Effects of antenna directivity and polarization on indoor multipathpropagation characteristics at 60 GHz

In millimeter-wave indoor communications systems, the radiation patterns and polarizations of the antennas at base stations and remote terminals have a significant influence on channel characteristics. The work reported in this paper investigated the effects of the radiation patterns of the antennas at remote terminals on multipath propagation characteristics. These effects were investigated by indoor propagation measurements at 60 GHz conducted in a modern office room and by ray-tracing simulations based on geometrical optics. Multipath channel characteristics are compared in terms of impulse responses and their root-mean-square (rms) delay spreads for an omnidirectional antenna and for three directive antennas with different beam widths. From the results of measurements and ray-tracing simulations, the use of a directive antenna at the remote terminal is demonstrated to be an effective method of reducing the effects of multipath propagation. Further reduction in the multipath effects is found to be achieved by the use of circular polarization instead of linear polarization with the directive antennas     

Propagation considerations for the design of an indoor broad-bandcommunications system at EHF

This paper reports the measurement and analysis of wideband propagation data for indoor radio channels at 40 GHz. Propagation characteristics are reported for two open-concept office areas of different sizes in two different buildings. Also, the results of measurements in one building are compared for system configurations in which either an omnidirectional or a narrowbeam antenna is employed at a base station for communications to multiple work stations with omnidirectional antennas. It is reported that, on a statistical basis, at the 90th percentile, multipath dispersion is the same for the two base-station antenna radiation patterns. Dispersion was, however, found to be lower in the smaller of the two measurement areas, where transmit/receive ranges were shorter. The 90th percentile of static RMS delay spread for this area was 19 ns compared with 45 ns for the larger area. Multipath spreads at the -25 dB relative power level were about 370 ns, compared with 140 ns in the larger area. In the larger area, global propagation loss was found to be well modeled by the one-way propagation equation with different range exponents (1.5 and 4) before and after a breakpoint at a range of 25 m. In the smaller area, the range exponent was found to be greater, being equal to 3.5. This is considered to be a result of reduced multipath infill, which would accompany the reduced dispersion. Temporal fading on fixed links with omnidirectional antennas was found to have depths such that a 14-dB fade margin is required for 99% reliability. Finally, spatial variations in received power at a given range indicated the requirement for a power margin between 4-7 dB for 99% reliability. These results are used in a link budget example for a broad-band indoor extremely high frequency (EHF) digital communications system     

基于TDOA 的室内定位系统中多径抑制方法

多径传播能显著降低基于到达时间差(TDOA)的定位精度。文中介绍了一种使用波束指向圆极化天线(BSCPA)抑制室内多径传播的方法。BSCPA 由一个波束开关网络、四个相同的六边形贴片单元及其馈电网络组成。通过控制波束开关网络中的射频(RF)开关的状态,可以分别激励四个指向圆极化波束以实现方位角全向覆盖。根据BSCPA 的指向波束和圆极化,可以减轻由室内多径造成的定位误差。在面积为10. 8 m×6. 6 m、视距(LOS)、复杂多径的室内环境中,当测试信号为20MHz 带宽的WLAN 时,得到的2D 定位平均误差为0. 71 m。与传统的全向线性极化天线(OLPA)相比,BSCPA 可以将定位精度提高52. 5%。该改进表明,所提出的方法可以显著抑制基于TDOA 的室内定位的多径传播。     

Sector antenna and DFE modems for high speed indoor radiocommunications

This paper examines the outage probabilities of BPSK and BPSK/DFE radio modems with omnidirectional and six-sector antennas. The effects of room size, data rate, transmitted power and sector antenna patterns on the performance of the systems are analyzed. A 2-D ray tracing algorithm is used to model the radio propagation in a typical indoor environment used for wireless LAN applications. The parameters of the radio propagation model are adjusted to fit the results of simulations to the results of empirical measurements with omnidirectional antenna. It is shown that in a line-of-sight (LOS) environment, a six-sector antenna is more effective than a DFE with an omnidirectional antenna at eliminating the effects of multipath. For an obstructed-line-of-sight (OLOS) environment where at least one wall exists between the transmitter and the receiver, the DFE is more effective than the six-sector antenna. It is shown that a BPSK/DFE modem with a six-sector antenna can support data rates close to 20 Mbps     

