Unified approach to prediction of propagation over buildings forall ranges of base station antenna height

Theoretical results for the dependence on base station antenna height of the average received signal for mobiles at street level are presented. The results apply to residential and commercial sections of cities and to all ranges of antenna height from well above to below that of the surrounding buildings. Assuming all buildings to be of equal heights, the range dependence of the average signal is found by evaluating multiple forward diffraction past rows of buildings. The solution for this diffraction problem for sources near to or below the rooftops gives the dependence of the range index on antenna height and base station height gain, which are in agreement with measurements. These results will be of importance for proposed systems for personal communication services, which envision the use of base station antennas at the height of lamp posts, as well as cellular mobile radio     

A theoretical model of UHF propagation in urban environments

The development is given of a model in which the rows or blocks of buildings are viewed as diffracting cylinders lying on the earth. When the buildings are represented as absorbing screens, the propagation process reduces to multiple forward diffraction past a series of screens. Numerical computation of the diffraction effect yields a power-law dependence for the field that is within the measured range. Accounting for diffraction down to street level from the roof tops gives an overall absolute path loss in good agreement with the average measured path loss     

Prediction of loss characteristics in built-up areas with variousbuildings' overlay profiles

We continue the analysis of a probabilistic approach and the corresponding stochastic multi-parametric model of wave propagation in built-up areas with randomly distributed buildings. We concentrate on the influence of buildings' overlay profiles on signal spatial decay, and on path-loss dependence in the frequency domain within UHF/X-band urban propagation channels. Using different buildings' overlay profiles, the field-intensity attenuation along radio paths is examined, taking into account single-scattering and multiple-scattering phenomena, and diffraction from buildings' corners and rooftops, for various positions of receiver and transmitter antennas with respect to surrounding obstacles. The comparison between experimental and theoretical predictions was motivated by the proposed stochastic multi-parametric model and the experimental data obtained for actual areas in Jerusalem (Israel) and Lisbon (Portugal), as well as by other models of multiple diffraction. The discussion is presented for realistic elevations of both terminal antennas to assess the accuracy and limits of the proposed stochastic model. A sensitivity analysis of the influence on the path loss of built-up terrain parameters and the elevation of antennas relative to the buildings surrounding them is presented     

UHF propagation prediction for wireless personal communications

Propagation characteristics of radio signals in the UHF band place fundamental limits on the design and performance of wireless personal communications systems, such as cellular mobile radio (CMR), wireless LANs, and personal communication services (PCS). Because the radio link is direct to each subscriber, the prediction of signal characteristics is most important in urban areas where subscriber density is high, and the buildings have a profound influence on the propagation. The paper starts by reviewing the characteristic signal variations observed in CMR systems employing high base station antennas to cover macrocells having radius out to 20 km. Theoretical models incorporating diffraction are shown to explain the observed range dependence and shadow loss statistics. For the low base station antennas envisioned to cover microcells of radius out to 1 km for PCS applications, signal propagation is more strongly dependent on the building environment and on the location of the antennas in relation to the buildings. Various levels of theoretical modeling of this dependence are discussed in conjunction with measurements made in various building environments. Finally, the paper discusses advances in site specific prediction for outdoor and indoor propagation     

Prediction of cellular characteristics for various urbanenvironments

The propagation channel for UHF/X-band waves in the city is modeled for two typical cases in the urban scene: (a) by regularly distributed rows of buildings placed on a flat terrain; and (b) by an array of randomly distributed buildings placed on rough terrain. The law of distribution of buildings in both cases is assumed to be Poisson. The loss characteristics in such urban propagation channels, as well as the co-channel interference parameter, the carrier-to-interference ratio (C/I), are investigated. In case (a), the three-dimensional multi-slit waveguide model is used for LOS conditions, and the two-dimensional multi-diffraction model is used for NLOS conditions. In case (b), the statistical parametric model of wave propagation is used, including single and multiple scattering effects, diffraction from buildings' roofs, the actual built-up relief, and various positions of receiver and transmitter antennas on rough terrain. The full algorithm for predicting propagation and cellular characteristics to increase the accuracy of radio and cellular maps is presented     

