Quadrature‐carrier amplitude phase shift keying

Abstract

Amplitude phase shift keying (APSK) is the emerging modulation scheme used in deep satellite communications and known to have a high spectral and energy efficiency among other two-dimensional (2-D) M-ary schemes. Besides, it provides a robust transmission in non-linear wireless channels and therefore it has been adopted and employed in the state-of-the-art digital video broadcasting standards DVB.S2/S2X. However, APSK is still away from utilising all available space dimensions such as its other counter-parts, where this potential gap provides the motivation to develop spectrally a more efficient modulation scheme. In this respect, a novel digital modulation scheme called quadrature-carrier APSK (QC-APSK) was proposed. QC-APSK uses two orthogonal carriers to convey ordinary APSK modulated signals to increase the spectral efficiency via doubling the transmission rate. It can be regarded as two orthogonal 2-D constellations which occupy 4-D signal space. This study covers the theoretical analysis of the proposed approach and further considers the effect of pulse shaping. The proposed scheme improves spectral efficiency by one-third and achieves better error performance against conventional APSK. Simulation results show that the obtained bit error rate and symbol error rate performances comply with the derived theoretical background which validates the effective use of the proposed modulation scheme.