A Compressive Sensing and Denoising RCAN-Based Channel Estimation Scheme for OTFS System

Orthogonal time frequency space (OTFS) systems effectual mitigate severe Doppler shifts, providing extensive prospects for high-mobility applications. Due to the sparsity of its delay-Doppler (DD) domain channel, compressive sensing (CS) is utilized as the method to address the majority of current OTFS channel estimation (CE) issues. However, these CS-based methods suffer from the drawback of challenging noise elimination for non-zero elements. In this paper, a denoising network-based CS algorithm is proposed for CE in the OTFS system. Specifically, we utilize the sparsity adaptive matching pursuit (SAMP) algorithm to perform the reconstruction of the DD domain channel and generate initial channel response. Then, a residual channel attention network (RCAN) is designed for denoising, which can generate an accurate channel response. The proposed RCAN trains a deep network model through the residual in residual (RIR) structure and can use the channel attention (CA) mechanism to consider different weights of channel-wise features. The simulation results demonstrate that the denoising RCAN-based CE scheme exhibits a commendable trade-off between achieving exceptional performance and maintaining low complexity. Furthermore, the scheme’s remarkable robustness to channel mismatch and variations in speed has been well substantiated.

I. Introduction

The sixth generation wireless communication aims to realize air-space-ground integration [1], enabling comprehensive and ubiquitous connectivity. The emerging high-mobility applications like low earth orbit satellite (LEOS) communication, mobile communication airborne (MCA) and underwater acoustic communication (UWA), all suffer from severe Doppler shift and require high reliability. Traditional and popular orthogonal frequency division multiplexing (OFDM) technology is considered to be used in the above mentioned high-mobility scenarios. However, the Doppler frequency shift problem in OFDM system can lead to inter-carrier interference, seriously destroying the orthogonality of sub-carriers and resulting in performance decline.