Multi-modal message dissemination in vehicular ad-hoc networks

As a fundamental network property, Inter-Contact Time (ICT) determines the critical performance metrics of a vehicular ad-hoc network (VANET). In this paper, we extract the contact information from the traces of Global Positioning System (GPS) from public and semi-public vehicles in a large modern city, including both buses and taxis. By exploring the spatial and temporal properties of the contact behaviors between both types of vehicles, we propose a multi-modal VANET message dissemination scheme, by allowing buses to assist the message dissemination among taxis. This scheme leverages the wide time and space coverage of taxis, and the high regularity of bus routes and schedules. The trace-driven simulation shows that with the help of buses, both the end-to-end delay and delivery ratio are significantly improved without introducing much overhead. This indicates the great potential of exploring heterogeneous mobility patterns in mobile ad-hoc networks.