Cell-Free and User-Centric Massive MIMO Architectures for Reliable Communications in Indoor Factory Environments

Factory automation is one of the use cases for 5G-and-beyond mobile networks where strict requirements in terms of latency, availability and reliability are required. In this paper, we investigate the potentials of massive MIMO in delivering those promises for industrial automation. Namely, communications between actuators (ACs) and Access Points (APs) inside an industrial scenario is considered and different transmission modes are compared: joint transmission (JT) where the distributed antennas are used to communicate with each AC, cell-free transmission (CFT) where all the ACs are served by all APs, single AP transmission (SAT) where each AC is served by only one AP, and user-centric transmission (UCT) where each AC is served by a subset of APs. A power control strategy, aimed at maximizing the minimum signal-to-interference plus noise ratio (SINR), is also introduced. Numerical results, shown in terms of downlink SINR and achievable rate, evaluated using the final block length capacity formula (FBLC), demonstrate that the use of distributed antenna setting and of power control bring substantial performance improvements in terms of reliability and latency.