Constant-Envelope Space-Time Shift Keying

From the power amplifier's perspective, the peak-to-average power ratio (PAPR) is of essential importance, especially for both single-RF and reduced-RF multiple-input multiple-output (MIMO) single-carrier schemes. In this context, many of the diversity-oriented index modulation schemes-including the full-RF space-time shift keying (STSK) and the single-RF asynchronous STSK (ASTSK) that invoke randomized signals-exhibit eroded energy-efficiency. To circumvent this problem, we propose a holistic signal construction approach for single-RF, reduced-RF, and full-RF MIMO setups, which always achieve both perfect 0 dB PAPR transmission and inter-channel interference (ICI) free signal detection. More explicitly, first of all, we conceive a new family of single-RF constant-envelope ASTSK (CE-ASTSK), which is capable of substantially outperforming conventional spatial modulation (SM) in both Rayleigh fading and Ricean fading associated with increasing line-of-sight (LoS) power. Second, we propose the new full-RF CE-STSK concept, which is capable of outperforming the orthogonal space-time block codes (STBCs) without either increasing PAPR or imposing ICI. This is particularly beneficial because the conventional linear dispersion code (LDC) approaches always compromise the orthogonality of STBC and hence impose ICI. Third, we also conceive the reduced-RF versions of CE-STSK, which outperform both generalized spatial modulation (GSM) and space-time block coded spatial modulation (STBC-SM). Finally, the proposed schemes are intrinsically amalgamated with turbo detection assisted channel coding, which further confirms the superiority of CE-ASTSK and CE-STSK over SM and STBC in the single-RF and full-RF modes, respectively.