The accuracy and the reactivity of link quality estimators are key concepts in Mobile Ad hoc networks (MANETs) and especially in Vehicular Ad hoc Networks (VANETs), since routing process uses link quality related metrics based on neighbour information for making routing decisions. The Expected Transmission Count (ETX) is the most salient metric that assesses the link quality for wireless ad hoc and mesh networks. Its estimation varies according to the link changes like disruption and bidirectional to unidirectional switching. Such changes occur more often in highly mobile networks like VANETs. In order to be efficient routing protocols have to deal with these events. It has been observed that current implementation of ETX leads to a limited accuracy and cannot be efficient in VANETs. In this paper is presented an algorithm which makes the ETX metric more adapted for VANETs. Our contribution significantly improves the reactivity and the accuracy of the metric. In addition, our metric is not limited to the link quality estimation but also brings a link stability information. This results a new metric called Fast-ETX (F-ETX). This metric has been tested under realistic physical layer and mobility patterns to evaluate its reactivity, accuracy and stability properties.

Due to their inherent features, Mobile Ad Hoc Networks have proven their efficiency to exchange data between mobile nodes. The main issue in this type of a network is the delivery of data to a destination. Unfortunately, the mobility of nodes and the disturbances of the propagation channel lead to the increase of the loss rate, which undermines routing performances. To address this issue, routing protocols use link quality estimators as a metric. However, current estimators have been designed for static wireless sensor networks and are not suitable in case of mobility. In order to overcome this issue, a novel metric called Fast ETX is suggested, which gives a reliable and accurate link quality assessment. It is setup by four estimators which assess and predict the link state. In addition, we design a framework to integrate this multi-estimator metric into a routing protocol.

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Abstract. In Mobile Ad hoc networks (MANETs), advanced routing metrics use Link Quality Estimators (LQE) for making routing decisions. To be efficient and in a strong interaction with the physical layer transmission conditions, the accuracy and the reactivity of LQE used by metrics are crucial for maintaining connectivity. Current LQE estimates the link quality into a single value. This method limits the accuracy of the estimators, especially in highly volatile environments such as VANETs in urban environments. In this paper we propose multi-estimators LQE approach that provides both a better link quality and a link behavior assessment. These novel estimators deal with LQE requirements, reactivity, stability and accuracy to become a reliable LQE. We evaluate they reactivity and accuracy with realistic physical layer and mobility patterns and also found their forecasting properties.