UHF radio propagation characteristics in straight open-groovestructures

The imperfect waveguide method is used to study UHF radio propagation characteristics in open-groove structures with particular interest being devoted to the frequency characteristics of the propagation attenuation constant. Attenuation of propagation has been characterized by the surrounding media absorption, the roughness of the sidewall, and the sidewall tilt. Our study shows that attenuation due to the surrounding media absorption is inversely proportional to the square of the frequency, whereas that due to the roughness on the sidewall surfaces is inversely proportional to the frequency and that due to the sidewall tilt is directly proportional to the frequency. The imperfectness of the actual open groove structures will cause additional electromagnetic mode conversion, thus increasing the propagation loss. The theoretical results are in agreement with the experimental data     

Mobile in-home UHF radio propagation for short-range devices

In-home propagation measurements, in the frequency range of 400, 860, and 2400 MHz, are evaluated for single, narrow-band applications of one-way domestic mobile alarm systems. In particular, the influence of multipath effects is investigated     

A measured delay-Doppler scattering function for multipath propagation at 910 MHz in an urban mobile radio environment

A delay-Doppler scattering function is presented for multipath propagation at 910 MHz from a vertical antenna 120 m above a street to a mobile vehicle on another street. The direct path between the transmitting antenna and the mobile vehicle was blocked by many tall (over 100 m) buildings. Major features of the scattering function correspond to gross features of the area.     

An experimental study of the propagation of 55 GHz millimeter wavesin an urban mobile radio environment

An experimental study of the propagation of 55 GHz millimeter waves between a fixed transmitter and a mobile receiver in an urban environment is described. Ranges up to 400 m are used and measurements of the received signal's “fast fading” envelope, “local mean,” signal versus distance power law, and coherence bandwidth are obtained in the presence of traffic     

STUDY ON GIS BASED PREDICTION SYSTEM FOR RADIO WAVE PROPAGATION IN UBAN REGION

In this letter, an integrated application of the prediction for radio wave propagation with the Geographic Information System (GIS) is presented and a real prediction system based on GIS is implemented.     

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     

Millimeter-wave propagation at street level in an urban environment

Measurements on point-to-point transmission at street level were performed in downtown Denver, CO, with RF probes that operated at 9.6, 28.8, and 57.6 GHz. All probes were mounted on self-contained vehicles, permitting a variety of path scenarios. Information on performance of these channels for propagation in an urban environment on both line-of-sight and non-line-of-sight paths is presented. For non-line-of-sight (non-LOS) paths obstructed by buildings of several common materials, results that showed signal attenuations in excess of 100 dB. When the LOS followed a path directly through clear glass walls, the attenuation was small at all probe frequencies. However, when the glass wall had a metalized coating to reduce ultraviolet and infrared radiation, the attenuation increased by 25 to 50 dB for each metallized layer. In most cases no signals could be detected through steel reinforced concrete or brick buildings     

A stochastical model of the urban UHF radio channel

A random model for urban ultrahigh frequency (UHF)- multipath propagation is proposed. The model uses an optical analogy, which can be well justified at these high frequencies. Several results are obtained. The transfer function and its autocorrelation properties are investigated. Also the time domain behavior is studied. The model is finally tested against experimental data from a field trial made in the town of Linköping, Sweden.     

Transmitter multiplexing system in UHF mobile radio

At a base station of a UHF mobile radio telephone system in a large city, many transmitters are used. In such a case it is not practical to use an individual antenna for each transmitter from the viewpoint of system economy and interference. Common use of one antenna for many radio-frequency channels is suitable and transmitter multiplexing devices should be used for this purpose. A transmitter multiplexer has been developed which can be used for multiplexing more than twelve 100-W transmitters in the 450-MHz band with a channel spacing of 150 kHz. The multiplexer consists of circulators, cavity resonators, and junction boxes. The principal features of this multiplexer are H101mode cavity resonators which are ultrastable with respect to the variation of environment conditions such as temperature and humidity. The resonators are temperature compensated to maintain the variation of resonant frequency within 5 kHz at the ambient temperature variation of 40°C. The voltage standing-wave ratio (VSWR) of the multiplexer, looking from the transmitter side, is less than 2.0 and the insertion loss is less than 3 dB at the operating frequency. Design objectives, over-all performance, and characteristics of cavity resonators and circulators are also presented.     

