Performance improvement techniques for the DVB-RCS2 return link air interface

This paper presents performance improvement techniques for the second-generation digital video broadcast return channel via satellite air interface, which can be used for supporting future demands for Tbit/s traffic requirements. In particular, we have investigated minimum-shift keying (MSK) type of continuous phase modulation (CPM) waveforms by considering both single-carrier and multi-carrier transmission and single-amplitude and multi-amplitude signals, which improve the spectral efficiency. In addition, we consider frame timing and synchronization techniques, which make synchronization more accurate and robust. Our research has shown that the MSK single-carrier frequency-division multiple access (SC-FDMA) outperforms the quadrature phase-shift keying SC-FDMA in terms of resilience to distortion with the performance gap increasing when the amplifier shows a milder distortion. The performance of a multi-amplitude CPM scheme, based upon the superposition of two single-amplitude MSK signals at the radio frequencies level, is also investigated. In comparison with other equivalent linear modulation schemes, performance evaluation results have been shown that the proposed multi-amplitude CPM scheme significantly improves the spectral efficiency in the presence of adjacent channel interference. Finally, we have proposed a viable and efficient methodology, which enables reliable and accurate timing and frequency synchronization for the SC-FDMA satellite return link. This involves a combination of global positioning system (GPS)-based pre-compensation of differential timing between user terminals, preamble detection in an integrated random access channel, and user channel frequency estimation based on repetitive symbols in the time domain.