9F-ETX: A Metric Designed for Vehicular Networks

9.1. Introduction

Due to their inherent characteristics, including self-organization, scalability, mobility and the fast changing transmission channel quality, vehicular ad hoc networks (VANET) address specific challenges. Vehicles move on the road network according to traffic patterns and they do not rely on a limited battery capacity. Vehicle-to-Vehicle (V2V) communications rely on the cooperation with each other to build opportunistic wireless networks. Since vehicles move with a wide range of speeds according to traffic patterns, the network topology is characterized by a potentially high dynamic. The road environment (e.g. urban, suburban and motorway) also plays a key role in the disturbance of the transmission channel.

Distributed applications require the cooperation of nodes, but they are bounded by connectivity and reliability issues. Those are partially solved by routing protocols, which ensure an end-to-end communication with a multi-hop relaying technique. To this end, protocols compute and share local information on the direct neighborhood to determine the best end-to-end path. A relevant challenge for routing protocols is the selection of the best kind of estimator to obtain reliable information on local links. Indeed, routing performance in terms of end-to-end delay and packet delivery ratio depends on the reliability of the selected path. The traditional hop count metric relates the cost of a path to the number ...

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