Exploiting Active Subareas for Multicopy Routing in VDTNs.

In vehicle delay tolerant networks (VDTNs), current routing algorithms select relay vehicles based on either vehicle encounter history or predicted future locations. The former method may fail to find relays that can encounter the target vehicle in a large-scale VDTN, while the latter method may not provide accurate location prediction due to traffic variance. Therefore, these methods cannot achieve high performance in terms of routing success rate and delay. In this paper, we aim to improve the routing performance in VDTNs. We first analyze vehicle network traces and observe that 1) each vehicle has only a few active subareas that it frequently visits, and 2) two frequently encountered vehicles usually encounter each other in their active subareas. We then propose an active area based routing method (AAR), which consists of two steps based on the two observations correspondingly. AAR first distributes a packet copy to each active subarea of the target vehicle using a traffic-aware shortest path spreading algorithm, and then in each subarea, each packet carrier tries to forward the packet to a vehicle that has high encounter frequency with the target vehicle. In addition to the basic AAR, we further propose an advanced AAR (AAAR). In the AAAR, we improve the routing efficiency in each subarea by exploiting spatio-temporal correlation and developing three strategies for calculating spatio-temporal correlation. Extensive trace-driven simulation demonstrates that AAR produces higher success rates and shorter delay in comparison with the state-of-the-art routing algorithms in VDTNs. Also, the simulation shows that our advanced AAAR has better performances than our AAR. [ABSTRACT FROM PUBLISHER]