8 research outputs found
Path Loss Modeling and Measurements for Reconfigurable Intelligent Surfaces in the Millimeter-Wave Frequency Band
Reconfigurable intelligent surfaces (RISs) provide an interface between the
electromagnetic world of wireless propagation environments and the digital
world of information science. Simple yet sufficiently accurate path loss models
for RISs are an important basis for theoretical analysis and optimization of
RIS-assisted wireless communication systems. In this paper, we refine our
previously proposed free-space path loss model for RISs to make it simpler,
more applicable, and easier to use. The impact of the antenna's directivity of
the transmitter, receiver, and the unit cells of the RIS on the path loss is
explicitly formulated as an angle-dependent loss factor. The refined model
gives more accurate estimates of the path loss of RISs comprised of unit cells
with a deep sub-wavelength size. Based on the proposed model, the properties of
a single unit cell are evaluated in terms of scattering performance, power
consumption, and area, which allows us to unveil fundamental considerations for
deploying RISs in high frequency bands. Two fabricated RISs operating in the
millimeter-wave (mmWave) band are utilized to carry out a measurement campaign.
The measurement results are shown to be in good agreement with the proposed
path loss model. In addition, the experimental results suggest an effective
form to characterize the power radiation pattern of the unit cell for path loss
modeling.Comment: Model refinements are introduced to previously proposed free-space
path loss model for RISs in order to make it simpler and easier to use. The
properties of a single unit cell are evaluated in terms of scattering
performance, power, and area, as it is the basic element of an RIS. We report
the world's first measurement campaign in the mmWave frequency band to
validate the path loss model for RIS