Optimising Replication Versus Redundancy In Window-Aware Opportunistic Routing

In this paper, the authors address the replication versus redundancy optimisation problem for a class of intermittently connected ad hoc networks with the following three characteristics: routing is performed by a store-carry-forward mechanism in an opportunistic manner, replication of custodian messages is used to increase the delivery ratio, and fragmentation combined with redundancy in the form of erasure coding is used to deal with large messages in short contact windows. They propose a novel mathematical model in which the merits of a high replication factor can be compared to a high level of redundancy in erasure coding. The purpose of the model is to identify the optimised level of replication and redundancy as a function of application-specific parameters like message size and time-to-live.