Precoded faster-than-Nyquist signaling using optimal power allocation for OTFS

TL;DR

This paper proposes a precoded OTFS scheme with faster-than-Nyquist signaling over doubly selective channels, improving spectral efficiency and Doppler resilience through optimal power allocation and eigenvalue decomposition for efficient demodulation.

Contribution

It introduces a novel FTN-based OTFS scheme with optimal power allocation and eigenvalue decomposition for enhanced spectral efficiency and Doppler resilience in doubly selective channels.

Findings

Enhanced spectral efficiency compared to Nyquist-based OTFS.

Achieved similar BER performance with higher information rate.

Optimized power allocation improves mutual information.

Abstract

A precoded orthogonal time frequency space (OTFS) modulation scheme relying on faster-than-Nyquist (FTN) transmission over doubly selective fading channels is {proposed}, which enhances the spectral efficiency and improves the Doppler resilience. We derive the input-output relationship of the FTN signaling in the delay-Doppler domain. Eigenvalue decomposition (EVD) is used for eliminating both the effects of inter-symbol interference and correlated additive noise encountered in the delay-Doppler domain to enable efficient symbol-by-symbol demodulation. Furthermore, the power allocation coefficients of individual frames are optimized for maximizing the mutual information under the constraint of the derived total transmit power. Our performance results demonstrate that the proposed FTN-based OTFS scheme can enhance the information rate while achieving a comparable BER performance to that of its conventional Nyquist-based OTFS counterpart that employs the same root-raised-cosine shaping filter.