On dual-mode index modulation in MIMO-OTFS systems

Abstract

International audienceOrthogonal time frequency space (OTFS) is a two-dimensional (2D) modulation scheme operating in the delay-Doppler domain. By mapping information symbols into this domain, OTFS effectively transforms a time-varying multipath channel into an almost non-fading 2D channel, enabling all symbols in a frame to experience the same channel gain. To further enhance the bit error rate (BER) performance and spectral efficiency compared to conventional MIMO-OTFS schemes, we consider the dual-mode OTFS system with index modulation (OTFS-DM-IM) in a MIMO setting, hereafter referred to as MIMO-OTFS-DM-IM. A novel low-complexity symbol detection algorithm, termed sparse message passing-energy detection (SMP-ED), is developed, and a formal diversity analysis of the proposed system is presented. Analytical and simulation results show that the scheme achieves full diversity in the delay-Doppler domain. In addition, the upper bound of the average bit error probability (ABEP) is derived using the pairwise error probability (PEP) framework. Simulation results confirm that the proposed MIMO-OTFS-DM-IM system outperforms existing schemes in terms of BER while maintaining low complexity, and achieves a higher diversity order than conventional MIMO-OTFS systems, demonstrating its strong potential for practical wireless communication deployments