Differential Spatial Modulation for APSK in Time-Varying Fading Channels

Abstract

Abstract-We develop a novel differential spatial modulation (DSM) scheme for amplitude phase shift keying (APSK) modulation, which can either improve throughput or performance over DSM for PSK. Then we investigate the impact of time-varying fading on DSM. We find performance degrades if the fading is too fast due to differential detection. The impact of a long outer error control code (ECC) is also considered. Its performance is limited by the slowly varying channel required for differential detection. We consider using reconfigurable antennas to periodically change the channel conditions and hence significantly improve coded performance for DSM systems.

Single-RF Index Shift Keying Aided Differential Space–Time Block Coding

“…More explicitly, the transmit-signal matrix is now given by S n = Γ n S n , where S n is the PSK-aided unitary transmitsignal matrix of (3) , and the throughput is increased to R = log 2 e I T = log 2 I+log 2 LA T . In order to guarantee that all the transmitted signals in S n are drawn from the equi-spaced star QAM constellation, we propose for the DSTM scheme to employ the ring-amplitude encoding methods of DASK and ASK in [11], [36], [37], which are summarized in Table VII. More explicitly, for DSTM using DASK, differential encoding is applied both to the unitary matrices and to the ring-amplitudes by:…”

“…We note that the LS-DD of DSTM using DASK may also be obtained based on the extension of the received signal model of (33) using the differential encoding of (31) as Y n = X n−1 (Y n−1 − V n−1 ) + V n , which was used in [11], [36], [37]. Similarly, the LS-DD of DSTM using ASK may be obtained according to the extension of (33) (32) as Y n = 1 Γn−1 X n−1 (Y n−1 − V n−1 ) + V n , which was employed in [13], [33], [68].…”

“…Similarly, the LS-DD of DSTM using ASK may be obtained according to the extension of (33) (32) as Y n = 1 Γn−1 X n−1 (Y n−1 − V n−1 ) + V n , which was employed in [13], [33], [68]. Therefore, the detectors relying on Y n−1 = S n−1 H that have been popularly used in the literature [11], [13], [33], [36], [37], [68] in fact correspond to the sub-optimal LS solution, which suffers from a performance loss compared to the ML-DD and MMSE-DD.…”

“…Unlike the solutions in [38], [39], the proposed DSM detector does not impose any performance loss. 3) Furthermore, in order to improve the performance of the finite-cardinality DSTM schemes at high throughputs, we propose to generalize Differential Amplitude Shift Keying (DASK) and Amplitude Shift Keying (ASK), which form the classic multi-level-ring star QAM constellation that subsumes the two/four-level-ring DASK solutions of [11], [36], [37] as special cases. Although the DASK approach has been popularly used in DSTM schemes [11], [36], [37], our generalized ASK technique is capable of achieving a higher capacity and a better performance in channel coding assisted systems.…”

“…3) Furthermore, in order to improve the performance of the finite-cardinality DSTM schemes at high throughputs, we propose to generalize Differential Amplitude Shift Keying (DASK) and Amplitude Shift Keying (ASK), which form the classic multi-level-ring star QAM constellation that subsumes the two/four-level-ring DASK solutions of [11], [36], [37] as special cases. Although the DASK approach has been popularly used in DSTM schemes [11], [36], [37], our generalized ASK technique is capable of achieving a higher capacity and a better performance in channel coding assisted systems. 4) Moreover, since the employment of star QAM constellations imposes the ring-amplitude dependent signal power problem for detection, we further develop bespoke Maximum-Likelihood (ML), Minimum Mean Squared Error (MMSE) and Least Square (LS) detectors for DSTM using star QAM, which exhibit different performance versus complexity tradeoffs.…”