Hybrid geo-routing in urban vehicular networks

It is expected that future vehicular networks will consist of a combination of ad-hoc network and infrastructure components. Road Side Units (RSUs) will form part of the infrastructure element. However, it is anticipated that a fully deployed RSU infrastructure may not be economically feasible in the short term, therefore, a partial infrastructure in urban environments is more likely, at least initially while vehicular networks are being adopted. It is further likely that low vehicle penetration rates will exist while 802.11p On-Board Unit (OBU) technology is being rolled out, thus routing schemes should exploit infrastructure where available to improve packet delivery. This paper presents a hybrid vehicular routing protocol that facilitates unicast routing by dynamically changing its routing decisions in the presence of RSU infrastructure in order to maximise packet delivery rate. A quantitative evaluation of the proposed Infrastructure Enhanced Geographic Routing Protocol (IEGRP) is provided as a function of varied source to destination distances, vehicular densities, infrastructure availability and application QoS characteristics. It exhibits much improved delivery rates with partial and full infrastructure compared to related protocols.