Otimização de pré-codificação conjunta com formação de clusters em um sistema cell-free auxiliado por RIS

Abstract

This final course project aims to present the theoretical foundations related to Reconfigurable Intelligent Surfaces (RIS) and the cell-free architecture, including construction aspects, phase-shift constraints of the RIS, performance analysis, and comparisons. Based on this, a clustering algorithm for RIS-aided cell-free networks is proposed, in which, for each user equipment (UE), a set of access points (APs) responsible for transmission is dynamically selected, as well as a subset of RISs that will assist in communication. In this way, cluster formation is carried out in a UE- centric manner, aiming to optimize the WSR (weighted sum-rate) and reduce signaling overhead. The optimization of the WSR with respect to the active precoding vector (precoding at the APs) and the passive precoding (RIS phase-shift matrix) is performed based on existing alternating optimization algorithms in the literature. Therefore, with the subdivided problem, the lustering part is introduced and solved here using a greedy algorithm.