  This paper explores the issue of enabling Ultra-Reliable Low-Latency
Communications (URLLC) in view of the spatio-temporal correlations that
characterize real 5th generation (5G) Industrial Internet of Things (IIoT)
networks. In this context, we consider a common Standalone Non-Public Network
(SNPN) architecture as promoted by the 5G Alliance for Connected Industries and
Automation (5G-ACIA), and propose a new variant of the 5G NR semi-persistent
scheduler (SPS) to deal with uplink traffic correlations. A benchmark solution
with a "smart" scheduler (SSPS) is compared with a more realistic adaptive
approach (ASPS) that requires the scheduler to estimate some unknown network
parameters. We demonstrate via simulations that the 1-ms latency requirement
for URLLC is fulfilled in both solutions, at the expense of some complexity
introduced in the management of the traffic. Finally, we provide numerical
guidelines to dimension IIoT networks as a function of the use case, the number
of machines in the factory, and considering both periodic and aperiodic
traffic.
