Isochronous wireless communication system for industrial automation

Wireless communication solutions are increasingly adopted in industrial automation systems, due to their well-known advantages, such as higher levels of flexibility and mobility, and possible cost reductions due to simpler installation and maintenance. However, the typical timing requirements of industrial applications (which imply determinism and often isochronous behavior) cannot be satisfied by legacy consumer market technologies, mainly ZigBee or Wi-Fi. Indeed, they are typically aimed at minimizing power consumption and/or improving network throughput, even though this is achieved at the expense of both a high level of randomness in data delivery time and a low reliability, so that large latencies are expected, leading to unacceptable overall network performance. The main reasons reside in a heavy (from the computational point of view) protocol stack; in particular, the typical non-deterministic medium access mechanisms are often based on a distributed contention of the channel among nodes, thus practically allowing collisions to exist. For these reasons, in the last years wireless communication solutions tailored for the industrial automation scenario and capable of satisfying determinism and isochronous behavior have been proposed. In this chapter, a brief résumé of the main characteristics of data delivery in industrial communication is proposed, especially in the light of wireless links. Subsequently, the importance of a purposely designed communication protocol stack, with a particular focus on the medium access control scheme, is detailed. Finally, a discussion on some significant proprietary and standard solutions currently available is provided.