Theory of the propagation of UHF radio waves in coal mine tunnels

The theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a corner is the concern of this paper. Of prime interest are the nature of the propagation mechanism and the prediction of the radio frequency that propagates with the smallest loss. The theoretical results are compared with published measurements. This work was part of an investigation of new ways to reach and extend two-way communications to the key individuals who are highly mobile within the sections and haulageways of coal mines.     

A novel 3-D scattering model of 1.8-GHz radio propagation inmicrocellular urban environment

This work presents a novel three-dimensional (3-D) scattering model to predict the path loss of a microcellular radio channel in an urban environment. The analytical scattering model combined with a patched-wall model predicts the median path loss more accurately than the conventional analytical ray-tracing model in the cases studied. Comparing the path loss with the measured one at 1.8 GHz demonstrates the effectiveness of the scattering model. The scattering model includes three major propagation modes: (1) a direct-path wave; (2) a ground-reflected wave; and (3) the scattered field from the walls aligned along a street. The proposed model with a polarization scattering matrix associated with the patched-wall model aptly describes the third mode, which is usually neglected or oversimplified     

Simulation of the urban radio propagation channel

A simulation program for the wide-band response of the urban multipath propagation channel has been developed. The program enables the generation of a sequence of "impulse responses" of the channel that would be observed by a moving vehicle communicating with a fixed station. The program incorporates empirical parameters covering four types of urban areas and three frequencies (in the 0.5-3- GHz range) and can be used in design of urban communication systems.     

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     

Performance evaluation of OFDM transmission over a challenging urban propagation environment

The paper introduces a performance evaluation of orthogonal frequency division multiplexing (OFDM) transmission schemes over a challenging urban propagation environment, considering 3D scattering, providing also a comparison with 2D considerations. After an analytic calculation of the power of received signal components (faded useful signal, intercarrier interference, intersymbol interference and noise) the authors present results of system performance evaluation under different propagation conditions (e.g., various Doppler shift values) and various values of key system parameters. BER (bit error rate) calculations are provided for a 16-QAM OFDM transmission scheme over Rayleigh fading channels, with and without Reed-Solomon coding techniques. Finally, the influence of carrier offset on the system performance is examined.     

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.     

Modified simulation of the urban radio propagation radio channel (SURP)

The authors propose a modification to a well known multipath fading channel simulation, SURP, that was originally developed to simulate the long term variations of the channel. They introduce a mechanism that allows the generation of channels which simulate short term fading. The proposed mechanism involves simulating the time development of the angle of arrivals of the individual rays. By using this modification, the Doppler spectrum shape is much closer to theoretical predictions.<>     

The effect of terrain on radio propagation in urban microcells

A model based on the geometrical theory of diffraction is proposed for predicting radio propagation in urban microcells in the presence of undulating terrain. Comparisons with data show that the model is appropriate for predicting shadowing by terrain, but the effect of terrain fluctuations which do not obscure the line of sight is smaller than the model predicts. It is also shown that the presence of buildings lining the streets, while causing considerable variations over short distances, has only a small effect on the large-scale trend of the average signal     

Analysis of multipath propagation structure in urban mobile radio environments

An analysis is made of the physical structure of multipath propagation in an urban area. The incident angle, path length, and field strength are measured for each principal component of the received multipath signal. The results of the analysis reveal that the observed principal waves compare fairly well with those propagating via geometrical optics. The experimental data indicate that a limited number of ray-theoretical wave components play an important role in propagation in urban mobile radio environments.     

Mobile radio propagation in British cities at frequencies in the VHF and UHF bands

Measurements of the received signal envelope magnitude have been made in three British cities at frequencies of 85.875, 167.2, and 441.025 MHz. In all cases unmodulated carrier waves were radiated from aerials atop tall buildings or prominent terrain features and detected using a vehicle-mounted receiver. These measurements have provided the basis for an analysis of the factors affecting the transmission loss in urban/suburban areas which, in turn, has enabled a propagation prediction model to be constructed. Close agreement between measured and predicted path losses has been found for the various terrain situations investigated. The statistical prediction errors produced by the proposed model for the three British cities analyzed are shown to be similar in magnitude to those obtained using an extrapolation of the Okumura method. Because the proposed model is much less complex and procedurally simpler, it is recommended for use, in the first instance, in British cities.     

Modern approaches in modeling of mobile radio systems propagation environment

In this article a review of popular propagation models for wireless communication channels is given. Macrocell, microcell, and indoor prediction methods are considered separately. Advantages and disadvantages of these models are discussed. Also, some practical improvements of the existing models as well as some new models are given.