Towards a lightweight protocol for Industry 4.0: An implementation based benchmark

The next industrial revolution, generally referred to as Industry 4.0, is already here. This envisions a rapid transformation in the design, operation and service of manufacturing systems, where machines, sensors and actuators are interconnected in the factories in order to enable spontaneous collaboration, monitoring and control. Currently, Cyber-Physical-Systems (CPS) use regular Internet protocols (e. g. SOAP or HTTP) to communicate with each other. However, these protocols inherently present certain drawbacks or disadvantages: large footprint, CPU usage, high memory and energy consumption, etc. In recent years, new Industrial Internet of Things (IIoT) protocols have emerged to solve this issue, such as the Constrained Application Protocol (CoAP) and MQ Telemetry Transport (MQTT). These are lightweight protocols designed to face the challenges of industrial environments with a small footprint and overhead. These protocols have different features in terms of communication model and Quality of Service (QoS), that make them more suitable to an specific domain. Thus, it is important to identify the right metrics to adopt the most appropriate. This paper presents a theoretical and empirical comparison of MQTT and CoAP in terms of network overhead and latency, to assist system designers with this decision. Furthermore we describe the quantitative comparison conducted with their implementation in hardware platforms with high constraints. The achieved results provide useful metrics and guidelines to help designers to choose the appropriate schemes for their implementations.