Energy Constrained Delay Tolerant Networks Research Articles

Energy Efficient Beaconing Control Strategy Based on Time-Continuous Markov Model in DTNs

In delay-tolerant networks (DTNs), unpredictable mobility leads to the uncertainty of network topology, and it is hard to maintain an end-to-end connection from the source to the destination. To realize the forwarding of the messages, beaconing is used to detect the contact probabilities. However, beaconing frequency not only influences the detection probability of the available communications but is concerned with the energy consumption rate as well. The higher the beaconing frequency is, the faster the energy is consumed. The energy consumption leads to the reduction of the network survival time, due to the lack of energy supply. In contrast, the lower the beaconing frequency is, the less frequently available communications are detected, which also leads to a decrease in delivery rate. Therefore, it is meaningful to find out the most suitable beaconing frequency in specific DTNs. In this paper, we propose an energy efficient dynamic beaconing control strategy in energy-constrained DTNs (DBCEC) based on the time-continuous Markov model. Six different dynamic function forms are, respectively, used to control the beaconing frequency. Simulations based on the synthetic mobility pattern and real mobility traces are conducted in the Opportunistic Network Environment (ONE), and the results show that DBCEC-E achieves a better delivery rate without affecting the average delay and the overhead ratio, compared with other beaconing control strategies.

Optimal Energy-Aware Epidemic Routing in DTNs

In this work, we investigate the use of epidemic routing in energy constrained delay tolerant networks (DTNs). In epidemic routing, messages are relayed by intermediate nodes at contact opportunities, i.e., when pairs of nodes come within the transmission range of each other. Each node needs to decide whether to forward its message upon contact with a new node based on its own residual energy level and the age of that message. We mathematically characterize the fundamental trade-off between energy conservation and a measure of Quality of Service as a dynamic energy-dependent optimal control problem. We prove that in the mean-field regime, the optimal dynamic forwarding decisions follow simple threshold-based structures in which the forwarding threshold for each node depends on its current remaining energy. We then characterize the nature of this dependence. Our simulations reveal that the optimal dynamic policy significantly outperforms heuristics.

A New Optimization Strategy Proposal for Multi-Copy Forwarding in Energy Constrained DTNs

Most routing algorithms in delay tolerant networks (DTNs) have not taken adequately into account the issue of energy constraint for communication. In this paper, we propose a new optimization strategy for different DTN routing algorithms that use an utility function to select the best nodes to relay messages, but that were originally proposed without regard to the issue of energy. Our proposed optimization strategy is based on the modeling of multi-copy forwarding as a Bayesian signaling game. A system for belief update concerning the energy of the other DTN nodes based on the accumulated observations of the destination nodes is considered. Simulation results show that our proposed optimization strategy can maintain the network nodes operational for a longer period of time.

Performance Evaluation of Routing Schemes for the Energy-Constrained DTN with Selfish Nodes

Due to the lack of end-to-end paths between the communication source and destination, the routing of Delay Tolerant Networks (DTN) exploits the store-carry-and-forward mechanism. This mechanism requires nodes with sufficient energy to relay and forward messages in a cooperative and selfless way. However, in the real world, the energy is constrained and most of the nodes exhibit selfish behaviors. In this paper, we investigate the performance of DTN routing schemes considering both the energy constraint and selfish behaviors of nodes. First, we model the two-hop relay and epidemic routing based on a two-dimensional continuous time Markov chain. Then, we obtain the system performance of message delivery delay and delivery cost by explicit expressions. Numerical results show that both the energy constraint and node selfishness reduce the message delivery cost at the expense of increasing the message delivery delay. Furthermore, we demonstrate that the energy constraint plays a more important role in the performance of epidemic routing than that of two-hop relay.