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. >

A theoretical model of UHF propagation in urban environments

A method is described for analyzing the mean effective gain (MEG) of antennas moving in a mobile communication environment. The MEG characteristics of a mobile antenna are determined by the mutual relation between the antenna patterns and the statistical distribution of incident waves in an environment. To analyze this relation theoretically, a general expression for the MEG using a statistical model of incident waves is derived, and a novel statistical model, whose distribution is uniform in azimuth and Gaussian in elevation, is proposed. The validity of the statistical model is confirmed through 900-MHz-band measurements carried out in a Tokyo urban area, and the empirical parameters for the statistical distribution are described. The MEG characteristics of a half-wavelength dipole antenna are investigated using the proposed method, and it is shown that the theoretical curves calculated using the empirical parameters are in excellent agreement with experimental results. This analysis is extremely applicable for evaluating the MEG characteristics of arbitrary mobile antennas in various mobile communication environments. >

Analysis for mean effective gain of mobile antennas in land mobile radio environments

Calculation of mean field strength for urban mobile radio has been made on a ray-theoretical basis assuming an ideal city structure with uniform building heights. The result shows that building height, street width, and street orientation as well as mobile station antenna height are controlling propagation parameters in addition to the ordinary factors. The major theoretical characteristics agree approximately with experimental data including conventional empirical predictions. This suggests a way of theoretically predicting mean field strength in an urban area.

Propagation factors controlling mean field strength on urban streets

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.

Modern approaches in modeling of mobile radio systems propagation environment

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. >

UHF propagation prediction for wireless personal communications

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.

F. Ikegami

Papers

Propagation factors controlling mean field strength on urban streets

Analysis of multipath propagation structure in urban mobile radio environments