Timed Broadcast via Off-the-Shelf WLAN Distributed Coordination Function for Safety-Critical Systems

Low cost wireless solutions for safety-critical applications are attractive to leverage safety-critical operation in new application areas. This work assesses the feasibility of providing synchronous and time bounded communication to standard IEEE 802.11 devices with low effort modifications. An existing protocol for time bounded communication in wireless systems is adapted to a generic safety-critical application with low bandwidth requirements, but strict bounds on time behavior. Experimental and simulation studies are conducted in which the protocol is implemented on top of IEEE 802.11e Distributed Coordination Function (DCF). The experimental results for packet loss ratio, communication delays, and broadcast completion are used to calibrate a stochastic simulation model that allows to extrapolate the expected long-term performance of the protocol. Both the experimental results and the simulation extrapolation show that necessary availability requirements can be met with 802.11e prioritization in the investigated cross-traffic and interference scenarios.