On the IRS Deployment in Smart Factories Considering Blockage Effects: Collocated or Distributed?

In this article, we study the collocated and distributed deployment of intelligent reflecting surfaces (IRS) for a fixed total number of IRS elements to support enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication (URLLC) services inside a factory. We build a channel model that incorporates the line-of-sight (LOS) probability and power loss of each transmission path, and propose three metrics, namely, the expected received signal-to-noise ratio (SNR), expected finite-blocklength (FB) capacity, and expected outage probability, where the expectation is taken over the probability distributions of interior blockages and channel fading. The expected received SNR and expected FB capacity for extremely high blockage densities are derived in closed-form as functions of the amount and height of IRSs and the density, size, and penetration loss of blockages, which are verified by Monte Carlo simulations. Results show that deploying IRSs vertically higher leads to higher expected received SNR and expected FB capacity. By analysing the average/minimum/maximum of the three metrics versus the number of IRSs, we find that for high blockage densities, both eMBB and URLLC services benefit from distributed deployment; and for low blockage densities, URLLC services benefit from distributed deployment while eMBB services see limited difference between collocated and distributed deployment

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