L.A.R. Silva Mello

Preliminary field tests results of ISDB-Tb digital TV transmission in the VHF-high band

This paper presents preliminary results of field measurements carried out for evaluating the operation of the ISDB-TB standard digital TV in the VHF-high band. Measurements were performed in urban, suburban and rural areas in a medium-sized Brazilian city. The analysis includes results of static reception measurements for evaluating the received field strength and the signal to noise ratio thresholds for correct signal decoding. A comparison with theoretical values of field strength is also presented.

Application of a ray tracing technique for coverage predictions in micro cellular environments

This work employs a 3D vector formulation for calculation of the field scattered by finite conductivity wedges, representative of obstacles usually encountered in both indoor and outdoor environments served by cellular communication systems, developed as an extension of the Uniform Theory of Diffraction (UTD) version for perfect conductors, to the calculation of propagation path losses and delay profiles for typical building layouts. Implementation aspects of launching, tracing and capturing relevant optical rays as well as applying the Quadtree method for spatial (scenario) discrimination are also discussed.

Rain attenuation prediction for the design of site-diversity LEO/SMS Gateway configuration in the tropics

This paper presents a propagation analysis regarding the set up of a LEO/SMS Gateway in a tropical region. The propagation effects considered are rain induced attenuation and gaseous absorption. The study is based on five years measurements of point rainfall rate and slant-path rain attenuation at 12 GHz performed in Rio de Janeiro. A method was developed and applied to scale the measured attenuation results to 19 and 29 GHz, the down and up-link frequencies of the Gateway.

Radioclimatic parameters for the prediction of multipath fading in radio links in Brazil

A propagation measurement campaign is being carried out in Brazil to provide long term cumulative distributions of single frequency multipath fading and statistics of the parameters of a two-ray multipath channel model (relative delay and notch depth). The correlation between fade events in consecutive hops in multihop links is also being investigated. Some of the results available are presented in this paper.

Differential rain attenuation in converging links

This paper presents results of differential attenuation measurements in 6 terrestrial line-of-sight microwave links with a common end at Sao Paulo, in the tropical region of Brazil. One link operates at 18 GHz and five links at 15 GHz. An empirical method used to estimate the differential attenuation exceeded at a given percentage of time as a function of the angle between links and their path length difference was developed based on the experimental results.