  The millimeter wave (mmWave) band, which is a prime candidate for 5G cellular
networks, seems attractive for wireless energy harvesting. This is because it
will feature large antenna arrays as well as extremely dense base station (BS)
deployments. The viability of mmWave for energy harvesting though is unclear,
due to the differences in propagation characteristics such as extreme
sensitivity to building blockages. This paper considers a scenario where
low-power devices extract energy and/or information from the mmWave signals.
Using stochastic geometry, analytical expressions are derived for the energy
coverage probability, the average harvested power, and the overall
(energy-and-information) coverage probability at a typical wireless-powered
device in terms of the BS density, the antenna geometry parameters, and the
channel parameters. Numerical results reveal several network and device level
design insights. At the BSs, optimizing the antenna geometry parameters such as
beamwidth can maximize the network-wide energy coverage for a given user
population. At the device level, the performance can be substantially improved
by optimally splitting the received signal for energy and information
extraction, and by deploying multi-antenna arrays. For the latter, an efficient
low-power multi-antenna mmWave receiver architecture is proposed for
simultaneous energy and information transfer. Overall, simulation results
suggest that mmWave energy harvesting generally outperforms lower frequency
solutions.
