Improving Message Delivery in Opportunistic Networks with Fragmentation and Network Coding

In opportunistic networks, no guarantees about network connectivity and node behavior can be made. Routing protocols aim at delivering messages by choosing promising paths throughout the network. These paths are created by nodes replicating messages and forwarding them to other nodes upon encountering them. The first replicated message reaching its destination node is the successful delivery, while others routed along different paths might arrive at a later time. The order and possibility of arrival depend on many factors such as the path length and sufficient transfer time for a complete message upon inter-node contact. We motivate the use of distinct paths throughout the network for fragmentation and Network Coding and propose Fragmentation Strategies on the edge of the opportunistic network improving general message delivery. By carefully choosing appropriate fragment sizes and the amount of network coding added, we show that our Fragmentation Strategies are able to improve message delivery for large messages regardless of the routing protocol in use. As the main contribution of this paper, we provide the mathematical equations needed for fragment creation, and make available an implementation of our Fragmentation Strategies.