Multipath propagation model for line-of-sight street microcells inurban area

This paper proposes a multipath propagation model for line-of-sight (LOS) street microcells with building roof base sites (BS) in urban areas, Multipath propagation characteristics are of great importance in evaluating the performance of digital systems and designing wireless links. Typical delay profiles are measured to clarify their statistical characteristics in LOS street microcells. The channel sounder used is a sliding correlator with 30-Mb/s PN code and a center frequency of 2.6 GHz. The measurements clarify the features of delay profile and mean RMS delay spread. The proposed delay profile model explains one plausible mechanism of multipath propagation. The delay profiles calculated using the model agreed well with the measured profiles. Furthermore, the factors influencing the RMSs delay spread are investigated, and the regression equation of medium RMS delay spread on a sidewalk is established. The proposed model can evaluate the transmission characteristics of wireless digital communication systems in multipath propagation environments     

基于改进射线跟踪法和BP神经网络算法的室外微蜂窝毫米波信道特性研究

在28 GHz与39 GHz毫米波频段室外微蜂窝场景下,基于改进射线跟踪法和反向传播(back propagation, BP)神经网络算法对毫米波单发单收信道及单发多收信道进行建模仿真研究. 在得到的无线信道仿真数据基础上,研究分析了毫米波信道的路径损耗、均方根(root-mean-square, RMS)时延扩展(delay spread, DS)、接收功率等传播特性. 通过与现有文献的测量结果对比分析验证了改进射线跟踪法的正确性与有效性. 通过BP神经网络方法拟合得到的路径损耗模型参数结果与改进射线跟踪法仿真得到的路径损耗参数结果对比发现,两者吻合程度很高,验证了BP神经网络算法能很好地对室外微蜂窝毫米波信道大尺度参数进行预测. 同时,文中给出了一种普遍适用的用来表征室外微蜂窝视距(line-of-sight, LoS)与非视距(non-line-of-sight, NLoS)场景下28 GHz与39 GHz毫米波信道的路径损耗模型. 结果表明:LoS场景下的RMS DS和接收功率都小于NLoS场景下得到的结果;LoS场景与NLoS场景下RMS DS、水平方向到达角、多径簇的个数累积分布函数均服从高斯分布;RMS DS在毫米波频段微蜂窝场景下,随着频率的升高而增大,到达接收端的多径成簇呈现稀疏性.     

Millimeter-Wave Propagation Channel Characterization for Short-Range Wireless Communications

This paper presents and analyzes the results of millimeter-wave 60-GHz frequency range propagation channel measurements that are performed in various indoor environments for continuous-route and direction-of-arrival (DOA) measurement campaigns. The statistical parameters of the propagation channel, such as the number of paths, the RMS delay spread, the path loss, and the shadowing, are inspected. Moreover, the interdependencies of different characteristics of the multipath channel are also investigated. A linear relationship between the number of paths and the delay spread is found, negative cross correlation between the shadow fading and the delay spread can be established, and an upper bound exponential model of the delay spread and the path loss is developed to estimate the worst case of the RMS delay spread at given path loss. Based on the DOA measurements that are carried out in a room [line of sight (LOS)] and in a corridor with both LOS and nonline-of-sight (NLOS) scenarios, radio-wave propagation mechanisms are studied. It is found that considering the direct wave and the first-order reflected waves from smooth surfaces is sufficient in the LOS cases. Transmission loss is very high; however, diffraction is found to be a significant propagation mechanism in NLOS propagation environments. The results can be used for the design of 60-GHz radio systems in short-range wireless applications.     

Indoor radiated-mode leaky feeder propagation at 2.0 GHz

This paper presents the results of narrow-band and wide-band propagation measurements carried out at 2.0 GHz in an indoor environment using a radiated-mode leaky feeder as the transmitting antenna. The narrow-band measurements were devised to measure attenuation of radio signals and the wide-band techniques to measure multipath impulse responses and their associated root mean square (RMS) delay spread. Analysis of the narrow-band data files shows that the received signal levels in the direction along the feeder generally decay exponentially due to the feeder-specific attenuation. The received signal levels in the direction radial to the feeder decrease slowly, and the distance-power law exponent is found to be smaller than one. The slow and fast variations of the received signal levels are also examined. The results reveal that the slow variations basically follow the log-normal distribution, while the fast variations fit the Rayleigh distribution in the direction parallel to the feeder and the Rician distribution in the direction radial to the feeder, respectively. Analysis of the wide-band data files reveals that the maximum value of the RMS delay spread is 60.6 ns and the RMS delay spread values are less than 42 ns 50% of the time. One therefore can conclude that the indoor channel excited by the radiated-mode leaky feeder has a broad coherent band-width and can support a data rate of up to 3.3 Mb/s without equalization     

RMS Delay Spread Assessment for Indoor UWB Propagation Channels

Wireless Personal Communications - The RMS delay spread is often used to quantify the probability of inter-symbol interference in a propagation channel. A novel and straightforward procedure to...     

