An Energy Efficient Dual IRS-Aided Outdoor-to-Indoor Communication System

Intelligent reflecting surfaces (IRSs) have emerged as a promising technology to realize energy- and spectrally efficient low-cost wireless communication systems. In this work, we propose a dual IRS-aided communication model for outdoor-to-indoor wireless communication. The scenario comprises an outdoor base station that communicates with the indoor users with the aid of two distinct IRSs. Specifically, we derived the closed-form expressions of the spectral efficiency (SE), energy efficiency (EE), and outage probability (OP) for the dual IRS-aided communication system. The results show that utilizing distributed IRSs, i.e., by dividing the large IRS into two smaller IRSs, significant performance gains in the SE and EE can be achieved over the single IRS scenario. Although the multiplicative pathloss effect impacts performance, it can be mitigated by increasing the number of reflecting elements. Initially, we evaluated the performance of a single-user scenario; later on, we generalized it to the multiuser scenario with nonorthogonal multiple access. Further, the performance is also compared with the baseline direct cellular transmission. The analytical derivations of the SE, EE, and OP are corroborated through simulations.