A Generalized Model for the Spatial Characteristics of the Cellular Mobile Channel

In this paper, we present an intensive study of the spatial characteristics of the cellular mobile channel for picocell, microcell, and macrocell environments. We review the previous physical channel models and make appropriate comments/corrections wherever needed. We find that almost all physical channel models proposed so far are specific to particular cellular environments and that no general model exists in the literature. Thus, we propose a generalized physical channel model, referred to as the eccentro-scattering model, and derive the expressions for the probability density function (pdf) in an angle of arrival (AoA) of the multipath signals at a base station (BS) for the picocell, microcell, and macrocell environments using the two most commonly used scatterers' distributions, i.e., uniform and Gaussian. The derived formulas, in closed form, can be further used in designing beamwidth and channel tracking algorithms and assessing the performance of smart antennas. We discuss the relations between the results obtained for different cellular environments in the uniform and the Gaussian scattering and investigate the effects of the standard deviation of the scatter density and size of the scattering disc on the pdf of AoA at the BS. Previous work on the AoA statistics considering either the shape of the scattering regions or the distribution of scatterers within that region can more easily be reproduced using the provided general formula. We prove that assuming the scatterers to be either uniformly or Gaussian distributed in sparsely populated areas gives almost the same distribution of AoA of multipaths at the BS.     

A Simple 3-D Geometric Channel Model for Macrocell Mobile Communications

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. Most of the proposed models disregard the three dimensional character of the signal spread or use techniques with excessive computational complexity. In this paper, we develop a simple 3-D geometric scattering model for the uplink of a macrocell mobile environment that provides the statistics of Angle-of-Arrival (AoA) of the multipath components. The model extends the 2-D geometrical-based single bounce macrocell (GBSBM) model. Explicit closed-form expressions are derived for the statistics of the AoA of the multipaths in the azimuth and elevation planes. Analysis of the results exhibits the advantages of our proposal compared to 2-D and 3-D ones published in the literature. Comparisons with experimental data confirm its validity. Interesting conclusions for the effective evaluation of mobile communication systems have been derived. Moreover, an application of the model to mobile location estimation has been developed and evaluated.     

An Extended One-Ring MIMO Channel Model

In this paper we develop a multiple input multiple output (MIMO) channel model and derive its spatial and temporal correlation properties. We present a generalized methodology to derive the spatial correlation when the angles of arrival (AoA) and angles of departure (AoD) are either independent or partly correlated. Our model therefore spans the full range from well-established single ring models, where AoA and AoD are fully correlated to complex industrial channel models where they are uncorrelated. It is shown that first order and second order approximations to the channel give rise to a single- Kroneckermodel and a sum-Kroneckermodel respectively. We compare our model to other MIMO channel models in terms of correlation structure and the ergodic mutual information (EMI) and study the effect of the non-Kronecker correlation structure.     

Angle of Arrival Statistics for a 3-D Cylinder Model

In this paper, a three-dimensional (3-D) geometric model is considered to simultaneously describe angle of arrival (AoA) of multipath waves in the azimuth and elevation planes. The model is suitable in a macrocellular environment with a low MS antenna and an elevated base station (BS), where scatterers are distributed in a cylinder with the radius of the cell and the height of the BS. Closed-form expressions for the probability density functions in the angles are provided as seen from the mobile station (MS). Results show that the azimuth AoA depends on the ratio of the distance between the BS and the MS to the radius of the cell whereas the elevation AoA depends on the height of the BS, the radius of the cell and the distance between the BS and the MS. Monte-Carlo simulations are performed to examine the accuracy of the proposed model.     

