Block-Wise Index Modulation and Receiver Design for High-Mobility OTFS Communications

TL;DR

This paper introduces two novel block-wise index modulation schemes for OTFS in high-mobility environments, along with efficient detection algorithms, improving performance and robustness over existing methods.

Contribution

Proposes delay-IM and Doppler-IM schemes for OTFS, along with low-complexity detection algorithms, enhancing system performance in high-mobility scenarios.

Findings

Proposed schemes outperform existing IM-OTFS in error rate performance.

MLJSAPD and CMPD algorithms achieve robust detection with low complexity.

Simulation results confirm improved performance under imperfect CSI.

Abstract

As a promising technique for high-mobility wireless communications, orthogonal time frequency space (OTFS) has been proved to enjoy excellent advantages with respect to traditional orthogonal frequency division multiplexing (OFDM). Although multiple studies have considered index modulation (IM) based OTFS (IM-OTFS) schemes to further improve system performance, a challenging and open problem is the development of effective IM schemes and efficient receivers for practical OTFS systems that must operate in the presence of channel delays and Doppler shifts. In this paper, we propose two novel block-wise IM schemes for OTFS systems, named delay-IM with OTFS (DeIM-OTFS) and Doppler-IM with OTFS (DoIM-OTFS), where a block of delay/Doppler resource bins are activated simultaneously. Based on a maximum likelihood (ML) detector, we analyze upper bounds on the average bit error rates for the proposed DeIM-OTFS and DoIM-OTFS schemes, and verify their performance advantages over the existing IM-OTFS systems. We also develop a multi-layer joint symbol and activation pattern detection (MLJSAPD) algorithm and a customized message passing detection (CMPD) algorithm for our proposed DeIMOTFS and DoIM-OTFS systems with low complexity. Simulation results demonstrate that our proposed MLJSAPD and CMPD algorithms can achieve desired performance with robustness to the imperfect channel state information (CSI).