Single-RF Spatial Modulation Requires Single-Carrier Transmission: Frequency-Domain Turbo Equalization for Dispersive Channels

In this paper, we propose a broadband single-carrier (SC) spatial modulation (SM)-based multiple-input-multiple-output (MIMO) architecture relying on a soft decision (SoD) frequency-domain equalization (FDE) receiver. We demonstrate that conventional orthogonal-frequency-division-multiplexing (OFDM)-based broadband transmissions are not readily suitable for the single-radio-frequency-assisted SM-MIMO schemes since this scheme exhibits no substantial performance advantage over single-antenna transmissions. To circumvent this limitation, a low-complexity SoD FDE algorithm based on the minimum mean square error (MMSE) criterion is invoked for our broadband SC-based SM-MIMO scheme, which is capable of operating in a strongly dispersive channel having a long channel impulse response at moderate decoding complexity. Furthermore, our SoD FDE attains a near-capacity performance with the aid of a three-stage concatenated SC-based SM architecture.