Joint AoA and Channel Estimation for SIMO- OFDM Systems: A Compressive-Sensing Approach

Millimeter-wave (mmWave) transmission has been considered in future fifth generation (5G) communication systems. Since the pathloss in mmWave is severe, beamforming with antenna arrays, an enabling technology in the 5G era, will become a must. To conduct receive beamforming, however, we need to know the information about the angle-of-arrival (AoA). In this paper, we consider joint AoA and channel estimation for single-input-multiple-output (SIMO) OFDM systems. As known, wireless channels are sparse, and this is particularly true for mmWave environments. Conventional compressive-sensing (CS) based channel estimation methods only consider single-input-single-output systems. We propose new matching-pursuit-based CS methods for channel estimation in SIMO-OFDM systems, using frequency-domain pilots. With the estimated channels, AoA’s are then estimated by the maximum-likelihood method. Since a hidden parameter is involved in the problem, an expectation-maximization (EM) algorithm is then employed. The Cramer-Rao lower bound (CRLB) is also derived for the AoA estimation. Simulation results show that the proposed channel estimation can significantly outperform existing methods while the proposed AoA estimation attains the CRLB.     

AoA-Based Channel Estimation for Massive MIMO OFDM Communication Systems on High Speed Rails

Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies.     

The Fisher–Bingham Spatial Correlation Model for Multielement Antenna Systems

In this paper, we study the effect of the elevation of incoming multipaths at a multielement antenna receiver by using a novel 3-D approach. It is shown that under a more general 3-D angle-of-arrival (AoA) model, namely, the Fisher–Bingham five-parameter (FB5) distribution, the spatial fading correlation (SFC) that is experienced between the adjacent antenna array elements decreases as the elevation increases. The FB5 distribution does not have a known series expansion, and therefore, the defining SFC integral can only numerically be evaluated. The proposed SFC function is further extended to capture the effect of multiple clusters of scatterers in the propagation channel. We, therefore, propose a mixture SFC function that is scaled according to the probability that each cluster contributes to the channel. The parameters of the individual components that constitute the mixture are estimated by using a soft expectation maximization (soft-EM) algorithm. The results indicate that the proposed model fits well with the data obtained from a multiple-input–multiple-output (MIMO) measurement campaign in the city of Ilmenau, Germany.      

Accuracy of geometric channel-modeling methods

When constructing a propagation channel model, a substitute is often created by giving an arbitrary shape or form to scatterer distributions based on its intuitive appeal for a certain radio environment. However, such models do not necessarily represent the actual propagation process and may yield inaccurate results. The main objective of this paper is to provide an insight into the underlying relationship between geometric models and the particular physical propagation process they represent. The workhorse is the semi-geometrically based statistical (SGBS) model and the two heuristic rules. The SGBS model defines the distribution of dominant scatterers contributing to the last reradiation of multipath components to the base station. The earlier multiple-reflection process is modeled using the composite Nakagami/log-normal probability density function. Two parameters are then introduced; namely, the effective path length and the normalized space-dependent intensity measure. Using these two metrics, two heuristic rules are subsequently proposed to provide the missing link between the canonical models and the physical channel. The rules are then applied to revisit several widely used geometric models in macro- and microcellular environments. As a working example, the Gaussian scatterer density model is further extended using such an approach. Important channel parameters such as power azimuthal spectrum, power delay spectrum, and azimuthal and delay spreads are then calculated and compared with simulation results.     

Doppler Shift and Capacity Analysis of MIMO Antenna Arrays in a Novel 3D Geometric Channel Model

One of the fundamental research areas in wireless communications is the development of realistic models that can efficiently and accurately describe the wireless propagation channel. In multi-path environments, the received signal frequency constantly varies as a result of the relative motion between the receiver and transmitter. In this paper, we bridged a novel 3D geometric channel model and the multiple-input and multiple-output (MIMO) antenna array, analyzed deeply the probability density functions (PDFs) of the Doppler shift (DS), its variance, and characteristic function and etc. For the particular channel model, analytical expressions for PDFs of the channel model and the DS of mobile station (MS) due to its motion, have been derived. Based on the analysis, we investigated MIMO receiving performance. Also developed a geometric channel model, and was firstly in the asymmetric geometry literature due to a directional antenna array employed at base station. For this channel model, it was assumed that each multi-path component of the propagating signal undergoes one bounce. It was also assumed that the scattering objects around MS, could be expressed as Gaussian and exponential density models, which are more suitable to simulate outdoor and indoor environments.

