Avaliação experimental do desempenho do canal móvel do sistema brasileiro de televisão digital.

Abstract

This work presents an experimental evaluation of the performance of the mobile channel of the Brazilian Digital Television System. With the advent of this system, diverse conditions must be emphasized, which pose an impact on the development of the transmission equipment. The key variables that influence the degradation of the quality of the digital signal are the mobile television speed, the number of fading components, the random phase shift, the carrier/noise relation, the propagation delay and the Doppler Effect. A robust knowledge about the behavior of those variables is important to evaluate the channel transmission, and to design the equipment in accordance with the available standards. The metric used to measure the quality of the digital signal was the modulation error ratio (MER), which reflects the constellation diagram state of the demodulated signal. The MER, unlike the bit error rate, gives a better idea of the channel state, mainly for low-order digital modulation schemes. Based on the study of the impact of those factors a separate assessment of the influence of each variable in the quality of the demodulated constellations is proposed, and its relevance on the transmission process.