Space-Time Multiple-Mode Orthogonal Frequency Division Multiplexing With Index Modulation

Multiple-mode orthogonal frequency division multiplexing with index modulation (MM-OFDM-IM) improves the spectral efficiency of the conventional OFDM-IM scheme by considering multiple distinguishable constellations for signal modulation. In this paper, we propose a novel scheme, called space-time MM-OFDM-IM (ST-MM-OFDM-IM), to increase the transmit diversity of MM-OFDM-IM. In ST-MM-OFDM-IM, the signal matrix, which consists of multiple signal vectors of MM-OFDM-IM, is transmitted over multiple time slots by following a specific rule. A low-complexity detection is proposed to mitigate the high burden of the optimal maximum-likelihood detection at the receiver side. A closed-form upper bound on the bit error rate is derived to evaluate the performance of ST-MM-OFDM-IM. Moreover, a diversity improving scheme of ST-MM-OFDM-IM is also studied to obtain full transmit diversity. Simulation results verify the theoretical analysis and show that ST-MM-OFDM-IM outperforms the conventional MM-OFDM-IM scheme.