Optical intelligent reflecting surfaces (OIRS) can improve the coverage of indoor visible light communication (VLC) systems, however, practical deployment requires a finite offline codebook to avoid repeated real-time optimisation of mirror orientations. A uniform codebook with fixed angular steps does not provide uniform coverage on the user plane, because the mapping from steering angles to reflection locations on the user plane is nonlinear. To address this problem, this paper proposes a geometric-optics-based non-uniform codebook design for OIRS-assisted VLC systems. The proposed method constructs an individual codebook for each IRS element according to its geometric position, so that the reflected beams are distributed more uniformly over the user plane. The codebook accuracy is evaluated using the Frobenius norm of the channel error matrix. Simulation results show that the proposed design provides more uniform spatial mapping with fewer codewords than the uniform codebook, and that the sweep-angle resolution has a stronger effect on the codebook accuracy than the tilt-angle resolution.

翻译：光学智能反射面（OIRS）可提升室内可见光通信（VLC）系统的覆盖范围，然而实际部署中需采用有限离线码本来避免对反射镜方向的重复实时优化。由于转向角到用户平面反射位置的映射具有非线性特性，采用固定角度步长的均匀码本无法在用户平面上提供均匀覆盖。为解决该问题，本文提出一种基于几何光学的非均匀码本设计方法，适用于OIRS辅助的VLC系统。该方法根据每个IRS单元的几何位置构建独立码本，使反射光束在用户平面上分布更均匀。通过信道误差矩阵的Frobenius范数评估码本精度。仿真结果表明，与均匀码本相比，所提设计能以更少码字实现更均匀的空间映射，且扫描角分辨率对码本精度的影响大于倾斜角分辨率。