USTLD mapper design for APSK constellations over satellite links

Abstract

Space-time block code (STBC)–based multiple-input–multiple-output techniques have been considered recently to enhance the performance of mobile satellite communication systems in terms of link reliability. Uncoded space-time labelling diversity (USTLD) is a diversity technique that is a direct extension of the STBC system and further improves its performance. A USTLD system is proposed in this paper that is designed specifically for satellite to mobile station links. The circular M-ary Amplitude Phase-Shift Keying (MAPSK) constellation, which is adopted by the most recent satellite broadcasting standard Digital Video Broadcasting standard for nonlinear satellite links (DVB-S2X), is applied to the USTLD system. The most critical aspect of developing a USTLD system is the design of the secondary mapper to achieve labelling diversity. Existing square M-ary Quadrature Amplitude Modulation (MQAM) approaches to USTLD mapper design are adapted for appropriate 16APSK and 64APSK constellations from the DVB-S2X standard. Various metrics are derived to quantitatively compare mapper designs for a Nakagami-q fading channel. Theoretical results, verified by Monte Carlo simulations, show that the best of the MAPSK USTLD mappers considered achieve a gain of approximately 4 dB for 16APSK and 5 dB for 64APSK when compared to the Alamouti STBC system. Furthermore, a study is conducted to analytically compare USTLD mappers using the derived metrics for both MQAM and MAPSK. It is concluded that a two-stage approach is the most accurate methodology for comparing USTLD mapper designs.