Formal Verification of Real-Time Wireless Sensor Networks Protocols: Scaling Up

Large scale ad hoc networks such as Wireless Sensor Networks are more and more deployed to ensure critical missions (such as forest fire detection, intrusion detection, etc). Critical applications require timeliness and reliability because human lives may depend on it. In order to give the strongest possible guaranties, the fulfillment of the timing requirements must be formally verified. In the literature, mainly two approaches are used for the formal verification of WSNs real-time protocols : Model Checking which consists in an exhaustive exploration of the behaviors of the system and Network Calculus which abstracts the elements of the system with composable mathematical functions. The Model Checking solution suffers from the combinatorial explosion problem which prevents from verifying large scale systems. On the contrary, Network Calculus scales well, but the abstraction made when defining the service curve is often made without proof that it actually corresponds to the worst case of the considered protocol. In this paper we propose a verification technique which takes advantage of the exhaustiveness of the Model Checking and the scalability of the Network Calculus. The Model Checking technique being used at the scale of a node in order to verify its behavior and the Network Calculus at the scale of the network to represent the interactions of every node with the rest of the network. We use the UPPAAL model checker and Sensor Network Calculus and apply our method to a WSN real-time protocol in order to evaluate the performance of the method.