On the cost/delay tradeoff of wireless delay tolerant geographic routing

Abstract

In Delay Tolerant Networks (DTNs), there is a fundamental tradeoff between the aggregate transport cost of a packet and the delay in its delivery. We study this tradeoff in the context of geographical routing in wireless DTNs.We ?rst specify the optimal cost/delay tradeoff, i.e., the tradeoff under optimal network operation, using a dynamic network construction termed the Cost/Delay Evolving Graph (C/DEG) and the Optimal Cost/Delay Curve (OC/DC), a function that gives the minimum possible aggregate transportation cost versus the maximum permitted delivery delay.We proceed to evaluate the performance of two known delay tolerant geographic routing rules, i.e., MOVE and AeroRP, a delay tolerant version of the geographic routing rule that selects as next relay the node for which the cost-per-progress ratio is minimized, and ?nally two novel rules, the Balanced Ratio Rule (BRR) and the Composite Rule (CR). The evaluation is in terms of the aggregate packet transmission cost as a function of the maximum permitted packet delivery delay. Simulations show that CR achieves a cost/delay tradeoff that is overall the closest to the optimal one speci?ed by the OC/DC, while BRR achieves the smallest aggregate transmission costs for large packet delays and a ?xed transmission cost model.

On the delay/cost tradeoff in wireless mobile Delay-Tolerant Networks

“…This tradeoff has already been identified in the study of numerous protocols proposed recently that combine geographic with delay-tolerant routing [1], [2], [3], [4], [5], [6], [7].…”

“…In [5] a very general formulation, applicable to all Delay-Tolerant Networks (DTNs), is introduced for quantifying the tradeoff between the delay in the delivery of a packet and the transport cost, comprised of a term due to the storage of the packet at intermediate buffers and a term due to its transmission from node to node. In contrast to our work, the tradeoff is established for specific instances of the network evolution, using network optimization tools, and without utilizing probabilistic analysis.…”

“…Under the hybrid geographic/delay-tolerant protocols of [1], [2], [3], [4], [5], packets are routed using combinations of transmissions to nodes that are closer to the destination than their current holder (as in geographic routing), and sojourns on the buffers of their current holders (as in delay-tolerant routing). Depending more on transmissions and less on physical transfers leads to reduced delays but increased transmission costs (e.g., more bandwidth required, which reduces the endto-end throughput in the network).…”

“…Under these protocols, packets are transported towards their destination using combinations of wireless transmissions (to nodes suitably placed closer to their destination) and physical transfers (along nodes suitably moving in the direction of their destination) [1], [2], [3], [4], [5], [6], [7].…”