Effects of a realistic channel model on packet forwarding in vehicular ad hoc networks

The discrepancy between real-world radio channel behavior and its standard modeling in simulations (unit disk graph) is a major reason for protocols to perform differently - often worse - than predicted when deployed in a real-world setup. As researchers having to deal with real ad hoc networks are aware of, assuming a fixed border for a node´s communication range might not only lead to inaccurate results but also to a wrong judgment on the comparison between different protocols. We have set up a simulation study to investigate the effects of realistic channel characteristics on packet forwarding strategies for vehicular ad hoc networks. The contributions of this paper are threefold: i) we provide a performance evaluation of various routing/forwarding strategies under the realistic non-deterministic Nakagami radio propagation model and compare the results with the ones obtained using the standard two-ray-ground model. Validated German highway movement patterns are used to model node mobility. ii) We demonstrate that realistic channel conditions present an opportunity and not only a drawback for some forwarding strategies. More specifically, we show that for contention-based forwarding (CBF) techniques, realistic channel characteristics provide a positive impact in terms of an increased average hop distance. iii) We provide an analytical derivation of the expected hop distance for CBF that provides a basis to optimally adjust CBF parameters