Pedro Vladimir Gonzalez Castellanos

New digital television standards are emerging to meet the demand for new services from TV broadcasters, as well as to support new high-resolution audio and video formats available on the market. In Brazil, the Brazilian Digital TV System (SBTVD) Forum defines the standard to be adopted. Among the currently available physical layer technologies, the Advanced Television Systems Committee (ATSC) 3.0 standard offers great flexibility in operating modes, depending on the broadcasters’ requirements and propagation conditions, for both fixed and mobile reception. This allows the system to be configured to balance robustness and transmission efficiency. This paper presents the performance test results in various mobile reception scenarios in the city of Rio de Janeiro, using an ATSC 3.0 signal with a transmission rate of 32.3 Mbps in a $2\times 2$ Multiple-Input Multiple-Output (MIMO) configuration. The results showed a reception success rate of 53.6%, with an increase in reception errors for Carrier-to-Noise Ratio (C/N) lower than 26 dB. Furthermore, reception errors were detected with greater intensity when the received signal level was below -70 dBm. Although the overall success rate was around 50%, the complementary metrics (C/N threshold, RSSI, and PLP0 error behavior) were consistent with theoretical expectations, demonstrating that ATSC 3.0 performs effectively under real urban mobility conditions at high spectral efficiency. ATSC 3.0 thus proved effective in broadcast transmission, meeting the needs for ultra-high-definition (UHD) audio and video broadcasting.

A swivel low-cost prototype is proposed for measuring the radiation pattern of millimeter wave antennas and antenna arrays applied to mobile services such as 5G and 6G and other wireless systems like RFID. Furthermore, the proposed measurement setup uses a pair of identical antennas to obtain the radiation pattern. The prototype uses a stepper motor controlled by Arduino Uno, an open-source software that allows a complete 360° rotation. The measurement setup utilizes a swivel model, where the transmitter antenna is connected to a signal generator, and the receiver antenna is connected to a signal analyzer, both controlled via a GPIB-USB interface. LabVIEW is employed to manage the equipment and measure the received power levels. Additionally, MATLAB, integrated into the same LabVIEW VI, plots the radiation pattern in rectangular and polar formats. A second calibration approach for verifying the radiation pattern diagram of a commercial directional antenna is also presented. The simulated and measured results are compared and validated in real-world environments and anechoic chamber.

This study investigates radio signal propagation at 5.8 GHz in an underground parking garage for vehicle-to-infrastructure (V2I) communication, a widespread scenario present in urban centers. Broadband measurements were conducted using orthogonal frequencydivision multiplexing (OFDM), enabling the characterization of the radio channel in terms of path loss (PL) and temporal dispersion. The power delay profile (PDP) was obtained via inverse Fourier transform of the channel impulse response (CIR). Multipath components were identified and compared using the constant false alarm rate (CFAR) and singular spectrum analysis (SSA) techniques. The results showed that the SSA technique is effective for multipath component identification.

O avanço das redes 5G torna possível o atendimento de novas aplicações e serviços não atendidos pelas gerações anteriores. Apesar disso, suportar aplicações críticas exigem da rede o cumprimento de rigorosos requisitos. Com o objetivo de investigar a viabilidade do uso da rede 5G para atender aplicações de Veículo de Superfície Não Tripulado (VSNT), este trabalho conduz uma análise de desempenho com base nos requisitos das aplicações, realizando experimentos em cenários reais de rede 5G. Os resultados obtidos nesses cenários, nos testes de capacidade da rede e das aplicações funcionando, indicam que, excetuando aplicações que exijam 25 Mbps, ou mais, para as quais há necessidade de planejar a cobertura, a rede 5G está habilitada a atender aos requisitos do VSNT.

In this work, we investigated the path loss (PL) profile of the outdoor radio channel in the 800 MHz band for the Icaraí region in the city of Niterói. This frequency band has recently been reserved by the brazilian National Telecommunications Agency (ANATEL) for utilization in Public Protection and Disaster Relief (PPDR) wireless networks, and Icaraí constitutes a potential area to receive coverage provided by a PPDR network whose implementation is of interest to the Niterói government. The investigation relies on narrowband large scale measurements, recorded at various places throughout the neighborhood. As a theoretical framework for the analysis, we consider four log-distance PL models, which have been widely used in recent outdoor channel sounding works. Our findings seek to facilitate the successful establishment and optimization of PPDR networks in Niterói city.

In communication system design, predicting radio signal coverage in channels with vegetation is challenging due to the way vegetation absorbs, reflects, spreads, and depolarizes the signal. Empirical models have been developed to predict signal coverage in these channels, such as parks and urban squares with vegetation, which are common in cities. To study these scenarios, this paper presents narrowband measurements taken in a public square with varied vegetation, using five carrier frequencies in the 700-4000 MHz band, including those used for cellular services, Wi-Fi 6 (Wireless Fidelity), and 5G (Fifth Generation) networks. Two transmitter antenna heights were used, and the measured data were analyzed graphically and quantitatively. The study found that an artificial neural network improved the signal prediction beyond that of the log-distance model, which is the basic model with the best results. Therefore, it can be used understand and model this kind of environment.

This letter presents an analysis of the radio propagation channel based on measurements at the 3.5 GHz frequency. The measurement campaigns were carried out inside the Valde-Cans airport using line-of-sight (LOS) transmissions. First, the channel small-scale dispersion parameters were extracted through channel probing and the results are similar to those obtained by ITU-R P.1238 for the bands below 15 GHz considering commercial indoor environments as well as for those using the 3.5 GHz band in outdoor environments utilizing WiMax OFDM-256 signals. Then, the floating-intercept (FI) and close-in (CI) models are applied and analyzed to evaluate the received signal behavior for co-polarized and cross polarized antennas. The results show that the CI path loss exponent values are close to the free space propagation loss model, while the FI model provides a lower root mean square error (RMSE) to the measured data. The results show that the FI and CI models are suitable for large-scale indoor propagation loss modeling for 5G networks with a frequency of 3.5 GHz.

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.

Due to the propagation characteristics in the 2.5 GHz band, the signal is significantly degraded by building entry loss (BEL), making coverage in indoor environments in some cases non-existent. Signal degradation inside buildings is a challenge for planning engineers, but it can be seen as a spectrum usage opportunity for a cognitive radio communication system. This work presents a methodology based on statistical modeling of data collected by a spectrum analyzer and the application of machine learning (ML) to leverage the use of those opportunities by autonomous and decentralized cognitive radios (CRs), independent of any mobile operator or external database. The proposed design targets using as few narrowband spectrum sensors as possible in order to reduce the cost of the CRs and sensing time, as well as improving energy efficiency. Those characteristics make our design especially interesting for internet of things (IoT) applications or low-cost sensor networks that may use idle mobile spectrum with high reliability and good recall.

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.