Non-Orthogonal Time-Frequency Space Modulation

TL;DR

This paper introduces a novel non-orthogonal time-frequency space modulation technique using TFST, enhancing spectral efficiency and low latency for high-mobility communication systems, supported by a new decoding algorithm.

Contribution

It proposes a new TFST-based non-orthogonal modulation scheme and a modified sphere decoding algorithm for efficient high-mobility communications.

Findings

Improved spectral efficiency in high-mobility scenarios

Low-latency performance demonstrated in simulations

Effective decoding with the proposed sphere decoding algorithm

Abstract

This paper proposes a Time-Frequency Space Transformation (TFST) to derive non-orthogonal bases for modulation techniques over the delay-doppler plane. A family of Overloaded Delay-Doppler Modulation (ODDM) techniques is proposed based on the TFST, which enhances flexibility and efficiency by expressing modulated signals as a linear combination of basis signals. A Non-Orthogonal Time-Frequency Space (NOTFS) digital modulation is derived for the proposed ODDM techniques, and simulations show that they offer high-mobility communication systems with improved spectral efficiency and low latency, particularly in challenging scenarios such as high overloading factors and Additive White Gaussian Noise (AWGN) channels. A modified sphere decoding algorithm is also presented to efficiently decode the received signal. The proposed modulation and decoding techniques contribute to the advancement of non-orthogonal approaches in the next-generation of mobile communication systems, delivering superior spectral efficiency and low latency, and offering a promising solution towards the development of efficient high-mobility communication systems.