An Event-Based Framework for the Specification and Runtime Checking of Timing Constraints in Wireless Sensor and Actuator Networks

Abstract

Distributed monitoring and control applications running on top of wireless sensor and actuator networks need to be developed in a structured and flexible way. Such applications also have strict timing constraints, which need to be properly captured and tested at development time. But these constraints can still be violated at runtime, due to a number of reasons, such as an overly high processing load at some node, or the typically unpredictable and unreliable nature of the wireless medium. For this reason, once the system is deployed, it is important to keep track of its performance in order to detect any violation of timing specifications. To this end, we present a event-oriented component model and runtime system that aims on the one hand to simplify the development of distributed event-based applications, and on the other hand to monitor their behavior in order to detect timing errors. The developer writes the code of the component's event handlers, and specifies the respective timing constraints. In turn, the runtime system records the time that elapses between the generation of an event and its delivery, as well as the time it takes for the corresponding handler to process the event, and reports a violation if the respective timing constraint is not met. We also discuss an implementation of this framework on top of the Contiki operating system, and provide an evaluation.