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.     

三维空间统计信道的空时参数AOA和TOA分析

针对在均匀散射体分布以及空间对称的3-D室内移动通信环境,细化了对于基站（BS,Base Station）以及移动台（MS,Mobile Station）端空间角度的研究。对在指向性天线覆盖下的室内微小区移动通信环境下,模型能估计多径衰落信道的重要空时信道参数,如波达信号在水平面以及竖直平面上的信号到达角度（AOA,Angle of Arrival）以及到达时间（TOA,Time of Arrival）。数值仿真结果与2一D多径衰落信道对比表明本模型的信道参数估计结果符合理论和经验,扩展了3一D空间统计信道模型的研究和应用。     

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.

     

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.     

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。     

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.     

Transmission Scheme for 2D Antenna Array MIMO Systems with Limited Feedback

Three-dimensional (3D) multiple-input multiple-output (MIMO) systems exploit spatial richness and provide another degree of freedom to transmit signals and eliminate spatial interference. Currently, however, there is no 3D codebook for two-dimensional (2D) antenna array MIMO systems with limited feedback. In this paper, based on the existing 2D codebook, we present a limited feedback and transmission scheme for 2D antenna array MIMO systems. In this scheme, the mobile station (MS) has imperfect channel knowledge, and the base station (BS) only acquires partial information relating the channel instantiation. MS must feed back two channel state information (CSI) instances, i.e., the horizontal and vertical CSIs. After receiving the two CSI instances, the BS interpolates a new vertical precoding vector using the vertical CSI. Then, the BS re-constructs a 3D beamforming vector using horizontal and vertical precoding vectors and compensates the reported horizontal channel quality indicator. System level simulation is employed, and the simulation results show that the proposed method improves the system spectral efficiency and the cell-edge SE significantly.     

Statistical scattering model in urban propagation environment

A statistical scattering model for mobile radio channels that has the following three features is proposed: 1) the effective scattering area (ESA) is expressed by an ellipse, the center of which is the mobile station (MS) location; 2) the major axis of the ellipse runs parallel along the street where the MS is located; and 3) the scattering power density function around the MS is expressed by a combination of two Laplacian distributions in which the standard deviations are different. To verify the proposed model and obtain realistic values for the model parameters, the spatiotemporal path data observed at a base station (BS) were measured using a 2.2-GHz band in a macrocell scenario (BS antenna height is 60 m) in a typical urban area. The scattering positions are detected from the path information such as the azimuth arrival angle and path length, assuming a single bounce. The spatial distribution of the scattering power is analyzed using principal component analysis. The results showed the ESA to be the anticipated ellipse with the major and minor axes of approximately 210 and 120 m, respectively (axis ratio: approximately 1.7). Furthermore, the power profiles that are projected for each axis of the ellipse can be approximated as Laplacian distributions. Finally, simplification of the proposed model is discussed.     

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.     

Joint Shadowing Process in Urban Peer-to-Peer Radio Channels

For multihop and ad hoc networks, a conventional 1-D channel model cannot capture the spatial correlation of the shadowing processes. This paper investigates the joint spatial correlation property of the shadowing process for peer-to-peer (P2P) radio links in urban environments. When a fixed base station is assumed, statistical analysis reveals that the shadowing process is mainly a result of spatial displacement at the mobile station (MS). Furthermore, the joint correlation property of the MS-MS channel shows that MS displacements at each end of the P2P link have an independent and equal effect on the correlation coefficient. A sum-of-sinusoids simulation model is proposed to generate the joint correlation shadowing process for urban P2P radio channels. The performance of the proposed channel simulator is analyzed in terms of the autocorrelation and joint correlation function of the simulated shadowing process. Simulations illustrate that the proposed model is able to output deterministic shadowing with a normal distribution (in decibels) and the desired correlation properties. It is thus suitable for use in system-level simulations, such as the evaluation of routing and radio resource management algorithms in ad hoc or mesh networks.     

Angle and time of arrival statistics for the Gaussian scatterdensity model

Starting from a Gaussian distribution of scatterers around a mobile station, expressions are provided for the probability density function (PDF) in the angle of arrival, the power azimuth spectrum, the PDF in the time of arrival, and the time delay spectrum, all as seen from a base station. Expressions are also provided for some of the quantities of practical interest such as the root-mean-square (RMS) angular spread, the RMS delay spread, and the spatial cross-correlation function. Results for the Gaussian scatter density model are compared with those for the circular scattering model and the elliptical scattering model as well as with experimental results available for outdoor and indoor environments. Comparison is shown for the PDFs as well as for the power spectra in angle and delay. It is shown that the present model, in contrast to the previous models, produces results that closely agree with experimental results. With an appropriate choice of the standard deviation of the scattering region, the Gaussian density model can be made suitable both for environments with very small angular spreads as well as those with very large angular spreads. Consequently, the results provided in the paper are applicable to both macrocellular as well as picocellular environments     

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。     

Angle and time of arrival statistics for circular and ellipticalscattering models

