Access Point Placement in Vehicular Networking

Providing wireless networking to vehicles has been identified as a near-term goal by the automotive industry in the support of basic Internet access as well as an enabler to a variety of safety enhancement applications. Network connectivity to on-board computers can be provided via existing mobile telephony; however, these systems rely on both expensive infrastructure (cell towers) and a strongly hierarchical and high-latency network model. In contrast, a short-range, multihop mode of communication can exploit the localization of information generation/consumption of vehicular data applications, and the need for low-latency in safety ones. In practice, both models have their merits and we seek to understand the best mix of fixed roadside infrastructure (“access points”) and use of multihop connectivity. In this paper, we consider the problem of access point placement in a hybrid vehicular networking environment comprised of multihop communication over moving vehicles supported by access points. Particularly, we consider varying vehicular traffic densities and various access point separations, under the assumption of delay tolerant messaging. We extend previous work on analytical modeling of message propagation in delay tolerant vehicular networks absent any infrastructure to study the average delay in cases with fixed infrastructure. Our simulation results depict various design choices as a function of vehicular traffic density, physical radio characteristics and vehicle speed. We show that large access point separations are possible in a hybrid scheme that supports multihop networking. The performance is dominated by vehicular traffic density. We demonstrate that under delay tolerant networking assumption, minimum delay and and maximum propagation rates can be achieved for low vehicular traffic densities of 20 vehicles/km. A path based messaging scheme would achieve similar performance at 40 vehicles/km. ∗In Proc. IEEE Wireless Access for Vehicular Environments (WAVE) 2008, Dearborn, MI. December 2008. This work is supported by the NSF under grant No. CNS-0721884 and EEC-0812056. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.