Unsourced Multiple Access: A Coding Paradigm for Massive Random Access

TL;DR

This paper introduces unsourced multiple access (UMAC), a new coding paradigm for massive random access in wireless networks, highlighting its evolution, classification, and practical benefits including energy efficiency and scalability.

Contribution

It provides a comprehensive tutorial, classification, and practical modification of existing standards based on UMAC theory, advancing the understanding and implementation of massive random access.

Findings

UMAC can significantly improve energy efficiency in 5GNR systems.

A simple modification to 5GNR enhances handling of many users.

UMAC enables high user capacity beyond current standards.

Abstract

This paper is a tutorial introduction to the field of unsourced multiple access (UMAC) protocols. We first provide a historical survey of the evolution of random access protocols, focusing specifically on the case in which uncoordinated users share a wireless broadcasting medium. Next, we highlight the change of perspective originated by the UMAC model, in which the physical and medium access layer's protocols cooperate, thus reframing random access as a novel coding-theoretic problem. By now, a large variety of UMAC protocols (codes) emerged, necessitating a certain classification that we indeed propose here. Although some random access schemes require a radical change of the physical layer, others can be implemented with minimal changes to existing industry standards. As an example, we discuss a simple modification to the 5GNR Release 16 random access channel that builds on the UMAC theory and that dramatically improves energy efficiency for systems with even moderate number of simultaneous users (e.g., $5-10$ dB gain for $10-50$ users), and also enables handling of high number of users, something completely out of reach of the state-of-the-art.