     

基于CSI的三维联合参数估计算法

针对商用Wi-Fi设备中由于天线数量和信道带宽有限而导致的到达角(AoA)和飞行时间(ToF)估计精度受限问题,以及现有基于最大似然估计的3维参数估计算法容易收敛于局部最优值,且依次对参数进行估计的方式使参数之间会互相影响的问题,该文提出一种基于Wi-Fi信道状态信息(CSI)的AoA,ToF和多普勒频偏(DFS)的3...     

一组电波传播环境描述参数的提出及应用

文中提出了一套新颖的用于描述小区传播环境的参数，它们定义明确，都有自己所代表的物理意义。论文在介绍了这套参数和椭圆模型后，利用它们对多径信号的到达分布，扩散参数作了计算。计算分别在时域和空域上进行。并对结果作了讨论，初步证实了这套参烽在仿真中的实用价值，最后，提出了可能的进一步工作方向。     

Effect of Antenna Directivity on Angular Power Distribution at Mobile Terminal in Urban Macrocells: A Geometric Channel Modeling Approach

We present a geometric channel model to study the effect of antenna directivity on angular power distribution at the mobile terminal in urban macrocells. The methodology reviewed in this paper integrates the antenna effect into the model geometry, thereby facilitating a system-dependent channel characterization. As each device is limited in terms of measurement sensitivity, the effective scatterer distribution is essentially dependent on the antenna beam pattern. Subsequently, two heuristic rules are proposed to establish the underlying relationship between the model geometry and the corresponding wave-propagation processes. It is shown that the influence of directional antenna is twofold. First, it alters the spatial distribution of scatterers by providing a different sample space for the random field, and secondly, it distributes signal components into the angles-of-departure or collects them from the angles-of-arrival by weighted combination. Important channel parameters measured at the mobile terminal such as the angular power distribution, Doppler spectrum, and multipath shape factors are also investigated to further exemplify the usefulness of the proposed model.     

Semi-Markov multistate modeling of the land mobile propagation channel for geostationary satellites

This paper describes a new semi-Markov propagation channel model for land mobile satellite systems using geostationary satellites. The multistate model switches between propagation states representing line-of-sight, shadowing, or blockage of the signal. The duration of times spent in each state follow probability distributions recommended by the radiocommunication sector of the International Telecommunication Union (ITU-R). The actual parameters to be used with the ITU-R distributions were modified and fitted to observed data. The open-area state durations follow a power-law distribution, while the state durations for both the shadowed and the blocked states follow a lognormal distribution. Parameters for both two- and three-state models are extracted from an L-band measurement campaign performed by Inmarsat in the United Kingdom. Propagation channel models characterizing the fading within the open, shadowed, or blocked propagation states are described as well. The semi-Markov models represent an improvement over the more commonly used Markov models where the duration in each state follows an exponential distribution. The new model enables more accurate prediction and simulation of system performance and availability.     

三维模型中的多普勒功率谱分析

多普勒效应是移动通信中最常见的现象,研究多普勒功率谱密度的分布,对建立更准确并贴合实际的无线信道模型具有重大意义。分析了两种不同几何模型中的多普勒功率谱,重点讨论了三维模型中入射波到达角度对多普勒功率谱的影响,仿真结果表明,方位角和高度角的分布及最大角取值范围共同决定了多普勒功率谱的分布特性。     

Channel Modeling for Multiple Satellite Broadcasting Systems

In this contribution we present the results of a study on land mobile satellite channel models for satellite systems with multiple satellites. The slow fading of our channel model for several satellites is based on a Markov channel state model for joint processes while the Probability Density Function (PDF) of the signal amplitude within each state is fitted to the Loo distribution. The correlation between two satellite channels and the channel spatial autocorrelation have also been studied. We show that a channel state model that uses a Markov state model of order one or of a fixed higher order is not appropriate if the state duration is of very high importance, which can be the case in the process of system planning. Therefore, we propose a dynamic higher order Markov state model for joint processes that depends on the current state duration. This approach models precisely any PDF of the channel state duration for both single and multiple satellite broadcasting systems while having a significantly lower computational complexity than a fixed higher order Markov model. It models the channel states of the whole system correctly, as well as the channel states of each satellite observed independently. It is able to capture the state correlation between multiple satellites. We also study possible approximations of the proposed models in order to reduce their computational complexity while having a good PDF match. Our channel state models are validated by measurements.      

