Grant-Free NOMA-OTFS Paradigm: Enabling Efficient Ubiquitous Access for LEO Satellite Internet-of-Things

TL;DR

This paper introduces a novel grant-free NOMA-OTFS paradigm designed to enable efficient, low-latency, and Doppler-robust access for IoT devices via LEO satellites, addressing current limitations in satellite-based multiple access schemes.

Contribution

It proposes a new NGMA scheme combining GF-NOMA and OTFS to improve connectivity, latency, and Doppler resilience in LEO satellite IoT networks.

Findings

Enhanced access latency reduction

Improved Doppler robustness

Potential for scalable satellite IoT connectivity

Abstract

With the blooming of Internet-of-Things (IoT), we are witnessing an explosion in the number of IoT terminals, triggering an unprecedented demand for ubiquitous wireless access globally. In this context, the emerging low-Earth-orbit satellites (LEO-SATs) have been regarded as a promising enabler to complement terrestrial wireless networks in providing ubiquitous connectivity and bridging the ever-growing digital divide in the expected next-generation wireless communications. Nevertheless, the harsh conditions posed by LEO-SATs have imposed significant challenges to the current multiple access (MA) schemes and led to an emerging paradigm shift in system design. In this article, we first provide a comprehensive overview of the state-of-the-art MA schemes and investigate their limitations in the context of LEO-SATs. To this end, we propose a novel next generation MA (NGMA), which amalgamates the grant-free non-orthogonal multiple access (GF-NOMA) mechanism and the orthogonal time frequency space (OTFS) waveform, for simplifying the connection procedure with reduced access latency and enhanced Doppler-robustness. Critical open challenging issues and future directions are finally presented for further technical development.