  Holographic Multiple Input Multiple Output (HMIMO), which integrates massive
antenna elements into a compact space to achieve a spatially continuous
aperture, plays an important role in future wireless networks. With numerous
antenna elements, it is hard to implement the HMIMO via phased arrays due to
unacceptable power consumption. To address this issue, reconfigurable
refractive surface (RRS) is an energy efficient enabler of HMIMO since the
surface is free of expensive phase shifters. Unlike traditional metasurfaces
working as passive relays, the RRS is used as transmit antennas, where the
far-field approximation does not hold anymore, urging a new performance
analysis framework. In this letter, we first derive the data rate of an
RRS-based single-user downlink system, and then compare its power consumption
with the phased array. Simulation results verify our analysis and show that the
RRS is an energy-efficient way to HMIMO.
