Propagation Model for Path Loss Through Vegetated Environments at 700 – 800 MHz Band

Abstract

-In almost all literature about propagation models through vegetated environments, path loss has been proposed based on specimens of temperate clime conditions. In this work, a new propagation model is proposed, based on measurements, carried out on vegetated environments with tropical specimens. These environments are common on suburban and rural areas in Brazil. Current models have presented pessimistic approach to propagation loss in these areas. The vegetal morphology and frequency effects, transmission height and distance are taken into consideration. Finally a comparison with existing models is presented.Index Terms-Path Loss over vegetated environments, UHF Propagation Model, Radio communication fading. I. INTRODUCTIONThere is a great interest in fading and attenuation of electromagnetic signals associated with vegetated environments at low UHF frequencies. However it remains under exploited in the literatureThe 700 -800 MHz band has been proposed in several countries to use on new communications technology, due to its very good propagation condition [2], leading to better signal coverage with less energy cost. In Brazil this is a very important issue and new 5G communication systems are being proposed to cope with the growing demand. The goal of this paper is to develop a prediction model for the signal attenuation due to the presence of typical tropical vegetal morphologies in the environments, using an empirical mathematic model.The problem of vegetated environment propagation has a great practical interest and it is considered a very complex propagation problem. The propagating wave experience absorption, scattering attenuation and depolarization and these aspects are related with frequency, atmospheric conditions, antenna height, electric properties of the medium, density and morphology of the vegetation specimens. The large amount of aspects makes the problem a very intricate to solve, since they introduce randomness and non-linearity. Vogel e Goldhirsh [3] demonstrated that an isolated tree can attenuate 10 dB the electromagnetic field. This motivates an empirical approach, based on measured data. In order to accomplish that, an extensive measurement campaign was carried out on the band of In built up areas, the edifications produce signal variations due to wave scattering. On vegetated environments, the trees can be characterized as such causing scattering and attenuation of the signal.According with Jao [5], it is possible to consider the vegetation as a randomly distributed medium with different kinds of trees. There is a great vegetal diversity, making its characterization difficult.However, due to the low attenuation produced by grassy and bushes, the characterization effort on this work will be concentrated over arborized environment, which play the major role in path loss.The characterization of the vegetation was a simplified form of the methodology presented by Kafaru [6], where the area is divided into squares, with specific morphology that includes density size and type of trees...

Cobertura de Sinal Rádio Móvel em Ambiente com Vegetação na Frequência de 850 MHz

“…É um modelo empírico, desenvolvido pelo ITU, em 1988, aplicável para a faixa de frequências de 0,2 a 95 GHz e distâncias menores que 400 metros. É conhecido como Early ITU [12]. O cálculo da perda em excesso à perda de espaço livre, devido à propagação através da vegetação, em dB, é dada por:…”

Influência da Vegetação na Cobertura de Sinal V2I em 5.8 GHz

“…É um modelo empírico, conhecido como Early ITU, aplicável para a faixa de frequências de 0,2 a 95 GHz e distâncias menores que 400 metros [9]. Fornece a perda em excesso devido à vegetação, que deve ser somada a do espaço livre, descrita no item seguinte.…”

“…Assim, o modelo parte das equações do modelo de SUI e faz ajuste de parâmetros, sendo calculada por: L = A + 10.γ. log 10 (9) onde f é a frequência de operação do sistema, em GHz, h t é a altura da antena transmissora, em metros, e P é o nível de sinal recebido.…”

Application of Weissberger Model for Characterizing the Propagation Loss in a Gliricidia sepium Arboretum

“…When a wireless signal propagates through an area covered with vegetation the total propagation loss, ( ) can be obtained as [15,16,17,18,19];…”

“…Determination of the received signal strength at any location within the arboretum can be done using some foliage propagation loss models [12,13,14]. In this paper, the Weissberger and the Early ITU foliage propagation loss models are used to characterize the propagation loss within an arboretum that consists of mainly Gliricidia sepium trees [15,16,17,18,19]. The arboretum is located within the annex campus of University of Uyo in Akwa Ibom state, Nigeria.…”