Reconfigurable Intelligent Surfaces Aided Energy Efficiency Maximization in Cell-Free Networks

As we move towards next-generation wireless networks, the need for sustainability through energy efficiency (EE) concepts becomes more important than ever. Meanwhile, technology enablers, such as beamforming and reconfigurable intelligent surfaces (RISs), if appropriately used in a synergetic manner, can deliver profound excellence in terms of EE. Motivated by this, in this paper, we introduce an EE maximization policy that accounts for the rate demands of the end-users in RIS-assisted cell-free networks. The policy aims at performing joint optimization of the transmit beamforming vectors and the RIS phase-shift matrices in order to maximize the EE. In this direction, we first formulate the corresponding optimization problem, which is non-convex. To solve it, we rely on advanced optimization methods such as quadratic and Lagrangian dual transforms. Numerical results highlight the superiority of the presented policy in comparison to baseline approaches and reveal the most impactful network parameters.