Design and Performance Analysis of Spatial-Index Modulation Based Orthogonal Time Frequency Space System

In order to enhance the effectiveness and the reliability of high mobility communication, we propose a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, which is a three dimensional index modulation (IM) adopting the transmit antenna, delay, and Doppler indexes in the space and delay-Doppler domains, respectively, to achieve higher transmission rate. The system model and the detailed signal processing of the SIM-OTFS system are provided. Then, we also analyze the average bit error rate (ABER) performance of the proposed SIM-OTFS system based on the union bound theory. Numerical results verify the correctness of the theoretical ABER analysis and demonstrate the ABER superiority of the SIM-OTFS system over the traditional multiple-input multiple-output OTFS (MIMO-OTFS) and spatial modulation (SM) and IM based orthogonal frequency division multiplexing (SM-OFDM-IM) systems under high mobility. Furthermore, the influence of the multipath channel on the ABER performance of the SIM-OTFS system is also illustrated.