Scalable Cache-Aided Cell-Free Massive MIMO Systems

In this letter, the scalable cache-aided cell-free (SCCF) massive multiple input multiple output systems are proposed to reduce the downlink transmit energy consumption (EC) via fronthaul and backhaul links. On the premise of ensuring the scalability of cell-free (CF) systems, we establish the total EC (TEC) models of SCCF systems with caching on both access points and the central processing unit. Through the proposed successive convex approximation algorithms, we obtain the near-optimal cache placements for the TEC minimization problems in various forms resulting from different caching strategies (CSs). Simulation results demonstrate that the proposed SCCF systems can significantly reduce the TEC of scalable CF systems while maintaining scalability, especially when utilizing the CSs based on proposed transmit caching scheme.