An Architecture for AoI and Cache Hybrid Multicast/Unicast/D2D With Cell-Free Massive MIMO Systems.

The leitmotif of this paper aims at providing an architecture for the age of information (AoI) and cache-assisted hybrid multicast/unicast/device-to-device (D2D) transmission with the promising cell-free massive multiple-input multiple-output (MIMO) technology, for enriching data transmission rate, slackening the burden of high-volume data traffic, and boosting the system efficiency. Then, we design the user-centric transmission scheme and talk about the feasibility of the preliminary solutions for the multigroup multicast, D2D, wireless caching, and AoI, typically for signal processing, transmission mode selection mechanism, and cache replacement strategy. Finally, we also shall afford a viable research prediction containing an ensemble of the potential challenges and promising research directions to set the path for re-inventing an efficient sixth-generation (6G) communication system.