5G毫米波频段不同天线形式信道参数测量及对比分析

基于5G毫米波应用频段,开展了全向天线、喇叭天线以及阵列天线的信道测量与信道参数对比分析研究. 利用空间交替广义期望最大化(space-alternating generalized expectation-maximization, SAGE)算法提取了多径信道参数,包括多径时延、到达角、多径强度等,基于多径分量距离（multipath component distance, MCD）对多径分量进行了分簇结果的对比,对比分析了相同测量点处不同天线形式得到的信道参数差异. 结果表明,同场景下不同天线的信道参数测量结果会有较大差别,全向天线路损指数最小,阵列天线均方根(root-mean-square, RMS)时延扩展和RMS角度扩展均最小,喇叭天线可以得到较多的簇. 本文为5G毫米波频段信道建模提供了不同天线形式信道参数结果对比分析数据.     

Distributed Antennas for Indoor Radio Communications

The idea of implementing an indoor radio communications system serving an entire building from a single central antenna appears to be an attractive proposition. However, based on various indoor propagation measurements of the signal attenuation and the multipath delay spread, such a centralized approach appears to be limited to small buildings and to narrow-band FDMA-type systems with limited reliability and flexibility. In this paper, we present the results of indoor radio propagation measurements of two signal distribution approaches that improve the picture dramatically. In the first, the building is divided into many small cells, each served from an antenna located in its own center, and with adjacent cells operating in different frequency bands. In the second approach, the building is divided into one or more large cells, each served from a distributed antenna system or a "leaky feeder" that winds its way through the hallways. This approach eliminates the frequency cell handoff problem that is bound to exist in the first approach, while still preserving the dramatic reductions in multipath delay spread and signal attenuation compared to a centralized system. For example, the measurements show that, with either approach, the signal attenuation can be reduced by as much as a few tens of decibels and the rms delay spread becomes limited to 20 to 50 us, even in large buildings. This can make possible the implementation of sophisticated broad-band TDMA-type systems that are flexible, robust, and virtually building-independent.     

Direction finding receiver for UWB impulse radio signal in multipath environment

In this paper, we propose a direction finding (DF) receiver for ultra wideband impulse radio (UWB‐IR) signal in a realistic multipath environment. The receiver uses an array of antenna, where each antenna is connected to a proposed propagation‐delay estimation structure. The advantage of the proposed structure is that it outputs a trapezoidal signal whose amplitude reflects the propagation delay and thus relaxes the sampling rate requirement of the analog‐to‐digital‐converter (ADC). The angle‐of‐arrival (AOA) is estimated from the vector of propagation delays measured with respect to reference antenna. Because these estimated delays contain outliers, we propose a simple AOA estimation algorithm based on minimum fractional‐distance search. Experimental results based on simulation show that the proposed DF receiver achieves better performance compared with the minimum ?₁‐ and ?₂‐based (least‐squares based) distance search. Copyright © 2010 John Wiley & Sons, Ltd.     

带漏泄段同轴电缆激励的2GHz无线电波在大型封闭区域内的传播

本文给出了在大型封闭区域,用带漏泄段的同轴电缆作为发射天线时,2GHz窄带和宽带无线电波传播特性的测量结果,对于窄带信号、主要测量了传播过程中的衰减,测量结果表明,在平行于电缆方向上,接收信号的电平比垂直于电缆方向的电平大;接收信号的快衰落服从瑞利分而,而慢衰落不服从正态分布。对于宽带信号,测量了多径脉冲响应,得到了均方根时延扩展及其概率分布。     

辐射模缝隙馈源激励的2GHz无线电波在室内的传播

本文给出了用辐射模缝隙馈源作为发射天线时，2GHz窄带和宽带无线电波在室内传播特性的测量结果。对于窄带信号，主要测量了传播过程中的衰减，测量结果表明，沿缝隙馈源方向，接收信号电平按指数规律衰减，在垂直于电缆方向上，接收信号电平的衰减较慢，损耗指数较小：在平行和垂直于馈源方向上慢衰落基本服从正态分布，而快衰落分别服从Rayleigh和Rician分布。对于宽带信号，测量了多径脉冲相应，得到了均方根时延扩展及其概率分布。     

