M. P. C. Almeida

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.

Modified rain attenuation prediction method considering the effect of wind direction

The method currently recommended by the ITU-R for the prediction of rain attenuation in terrestrial line-of sight links considers an equivalent path length over which the rain intensity is assumed to be constant. In other methods, the spatial and temporal variations of the rainfall rate along the path are characterized by an effective rainfall rate that is dependent on the actual path length. Based on experimental measurements, this paper presents a modified effective rainfall rate method that includes the prevailing wind direction during rainy conditions as an additional parameter for the prediction of rain attenuation. The wind direction, which can be obtained from meteorological databases with global coverage, is shown to significantly improve prediction accuracy.

Influence of wind direction on rain attenuation in terrestrial line-of-sight links

In this paper, the influence of wind direction on rain attenuation is investigated based on concurrent measurements of rainfall rate and signal attenuation in converging links with different path lengths, spatial orientations and operation frequencies. A simple but efficient method for predicting the cumulative distribution of rain attenuation in terrestrial line-of-sight links is derived.

Analysis of the interference from LTE system in ISDB-TB Digital TV system at 700 MHz

This paper presents the results of field measurements and computer simulation of the interference from LTE in the ISDB-TB Digital TV systems in the 700 MHz band. The measurements campaign results were used to validate the use of SEAMCAT software to simulate this interference problem. The software tool was then used for the characterization of the measurement scenarios aiming the evaluation of the coexistence of these services.

Experimental analysis of the signal-to-noise ratio of digital ISDB-TB TV receivers and multipath in the VHF-high band

This paper presents an evaluation of the performance of digital TV receivers focusing the parameter signal-to-noise ratio achieved from measurements in laboratory tests and from field tests, and also the multipath data achieved from field tests. The mentioned field tests are a field measurement campaign performed in Brazil aiming the evaluation of ISDB-TB standard digital TV operation in the VHF-high band. From the static measurements of field tests, the parameter signal-to-noise ratio was achieved employing two methodologies, one from direct measurements and the second from noise injection. These results were compared to laboratory tests and to the technical norm of operation in the VHF band. An assessment of the influence of multipath in the digital signal reception and some correlation to the measured signal-to-noise ratio values is also presented.

Measurements of Field Strength and HD Radio Reception Quality at VHF

This letter presents the results of field trials conducted in Brazil to evaluate the performance of digital broadcasting systems. Analog FM and digital HD radio signals broadcasting the same content were simultaneously transmitted in the urban and suburban areas of the city of Belo Horizonte in Brazil. A mobile unit recorded the received signal intensity and reception quality along radial routes of up to 24 km from the transmitter, thereby enabling the comparative assessment of the systems performance and the evaluation of the propagation loss.

New methods for the prediction of rain attenuation in terrestrial links

Rain attenuation is the main cause of unavailability in radio links operating at frequencies above 10 GHz. Attenuation due to rainfall along a path may be calculated by integrating the specific attenuation over the path length if the rainfall rate variation along the path is known. Rainfall rate, however, is inhomogeneous in both space and time posing a major difficulty in predicting rain attenuation for link design. Most practical methods make use of cumulative distributions of rainfall rate measured at a point. The statistical rain profile is simply characterized by an effective rainfall rate derived from measurements. An alternative procedure is to apply the reduction coefficient to the actual path length, which yields an equivalent path length over which the rain intensity may be assumed to be constant. This type of procedure is currently adopted in the methodology of Recommendation ITU-R P.530. One limitation in the current ITU-R method is that the attenuation is predicted using only the measured rainfall rate exceed at 0.01% of the time. For other percentages of time, the attenuation is obtained using extrapolation functions. More importantly, the method is based on fitting of the path reduction factor using limited experimental data, without an actual physical basis. This paper will discuss possible new approaches to develop a prediction method relying on a stronger physical basis. One possibility is to include in the method parameters such as the wind speed and direction during rainy conditions, which should affect the attenuation along the links in addition to the cumulative distribution of rainfall rate and link geometry already considered in the current method. A tentative method will be presented, derived based on measurements of signal attenuation in converging links with different path lengths, spatial orientations and operation frequencies, as well as information on wind speed and direction during rainy periods. Another approach is the use of rain attenuation synthesizers to predict not only attenuation statistics but also its dynamic behaviour. Recently there has been extensive work being carried out in time series synthesizers using the synthetic storm technique to provide attenuation time series. The main challenge here is to obtain the synthesizer parameters for different link characteristics and radiometorological regions. This kind of modelling is still in its early stages but some available results will be reviewed.

Medium wave DRM trials in Brazil — Initial results

This paper describes the experimental setup and presents initial results of medium wave propagation measurements campaigns that are being carried out in Brazil. The experiment is part of a series of field trials that are being conducted by the Brazilian Government to evaluate the performance of DRM standard in this country, which includes campaigns at MW, HF and VHF frequency bands in the cities of São Paulo, Rio de Janeiro and Belo Horizonte. A hybrid signal, composed of an analog AM signal and a digital DRM signal, with the same content, were broadcasted in diurnal and nocturnal transmissions. The results presented here include daytime and nighttime statistics of the measurements performed in São Paulo.