Index Modulation Aided Orthogonal Time Sequency Multiplexing

In this paper, the concept of index modulation (IM) is introduced to the field of orthogonal time sequence multiplexing (OTSM), and an IM-aided OTSM (IM-OTSM) scheme is proposed to improve the bit error rate (BER) performance under high mobility. In IM-OTSM, information bits are transmitted simultaneously through constellation symbols and the indices of the active delay sequence (DS) grid, which further enhances both spectral efficiency (SE) and energy efficiency (EE). In addition, the inactive grid naturally acts as a protection interval which alleviates inter-block interference (IBI). A two-stage detector is employed to reduce the detection complexity and The mathematical expression for the average bit error probability (ABEP) is derived in this paper. Finally, simulation results validate the accuracy of the derived ABEP expression in the high signal-to-noise ratio (SNR) region, demonstrating that the IM-OTSM scheme outperforms its competitors in terms of performance.