ABSTRACT
This chapter focuses on some of the most relevant aspects concerning the hybrid networks. It describes the basic operating principles and the main features of some relevant wireless and wired industrial networks that are considered as possible candidates for setting up hybrid communication systems. Adopting wireless communications in industrial environments is particularly appealing as, in principle, it avoids cabling, which turns out to be cumbersome and/or expensive in many real cases. A more viable choice is relying on several separate wireless subnetworks, possibly operating on different channels, interconnected by means of a wired backbone to limit the packet rate on each one of them. In particular, the size of the frames sent by stations on wireless extensions has to be limited to the maximum value achieved on the wired segment. If a Quality-of-Service-enabled network is adopted on the wireless side, such as for example IEEE 802.11e, an improved real-time behavior could be achieved.
