Distributed architectures for industrial applications are a new opportunity to realize cost-effective, flexible, scalable and reliable systems. Direct interfacing of sensors and actuators to the industrial communication network improves the system performance, because process data and diagnostics can be simultaneously available to many systems and also shared on the Web.
However, sensors, especially low-cost ones, cannot use standard communication protocols suitable for computers and PLCs. In fact, sensors typically require a cyclic, isochronous and hard real-time exchange of few data, whereas PCs and PLCs exchange a large amount of data with soft real-time constrains. Looking at the industrial communication systems, this separation is clearly visible: several fieldbuses have been designed for specific sensor application areas, whereas high-level industrial equipments use wired/wireless Ethernet and Internet technologies.
Recently, traditional fieldbuses were replaced by Real-Time Ethernet protocols, which are ''extended'' versions of Ethernet that meet real-time operation requirements. Besides, real-time wireless sensor networking seems promising, as demonstrated by the growing research activities.
In this paper, an overview of the state-of-art of real-time sensor networks for industrial applications is presented. Particular attention has been paid to the description of methods and instrumentation for performance measurement in this kind of architectures.