Breadcrumb routing: Query-response geocast for mobile originators in vehicular networks

Vehicular ad hoc networks allow connected vehicles to exchange and share information in order to improve traffic efficiency and safety as well as to provide infotainment functions. In order to cope with the challenging network conditions of the vehicular domain (e.g., intermittent connectivity), a disruption-tolerant networking architecture is suitable. In contrast to push-based communications (e.g, cooperative awareness messages) used in many proposed vehicular applications, we focus on a query-response model for requesting sensor information. Of particular interest to us is the question how vehicular queries can be efficiently routed to a destination area in such challenged environments, and, more importantly, how the response can be routed back to a moving query originator. We therefore present Breadcrumb Geocast Routing (BGR), a novel disruption-tolerant georouting protocol based on a trail of breadcrumbs left by the query originator. As an overlay protocol, BGR can be used on top of different georouting mechanisms, providing an efficient means to address moving originators. We study the influence of parameters, e.g., breadcrumb size and distance, and prove the effectiveness of the proposed solution in an extensive experimental evaluation, showing that BGR achieves significantly higher delivery rates compared to traditional geocast approaches, while avoiding up to 97% of the traffic overhead of Epidemic and PRoPHET routing.