Max-Min Area Coverage in IRS Assisted Networks: Rotatable Design and Experimental Verification

Intelligent reflecting surfaces (IRSs) have been proven to be high gain from the validation perspective of commercial mobile networks. However, the rotation of the IRS is ignored by most works, and real-time adjustment of IRS parameters for dynamic discrete user locations is difficult to achieve in practice due to the difficulty of the instantaneous cascaded channel estimation. In this paper, a new deployment design and experimental measurement for IRS-aided indoor communications is carried out, where the rotation of the IRS is considered to maximize the worst signal to noise ratio (SNR) over all locations in a target area, and the sub-optimal closed solution is obtained and verified by experiment. Specifically, the size of the target coverage area is modeled into the objective problem and an accurate IRS-aided wireless communication network model with IRS rotation is established. Furthermore, by dividing the IRS/area into an equal number of sub-IRS/sub-areas, theoretical closed-form formulas for sub-optimal IRS phase shift and rotation angle for area coverage are given by using the beam-broadening technique and the approximation of regional center alignment. Besides, a physical demonstration system is constructed and a large number of experimental measurements are carried out, which shows that the optimal rotation angle is very close to the theoretical formula given by us. Additionally, numerical comparison of simulation results show that our proposed scheme can obtain 14.1 dB gain for the worst SNR compared with the well-known baseline.