Message forwarding in Cyclic MobiSpace: the multi-copy case

A key challenge of message forwarding in delay tolerant networks (DTNs) is to increase delivery rate and decrease delay and cost. When information for future connectivity is not available, opportunistic routing is preferred in DTNs in which messages are forwarded opportunistic (non-deterministically) to nodes with higher delivery probabilities. Many real objects have non-deterministic but cyclic motions; however, few prior research work has investigated a multi-copy opportunistic message forwarding algorithm for DTNs with cyclic mobility patterns. Cyclic MobiSpace is a generalization of DTNs with cyclic mobility patterns. In this paper, we propose an optimal opportunistic multi-copy message forwarding algorithm in Cyclic MobiSpace. Specifically, we model a Cyclic MobiSpace as a state-space graph, and apply the optimal stopping rule to derive a delivery metric for each message state using the state-space graph. We perform simulations to compare our protocol, called Multi-copy Forwarding in Cyclic MobiSpace (MFC), against existing forwarding protocols using UMassDieselNet trace. Simulation results show that MFC delivers up to 100% more messages than the compared forwarding protocols under the same delay and forwarding cost.