Robust Consensus-Based Distributed Beamforming for Wideband Cell-free Multi-RIS MISO Systems
This work addresses the high coordination overhead and poor robustness of centralized beamforming in wideband cell-free multi-RIS-assisted MISO systems, which arise from imperfect channel state information and the frequency-selective response of reconfigurable intelligent surfaces (RISs). To overcome these challenges, the paper proposes a consensus-based distributed framework for joint active and passive beamforming. For the first time, consensus optimization is introduced into wideband multi-RIS cell-free systems, enabling distributed and robust phase control of RISs without requiring a central processing unit. The approach integrates Lorentzian-based RIS modeling with imperfect channel information handling to ensure practical feasibility. Simulation results demonstrate that the proposed method significantly reduces coordination overhead, enhances system robustness, and outperforms existing Lorentzian-model-based centralized schemes in terms of overall performance.