  Millimeter-wave (mmWave) technology holds the potential to revolutionize
head-mounted displays (HMDs) by enabling high-speed wireless communication with
nearby processing nodes, where complex video rendering can take place. However,
the sparse angular profile of mmWave channels, coupled with the narrow field of
view (FoV) of patch-antenna arrays and frequent HMD rotation, can lead to poor
performance.
  We introduce six channel performance metrics to evaluate the performance of
an HMD equipped with mmWave arrays. We analyze the metrics using analytical
models, discuss their impact for the application, and apply them to 28 GHz
channel sounding data, collected in a conference room using eight HMD
patch-antenna arrays, offset by 45 degrees from each other in azimuth.
  Our findings confirm that a single array performs poorly due to the narrow
FoV, and featuring multiple arrays along the HMD's azimuth is required. Namely,
the broader FoV stabilizes channel gain during HMD rotation, lessens the
attenuation caused by line of sight (LoS) obstruction, and increases the
channel's spatial multiplexing capability. In light of our findings, we
conclude that it is imperative to either equip the HMD with multiple arrays or,
as an alternative approach, incorporate macroscopic diversity by leveraging
distributed access point (AP) infrastructure.
