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.     

基于 Inverted-Parabolic 分布的空间统计信道模型

针对在非均匀散射体分布下信号到达角度、到达时间以及多普勒效应等信道参数估计的复杂性,提出一种合理的空间信道模型,并引入几何分割法导出基于散射体Inverted-Parabolic分布的空间统计信道模型。模型能方便地估计室外宏小区和微小区移动通信环境下各种重要的空时信道参数,如AOA、TOA概率分布密度函数和多普勒功率谱以及信号的空—时相关性。数值结果与均匀散射体圆模型和高斯散射体圆模型对比表明本模型的信道参数估计结果符合理论和经验,且与实测结果吻合较好。在基站设计采用指向性天线时研究了移动台MS的多普勒效应,修正了Clarke U-shaped经典模型,阐明了天线主瓣宽度 、空间模型参数D/R和MS移动参数影响信道参数的机理。     

Research on characterization and modeling for 3D wideband time-varying channels for urban microcells at 2.55 GHz

Based on the outdoor microcell MIMO channel measurement campaign at 2.55 GHz,the time-evolution characteristics of three-dimensional wideband channel were studied.The SAGE algorithm was used to extract multipath parameters such as azimuth and elevation angle of departure and arrival.A bidirectional matching algorithm was applied to tracing multipath and the "birth-death" process.The statistical characteristics of multipath birth,lifespan,multipath initial and evolution parameters were analyzed and modeled based on the cross-correlations of multipath parameters.A time-varying channel model with multipath birth-death process was developed.The model parameter table and a detailed flowchart were offered for time-varying channel simulations.The proposed model was validated by comparing the root-mean-square (RMS) of delay spread and angular spread between the simulated and measured results.The channel model proposed can be applied in time-varying channel simulation for urban microcells and it’s also very important to be referred in 5G dynamic channel modeling.     

多输入多输出信道空域相关性评估简化模型

针对任意散射环境的多输入多输出(MIMO)信道,提出一种基于角度域脉冲采样的空域相关性评估简化模型,推导常见采样脉冲空域相关系数的近似简化解析式,并详细分析简化模型中采样脉冲数目和加权系数的选取依据,大大降低MIMO衰落信号空域相关性分析的复杂度.仿真结果表明:当到达波角度扩展为5到20度且采样脉冲数目大于36时,本文...     

无人机毫米波信道建模及统计特性研究

针对传统移动信道模型不适用于无人机毫米波通信场景的问题,本文基于射线追踪原理构建了一个无人机毫米波三维几何信道模型,并提出了一种针对该模型的信道参数更新算法,该算法考虑了通信距离、信号角度、路径时延和功率等传播参数的随时间演进过程。在此基础上,针对南京航空航天大学校园传播场景,研究分析了时延分布、时延扩展、角度分布和角度扩展等信道统计特性。数值仿真结果表明,本文模型能够有效复现无人机信道的时变非平稳特性,输出信道统计特性与实测结果吻合,可用于无人机毫米波通信系统的方案设计、性能优化和评估验证等领域。      

新型动态簇非平稳MIMO信道模型与信道特性分析

针对传统移动-移动场景未能考虑阵列域和时间域双重非平稳特性,且不能模拟移动发射机和移动接收机间动态簇链路信道状态的问题,提出了一种新型三维动态簇非平稳多输入多输出(Multiple-Input Multiple-Output,MIMO)信道模型.该模型结合了天线阵列切换和收发端移动过程中信道非平稳特性,且利用生灭过程对非视距分量进行模拟.并针对径时延、径功率、径到达离开角等参数,对时空演进算法进行了改进.在小尺度角度参数谱服从Von Mise Fisher(VMF)分布情况的基础上,对时间和空间相关函数进行了推导.仿真结果表明,理论值与仿真值具有很好的拟合度,表明所提出的信道模型可以作为动态簇三维非平稳MIMO信道建模的设计方案.     

三维空间MIMO信道接收天线阵列互耦效应及系统容量分析

针对非频率选择性瑞利衰落MIMO(multiple-input multiple-output)信道,建立了接收天线阵列的三维空间信道模型,将MIMO的一般信道建模推广到三维空间域。在建模过程中利用天线阵列在互耦效应下的等效网络模型,推导出三维空间域模型下的互耦相关性的通用表达式,阐明了互耦效应下相关性与无互耦相关性之间的关系。应用通用表达式分析了当接收端为不同的天线阵列结构时,入射信号的中心到达角和角度扩展分别对于在互耦效应下信道容量的影响。分析结果验证了不同的角度扩展对于互耦相关性的影响,揭示了在互耦效应下影响系统容量的主要因素为入射信号的平均中心到达角。     