Mechanisms governing propagation between different floors inbuildings

The potential implementation of wireless radio local area networks (LANs) and personal communication services inside buildings requires a thorough understanding of signal propagation within buildings. In this work the authors develop a theory which explains propagation between a transmitter and a receiver located on different floors of a building. Depending on the structure of the building and the location of the antennas, either direct ray propagation through floors or diffraction outside the building will determine the propagation characteristics and range dependence of the signal sector average as the number of floors between the transmitter and the receiver is increased     

Analysis of the influence of building modelling in the prediction of over-rooftop multiple diffraction losses in urban areas

A study of the influence of building modelling when predicting the signal attenuation due to over-rooftop multiple diffraction in urban environments is presented. A straightforward formulation expressed in terms of Uniform Theory of Diffraction (UTD) coefficients is used for the above-mentioned analysis assuming a spherical-wave incidence over the array of buildings and considering the latter modelled as series of different representations such as knife edges, double knife edges, wedges and rectangular sections. The results clearly indicate the importance of an appropriate building modelling in obtaining realistic path-loss predictions in urban environments when multiple diffraction has to be considered.     

A propagation model for urban microcellular systems at the UHF band

This paper presents a new propagation model for urban environments, which takes into account propagation over buildings and inside streets. The formulation for multiple diffraction loss over rooftops results from a combination of the Vogler (1982) and Xia and Bertoni (1992) models, which enables its application to profiles of buildings with nonuniform heights and spacings, keeping the calculation time low. A ray-tracing tool based on the image method and on the uniform theory of diffraction (UTD) has been developed to estimate the attenuation inside streets; loss introduced by vegetation is also accounted for. The results obtained with the application of the model to two areas of Lisbon show the importance of rays conducted by transversal streets and diffracted by vertical edges when predicting the signal near crossroads. Average values of 3.5 dB, -0.07 dB, and 2.6 dB were obtained for the mean absolute and relative errors and for the standard deviation error, respectively     

Prediction of mobile radio wave propagation over buildings ofirregular heights and spacings

Two models of mobile radio wave propagation over buildings are presented. The first, the flat edge model, provides a simple yet accurate representation when buildings are assumed to be of constant height and spacing. The second model combines the first with a rapid new method of calculating multiple edge diffraction to allow deterministic predictions with arbitrary buildings and spacings. This allows predictions to be made with real building data, and the effect of building variations on location variability of the received signal to be assessed. Both models are compared with measurements made in suburban areas in the 900 and 1800 MHz bands and excellent agreement is obtained     

Effects of buildings and trees on satellite mobile communications

A propagation model for lossy building with tree attenuation in urban and residential areas is developed for satellite mobile communications. This model is used to characterize the signal transmitted from medium earth orbit (MEO) satellite when there are buildings and trees in the path of the signal. The analysis is performed using the uniform theory of diffraction (UTD). The tree attenuation is evaluated through the modified exponential decay model (MED).

The normalized signal level and signal attenuation rate are computed. Such information is useful in developing the mobile system's hand-off algorithm. In narrowband systems, the propagation attenuation and fading statistics are the main causes of signal degradation. So, the probability of error is calculated with and without the existence of the tree. Also the axial ratio (AR) is computed as function of satellite elevation angle. In wide band systems, the delay-spread is dominant because of the inter-symbol interference. For such case, the coherence bandwidth and impulse response are computed. Along with that, computed results are compared with actual measured data.     

Propagation prediction in and through buildings

The potential implementation of wireless radio local area networks and personal communication services inside buildings require a thorough understanding of signal propagation in a building. In this paper, an in-building prediction is presented. This prediction model focuses on a single floor of a building, but is applicable to different floors of the building. This model is also applicable to the through-building propagation loss by applying the same principle. The validation of this model was done in two different buildings of similar construction in the 900-MHz band. A special feature of this model is its capability to handle different types of obstructions. The model is validated by gathering the measured values for a specific floor of a building and comparing them with the predicted values. The standard deviation for measured versus predicted signal is within 3 dB     

Modeling tree effects on path loss in a residential environment

A theoretical model is proposed to compute the path loss in a vegetated residential environment, with particular application to mobile radio systems. As in the past, rows of houses or blocks of buildings are viewed as diffracting cylinders lying on the Earth and the canopy of the trees is located adjacent to and above the houses/buildings. In this approach, a row of houses or buildings is represented by an absorbing screen and the adjacent canopy of trees by a partially absorbing phase screen. The phase-screen properties are found by finding the mean field in the canopy of the tree. Physical optics (PO) is then used to evaluate the diffracting field at the receiver level by using a multiple Kirchhoff-Huygens integration for each absorbing/phase half-screen combination     

