Energy Efficiency of MIMO Massive Unsourced Random Access with Finite Blocklength

TL;DR

This paper analyzes the energy efficiency limits of massive unsourced random access in MIMO channels, providing bounds and practical insights, revealing that URA can outperform sourced access in spectral efficiency.

Contribution

It derives tight bounds on energy-per-bit for URA in MIMO channels and compares practical schemes against these bounds, highlighting the efficiency advantages of URA.

Findings

Achievability and converse bounds are within 5 dB in the considered regime.

Practical schemes are less energy-efficient than theoretical bounds, especially with many users.

URA achieves higher spectral efficiency than sourced random access.

Abstract

This paper investigates the energy efficiency of massive unsourced random access~(URA) in multiple-input multiple-output quasi-static Rayleigh fading channels. Specifically, we derive achievability and converse bounds on the minimum required energy-per-bit under the per-user probability of error constraint, where the converse bounds contain two parts: one is general and the other is a weaker ensemble bound. Numerical evaluation shows that the gap between our achievability and converse bounds is less than $5$~dB in the considered regime. Some practical schemes are energy-inefficient compared with our bounds especially when there are many users. Moreover, we observe that in contrast to the sourced random access paradigm, the URA paradigm achieves higher spectral efficiency.