  We address the problem of pedestrian blockage in outdoor mm-Wave networks,
which can disrupt Line of Sight (LoS) communication and result in an outage.
This necessitates either reacquisition as a new user that can take up to 1.28
sec in 5G New Radio, disrupting high-performance applications, or handover to a
different base station (BS), which however requires very costly dense
deployments to ensure multiple base stations are always visible to a mobile
outdoors. We have found that there typically exists a strong ground reflection
from concrete and gravel surfaces, within 4-6 dB of received signal strength
(RSS) of LoS paths. The mobile can switch to such a Non-Line Sight (NLoS) beam
to sustain the link for use as a control channel during a blockage event. This
allows the mobile to maintain time-synchronization with the base station,
allowing it to revert to the LoS path when the temporary blockage disappears.
We present a protocol, Terra, to quickly discover, cache, and employ ground
reflections. It can be used in most outdoor built environments since pedestrian
blockages typically last only a few hundred milliseconds.
