Métodos assintóticos para caracterização do canal rádio em ambientes externos

Abstract

This work presents the radio channel characterization in outdoor environments using the implementation of asymptotic methods to calculate deterministically of electromagnetic radiowaves scattering in wireless communications systems. The technique used to model the multipath propagation is the ray tracing. It allows a individual analysis about the contribution that each ray has on the electric field. The analysis will be done in the frequency domain using Geometrical Optics (GO) and Uniform Theory of Diffraction (UTD) in homogeneous, linear and time invariant mediums. In relation to UTD will be studied three heuristic coefficients cited in the literature. These will be used to determine the diffracted field on lossy conducting wedges. To achieve this, the canonical case of diffraction on a lossy wedges will be presented. In addition to this, will be done a comparative analysis between the radio coverage prediction simulations according to each coefficient and the measurenments in three realistic urban scenarios, Ottawa, Cali and Valencia. In order to evaluate the accuracy of each coefficient, it will be computed the statistical behavior given by the mean and standard deviation of the absolute errors between the estimated values and the measured data of path loss in a large number of receptor points localized on the measurements routes. The real environments model are characterized by containing a high density of buildings with geometric diversity, common aspects of urban environments. The environment obstacles were defined according to the material type and its electromagnetic properties that were taken from researches. The characteristics of the radio links will be established according to the description given for the measurement campaigns, such as the location of the transmitter antenna and the receiver points. Finally, it will be showed the path loss prediction for each UTD coefficients in the proposed urban environments.