Formal Verification of a MAC Protocol for Underwater Sensor Networks

The use of Underwater Sensor Networks (UWSN) for underwater ocean applications such as seismic event detection, target detection, marine resource monitoring, and oil bed monitoring is growing. In contrast to conventional WSNs, these networks communicate via acoustic channels. Many communication protocols for UWSN have been proposed, including MAC layer protocols, time synchronization protocols, and routing protocols. Formal verification of these protocols is rarely investigated. In this paper, we propose two abstraction methods for UWSN that capture multi-channel models and variable propagation delay. These abstraction methods are used to create a validation model of the Time Delay Allocation MAC (TDA-MAC) protocol, which is used in UWSN. Formal verification of TDA-MAC is accomplished by performing a reachability analysis and the occurrence of design faults on certain marked states in the model. The verification results detect non-progress cycles of marked states in the event of a PING message loss. A modification to the existing protocol specification of TDA-MAC protocol is proposed. Formal verification on the refined validation model shows that the protocol is free from non-progress cycles and unreachable states. The proposed abstraction methods can be used to create formal models and perform formal verification of existing and emerging protocols used in UWSN.