A soft real-time scheduling framework for wireless industrial sensor actuator networks

Wireless networks are typically deemed not reliable enough to address real-time requirements typical of industrial distributed control applications. Several solutions were proposed in the past years to overcome their limitations and make them suitable for those (soft) real-time applications where a limited percentage of deadlines can be missed. A promising approach relies on centralized transmission (and retransmission) scheduling and exploits well-known results for feasibility analysis to provide a priori guarantees on performance. This paper focuses on a framework based on non-preemptive EDF transmission scheduling and takes into account two retransmission strategies. A prototype framework implementation, relying on conventional Linux platforms and employing Wi-Fi technology, is then exploited to perform a preliminary performance assessment. To provide useful implementation guidelines, the paper investigates how the choice of retransmission strategy and of the parameters to be used in feasibility analysis may affect performance.