  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outdated channel information can result in severe detection and precoding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.
