A Disruption Tolerant Connectivity Service for ITS Applications Using IEEE 802.11p

This work addresses the intermittent connectivity observed in a vehicular ad hoc network and proposes a Disruption Tolerant Network (DTN) service that is shown to degrade gracefully in case of bad channel conditions or load increase, if compared to plain datagram transmission case. The considered infrastructure is a mesh network of road side units (RSUs) forming an overlay in which data can be stored, replicated and disseminated. The vehicles arriving in a RSU range open communication dialogs, using IEEE 802.11p WAVE Short Messages, however these dialogs may be interrupted by packet losses due to channel condition or mobility. The resulted intermittent connectivity lasts from seconds to several minutes. This paper gives an insight into the design of a seamless and efficient disruption tolerance mechanism and discusses the trade-offs in managing storage and processing resources in the infrastructure nodes. The performance of DTN and non-DTN operation is compared. In order to evaluate the performance of the DTN system in terms of successful transactions, we use real-world traces from a field trial performed on the Austrian highway and feed them into the DTN system. The results are promising showing high cumulative throughput, good delay behavior and efficient use of storage resources.