Modular wireless fieldbus gateway for fast and reliable sensor/actuator communication

The AS-interface (AS-i) is a simple and cost-effective network solution connecting simple I/O devices to the upper fieldbus levels. A fully loaded AS-i Version I network with one master and 31 slaves has a maximum response time of 5 ms per I/O. The AS-Interface has been chosen as reference system for the development of a wireless fieldbus gateway, which will be presented in this paper. Standard modules have been employed to achieve a price-competitive solution. A high reliability level with wireless system can only be achieved if radio wave propagation characteristics and coexistence to other radio services are taken into account. Especially wireless local area network (WLAN) technologies already installed in the field can affect proper sensor/actuator network operation. Therefore bit and frame error probabilities in the presence of WLAN systems also have been investigated.