基于雨衰雪衰影响的空间信道统计模型

针对某些特殊的移动通信环境中信号的到达角度( TOA)、到达时间( AOA)等信道参数估计的复杂性,提出一种基于散射体均匀分布室外统计信道模型。该模型将树木中的树冠层作为散射体呈均匀分布在移动台与基站周围的椭圆形区域内,通过树冠层在雨雪环境中的相对介电常数来分析降雨降雪量对信号传输带来的影响,可以方便地估计出此室外微小区的空时信道参数,如AOA概率密度分布函数、TOA概率密度分布函数以及到达角度/到达时间( AOA/TOA )联合概率密度分布函数。仿真结果表明,信号的到达时间TOA以及到达角度AOA随着降雨降雪量的增大而增大,尤其当降雪量增大使得树冠层相对介电常数达到4.5时,信号的传输将被阻塞。该模型的信道参数估计结果符合理论与经验,扩展了移动无线通信信道模型的研究与应用。     

5G网络中无人机-车辆非平稳信道模型与统计特性分析

针对无人机到车辆通信场景,提出了一种椭圆-圆柱-半球几何非平稳无人机-车辆信道模型。为了描述收发端周围散射体分布情况,一次散射径的散射体分布用同心椭圆面模拟;在二次散射径建模中,无人机侧散射体分布采用同心圆柱体模拟,并且车辆侧散射体分布使用同心半球体模拟;地面一次反射径的反射点分布则通过半球底面同心圆来模拟。为了进一步研究信道的非平稳特性,在各路径分量的二维角度服从Von Mises分布、Laplacian分布以及Von Mises Fisher分布的基础上,推导了时间自相关函数、空间互相关函数和多普勒频谱密度函数。仿真结果表明,理论值与测量值具有较好的拟合度,所提出的信道模型可以作为无人机到车辆非平稳信道建模的设计方案。     

28 GHz MIMO无线信道特性分析与研究

基于室内视距(Line-of-Sight,LOS)和非视距(Non-Line-of-Sight,NLOS)无线信道测量数据,研究了28 GHz多输入多输出(Multiple-Input Multiple-Output,MIMO)信道参数和容量特性.具体地说,分析了莱斯K因子、时延扩展、出发角和到达角的角度扩展等信道参数,研究了MIMO信道容量及空间相关性对容量的影响.结果表明:莱斯K因子、时延扩展以及角度扩展值取决于测量环境及场景;LOS条件下时延扩展的累积分布函数(Cumulative Distribution Function,CDF)曲线与正态分布拟合优于NLOS条件下的数据;MIMO天线空间相关性越大信道容量越小.本文结果可为28 GHz无线通信系统设计提供有用信息.     

Dynamic simulation model of indoor wideband directional channels

Culled from existing channel measurements, a dynamic indoor wideband directional-channel simulator is constructed by incorporating the spatial-temporal properties as well as the time-varying nature of propagation environments. A two-state semi-Markov model is used to account for the births and deaths of scattering clusters, which represents an improvement over the conventional Markov model where the duration in each state is forced to follow an exponential distribution. The spatial-temporal variations of clusters within their lifespan are modeled based on the real-life measurement results. The ranges of angle of arrival (AOA), angle of departure (AOD), and time of arrival (TOA) for each cluster are partitioned into finite number of intervals using the deterministic simulation methods. Subsequently, the cluster properties at different intervals can be derived from the empirical findings in previous channel-measurement campaigns. The efficacy of the proposed simulator is demonstrated by applying it to characterize a time-varying multiple-input multiple-output (MIMO) channel.     

移动通信室内外空间几何信道模型的分析与比较

针对频率非选择性无线多径衰落信道,基于室外通信环境下的空心圆模型,提出了一种改进的适应于室内通信环境的空心圆模型。通过推导接收信号的空时联合分布以及边缘分布概率密度函数,分析和比较了两种空心圆几何信道模型的空时统计特性。通过空心圆的空心率以及收发机间距的信道参数变化,仿真结果阐明了空心圆模型在圆盘模型和圆环模型之间过渡的变化机理,以及不同无线通信环境下的信道信息。     

Mobile-to-mobile fading channels in amplify-and-forward relay systems under line-of-sight conditions: statistical modeling and analysis

This paper deals with the modeling and analysis of narrowband mobile-to-mobile (M2M) fading channels for amplify-and-forward relay links under line-of-sight (LOS) conditions. It is assumed that a LOS component exists in the direct link between the source mobile station (SMS) and the destination mobile station (DMS), as well as in the links via the mobile relay (MR). The proposed channel model is referred to as the multiple-LOS second-order scattering (MLSS) channel model. The MLSS channel model is derived from a second-order scattering process, where the received signal is modeled in the complex baseband as the sum of a single and a double scattered component. Analytical expressions are derived for the mean value, variance, probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the received envelope of MLSS channels. The PDF of the channel phase is also investigated. It is observed that the LOS components and the relay gain have a significant influence on the statistics of MLSS channels. It is also shown that MLSS channels include various other channel models as special cases, e.g., double Rayleigh channels, double Rice channels, single-LOS double-scattering (SLDS) channels, non-line-of-sight (NLOS) second-order scattering (NLSS) channels, and single-LOS second-order scattering (SLSS) channels. The correctness of all analytical results is confirmed by simulations using a high performance channel simulator. Our novel MLSS channel model is of significant importance for the system level performance evaluation of M2M communication systems in different M2M propagation scenarios. Furthermore, our studies pertaining to the fading behavior of MLSS channels are useful for the design and development of relay-based cooperative wireless networks.     

