Flow-Based Transmission Scheduling in Constrained Delay Tolerant Networks

—Routing is one of the most challenging problems in Delay-Tolerant Networks (DTNs) due to network partitioning and intermittent connectivity. Most existing protocols are based on unlimited bandwidth and buffer size. Previous protocols based on limited bandwidth or buffer size (e.g., MaxProp, RAPID, etc) only consider the scenario that each node has at most one contact opportunity during any time interval, and discuss the packet scheduling mechanisms for each separate contact to minimize the average delivery delay. However, in many applications of DTNs, more than one contact opportunities with the same source node, which are called as related contact opportunities, may arise in the same time interval. But previous scheduling algorithms cannot apply to such applications. Therefore, we propose a more general scheduling algorithm to optimize the delivery delay in constrained DTNs including the scenario that multiple related contact opportunities may arise in the same interval, called Flow-Based Transmission Scheduling (FBTS). We evaluate it on publicly available data sets against MED, MaxProp and RAPID. The results show that the delivery delay of FBTS is at least 35% shorter than that of existing works.