Spatial-Index Modulation Based Orthogonal Time Frequency Space System in Vehicular Networks

In this paper, a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, is proposed to enhance the effectiveness and the reliability of high mobility vehicular networks in intelligent transportation systems. The SIM-OTFS system adopts a three dimensional index modulation (IM) technique which utilizes the transmit antenna, delay, and Doppler indexes in the space and delay-Doppler domains, respectively, to achieve a higher transmission rate. Considering the characteristics of vehicular networks, we first present the SIM-OTFS system design and the corresponding signal processing. Then, we derive the average bit error rate (ABER) upper bound of the SIM-OTFS system by the union bound theory. Moreover, the diversity, the coding gain, and the complexity of the SIM-OTFS system are further investigated. Numerical results verify the theoretical analysis of the ABER and the diversity of the SIM-OTFS system, which shows the superiority of the SIM-OTFS system in the ABER performance over the multiple-input and multiple-output (MIMO) based OTFS (MIMO-OTFS) system. Meanwhile, the SIM-OTFS system realizes better performance than the spatial modulation (SM) and IM based orthogonal frequency division multiplexing (SM-OFDM-IM) system in high mobility vehicular communication with reasonable complexity sacrifice. Furthermore, the influence of the resolvable multipaths of the channel in vehicular networks on the ABER performance of the SIM-OTFS system is also illustrated.

Automated summary

This paper proposes a spatial-index modulation (SIM) based orthogonal time frequency space (OTFS) system, named SIM-OTFS, to enhance the performance of high mobility vehicular networks. The SIM-OTFS system utilizes a three dimensional index modulation (IM) technique to achieve higher transmission rate. The design, signal processing, and theoretical analysis of the SIM-OTFS system are presented, demonstrating its superiority over other systems in terms of average bit error rate (ABER) and diversity. Numerical results also show the influence of resolvable multipaths on the ABER performance of the SIM-OTFS system.