Performance Characterization of a Real-Time Massive MIMO System with LOS Mobile Channels

TL;DR

This paper presents real-world measurements of a massive MIMO system with 100 antennas in a LOS scenario with mobility, analyzing how mobility affects channel state information and system performance.

Contribution

It provides the first measured results of massive MIMO performance in LOS with mobility, highlighting the impact on CSI update rates and system robustness.

Findings

CSI update rate may need to increase by 7 times with 100 antennas.

Power control update rate can decrease by at least 5 times.

Mobility significantly affects massive MIMO channel characteristics.

Abstract

The first measured results for massive MIMO performance in a line-of-sight (LOS) scenario with moderate mobility are presented, with 8 users served in real-time using a 100-antenna base Station (BS) at 3.7 GHz. When such a large number of channels dynamically change, the inherent propagation and processing delay has a critical relationship with the rate of change, as the use of outdated channel information can result in severe detection and precoding inaccuracies. For the downlink (DL) in particular, a time division duplex (TDD) configuration synonymous with massive multiple-input, multiple-output (MIMO) deployments could mean only the uplink (UL) is usable in extreme cases. Therefore, it is of great interest to investigate the impact of mobility on massive MIMO performance and consider ways to combat the potential limitations. In a mobile scenario with moving cars and pedestrians, the massive MIMO channel is sampled across many points in space to build a picture of the overall user orthogonality, and the impact of both azimuth and elevation array configurations are considered. Temporal analysis is also conducted for vehicles moving up to 29km/h and real-time bit error rates (BERs) for both the UL and DL without power control are presented. For a 100-antenna system, it is found that the channel state information (CSI) update rate requirement may increase by 7 times when compared to an 8-antenna system, whilst the power control update rate could be decreased by at least 5 times relative to a single antenna system.