Geographic Routing on Vehicular Ad hoc Networks

Introduction

VANETs are constituted of vehicles that are equipped with onboard units with GPS receivers. Therefore, it is natural to assume each vehicle knows its location. GPS provides position information with accuracy of 10m, and the differential GPS (DGPS) technology can complement it up to 1-3m (Navigation Center, U.S. Department of Homeland Security, 2009). Also technologies such as dead reckoning and map matching using information from multiple sensors can enhance the accuracy. Also, other useful information on movement such as velocity and acceleration can be obtained. Using such information, position-based routing can be developed; we may let each vehicle transmit data packets to appropriate neighbors so as to maximize throughput and reliability or to minimize delay and traffic overhead. Furthermore, it is often difficult to know the destination vehicles' IDs in VANETs. Due to this nature, applications may want to deliver data to vehicles in a specific region (and in a certain period of time). This suggests the necessity for geocast communication. In this chapter, we use the term “geographic routing” to indicate “geocast communication realized by position-based forwarding”.