Channel Characterization of IRS-assisted Resonant Beam Communication Systems

TL;DR

The paper tackles the challenge of maintaining high-rate optical wireless links when line-of-sight is disrupted by obstructions. It introduces an Intelligent Reflecting Surface (IRS) aided resonant beam communication (RBC) system that uses optical frequency doubling to carry data on the downlink while preserving resonant cavity dynamics. A near-field Fresnel-diffraction channel model is developed for both direct and IRS-assisted paths, and a dynamic beam-splitting strategy optimizes the split between channels to maximize the frequency-doubled output power and channel capacity. Numerical results show that the IRS-assisted path can compensate for losses due to obstruction and misalignment, achieving high SNR and roughly 11 bps/Hz of spectral efficiency under favorable conditions. This approach offers a practical path to robust, high-speed OWC in indoor environments with dynamic obstructions.

Abstract

To meet the growing demand for data traffic, spectrum-rich optical wireless communication (OWC) has emerged as a key technological driver for the development of 6G. The resonant beam communication (RBC) system, which employs spatially separated laser cavities as the transmitter and receiver, is a high-speed OWC technology capable of self-alignment without tracking. However, its transmission through the air is susceptible to losses caused by obstructions. In this paper, we propose an intelligent reflecting surface (IRS) assisted RBC system with the optical frequency doubling method, where the resonant beam in frequency-fundamental and frequency-doubled is transmitted through both direct line-of-sight (LoS) and IRS-assisted channels to maintain steady-state oscillation and enable communication without echo-interference, respectively. Then, we establish the channel model based on Fresnel diffraction theory under the near-field optical propagation to analyze the transmission loss and frequency-doubled power analytically. Furthermore, communication power can be maximized by dynamically controlling the beam-splitting ratio between the two channels according to the loss levels encountered over air. Numerical results validate that the IRS-assisted channel can compensate for the losses in the obstructed LoS channel and misaligned receivers, ensuring that communication performance reaches an optimal value with dynamic ratio adjustments.

Figures (10)

• Figure 1: The example system structure of IRS-assisted RBC system.
• Figure 2: The schematic of the near-field and far-field according to Rayleigh distance.
• Figure 3: The schematic illustration of LoS channel with misalignment receivers.
• Figure 4: The example coordinate system of IRS-assisted RBC system.
• Figure 5: The changes of E2E efficiency $\eta$ in direct LoS and IRS-assisted channels under different parameters ($P_{\rm{in}}=200$ W).