A Journey from Traditional to Machine Learnig of Radio Wave Attenuation Caused by Rain: A State of Art

Given the massive rapid growth for capacity in wireless data telecommunications every year, wireless carriers must be planned for a thousand-fold increase in mobile traffic in 2020. It compels scientists to explore for new wireless airwaves that can accommodate large data rates. Next-generation technologies must address issues such as increased spectrum allocation in millimetre wave frequency bands, the installation of directional antennas beam forming antennas, better battery life, high data transmission rates with reduced outage probability, lower capital costs, and increased capacity for multiple simultaneous users. There are two types of telecommunication links: terrestrial and satellite. Terrestrial links are also known as radio relay links. This connects the troposphere, which is located between the earth’s surface and the high atmosphere, to the propagation of radio waves. Gases, water vapour, and other weather phenomena such as rain, storms, snow, and hail all interfere with higher frequency radio signals in this region. Due to these difficulties, energy is absorbed and diffused, resulting in signal attenuation. Another form of obstruction generated by radio waves on terrestrial paths is buildings, trees, lampposts, grill, and other urban features. Under these conditions, reflection, diffraction, refraction, scattering, depolarization, and other phenomena are studied. This study discusses the effects of rain on satellite and terrestrial communications.

     

Comparative study of lateral profile knife-edge diffraction and raytracing technique using GTD in urban environment

In an urban environment, radio wave interaction with buildings may affect considerably the propagation of radio waves, mainly because of multipath, diffraction, and shadowing effects. This paper outlines the effect of two-dimensional (2-D) (vertical and lateral) diffraction and compares a Fresnel-Kirchhoff scalar approach to a vectorial geometrical theory of diffraction (GTD) approach applied to a four-ray system. The former can be considered as a generalization of conventional knife-edge diffraction theory while the latter (GTD) is useful in the context of ray tracing. A very good agreement between the Fresnel-Kirchhoff and GTD results is found within the limits of validity of both methods. Moreover, it is shown that conventional knife-edge diffraction theory can largely overestimate attenuation (10-15 dB) behind tall buildings in the center of a city environment. Different frequency bands have been tested for the sake of comparison, and emphasis has been put on the radio communications frequency bands used for the global system for mobile communications (GSM) and DCS/DECT systems at 900 and 1800 MHz     

An indoor radio propagation model considering angles for WLAN infrastructures

Wireless local area network fingerprint‐based indoor location system is a hot topic these years because it needs no extra hardware and is very easy to deploy. However, it demands a database containing the distribution of received signal strength (RSS) of the area of interest,called radio map. Conventionally, we need to grid the area densely and manually measure RSS values on intersections, which will consume a lot of time and human resources. What is worse, change of the environment may render this database totally useless. Our consideration is to measure RSS on a small amount of these intersections and use them to build a radio propagation model. Then, this model can be deployed to predict RSS values of other intersections and reconstruct the radio map. In other words, we only need to collect a very small part the radio map and utilize the radio propagation model to recover the whole one. So far, many models have been proposed, among which the one suggested by Seidel, named floor attenuation factor propagation model, achieves great balance between computational request and accuracy. But it is not compatible with environments in some scenarios. So as to compensate for this deficiency, we take into account the angles formed by signal and surfaces of obstacles, and the results show better compatibility. The proposed model has four parameters that are related to the environments, and our second contribution in this paper is to propose a method to determine them. In fact, after collecting a small part of the radio map, we can estimate these parameters with least square method. Then, these parameters can be used to predict the signal strength at any other points in the same environment, and the whole radio map is rebuilt. According to practical experiments, performance of the radio map built by the proposed model is not as good as the manually collected one, but 80% of collecting labor is saved. Copyright © 2015 John Wiley & Sons, Ltd.     

