Gateway Placement and Packet Routing for Multihop In-Vehicle Internet Access

In-vehicle Internet access is one of the main applications of vehicular ad hoc networks (VANETs), which aims at providing the vehicle passengers with a low-cost access to the Internet via on-road gateways. This paper introduces a new strategy for deploying Internet gateways on the roads, together with a novel scheme for data packet routing, in order to allow a vehicle to access the Internet via multihop communications in a VANET. The gateway placement strategy is to minimize the total cost of gateway deployment, while ensuring that a vehicle can connect to an Internet gateway (using multihop communications) with a probability greater than a specified threshold. This cost-minimization problem is formulated using binary integer programming, and applied to a realistic city scenario, consisting of the roads around the University of Waterloo, Waterloo, ON, Canada. To the best of our knowledge, the proposed deployment strategy is the first study to address the probability of multihop connectivity among the vehicles and the deployed gateways. On the other hand, the developed packet routing scheme is based on a multichannel medium access control protocol, known as VeMAC, using time division multiple access. The performance of this cross-layer design is evaluated for a multichannel VANET in a highway scenario, mainly in terms of the end-to-end packet delivery delay. The end-to-end delay is calculated by modeling each relay vehicle as a queuing system, in which the packets are served in batches of no more than a specified maximum batch size. The proposed gateway placement and packet routing schemes represent a step toward providing reliable and ubiquitous in-vehicle Internet connectivity.