Communication capacity-based message exchange mechanism for delay-tolerant networks

Delay-tolerant networks (DTNs) are wireless networks where connectivity is sporadic because of node mobility, wireless signal blockage, sleep schedules, and power outages. The absence of contemporary routes between nodes can significantly delay message delivery. To accomplish data delivery in such challenging environments, researchers have proposed the use of store-carry-forward protocols, according to which a node stores a message and carries it until a forwarding opportunity arises by encountering another appropriate node. Since the encounter duration follows the power-law or exponential distribution mostly being short, the message exchange mechanism should avoid message losses. In this paper, we propose a communication capacity-based message exchange mechanism (CCME) that extends the existing DTN routing protocols. With CCME, the communication capacity is estimated by using both predicted encounter duration and communication bandwidth. Predicting encounter duration and estimating communication bandwidth are challenging issues. In this paper, we mainly focus on predicting encounter duration. We present a statistical method of predicting encounter duration to show the baseline for encounter duration estimation, and propose a real-time estimation mechanism for encounter duration. Our mechanism can be fine-tuned either to minimize the average delivery delay or to maximize the average delivery rate. The simulation results show that CCME successfully approximates the communication capacity. The performance of the existing protocols increases significantly with CCME.