Location-Based Routing for Vehicular Ad-Hoc Networks

Communication between vehicles is likely to be one key area where mobile ad-hoc networks will be used in the near future. Currently there are several projects ([1, 3]) that investigate this application area, while car manufacturers and their suppliers aim at the development of products within the next few years. This raises the question what kind of routing algorithm is suited for communication between vehicles. Existing performance studies for various ad-hoc routing protocols do not use movement patterns which resemble the movement of cars and are thus not well suited to answer this question. We have conducted an extensive simulation study based on realistic vehicle movement patterns. Our main aim was to investigate how a topology-based approach compares to a location-based routing scheme when applied to vehicular networks. As representatives we have chosen DSR [4] as a topology-based approach and GPSR [5] complemented with a simple location service as a location-based scheme. For a general discussion of topology-based and location-based ad-hoc routing please refer to [2] and [6]. Vehicular ad-hoc networks have several unique characteristics. The main challenge is the high speed with which nodes move in respect to each other. If oncoming traffic is included in the forwarding of packets, then relative speeds of 250 km/h to 300 km/h are common. This implies a very high rate of topology changes. Also it is not clear if one single partition spans sufficient distance to enable meaningful applications such as emergency warnings or vehicle-to-vehicle entertainment. On the other hand it is safe to assume that battery power is not an issue for vehicular ad-hoc networks. Location-based approaches further benefit from the fact that vehicles are aware of their geographical positions through the use of on-board navigation systems.