Integrating Reconfigurable Intelligent Surfaces (RISs) into Indoor D-MIMO Networks for 6G

In this paper, we study integration strategies for reconfigurable intelligent surfaces (RISs) in distributed MIMO (D-MIMO) systems as one of the promising techniques for evolving 5G networks and beyond (6G). The scalability of D-MIMO systems to large networks in a practically feasible way is challenging. The exploitation of cost-effective and energy-efficient dynamic access point (AP) clustering techniques and densification enablers is crucial for such systems to sustain the required level of performance and reliability while mitigating the environmental and economic challenges related to future network operations. RIS is well regarded as a low-cost, rapidly deployable, energy-efficient candidate offering extra diversity in the spatial domain. This work explores RIS-aided multi-AP systems attaining certain prescribed key performance indicators (KPIs) while considering the energy consumption in the system.We concentrate on indoor use cases with large user equipment (UE) populations where the service coverage is low due to the high obstacle density. To that end, we propose dynamic user-centric AP clustering and RIS placement techniques adapted for serving multi-user indoor systems. Here, we use an alternating optimization method as a sub-optimal solution for RIS phase-shift configuration, keeping the computation complexity low. We show that the integration of RISs in D-MIMO systems is an attractive approach to enhance energy efficiency and provide the scalability required in 5G and beyond (6G).