Massive MIMO goes Sub-GHz: Implementation and Experimental Exploration for LPWANs

TL;DR

This paper explores the use of massive MIMO technology at sub-GHz frequencies for LPWANs, demonstrating potential benefits in reliability and coverage through experimental measurements of array gain and channel hardening.

Contribution

It provides the first experimental assessment of massive MIMO at sub-GHz frequencies, analyzing antenna configurations, propagation effects, and their impact on system performance.

Findings

Massive MIMO improves reliability and coverage in sub-GHz LPWANs.

Channel hardening effects are observed at sub-GHz frequencies.

Array gain benefits are demonstrated through real-world measurements.

Abstract

Low-Power Wide-Area Networks operating in the unlicensed bands are being deployed to connect a rapidly growing number of Internet-of-Things devices. While the unlicensed sub-GHz band offers favorable propagation for long-range connections, measurements show that the energy consumption of the nodes is still mostly dominated by the wireless transmission affecting their autonomy. We investigate the potential benefits of deploying massive MIMO technology to increase system reliability and at the same time support low-energy devices with good coverage at sub-GHz frequencies. The impact of different antenna configurations and propagation conditions is analyzed. Both actual average experienced array gain and channel hardening are examined. The assessment demonstrates the effect of channel hardening as well as the potential benefits of the experienced array gain. These measurements serve as a first assessment of the channel conditions of massive MIMO at sub-GHz frequencies and are, to the best of our knowledge, the first of its kind.