A ray-tracing propagation model for digital broadcast systems inurban areas

A propagation model is presented for characterizing the channel response for digital systems in urban areas where multiple reflections from buildings are encountered. A deterministic ray-tracing propagation model is used to predict the time delay and fading characteristics for the channel in a hypothetical urban area. The analysis shows that due to multiple reflection and diffraction sources, the RMS delay spread of the channel in urban areas can be several hundred nanoseconds, so that very effective equalizers will be required to achieve successful performance of high-data-rate digital systems such as 20-Mb 16-QAM digital HDTV. The channel response results presented also suggest that polarization diversity may be a useful technique for mitigating some of the channel impairments predicted by the propagation model     

Path loss and delay spread for the stairwell channel at 5 GHz

Measured channel characterization results are provided for six stairwells in the 5‐GHz band, for two distinct stairwell types and two antenna polarizations. The stairwell channel is of interest for several applications, including Wi‐Fi and public safety. Although other authors have reported stairwell path loss for other frequency bands (900 MHz, 2.4, 5.8 GHz), to our knowledge, ours is the first work at 5 GHz. More significantly, we report on floor attenuation factors and delay spread, which prior work has not thoroughly addressed. We measured power delay profiles and from these estimated propagation path loss and root‐mean square delay spread (RMS‐DS). Path loss exponents were between 5.5 and 8.3, and vertically polarized monopoles yield larger path loss and path loss exponents than horizontal polarization. Mean RMS‐DS values ranged from 15 to 57 ns for link distances covering up to three flights of stairs. Copyright © 2015 John Wiley & Sons, Ltd.     

A model for predicting the power delay profile characteristicsinside a room

Multipath effects in indoor wireless communication systems exhibit a characteristic power delay profile (PDP) and can be a detriment to the system's performance. We present a simplified model for calculating the decay rate of the PDP for propagation within rooms. This simplified model provides a time-efficient means of predicting system performance. Predictions of this in-room PDP model are compared to results obtained from a finite-difference time-domain (FDTD) model. Additionally, comparisons of the IPDP model to measured data are presented. The RMS delay spread is the second central moment of the PDP of a propagation channel and is a measure of the communication link degradation due to multipath. We also show results of the estimated RMS delay spread from this model and show comparisons to the measured data. This IPDP model can be used to investigate the effects of variable room size and properties of the surfaces (or walls) on the decay characteristics of the PDP     

Simulating radio channel statistics for different buildingenvironments

The design of advanced radio systems requires knowledge of higher order channel statistics, such as the time delay spread and the angle of arrival spread. Time delay has been measured in a number of cities, while angle of arrival has been measured in only a few. Since the link geometry is not the same for all measurements, it is not clear how to compare the measured values, or if they are applicable to other building environments, antenna height, etc. To clarify these issues, we have used a three-dimensional ray tracing code, called the vertical plane launch (VPL) method, to simulate time delay spread and angle of arrival spread in different building environments. Results for elevated base station antennas show that the distribution of root mean square (RMS) delay spreads is not sensitive to the statistical properties of the buildings but increases with distance to the mobiles and increases as the base antenna is lowered below the rooftops. In contrast, the distribution of RMS angle spread is sensitive to the distribution of building heights and to the height of the base station antenna but not to the distance to the mobile. The influence of street geometry on delay and angle spread for low base station antennas is also discussed     

A microcellular ray-tracing propagation model and evaluation of itsnarrow-band and wide-band predictions

Due to the site specific nature of microcellular operational environments, propagation models are required to take into account the exact position, orientation and electrical properties of individual buildings, and hence, ray-tracing techniques have emerged as the dominant methods to predict propagation in such environments. A novel hybrid three-dimensional (3-D) ray-tracing algorithm which can evaluate scenarios incorporating many thousands of objects by utilising the concept of “illumination zones,” is presented. In order to evaluate the accuracy of the presented model, comparisons of narrow-band and wide-band predictions with measurements are performed for a variety of scenarios. First, power comparisons show that very accurate predictions can be achieved (RMS errors less than 3.7 dB). Then, wide-band analysis shows that since the RMS delay spread for systems with finite bandwidth is a function of the multipath phase, only average measured and predicted RMS delay spread values can be compared and as a result, limited averaging can produce large RMS errors. With sufficient averaging the achieved wide-band accuracy in terms of the predicted RMS delay spread, is adequate for most planning purposes     

Path loss, scattering and multipath delay statistics in fourEuropean cities for digital cellular and microcellular radiotelephone

The authors present typical and worst-case root mean square (RMS) delay spreads and excess delay spreads (10 dB) and mean channel path loss at 900 MHz in four European cities using typical cellular and microcellular antenna locations. Several thousand power delay profile measurements were made at six typical cellular and microcellular base station locations in the four cities. The data were obtained at local worst-case time-dispersion locations over hundreds of kilometers of typical operating routes, such as highways, bridges, and city streets, and form the basis for statistical models which can be used to predict the percentage of locations or the percentage of time in which channels will possess particular values of RMS delay spread and excess delay spread. The effect of reference distance on wideband path loss and the propagation path loss laws for cellular and microcellular radio channels are given. Radar cross sections computed from the data for typical scatterers in cellular and microcellular radio channels are given     

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.     

