Ferry replacement protocols in sparse MANET message ferrying systems

The message ferrying (MF) scheme has been proposed as a strategy for providing connectivity in sparse partitioned ad hoc networks. A set of nodes, called ferries, are responsible for carrying messages for all nodes in the network. A ferry periodically moves around the deployed area along a pre-determined route and relays messages between mobile nodes which otherwise cannot communicate with each other directly. The MF scheme relies on the ferry to provide connectivity and is vulnerable to a single point of failure. Also, mobile nodes might take turns to be a ferry since they normally have limited resources. Therefore, ferry replacement is important for robustness in MF deployment. We propose two ferry replacement protocols: in the designation scheme, the ferry designates its successor; in the distributed election approach, nodes collaborate and elect one node among themselves as the ferry replacement. We evaluate the performance of these two replacement protocols through comprehensive simulation.