Sergio Martínez Tornell

DTN Protocols for Vehicular Networks: An Application Oriented Overview

This survey provides an in-depth analysis of the different proposals for Vehicular Delay Tolerant Networks (VDTNs). We introduce the DTN architecture and classify VDTN proposals according to the type of knowledge needed to route messages. This classification also includes some Delay Tolerant Network (DTN) protocols originally designed for Opportunistic Networks to illustrate the evolution from Opportunistic DTN protocols to VDTN protocols. We also identify a set of common mechanisms that can be applied to almost all the VDTN protocols, heavily influencing their performance. Finally, we present some applications where VDTNs can be applicable and evaluate the suitability of the different proposals for each specific application. Moreover, this survey is not only limited to describing the different protocols but also focuses on the reproducibility and repeatability of experiments. With this in mind, we also review the evaluation methods used by VDTN researchers. We identify a lack of realism in most of the simulation models used by the VDTN research community, providing certain guidelines to address this issue.

VACaMobil: VANET Car Mobility Manager for OMNeT++

The performance of communication protocols in vehicular networks highly depends on the mobility pattern. Therefore, one of the most important issues when simulating this kind of protocols is how to properly model vehicular mobility. In this paper we present VACaMobil, a VANET Car Mobility Manager for the OMNeT++ simulator which allows researchers to completely define vehicular mobility by setting the desired average number of vehicles along with its upper and lower bounds. We compare VACaMobil against other common methods employed to generate vehicular mobility. Results clearly show the advantages of the VACaMobil tool when distributing vehicles in a real scenario, becoming one of the best mobility generators to evaluate the performance of different communication protocols and algorithms in VANET environments.

GRCBox: extending smartphone connectivity in vehicular networks

The low penetration of connectivity-enabled OBUs is delaying the deployment of vehicular networks (VNs) and therefore the development of vehicular delay tolerant network (VDTN) applications, among others. In this paper we present GRCBox, an architecture based on RaspberryPi that allows integrating smartphones in VNs. GRCBox is based on a low-cost device that combines several pieces of software to provide ad hoc and multi-interface connectivity to smartphones. Using GRCBox each application can choose the interface for its data flows, which increases flexibility and will allow developers to easily implement applications based on ad hoc connectivity, such as VDTN applications.

Evaluating the Feasibility of Using Smartphones for ITS Safety Applications

Driving security and comfort can be improved by applying Intelligent Transportation Systems (ITS) proposals. The low adoption rate of new ITS hardware and software products is slowing down the market introduction of these solutions. In this paper we present a driving safety application for smartphones based on a warning dissemination protocol called eMDR. The use of smartphones minimizes the hardware cost and eliminates most of the adoption barriers; users will no longer have to install new dedicated devices in their vehicles. Instead, they will simply have to install an application in their smartphone. Our application is integrated with a Navigation System which provides access to road maps, current location, and route information. We analyzed the behavior of the wireless channel and the GPS location service under different conditions to assess the feasibility of our proposal. Results showed that, in C2C communications, smartphones are able to provide a reasonable degree of connectivity, and that the degree of precision achieved is enough for certain types of driving safety applications.

Implementing and testing a driving safety application for smartphones based on the eMDR protocol

Vehicular Ad-Hoc Networks (VANETs) offer opportunities for improvements in driving security and comfort. Vehicles can take advantage of collaboration schemes to disseminate important information. In this article we present a a driving safety application based on warnings dissemination for smart-phones based on our eMDR protocol. The use of smartphones allows a quick development and deployment, avoiding the cost of specific hardware. Additionally, since most users are familiar with the use of smartphones, this alleviates the adoption barrier. Our application is integrated into a Navigation System which allows accessing road maps, current location and route information through an interface that we have created. We have analyzed the behavior of the wireless channel and the GPS location service under different conditions to assess the feasibility of our proposal. Result showed that, in C2C communications, smartphones provide a reasonable connectivity and enough precision even for certain type of driving safety applications.

Assessing the effectiveness of DTN techniques under realistic urban environments

Intelligent Transportation Systems (ITS) require collecting and distributing as much relevant information as possible to provide their services. Such information could also offer new possibilities to various service providers in the wider Smart City context. The distribution of this intelligence is carried out through various vehicular networking strategies, the most flexible of all being Delay Tolerant Networking (DTN). DTN protocols can cope with the problems derived from high mobility and the possibility of high node sparsity. Nevertheless, achieving a fair comparison of DTN solutions in an urban environment is a hard task. In this paper we present a generic DTN model that we use to compare various representative DTN solutions in a metropolitan scenario. We highlight the weak and strong points of each evaluated proposal by also taking into consideration different sending strategies adopted to improve the performance of DTN protocols.

A Tool Offering Steady-State Simulations for VANETs

This work was partially supported by the Ministerio de Economia y Competitividad, Spain, under Grants TIN2011-27543- C03-01 and BES-2012-052673, by the Ministerio de Educacion, Spain, under the FPU program, AP2010-4397, AP2009-2415, and by the Universitat Politecnica de Valencia under project ABATIS (PAID-05-12).

An analytical evaluation of a Map-based Sensor-data Delivery Protocol for VANETs

The Delay Tolerant Networks (DTN) approach is considered the best strategy to address the specific issues of the VANETs, namely high mobility, variable node density or frequent radio obstacles. Several protocols have been proposed for DTNs, being the epidemic routing (and variations of it) the most representative protocol. Nevertheless, the availability of navigation systems, thanks to which each vehicle is aware of its location within a map, introduces the possibility for a new routing approach, known as Geographic Routing. In this paper we analytically evaluate the performance of our previously presented Map-based Sensor-data Delivery Protocol (MSDP). We introduce an analytical model that takes into account the effect of constrained buffers. The results show that adopting the Map-based Sensor-data Delivery Protocol (MSDP) routing mechanism allows achieving a reasonable delivery time with an insignificant overhead compared with epidemic routing.

Accelerating vehicle network simulations in urban scenarios through caching

When designing new Vehicular Network (VN) protocols, the cost and time required for deploying real prototypes to run tests and evaluate new proposals becomes excessive. Consequently, simulation plays a key role in Vehicular Networks development. Simulation models and tools have been improved to better mimic the different factors that affect communications in real world scenarios. In terms of the communications channel, models have evolved from simplistic distance-based models to elaborated stochastic models that take into account both distance and the obstacle layout. However, increasing the complexity of the models also increases the time needed to run simulations. In this paper, we present an optimization applicable to the obstacle model included in VEINS, a well-known VN simulator, which relays on a cache table to accelerate ray-tracing calculations at the physical layer. Our results show that the proposed optimization can reduce by up to 75% the simulation time with minimal differences in terms of simulation results.

A novel On-Board Unit to accelerate the penetration of ITS services

In-vehicle connectivity has experienced a big expansion in recent years. Car manufacturers have mainly proposed OBU-based solutions, but these solutions do not take full advantage of the opportunities of inter-vehicle peer-to-peer communications. In this paper we introduce GRCBox, a novel architecture that allows OEM user-devices to directly communicate when located in neighboring vehicles. In this paper we also describe EYES, an application we developed to illustrate the type of novel applications that can be implemented on top of the GRCBox. EYES is an ITS overtaking-assistance system that provides the driver with real-time video fed from the vehicle located in front. Finally, we evaluated the GRCbox and the EYES application and showed that, for device-to-device communication, the performance of the GRCBox architecture is comparable to an infrastructure network, introducing a negligible impact.