A measurement system for ultrawide-band communication channel characterization

In this paper a novel wide-band propagation channel measurement system with high dynamic range and sensitivity is introduced. The system enables the user to characterize signal propagation through a medium over a very wide frequency band with fine spectral resolution (as low as 3 Hz) by measuring the attenuation and phase characteristics of the medium. This system also allows for the study of temporal, spectral and spatial decorrelation. The high fidelity data gathered with this system can also be utilized to develop empirical models or used as a validation tool for physics based propagation models which simulate the behavior of radio waves in different environments such as forests, urban areas or indoor environments. The mobility and flexibility of the system allows for site specific measurements in various propagation scenarios.     

A Packet-Level Model for UWB Channel with People Shadowing Process Based on Angular Spectrum Analysis

Ultra-wideband (UWB) wireless communication technologies have been proposed to support high data rate multimedia services in office or residential environments. Due to the low transmission power of UWB, the shadowing effect by moving people can considerably reduce the received signal quality and thus significantly degrade the quality of service (QoS) of on-going transmissions. An open issue is to build a simple model which captures the temporal variation of UWB channels and the packet error rate (PER) due to the people shadowing effect (PSE), which will be a useful tool for upper layer protocol performance analysis and simulation. This paper presents an analytical study of the PSE and the temporal variation of UWB channels induced by the motion of a person. First, we derive the angular power spectral density (APSD) of the indoor UWB channel impulse response (CIR), and the PSE in terms of signal power attenuation. Second, based on a two-dimensional random walk mobility model, the PER variation due to people shadowing is modeled as a finite-state Markov chain (FSMC). The investigation of APSD provides important insights on the spatial propagation characteristics of UWB signals. The proposed packet-level channel model can be conveniently incorporated into analytical frameworks and simulation tools for evaluating upperlayer protocols of UWB networks.     

An SBR/image approach for radio wave propagation in indoorenvironments with metallic furniture

In this paper, we propose a deterministic approach to model the radio wave propagation channels in complex indoor environments. This technique applies the modified shooting-and-bouncing-ray (SBR) method to find the equivalent sources (images) for each launched ray tube. In addition, the first-order wedge diffraction from furniture is included and the diffracted rays also can be attributed to the corresponding images. By summing the contributions of all these images coherently, we can obtain the total received field at a receiver. Besides, the vector-effective height (VEH) of an antenna is introduced to consider the polarization coupling effect resulting from multiple reflection inside the rooms. We verify this approach by comparing the numerical results in three canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside rooms where multiple reflection is dominant. Work reported in this paper has shown that the propagation loss in indoor environments varies considerably according to furniture and polarizations     

预测毫米波雾衰减的抛物方程模型研究

雾是影响毫米波通信系统性能的典型气象条件之一.针对传统经验模型无法精确预测多径效应下的电波传播问题,给出了基于抛物方程的雾衰减预测模型.以自由空间雾特征衰减的预测为例,将本文模型与Rayleigh近似及经验模型的计算结果进行对比,验证了该方法的可靠性.最后将该模型应用于预测35 GHz和94 GHz毫米波在分别含有平流雾和辐射雾的复杂环境中的传播特性,仿真结果表明该模型有效地反映了地形绕射、地表反射等对电波传播的影响,为快速准确地预测复杂地理环境及特殊气象条件中的电波传播特性提供了一种有效的预测模型.     

A theory for propagation path-loss characteristics in a city-streetgrid

Presents a new propagation model for micro-cellular communications in an urban scene in which the buildings and streets form a rectangular grid. The model is a quasi-three-dimensional one in the sense that the building walls are assumed to be much higher than the transmitter height so that the diffractions from the rooftops can be neglected. It is based on the uniform theory of diffraction (UTD) and takes into account multiple reflections between wall-to-wall, wall-to-ground and ground-to-wall, as well as the diffraction from corners of buildings and also subsequent reflections from such diffracted signals. These multiple reflections and diffraction result in an extremely complex problem of tracking the wave or ray propagation. The authors use the concept of multiple images and the generalized Fermat's principle to facilitate the location of each point of reflection in a wall or ground or a point of diffraction at an edge, and to determine which of the multiply scattered rays will reach the receiver at a line-of-sight (LOS) or out-of-sight (OOS) position. The signal path loss along the LOS street, OOS side streets, as well as a street which runs parallel to the LOS street, are calculated and the general features and trends of the propagation characteristics are highlighted. Calculations are also done to study the profile of the signal distribution across a street width at various points in a OOS street