Extending real-time networks over WiFi: related issues and first developments

Abstract

The flexibility of wireless connectivity is appealing in the context of real-time industrial networks. This paper discusses the use of wireless communication protocols to interconnect remotely located fieldbuses. The focus of this paper is to analyze the feasibility and design issues related to this type of hybrid real-time network architecture. Investigations are presented by addressing an interconnection through the well-mastered WiFi technology. On an example architecture, we discuss the impact of the different distributed medium access protocols available (DCF, EDCA) on the real-time flows. We outline the main design issues related to these choices and illustrate them on a first case study where remotely located CAN buses are interconnected through an IEEE802.11g network in DCF mode. Using this very simple and cost-effective architecture, we show as a first result that transmitting soft real-time data over such an architecture is feasible.