This paper presents a radio propagation model for macrocell coverage predictions in built-up areas for sub-6 GHz frequency band. The proposed two ray model is the combination of various individual propagation models available in the literature, namely the Discrete Mixed Fourier Transform Split-Step Parabolic-Equation (DMFT-SSPE) to characterize reflection and diffraction phenomena due to the presence of buildings and terrain irregularities, the building-transmission model (BTM) to account for the signal attenuation through the nearby buildings and the International Telecommunication Union of Radio-communications (ITU-R) model for attenuation in vegetation to weight the excess attenuation caused by the surrounding vegetation. The performance of the proposed modeling approach was assessed against measurement results obtained from an extensive measurement campaign conducted in Rio de Janeiro, Brazil. The receiver (RX) antenna was assembled on an automotive van, and it was made to travel around the city recording the received signal level. Several drive tests were conducted, including different transmitter (TX) locations and scenarios, and at various frequencies foreseen for 5G systems, namely 750 MHz, 2.5 GHz and 3.5 GHz.

Vehicular communications are becoming increasingly important due to the need for safer, more efficient, and sustainable transportation. They require the development of accurate radio channel models for vehicular environments. This study compares vehicle-to-infrastructure path loss predictions obtained using four machine learning models: artificial neural network, support vector regression, random forest, and gradient tree boosting. The model design employs predictors from the profile environment between the transmitter and receiver positions. A methodology to select the best predictor subset is applied by examining their contribution to performance and interpretability. We propose a generalization test considering unknown streets (scenarios), and the results demonstrate that the gradient tree boosting model significantly improves the path loss prediction compared to the log-distance path loss model.

The next-generation TV broadcasting systems must meet the demand for better audio and video quality, higher accessibility and interactivity, and personalized services on fixed and mobile devices. In Brazil, field measurement tests are being performed to evaluate the performance of candidate technologies. The Advanced ISDB-T is a promising Japan Broadcasting Corporation (NHK) technology. It evolves from the current ISDB-T standard, already adopted in Brazil, increasing the system’s flexibility, robustness, and spectrum efficiency. It also includes MIMO technologies to allow for high transmission rates. This work assesses the Advanced ISDB-T system performance in field tests, considering a 2x2 MIMO transmission through a Rayleigh channel, considering the requirements defined for the next generation of Brazilian Digital TV systems. We evaluate the channel power, threshold C/N ratio, and reception threshold on 20 measurement sites with outdoor reception. The measurements of the parameter Condition Number, which quantifies the suitability of the radio channel for MIMO transmission, indicate that the channel was well-conditioned at all measurement sites but one and that the tested system efficiently demodulated the MIMO received signal, even under less unfavorable conditions. This occurs when the C/N threshold is less than zero and the corresponding condition number is equal to or less than 2 dB.

Optical and mmWave terrestrial links are somewhat considered complementary as they have a different sensitivity to fog and rain, i.e. the most frequent atmospheric impairments at mid-latitude. Hence, hybrid optical-mmWave systems that back-up each other according to weather conditions, have been proposed as they put together extremely large-bandwidth and high availability. However, in order to assess whether optical and mmWave systems can be considered complementary rather than competitors, the propagation effects should be quantified, possibly on a statistical basis. This paper presents preliminary results of the effects of rain on a commercial optical link at 1550 nm and a co-located dual-band mmWave link. It is shown that the degradation of the optical signal is not always well correlated with the microphysical properties of rain, Signal attenuation can be substantially underestimated if predicted by the electromagnetic theory, due to the concurrent action of other factors.

This article analyses low-density parity-check (LDPC) codes for forward error correction (FEC) in the next generation of digital terrestrial broadcasting systems for transmitting high-volume content services, such as ultra high definition television (UHDTV). We assess the performance of the LDPC codes used by the Advanced ISDB-T system with 2x2 MIMO transmission using experimental data obtained in field measurements in Brazil. Channel power, carrier-to-noise threshold, and receiving threshold were measured for four different low-rates LDPC codes, two modulation types, and three receiving antenna heights at outdoor sites in urban areas. The coverage analysis shows that the channel power presents a similar distribution for horizontal and vertical polarized signals. C/N threshold analysis shows that in sites with high vehicular traffic, the C/N threshold and reception threshold values were much higher than in other sites with less heavy vehicular traffic. Among the five coding-modulation combinations used in the field tests, the transmission configuration with LDPC code rate 2/16 and QPSK modulation was the one that presented the best results partially meeting the requirement of C/N $\leq $ 0dB. The transmission configuration with LDPC code rate 3/16 and QPSK modulation showed C/N results just above 0dB, but offering 50% higher data transmission rate.

In the present study, rainfall rate statistics for radio propagation applications collected during 1‐year measurement with a 1‐min integration time in three locations of Venezuela are presented and analyzed for the first time in the country. Specifically, the statistics of the worst‐month (WM) are assessed and compared with the Recommendation ITU‐R P.841‐7 prediction model. The results indicate that the model does not accurately predict the statistics of the WM in the country. Also, the performance of Recommendation ITU‐R P.837‐7 (Annex 1 and Annex 2) in estimating the rain rate for a 1‐min integration time at the three locations is examined, with the ITU‐R P.837‐7 Annex 1 exhibiting the best performance and providing results that encourage its use in the prediction of complementary cumulative distributions of rain rate in the country.