MQTT-UNS and OPC UA in RAMI4.0: A Comparative Analysis for Industrial Communication

Abstract Interoperability and data integration are critical challenges in the transition toward Industry 4.0. The Reference Architecture Model for Industry 4.0 (RAMI 4.0) provides a structured approach to address these challenges across system hierarchies, lifecycle phases, and functional layers. This study investigates the applicability of two widely used communication protocols—Open Platform Communications Unified Architecture (OPC UA) and Message Queuing Telemetry Transport (MQTT) combined with a Unified Namespace (UNS)—within the RAMI 4.0 framework. While OPC UA is recommended within RAMI 4.0 for its standardized data exchange and robustness, MQTT has gained attention for its lightweight nature and efficiency in Industrial Internet of Things (IIoT) contexts. Through technical analysis and literature review, this research explores whether the integration of UNS enables MQTT to meet the communication and information layer requirements of RAMI 4.0. The findings suggest that MQTT-UNS can serve as a viable, and in some cases complementary, alternative to OPC UA, offering scalability, structured data handling, and reduced overhead. This work contributes to ongoing efforts in digital manufacturing by informing protocol selection strategies that align with RAMI 4.0-based architectures and interoperability goals.