The Adaptive-Intervals MAC protocol for a wireless PROFIBUS
For the PROFIBUS, a standardized and well-known fieldbus system, it is attractive to use wireless media. A natural approach in creating such a system is to re-use as much existing technology as possible. In the area of wireless local area networks (WLANs) clearly the IEEE 802.11 standard is the leading technology. Hence, the question comes up, how this technology can be used in the creation of a wireless PROFIBUS. The PROFIBUS is used for its abilities in matching realtime requirements even under harsh environmental conditions. On the other hand, wireless links are error-prone and show time-variable behavior. Hence, an important question is, how good the so-called realtime performance, a set of measures taking reliability and timeliness into account, of the PROFIBUS protocol over wireless links is. This paper presents corresponding results and compares them with those of a new, polling-based class of protocols, called adaptive intervals. It shows up, that the adaptive intervals protocols achieve up to an order of magnitude better realtime performance than the PROFIBUS protocol. We conclude from this that it is a promising approach to replace the existing PROFIBUS MAC protocol by another protocol for creation of a wireless PROFIBUS.