Delay-Doppler Domain Pulse Design for OTFS-NOMA

TL;DR

This paper proposes a novel Hermite function-based pulse design for OTFS-NOMA systems, improving spectral efficiency and BER performance in high-mobility channels with minimal complexity.

Contribution

Introduction of Hermite functions for OTFS-NOMA pulse design, extending biorthogonal train-pulse concept, leading to superior performance over traditional schemes.

Findings

Hermite functions outperform traditional OTFS-NOMA in BER.

Spectral efficiency is K times higher than OTFS-CDM-NOMA.

Minimal demodulation complexity involved.

Abstract

We address the challenge of developing an orthogonal time-frequency space (OTFS)-based non-orthogonal multiple access (NOMA) system where each user is modulated using orthogonal pulses in the delay Doppler domain. Building upon the concept of the sufficient (bi)orthogonality train-pulse [1], we extend this idea by introducing Hermite functions, known for their orthogonality properties. Simulation results demonstrate that our proposed Hermite functions outperform the traditional OTFS-NOMA schemes, including power-domain (PDM) NOMA and code-domain (CDM) NOMA, in terms of bit error rate (BER) over a high-mobility channel. The algorithm's complexity is minimal, primarily involving the demodulation of OTFS. The spectrum efficiency of Hermite-based OTFS-NOMA is K times that of OTFS-CDM-NOMA scheme, where K is the spreading length of the NOMA waveform.