Statistical AR models for the frequency selective indoor radio channel

A statistical model of the indoor radio channel is proposed that is derived from a second order autoregressive process representation of the channel frequency response. The accuracy of the statistical model is examined by comparing the cumulative distribution functions of the RMS delay spread and the 3 dB width of the frequency correlation function computed from the regenerated data with that of the measurements performed in two indoor radio propagation studies in the 0.9-1.1 GHz band.<>     

室内环境下2.6GHz同时同频全双工自干扰信道测量与建模

目前,对同时同频全双工的自干扰信道特性尚未进行研究.针对这一现状,采用基于网络分析仪的信道测量平台,对室内环境下2.6GHz同时同频全双工自干扰信道特性进行测量与分析.基于实测数据统计分析,得出了传输损耗模型与均方根时延扩展统计模型.结果表明：传输损耗服从断点损耗模型,天线间距在大于1m的传输损耗指数为1.86,天线间距小于1m的传输损耗指数为1.52;均方根时延扩展的统计特性随着天线间距在不同范围而不同,在天线间距大于1m时的均方时延扩展服从lognormal分布,在天线间距小于1m时,RMS时延扩展在不同的天线间距下服从lognormal分布,并且其分布的均值与标准差与天线间距呈现线性关系.     

Delay Spread Statistics in a Two-Path Distributed Antenna System with Gamma-Lognormal Fading Channels

This letter analyzes the statistical properties of the root-mean-square (RMS) delay spread in a two-path distributed antenna system, where the received signal power from each path is subject to composite gamma fading and lognormal shadowing. The channel power delay profile considered consists of two delta functions with correlated power levels. We present analytical expressions for the probability density function of the RMS delay spread, as well as the cumulative distribution function, mean value and standard deviation. These analyses are validated through comparison with Monte-Carlo simulation results.     

Gaussian beam launching for 3D physical modeling of propagation channels

Gaussian beam launching is proposed as an alternative to ray-based techniques for propagation channel modeling, and it is implemented and validated in the context of indoor propagation. A rigorous Gabor frame decomposition of source fields is used to represent a radiated field as a superposition of shifted and rotated Gaussian beams, conveniently expressed as complex rays. Beam tracking through multiple reflections and transmissions is straightforward, and fields can then be evaluated by summation of closed form expressions. The parameters of a given transformed Gaussian beam have to be calculated only once for all observation points, leading to easy implementation, and computationally efficient algorithms. Simulations of amplitude–delay profiles, mean excess delay, and RMS delay spread are performed in an indoor environment at 60 GHz and compared to measured and published results.     

A comparison of two radio propagation channel impulse responsedetermination techniques

A comparison of two radio propagation channel impulse response determination techniques is described. Presented are typical impulse response and transfer functions obtained from each measurement system. Also included for comparison are average impulse response envelopes and cumulative probability distributions for the RMS delay spread of static indoor radio channels calculated from 120 measurements using each system. The comparisons show good agreement between results     

Empirical characterization of wideband indoor radio channel at 5.3GHz

Characteristics of wideband indoor radio channel at 5.3 GHz were defined based on an extensive measurement campaign using a wideband channel sounder with 19 ns delay resolution. Pathloss exponents were 1.3-1.5 in LOS and 2.9-4.8 in non-line of sight (NLOS). Large difference in NLOS exponents was due to different dominating propagation mechanisms in different types of building structures. The delay dispersion was characterized by cumulative distribution functions (CDF) of the RMS delay spreads, the values for CDF=0.9 varied from 20 to 180 ns in different setups in an office building and large hall environments. The correlation functions of the radio channel in spatial and frequency domains were extracted. Small scale models for five typical indoor scenarios were developed using tapped delay lines     

Top-down random channel generator for the narrowband power line communication

This paper proposes a random channel generator for the narrowband power line communication (PLC). Based on the top-down approach, an analytical formulation with a limited set of parameters is established for the PLC channel transfer function in the frequency band below 500 kHz. Then, the extracted parameters deduced from measurements are fitted with proper distribution functions. The top-down random channel generator is validated through the comparison between measured and generated channels in terms of time–frequency characterization metrics, especially the average channel attenuation, the root mean square (RMS) delay spread and the coherence bandwidth. Obtained results show the good agreement between the proposed modeled channels and the experimental ones with very close mean values and distributions of the main metrics.     

Wideband indoor channel characterisation using microstrip patchantennas at 1.95 GHz with different antenna height configurations

Results highlighting the improvement in power loss factor n, RMS delay spread and correlation with distance of the indoor channel employing microstrip patch antennas mounted in an optimised height configuration are presented. Extensive power delay profile measurements with four different antenna height configurations in two laboratory environments were conducted using a vector network analyser at 1.95 GHz. Analysis of the measurement results shows improvement of n values from 2.9 to 2 and median RMS delay spread of 10.4 ns to 6.2 ns with changes of antenna configuration