Joint coding and decision feedback equalization for broadbandwireless channels

This paper introduces a new approach for joint convolutional coding and decision feedback equalization (DPE). To minimize error propagation, the DFE uses a combination of soft decisions and delayed tentative decisions to cancel intersymbol interference (ISI). Soft decisions are obtained by passing the DFE output through a (soft) nonlinear device. This simple method is shown to perform almost as well as an optimum soft feedback approach on wireless channels with diversity. Tentative decisions from the Viterbi decoder are used to cancel ISI due to multipath with large delays, thus remedying the increasing effect of error propagation in channels with large delay spreads. We consider the use of this soft/delayed feedback DFE (S/D-DFE) technique in broadband wireless channels (with delay spreads up to several tens of the symbol period) typical in high-bitrate mobile data applications. Simulation results indicate that the proposed joint coding and S/D-DFE technique performs to within 1-2 dB [in required signal-to-noise ratio (SNR)] of an ideal coded DFE without error propagation. When combined with antenna diversity and a reduced-complexity DFE concept with adaptive feedforward tap assignment, it provides high packet throughput against Rayleigh fading, severe delay spreads, and high Doppler rates     

A novel antenna concept for double-directional channel measurements

In this paper, a novel concept for the characterization of the double-directional mobile radio channel is presented. It is based on a broad-band real-time channel-sounding device together with appropriate antenna arrays, thus forming a multiple-input-multiple-output system. For the propagation measurements within the 5.2-GHz wireless local area network band presented here, a uniform linear antenna array at the receiver site and a switched multibeam antenna at the transmitter site have been employed. By application of the multibeam antenna, the entire azimuthal range of 360/spl deg/ is covered without ambiguities. The measurement data obtained with this platform in a simple synthetic scenario, as well as in a typical multipath environment, is then analyzed in terms of the propagation path properties. Using the three-dimensional estimation of signal parameters via rotational invariance techniques algorithm together with a proper Fourier transform, the channel parameters of all relevant multipaths such as delay, direction of arrival, direction of departure, and path loss are extracted from the measurement data. For both scenarios, the obtained estimated paths are verified to the underlying physical propagation environment by means of geometrical considerations. This geometrical matching accounts for multipath components due to single-bounce as well as multiple-bounce reflections and demonstrates the high suitability and good performance of the proposed concept.     

Ultrawideband Antenna Distortion Compensation

The radiation characteristics of ultrawideband (UWB) antennas vary with frequency, introducing directionally asymmetric bandwidth reduction and waveform dispersion. In this paper, we develop a simple technique to alleviate the distortion due to nonisotropically dispersive antennas, and use indoor channel measurements to verify its performance. The approach is based on multipath direction estimation and therefore involves antenna arrays. We show that antenna distortion can enhance sensor localization ambiguity and introduce errors in its estimate. Antenna compensation mitigates this effect, significantly improving the location estimation accuracy. We further demonstrate that antenna compensation helps reduce the small-scale fading artifacts that arise due to the antennas, thus reducing the channel spatial variability and delay spread. Our technique can also aid empirical channel characterization by providing antenna-independent propagation data.      

910 MHz urban mobile radio propagation: Multipath characteristics in New York city

Small scale statistics of multipath propagation in a heavily built-up urban mobile radio environment are presented. The statistics cover vehicle travel distances on the order of 30 m along streets. Measuring equipment time delay resolution is about 0.1 µs. In some locations, paths with significant amplitudes are observed with excess delays of 9 to 10 µs. The delay spreads (√second central moment of power delay profile) in this environment are on the order of 2 µs. Often the signal at fixed delays has a Rayleigh-distributed amplitude but large departures from the Rayleigh distribution also occur. From the measurements it appears reasonable to model the urban mobile radio channel as a Gaussian quasi-wide-sense stationary uncorrelated scattering channel within a bandwidth of 10 MHz and for intervals along the street of up to 30 m.     

