Formal Development of a Delay-Tolerant Multicast Protocol for Wireless Sensors

We consider environmental monitoring in a remote area with limited connectivity where motes can join and leave the network arbitrarily, the topology is dynamic, transmission is highly unreliable, power is restricted, data points are sampled in large intervals, the data volume is low, a delay of the reception of data points can be tolerated, and motes have large memory. We propose a new protocol with blind multicasting of data points, blind multicasting of acknowledgements, and caching of data points and acknowledgements. This paper presents the protocol by stepwise refinement with Event-B. The unreliability of transmissions is modelled by finitary fairness. Rodin is used to prove the correctness and an upper bound for the transmission delay. The protocol has been implemented using LoRa for the physical layer.