference model with specified correlation properties in the time, frequency and spatial domain. As an application example of the new MIMO frequency‐selective fading channel model, we study the influence of various channel model parameters on the system performance of a space‐time coded orthogonal frequency division multiplexing (OFDM) system. For example, we investigate the influence of the antenna element spacings of the base station (BS) antenna as well as the mobile station (MS) antenna. It turns out that an increasing of the antenna element spacing at the BS side results in a higher diversity gain than an increasing of the antenna element spacing at the MS side. Furthermore, the diversity gain brought in by space‐time block coding schemes is investigated by simulation. Our results show that transmitter diversity can significantly reduce the symbol error rate (SER) of multiple antenna systems. Finally, the influence of the Doppler effect and the impact of imperfect channel state information (CSI) on the system performance is also investigated. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Effect of keyholes on the symbol error rate of space-time block codes

In multiple-input multiple-output (MIMO) fading environments, degenerate channel phenomena, so-called keyholes or pinholes, may exist under realistic assumptions where a MIMO channel has uncorrelated spatial fading between antenna arrays but a rank-deficient transfer matrix. In this letter, we analyze the average symbol error rate (SER) of orthogonal space-time block codes (STBCs) with M-PSK and M-QAM constellations over keyhole channels.     

天线阵列方位对MIMO无线信道性能的影响

分析收发天线阵列的方位对MIMO无线信道的空域相关性及其容量的影响,得出在散射信号角度扩展较小时,这种影响不容忽视,为得到更大的信道容量,应使阵列法线尽可能指向来波/去波平均方向.数值结果证实了天线阵列方位对相关系数的影响,并指出这种影响随天线阵列法线偏离其信号平均方向而增大.仿真结果表明信号角度扩展较小的阵列的方位对信道容量影响更大,增大信号角度扩展可以削弱以至消除这种影响.