Dual-Mode Index Modulation Schemes for CPSC-MIMO Systems

Abstract

Dual-mode index modulation schemes are those where a subset of the transmitted modulation symbols are from a different constellation than the rest of the transmitted modulation symbols. The indices of the symbols from two different constellations convey information bits in addition to those conveyed by the modulation symbols. In this paper, we employ this constellation-indexing technique to develop two new modulation schemes for frequency selective fading channels using cyclic-prefixed single-carrier (CPSC). We refer to these schemes as the dual-mode time index modulation (DM-TIM) and dual-mode space-time index modulation (DM-STIM). The DM-TIM is a single transmit antenna modulation scheme and DM-STIM is a multi-antenna multiple-input multiple-output (MIMO) modulation scheme. In DM-TIM, information bits are conveyed through constellation indexing in the time domain as well as M-ary modulation symbols. In DM-STIM, in addition to the above two modes, information bits are also conveyed through antenna indexing in the spatial domain. Hence, the proposed index modulation schemes provide high data rate. We compare the proposed dual-mode index modulation schemes with state-of-art index modulation schemes and show that the proposed schemes can achieve better bit-error performance. Further, we present low-complexity message passing based algorithm for the detection of large-dimensional DM-TIM and DM-STIM signals.