5G Ultra-Reliable Low-Latency Communications in Factory Automation Leveraging Licensed and Unlicensed Bands

Factory automation (FA) applies ultra-reliable low latency communications (URLLC) to support closed-loop control systems with millisecond cycle times. Presently, many of these applications rely on maintenance-prone wireline bus systems since existing wireless technologies cannot meet the stringent latency and outage requirements. The cellular standards body, the Third Generation Partnership Project (3GPP), aims to change this predicament by incorporating support for FA and URLLC into the fifth generation (5G) communication networks. We investigate how combining operation in the unlicensed and licensed band can appropriately balance the technical, regulatory and economic constraints to enable large-scale deployments of bandwidth-hungry FA applications. We present 5G physical layer/MAC layer (PHY/MAC) designs, which carry the bulk of traffic in the cost-effective unlicensed band but switch to the licensed band within the available latency budget to circumvent unlicensed-band interference. We discuss design trade-offs between licensed band occupation, link outage and transmission power level.