With the introduction of antenna array systems into wireless communication networks comes the need to better understand the spatial characteristics of the channel. Scattering models provide both angle of arrival (AOA) and time of arrival (TOA) statistics of the channel. A number of different scattering models have been proposed in the literature including elliptical and circular models. These models assume that scatterers lie within an elliptical and circular region in space, respectively. In this paper, the joint TOA/AOA, the marginal TOA, and the marginal AOA probability density functions (PDFs) are derived for the elliptical and circular scattering models. These PDFs provide insight into the properties of the spatial wireless channel     

Generation of base station DOA distributions by Jacobitransformation of scattering areas

The author describes a simple method for transforming angular distributions of a radio scattering area located around a mobile station (MS) into a direction-of-arrival (DOA) distribution at a base station (BS). Tractable closed form solutions for circular uniform and conical (nonuniform) scattering areas, are presented     

A CSI Estimation Method for Wireless Relay Network

This letter proposes a method for channel state information (CSI) estimation in a wireless relay network, which consists of a base station (BS), a relay station (RS), and a mobile station (MS). The proposed method exploits the fact that the link condition between fixed BS and fixed RS tends to be stable, and the frequent CSI update is not necessary for this link. In order for the BS to obtain the CSI of the distant link (i.e. RS-MS link), RS amplifies a pilot signal received from MS with a pre-defined amplification factor, and forwards it to BS. This enables the BS to obtain the CSI of the RS-MS link based on the received pilot signal and pre-knowledge on the CSI of BS-RS link, which can reduce the required overhead to explicitly exchange CSI.     

Generalized multiuser orthogonal space-division multiplexing

This paper addresses the problem of performing orthogonal space-division multiplexing (OSDM) for downlink, point-to-multipoint communications when multiple antennas are utilized at the base station (BS) and (optionally) all mobile stations (MS). Based on a closed-form antenna weight solution for single-user multiple-input multiple-output communications in the presence of other receiver points, we devise an iterative algorithm that finds the multiuser antenna weights for OSDM in downlink or broadcast channels. Upon convergence, each mobile user will receive only the desired activated spatial modes with no cochannel interference. Necessary and sufficient conditions for the existence of OSDM among the number of mobile users, the number of transmit antennas at the BS, and the number of receive antennas at the MS, are also derived. The assumption for the proposed method is that the BS knows the channels for all MS's and that the channel dynamics are quasi-stationary.     

Smart antenna arrays with oscillating beam patterns: characterization of transmit diversity in semi-elliptic coverage

By applying carefully selected time-varying delays to the array elements of a smart antenna located at the base station (BS), small oscillations are generated in the beam pattern. These oscillations create a time-varying channel demonstrating intra-symbol time variation and characterized by coherence time T/sub C/. At a single-antenna mobile station (MS), the time-varying channel (with coherence time T/sub C/) creates a time diversity which is exploited to enhance the mobile's performance (by introducing oversampling to the mobile receiver). We present a channel model which characterizes the time-varying channel that results from beam pattern oscillation. We then use our channel model to evaluate the coherence time, T/sub C/, at the mobile station (MS). The channel model presented corresponds to the so-called geometric-based stochastic channel model (GSCM), with a semi-elliptic coverage area. This geometric approach allows us to stochastically model the parameters of the time-varying channel impulse response. Simulations based on the GSCM show that 7-fold time diversity can be exploited at the MS (when beam pattern movement is small), which significantly improves the MS receiver probability-of-error performance.     

一种基于单次散射体定位的TOA/AOA混合定位算法

为了降低非视距(Non-Line-of-Sight,NLOS)误差对定位精度的不利影响,提出了一种基于散射体定位的到达时间(Time of Arrival,TOA)/到达角(Angle of Arrival,AOA)混合定位算法.假设各基站(Base Station,BS)接收的多径信号都经历了散射体单次散射,首先利用...     

A simple linear multiuser precoding technique in cellular relay networks

In this paper, we propose a simple linear multiuser precoding scheme for downlink cellular systems with a decodeand forward (DF) based relay, where the available information at a base station (BS) and a relay station (RS) is asymmetric. The proposed scheme not only eliminates the interference from a RS for the mobile station (MS) served by a BS but also provides the MS supported by a RS with a macro diversity gain without any information exchange between a BS and a RS. Consequently, the proposed scheme outperforms a conventional scheme and approaches an ideal scheme using dirty paper coding (DPC) in the information asymmetric configuration.     

A stochastic MIMO radio channel model with experimental validation

Theoretical and experimental studies of multiple-input/multiple-output (MIMO) radio channels are presented. A simple stochastic MIMO model channel has been developed. This model uses the correlation matrices at the mobile station (MS) and base station (BS) so that results of the numerous single-input/multiple-output studies that have been published in the literature can be used as input parameters. The model is simplified to the narrowband channels. The validation of the model is based upon data collected in both picocell and microcell environments. The stochastic model has also been used to investigate the capacity of MIMO radio channels, considering two different power allocation strategies, water filling and uniform and two different antenna topologies, 4/spl times/4 and 2/spl times/4. Space diversity used at both ends of the MIMO radio link is shown to be an efficient technique in picocell environments, achieving capacities within 14 b/s/Hz and 16 b/s/Hz in 80% of the cases for a 4/spl times/4 antenna configuration implementing water filling at a SNR of 20 dB.