Vehicular Ad Hoc Networks and Delay/Disruptive Tolerant Networks

Vehicular Netowrks are a kind of MANETs in which nodes are vehicles that follow particular mobility patterns regulated by vial normatives. In the last years, several organizations have supported standardization activities such as IEEE 802.11p and WAVE (Wireless Access Vehicular Environment), ISO TC204 WG-16 CALM architecture, ETSI-ERM TG37, applied to vehicular communications. Organizations such as C2CCC (Car to Car Communications Consortium) have brought the European vehicle  manufactures to join in an initiative with the objective of further increasing road traffic safety and efficiency by means of inter-vehicle communications.

Communications in VANETs mainly may be of two types: single-hop to neighbor cars to advise of an event (e.g. braking) or multi-hop to either disseminate information or to query for a service. From the application perspective, applications can be categorized as Transportation-related applications and Convenience and personalized applications.

As in MANETs, communications in VANETs may be impacted by several factors: 

• High velocity of the vehicles
• Environment factors: obstacles (e.g. urban scenarios), tunnels, traffic jams, etc.
• Determined mobility patters that depends on source to destination path and on traffic conditions
• Low duration of the communications (aprox. 4-6 hops)
• Intermittent communications (isolated networks of cars due to the fragmentation of the network)
• High congestion channels

These factors result in a network with frequent fragmentation in small parts, rapid changes in the network topology due to high node speeds, small effective network diameters and limited redundancy. In fact some papers show that at nine hops, before a request packet may be ACK, the path has dissapeared. This makes that proactive and reactive MANET protocols behave poorly in a VANET scenario.

The Research group has been participating from year 2006 in the VNET-2 project (together with the Univ. of  Milano, Univ. of Torino and Univ. of Antwerp) under the umbrella of EuorNGI NoE. The objective of this project was to study routing algorithms applied to safety communications.

From June 2007, the research group continues with an extension of the project called VNET-3 (together with the Univ. of  Milano, Univ. of Torino and Univ. of Passau) whose objective is to study how to bring convenience applications to Vehicular Networks.

Current research activities: due to the harsh conditions in VANETs, packet losses are quite high. In order to reduce these packet losses and improve both throughput, transfer delay and network coordination we are integrating concepts coming from Cooperative Networks, Disruptive Delay Tolerant Networks (DTN) and Network Coding to vehicular scenarios. We have developed a prototype including C-ARQ (Cooperative-ARQ) and tested how losses may be recovered in vehicular scenarios. We are now defining DTVP (Delay Tolerant Vehicular Protocol), a protocol that includes carry-and-forward concepts coming from DTN and will be integrated with C-ARQ.

Publications

• David Fuste-Vilella, Jose Miguel Pulido,Jorge Garcia-Vidal, Steluta Gheorghiu, TrafficNET: A traffic network architecture for Road-to-Vehicle Communication, Third International Workshop of Wireless and Mobility, Sitges, Spain, June 2006. In Lecture Notes in Computer Science (LNCS), Volume 4396, pp 43-61 (publication under the umbrella of project VNET-2 in Euro-NGI).

• J. Morillo-Pozo, J. M. Barcelo-Ordinas, O. Trullos-Cruces, J. Garcia-Vidal, A Cooperative ARQ for Delay-Tolerant Vehicular Networks, IEEE International Workshop on Delay/Disruption-Tolerant Mobile Networks (DTMN'08), in conjunction with ICDCS 2008, Beijing, China, June 20, 2008
• O. Trullos-Cruces, J. Morillo-Pozo, J. M. Barcelo-Ordinas, J. Garcia-Vidal, A Cooperative Vehicular Framework Network, submitted for Conference publication

People

Oscar Trullols-Cruces, David Fusté-Vilella, Julian Morillo-Pozo, José Mª Barceló-Ordinas, Jorge García-Vidal

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