A Three-Dimensional Scenario Oriented Routing Protocol in Vehicular Ad Hoc Networks

In realistic Vehicular Ad hoc NETworks (VANETs), due to the existence of three-dimensional (3D) scenarios, such as the viaduct, tunnel and ramp, the distribution of vehicles is non-planar. However, existing routing protocols in VANETs are mainly analyzed and designed based on ideal plane scenarios. We call them plane-based routing protocols. In this paper, we focus on routing issues in 3D scenarios of VANETs. Through analysis, we demonstrate that applied in 3D scenarios, the plane-based routing protocols suffer a series of severe problems, i.e., hop count increases and delivery ratio decreases. To address the issues, we propose a Three-dimensional scenario oriented Routing (TDR) protocol for VANETs. Utilizing three-dimensional information, TDR establishes a route hop by hop and transmits packets as far as possible to the optimal immediate neighbor node which is located on the same plane with the current forwarding node. In the end, a comparison between TDR and the existing protocol GPSR is conducted on the network simulator NS2. The results show that TDR has higher delivery ratio but lower end-to-end delay and average hops.