Reconfigurable Intelligent Surface-assisted Indoor Millimeter-wave
Communications for Mobile Robots
Abstract
Reconfigurable intelligent surfaces (RISs) and millimeter-wave (mmWave)
communications have been considered for providing wireless connectivity
to mobile robots used in industrial plants and other indoor
environments. However, the existing works have not sufficiently studied
how the number and deployment locations of RISs should be optimized for
serving a mobile robot. In this paper, we study RIS-assisted mmWave
communications for a robot moving around fixed obstacles in an indoor
industrial environment. For a fixed total number of reflecting elements,
we formulate an optimization problem to minimize the transmission energy
consumption of the access point (AP) while ensuring the robot’s received
signal-to-noise ratio (SNR) above a threshold throughout its journey by
jointly optimizing the number, positions and phase shifts of RISs and
the beamforming vectors of the AP. To solve the formulated nonconvex
optimization problem, we devise an iterative algorithm that decomposes
it into two subproblems (i.e., optimizing the phase shifts of RISs and
the beamforming vector of the AP, and optimizing the number and
locations of RISs) and solves them alternately. Simulation results show
that the proposed algorithm converges fast and can obtain the best
number and locations of RISs that lead to a transmission energy
consumption of the AP much lower than the benchmark schemes.