Modeling and verifying clustering properties in a vehicular ad hoc network protocol with Event-B

Patrick Sondi,Imed Abbassi,Mohamed Graiet,Emna Chebbi,Eric Ramat

doi:10.1038/s41598-021-97063-3

Abstract

Vehicular ad hoc network (VANET) routing protocols resort to clustering in order to optimize broadcast traffic flooding. Clustering schemes usually rely on rules which apply to each vehicle in order to reach a targeted organization in a VANET. Most of the literature works which evaluate clustering for VANET focus on performance analysis. However, with autonomous vehicles coming to roadways, more rigorous relationships will be required between clustering rules and the resulting organization, so as to anticipate road safety in a better way. We propose a formal description of the properties which are expected in a VANET, while considering the rules of a given clustering scheme. Using Event-B, we first present a description of the VANET, the vehicles movement and the traffic generated by both routing and application messages. Then, based on an Event-B model of a basic routing protocol of the literature, we describe how the specific rules of a clustering scheme can be modeled along with the properties expected in the resulting organization. Finally, we propose a validation process of the model. This paper aims at showing how our proposals have been applied to the Chain-Branch-Leaf scheme, although they can be adapted to any rule-based clustering scheme for VANET.

Highlights

Vehicular ad hoc network (VANET) routing protocols resort to clustering in order to optimize broadcast traffic flooding
We present the main result of this work, which is a formal model of the Chain-Branch-Leaf clustering scheme allowing verifying its properties in a VANET
The assessment of the CBL clustering scheme implies two steps, which are requirement validation for verifying that the protocol specification fulfills the functional needs envisaged by the designer[25], and consistency checking for ensuring that the clustering scheme does not introduce contradictions in the relations linking the nodes

Summary

Introduction

Vehicular ad hoc network (VANET) routing protocols resort to clustering in order to optimize broadcast traffic flooding. Chain-Branch-Leaf (CBL), a distributed clustering scheme exploiting this particularity, has been recently proposed[8] It combines road configuration data, vehicle mobility and link quality indicators in order to build a structure similar to a vehicular network infrastructure, while relying only on vehicle-to-vehicle communications only. It organizes VANET nodes into a backbone of clusters (which is called “chain”), composed of branch nodes (cluster heads) to which leaf nodes (cluster members) attach themselves. We use the Event-B formal method to model and verify the properties of the CBL clustering scheme in order to show how such evaluation approach can be applied to VANET protocols

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