910 MHz Urban Mobile Radio Propagation: Multipath Characteristics in New York City

Small scale statistics of multipath propagation in a heavily built-up urban mobile radio environment are presented. The statistics cover vehicle travel distances on the order of 30 m along streets. Measuring equipment time delay resolution is about 0.1 μs. In some locations, paths with significant amplitudes are observed with excess delays of 9 to 10 μs. The delay spreads (sqrt{second central moment of power delay profile}) in this environment are on the order of 2 μs. Often the signal at fixed delays has a Rayleighdistributed amplitude but large departures from the Rayleigh distribution also occur. From the measurements it appears reasonable to model the urban mobile radio channel as a Gaussian quasi-wide-sense stationary uncorrelated scattering channel within a bandwidth of 10 MHz and for intervals along the street of up to 30 m.     

Impulse response modeling of indoor radio propagation channels

If indoor radio propagation channels are modeled as linear filters, they can be characterized by reporting the parameters of their equivalent impulse response functions. The measurement and modeling of estimates for such functions in two different office buildings are reported. The resulting data base consists of 12000 impulse response estimates of the channel that were obtained by inverse Fourier transforming of the channel's transfer functions. It is shown that the number of multipath components in each impulse response estimate is a normally-distributed random variable with a mean value that increases with increasing antenna separations; a modified Poisson distribution shows a good fit to the arrival time of the multipath components; amplitudes are lognormally distributed over both local and global areas, with a log-mean value that decreases almost linearly with increasing excess delay; for small displacements of the receiving antenna, the amplitude of the multipath components are correlated; the amplitudes of adjacent multipath components of the same impulse response function show negligible correlations; and the RMS delay spread over large areas is normally distributed with mean values that increase with increasing antenna separation     

Joint angle and delay estimation (JADE) for multipath signalsarriving at an antenna array

In wireless communications, mobiles emit signals that arrive at a base station via multiple paths. Estimating each path's angle-of-arrival (AOA) and propagation delay is necessary for several applications, such as mobile localization for emergency services. We propose a novel subspace approach to estimate the AOA and delays of multipath signals from digitally modulated sources arriving at an antenna array. Our method uses a collection of estimates of a space-time vector channel. The Cramer-Rao bound (CRB) and simulations are provided     

Estimation of multipath parameters in wireless communications

In a parametric multipath propagation model, a source is received by an antenna array via a number of rays, each described by an arrival angle, a delay, and a fading parameter. Unlike the fading, the angles and delays are stationary over long time intervals. This fact is exploited in a new subspace-based high-resolution method for simultaneous estimation of the angle/delay parameters from multiple estimates of the channel impulse response. A computationally expensive optimization search can be avoided by using an ESPRIT-like algorithm. Finally, we investigate certain resolution issues that take the fact that the source is bandlimited into account     

一种抑制多径影响的全向高增益天线

为抑制机载异形地板多径效应对天线方向图的影响,本文提出了一种抑制多径影响的全向高增益垂直极化天线.该天线由四个对称分布的蝶形电偶极子单元构成,阵子臂采用渐变结构来展宽带宽.蝶形电偶极子依次布置于微带地板走线两侧,可优化水平面方向图不圆度.设置四个垂直分布的蝶形电偶极子的馈电相位来降低天线方向图的打地电平,进而抑制地板多径效应的影响.通过理论分析及电磁仿真计算,确定了天线的最优结构以及单元馈电相位差,并进行了实物加工和测量.实测结果表明,在约束尺寸下四单元相位差为25°时能够有效抑制由y轴长地板引起的多径零深,实测与仿真结果吻合较好.该天线的提出为安装于异形地板上的高增益天线阵提供了一种抑制多径影响的方案.     

A random matrix model of communication via antenna arrays

A random matrix model is introduced that probabilistically describes the spatial and temporal multipath propagation between a transmitting and receiving antenna array with a limited number of scatterers for mobile radio and indoor environments. The model characterizes the channel by its richness delay profile which gives the number of scattering objects as a function of the path delay. Each delay is assigned the eigenvalue distribution of a random matrix that depends on the number of scatterers, receiving antennas, and transmitting antennas. The model allows one to calculate signal-to-interference-and-noise ratios (SINRs) and channel capacities for large antenna arrays analytically and quantifies to what extent rich scattering improves performance.