  This paper studies the effect of the user hand grip on the design of
beamforming codebooks for 5G millimeter-wave (mmWave) mobile handsets. The
high-frequency structure simulator (HFSS) is used to characterize the radiation
fields for fourteen possible handgrip profiles based on experiments we
conducted. The loss from hand blockage on the antenna gains can be up to 20-25
dB, which implies that the possible hand grip profiles need to be taken into
account while designing beam codebooks. Specifically, we consider three
different codebook adaption schemes: a grip-aware scheme, where perfect
knowledge of the hand grip is available; a semi-aware scheme, where just the
application (voice call, messaging, etc.) and the orientation of the mobile
handset is known; and a grip-agnostic scheme, where the codebook ignores hand
blockage. Our results show that the ideal grip-aware scheme can provide more
than 50% gain in terms of the spherical coverage over the agnostic scheme,
depending on the grip and orientation. Encouragingly, the more practical
semi-aware scheme we propose provides performance approaching the fully
grip-aware scheme. Overall, we demonstrate that 5G mmWave handsets are
different from pre-5G handsets: the user grip needs to be explicitly factored
into the codebook design.
