Unsourced Random Access with Threshold$-$Based Feedback

TL;DR

This paper introduces a threshold-based feedback mechanism for unsourced random access that reduces user complexity and improves error rates and SNR efficiency in multi-user communication systems.

Contribution

It presents a novel feedback algorithm and packet format enabling users to estimate channels and infer feedback with lower complexity than traditional acknowledgment methods.

Findings

Reduces user complexity compared to positive/negative acknowledgments

Significantly lowers packet error rates and required SNR levels

Effective for systems with varying numbers of active users

Abstract

In this paper we focus on a feedback mechanism for unsourced random access (URA) communications. We propose an algorithm to construct feedback packets broadcasted to the users by the base station (BS) as well as the feedback packet format that allows the users to estimate their channels and infer positive or negative feedback based on the presented thresholding algorithm. We demonstrate that the proposed feedback imposes a much smaller complexity burden on the users compared to the feedback that positively acknowledges all successful or negatively acknowledges all undecoded users. We also show that the proposed feedback technique can lead to a substantial reduction in the packet error rates and signal-to-noise ratios (SNR)s required to support various numbers of active users in the system.