A Study of the Influence of Shadowing on the Statistical Properties of the Capacity of Mobile Radio Channels

This paper studies the influence of shadowing on the statistical properties of the channel capacity. The problem is addressed by using a Suzuki process as an appropriate statistical channel model for land mobile terrestrial channels. Using this model, exact solutions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity are derived. The results are studied for different levels of shadowing, corresponding to different terrestrial environments. It is observed that the shadowing effect has a significant influence on the variance and the maximum value of the PDF and LCR of the channel capacity, but it has almost no impact on the mean capacity of the channel. The correctness of the theoretical results is confirmed by simulation using a stochastic channel simulator based on the sum-of-sinusoids principle.     

毫米波时变信道仿真中实现空间一致性的方法研究

为满足终端移动场景下5G毫米波信道建模及仿真的需求,开展了毫米波时变信道仿真中实现空间一致性的研究.基于通用的5G毫米波信道模型开展了仿真和分析,将终端移动轨迹进行分割,确定连续仿真窗口间大尺度参数的相关性.同时,引入马尔可夫链实现窗口间多径簇数目的动态演化.对于窗口内信道小尺度参数,基于多径的几何分布结构实现对其状态...     

Approximate Outage Analysis of Land Mobile Satellite Systems in Lognormally Shadowed Rician Channels

Among the proposed models for land mobile satellite (LMS) channels, the shadowed Rice model proposed originally by Loo, has found wide applications in different frequency bands. In Loo’s model, it is assumed that the received signal is affected by nonselective Rice fading with lognormal shadowing on the direct component only, while the diffuse scattered component has constant average power level. The resulting composite probability density function (PDF) includes an infinite-range integral and is not available in closed-form, thereby making the performance evaluation of LMS communication links in these channels cumbersome. To bypass this problem, in this paper an approximation method is developed which makes it possible to describe the envelope PDF as a sum of weighted Rice’s PDFs. Therefore, in contrast with Loo’s PDF, the proposed method leads to an easy-to-use, closed-form approximate expression for the PDF and also for the most statistical characteristics, such as cumulative distribution function and moments of the signal envelop in shadowed Rice channels. Based on the derived expressions, the performance analysis of a single receiver operating over lognormally shadowed Rice channel is investigated in terms of the outage probability. Numerically evaluated results show the good accuracy of the proposed approximation method.     

Geometrical statistical channel model arisen from scatterers around the mobile with an inverted-parabolic spatial distribution

In this paper,firstly presented a geometrically based statistical channel model with scatterers that are with an inverted parabolic spatial distribution around mobile station(MS) within a circle wherein the base station(BS) and MS are included.This paper proposed a technique to simply derive probability density functions(PDFs) of angle of arrival(AOA),time of arrival(TOA) and Doppler spectra to characterize the outdoor macrocell and microcell environments by employing various distances between BS and MS,or different size of circular region.Employing this channel model,we analyze the impacts of a directional antenna at BS with the main-lobe width 2 on the fading and the Doppler spectra.     

A stochastic multipath channel model including path directions for indoor environments

A novel stochastic channel model for the indoor propagation channel is presented. It is especially for, but not limited to future communication systems with multiple antennas like space division multiple access (SDMA), spatial filtering for interference reduction (SFIR), or multiple-input/multiple-output (MIMO). The model is designed for indoor scenarios, straight forward extendable to urban environments. It is based on physical wave propagation. The new approach describes the channel by multipath components, each characterized by its transfer matrix (including loss), delay, direction of arrival, and departure. The appearance and disappearance of multipath components over time is modeled as a birth and death process, a marked Poisson process. This enables first-time the correct modeling of spatial and temporal correlations. In each modeling step, path properties change according to the motion of transmitter and receiver. The changing delay times of propagation paths yield a realistic Doppler behavior of the channel. Deterministic ray tracing results are used to produce the huge data sets required for the statistical evaluation of the parameters of the proposed model. This method enables an automated parameter extraction for new environments or frequencies. The ray tracing tool has been verified by narrowband, wideband, and directional channel measurements. The novel stochastic spatial channel model allows the simulation of third-generation broadband radio systems including arbitrary antenna configurations and patterns. System simulations for the bit-error rate of radio links can be performed including intelligent antenna configurations like SDMA, SFIR, or MIMO. Furthermore, the capacity of complete systems can be investigated.