Interference Nomenclature in Wireless Mesh Networks

The Quality of Service of Multi-Channel Multi-Radio Wireless Mesh Networks is adversely affected by the complex behavior of interference patterns present between the sender and receiver of a link. This behavior is usually captured using wireless channel interference models. The accuracy of the interference model is highly dependent on the interaction of the Carrier Sense Multiple Access with Collision Avoidance Medium Access Control (CSMA/CA MAC) protocol based on the geometric location of the sender and receiver of the link. Therefore, this paper presents a nomenclature of interference modeling schemes available in Wireless Mesh Network (WMN) literature with respect to the geometric location of the sender and receiver of a link. The behavior and limitations of each model are analyzed with the help of empirical examples. The results indicate that Garetto’s model of interfering links is the best choice to model wireless channel interference in WMNs. In addition, this study provides an interference analysis of Garetto’s model for the two link case by computing the conditional packet loss probability of each class of interfering link. The probability analysis concluded that the links with disconnected senders are highly interfering compared to sender connected links. Further, the analysis will assist researchers and engineers in relay node placement, capacity analysis, channel assignment, and topology control schemes in the WMN.     

Analysis of Non-WSSUS Fading Dispersive Channel Model

1Introduction Basically,whenthepropagationcharacteristicsofra diomobilecommunicationsarestudied[1],italways comestheWSSUSmodel,introducedbyBello[2]first ly,whichregardstheradiomobilechannelasafully stochasticchannelandassumestheuncorrelateddisper sivitybo…     

Integral equation formulation for scatter density problem

Integral equation formulation for the problem of finding a circularly symmetric scatter density (SD) around the mobile is deduced, and the SD is computed assuming that the distribution of angle-of-arrival (AoA) in the base station is known. The corresponding integral equation is solved by using the spline collocation method. Thus, instead of fitting a priori selected SD to estimated AoA distribution, the SD is solved based on AoA characteristics.     

Research on the spatial characterization of a 3D UAV air-to-ground channel model

To cope with the problem that the distribution assumptions of arrival angle and departure angle in existing geometry-based stochastic modeling (GBSM) for the unmanned aerial vehicle (UAV) air-to-ground (A2G) channel are too ideal to describe the spatial statistical property of the UAV A2G propagation environment precisely,considering the three-dimensional (3D) cylindrical A2G channel model,the spatial geometric characteristics of scattering regions were investigated analytically as corresponding to the angles of arrival and departure in both elevation and azimuth planes,which derived the probability density function (PDF) for the distribution of each angle.The effects of various parameters of channel model on the PDF were studied and simulation results prove that the derived PDF can describe the spatial statistical properties of UAV A2G channels more accurately,and can support the modeling of A2G communication channels well.     

Joint Estimation of MIMO Channel Parameters Using Space–Time Correlation Matrix for Different Angular Distributions

In this paper, we propose a new low-complexity method to jointly estimate the multiple-input multiple-output (MIMO) channel parameters namely the mean angle of arrival (AoA), the angular spread (AS) and the maximum Doppler spread (DS). We consider Gaussian and Laplacian angular distributions for the incoming AoAs in the case of a Rayleigh channel model. Our estimator is based on the magnitudes and phases of the space–time correlation functions of the received signals. To this end, closed-form expressions of the required functions were derived. Two different approaches are studied using these cross-correlation functions; first at a non zero time lag and second at two different time lags. To evaluate the robustness of the proposed estimator, the two Stage approach and the improved maximum likelihood method based on the Gauss Newton algorithm are taken as benchmarks for the mean AoA and the AS estimation. For the maximum DS, the two Rays and the auto-correlation based algorithms are chosen. Simulation results show that the proposed estimator offers more accurate estimates in almost all considered scenarios. We also compare our work to a recent joint estimator which exploits the Derivatives of the cross-correlation function (DCCF). Our method outperforms the DCCF algorithm at a lower computational cost.