Profuse Channel Estimation and Signal Detection Techniques for Orthogonal Time Frequency Space in 6G Epoch: A Survey

Orthogonal time frequency space (OTFS) modulation is a booming multicarrier modulation technique and a promising candidate for achieving quality of services in high mobility scenarios of 5G new radio (NR) and beyond wireless communication systems. OTFS addresses the high Doppler channel environment aiding the 2D delay-Doppler (DD) domain rather than the conventional time frequency domain. OTFS exploits several 2D transformations to transform a temporally variant multipath channel into a nearly invariant DD. The information symbols are embedded and the channel is represented sparsely in the DD domain. OTFS combats the challenges like inter-symbol interference, inter-carrier interference, etc., and outperforms the orthogonal frequency division multiplexing scheme. This paper presents a detailed survey of various channel estimation (CE) and signal detection (SD) techniques with vital mathematical expressions adopted to achieve enhanced performance. The significant benefits, techniques aided, and challenges in CE and SD for OTFS to a wide range of applications in high mobility scenarios are also discussed. Moreover, the crucial lessons erudite from the review along with the future research directions and key challenges in integration of OTFS with recent technologies for achieving 6G benchmarks are conversed in this paper.