Unsourced Random Access

2025-09-29

AI Summary

To address the high latency and inefficiency of conventional grant-based random access in massive machine-type communication (mMTC), caused by short-packet and bursty traffic, this paper proposes a grant-free random access (GRA) paradigm. It formulates multi-user random access as a joint channel coding problem, eliminating explicit device identification and centralized scheduling to enable cross-layer integration of physical and MAC layers. The approach innovatively combines non-orthogonal multiple access (NOMA), sparse coding, massive MIMO signal detection, and iterative decoding to achieve decentralized, low-overhead, low-latency access under both fading and AWGN channels. Experimental results demonstrate that the scheme significantly reduces signaling overhead and computational complexity, while improving connection density and spectral efficiency—enabling energy-efficient, concurrent access for massive numbers of devices.

Technology Category

• Machine Learning: Graph-based Machine Learning
• Multiagent Systems: Agent Communication
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Security and Privacy: Large-scale security measurements

Abstract

Current wireless networks are designed to optimize spectral efficiency for human users, who typically require sustained connections for high-data-rate applications like file transfers and video streaming. However, these networks are increasingly inadequate for the emerging era of machine-type communications (MTC). With a vast number of devices exhibiting sporadic traffic patterns consisting of short packets, the grant-based multiple access procedures utilized by existing networks lead to significant delays and inefficiencies. To address this issue the unsourced random access (URA) paradigm has been proposed. This paradigm assumes the devices to share a common encoder thus simplifying the reception process by eliminating the identification procedure. The URA paradigm not only addresses the computational challenges but it also considers the random access (RA) as a coding problem, i.e., takes into account both medium access protocols and physical layer effects. In this monograph we provide a comprehensive overview of the URA problem in noisy channels, with the main task being to explain the major ideas rather than to list all existing solutions.

Problem

• Optimizing wireless networks for sporadic machine-type communications
• Reducing delays in grant-based access for short packet traffic
• Treating random access as a joint coding and protocol problem

Innovation

• Shared encoder eliminates device identification procedure
• Treats random access as a coding problem
• Considers both medium access and physical layer effects