This report summarizes some considerations on possible evolutions of grant-free random access in the next generation of the 3GPP wireless cellular standard. The analysis is carried out by mapping the problem to the recently-introduced unsourced multiple access channel (UMAC) setup. By doing so, the performance of existing solutions can be benchmarked with information-theoretic bounds, assessing the potential gains that can be achieved over legacy 3GPP schemes. The study focuses on the two-step random access (2SRA) protocol introduced by Release 16 of the 5G New Radio standard, investigating its applicability to support large MTC / IoT terminal populations in a grant-free fashion. The analysis shows that the existing 2SRA scheme may not succeed in providing energy-efficient support to large user populations. Modifications to the protocol are proposed that enable remarkable gains in both energy and spectral efficiency while retaining a strong resemblance to the legacy protocol.
@article{arxiv.2405.03348,
title = {Evolution of the 5G New Radio Two-Step Random Access towards 6G Unsourced MAC},
author = {Patrick Agostini and Jean-Francois Chamberland and Federico Clazzer and Johannes Dommel and Gianluigi Liva and Andrea Munari and Krishna Narayanan and Yury Polyanskiy and Slawomir Stanczak and Zoran Utkovski},
journal= {arXiv preprint arXiv:2405.03348},
year = {2024}
}