Evaluating H.265 real-time video flooding quality in highway V2V environments

© 2014 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works[EN] Video transmission over VANETs is an extremely difficult task not only due to the high bandwidth requirements, but also due to typical VANET characteristics such as signal attenuation, packet losses, high relative speeds and fast topology changes. In future scenarios, vehicles will provide other vehicles with information about accidents or congestion on the road, and in these cases offering visual information can be a really valuable resource for both drivers and traffic authorities. Hence, achieving an efficient transmission is critical to maximize the user-perceived quality. In this paper we evaluate solutions that combine different flooding techniques, and different video codecs to assess the effectiveness of long-distance real-time video streaming. In particular, we will compare the most effective video coding standard available (H.264) with the upcoming H.265 codec in terms of both frame loss and PSNR.This work was partially supported by the Ministerio de Economía y Competitividad, Spain, under Grant TIN2011- 27543-C03-01, and by the Ministerio de Educación, Spain, under the FPU program, AP2009-2415.Torres Cortés, Á.; Piñol, P.; Tavares De Araujo Cesariny Calafate, CM.; Cano Escribá, JC.; Manzoni, P. (2014). Evaluating H.265 real-time video flooding quality in highway V2V environments. En 2014 IEEE Wireless Communications and Networking Conference (WCNC). IEEE. 2758-2763. https://doi.org/10.1109/WCNC.2014.6952858S2758276

An Infrastructureless Approach to Estimate Vehicular Density in Urban Environments

In Vehicular Networks, communication success usually depends on the density of vehicles, since a higher density allows having shorter and more reliable wireless links. Thus, knowing the density of vehicles in a vehicular communications environment is important, as better opportunities for wireless communication can show up. However, vehicle density is highly variable in time and space. This paper deals with the importance of predicting the density of vehicles in vehicular environments to take decisions for enhancing the dissemination of warning messages between vehicles. We propose a novel mechanism to estimate the vehicular density in urban environments. Our mechanism uses as input parameters the number of beacons received per vehicle, and the topological characteristics of the environment where the vehicles are located. Simulation results indicate that, unlike previous proposals solely based on the number of beacons received, our approach is able to accurately estimate the vehicular density, and therefore it could support more efficient dissemination protocols for vehicular environments, as well as improve previously proposed schemes.This work was partially supported by the Ministerio de Ciencia e Innovacion, Spain, under Grant TIN2011-27543-C03-01, as well as by the Fundacion Universitaria Antonio Gargallo (FUAG), and the Caja de Ahorros de la Inmaculada (CAI).Sanguesa, JA.; Fogue, M.; Garrido, P.; Martinez, FJ.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). An Infrastructureless Approach to Estimate Vehicular Density in Urban Environments. Sensors. 13(2):2399-2418. doi:10.3390/s130202399S2399241813

A Survey on platoon-based vehicular cyber-physical systems

Vehicles on the road with some common interests can cooperatively form a platoon-based driving pattern, in which a vehicle follows another one and maintains a small and nearly constant distance to the preceding vehicle. It has been proved that, compared to driving individually, such a platoon-based driving pattern can significantly improve the road capacity and energy efficiency. Moreover, with the emerging vehicular adhoc network (VANET), the performance of platoon in terms of road capacity, safety and energy efficiency, etc., can be further improved. On the other hand, the physical dynamics of vehicles inside the platoon can also affect the performance of VANET. Such a complex system can be considered as a platoon-based vehicular cyber-physical system (VCPS), which has attracted significant attention recently. In this paper, we present a comprehensive survey on platoon-based VCPS. We first review the related work of platoon-based VCPS. We then introduce two elementary techniques involved in platoon-based VCPS: the vehicular networking architecture and standards, and traffic dynamics, respectively. We further discuss the fundamental issues in platoon-based VCPS, including vehicle platooning/clustering, cooperative adaptive cruise control (CACC), platoon-based vehicular communications, etc., and all of which are characterized by the tight coupled relationship between traffic dynamics and VANET behaviors. Since system verification is critical to VCPS development, we also give an overview of VCPS simulation tools. Finally, we share our view on some open issues that may lead to new research directions

Adaptive Mechanisms to Improve Message Dissemination in Vehicular Networks

En el pasado, se han dedicado muchos recursos en construir mejores carreteras y autovías. Con el paso del tiempo, los objetivos fueron cambiando hacia las mejoras de los vehículos, consiguiendo cada vez vehículos más rápidos y con mayor autonomía. Más tarde, con la introducción de la electrónica en el mercado del automóvil, los vehículos fueron equipados con sensores, equipos de comunicaciones, y otros avances tecnológicos que han permitido la aparición de coches más eficientes, seguros y confortables. Las aplicaciones que nos permite el uso de las Redes Vehiculares (VNs) en términos de seguridad y eficiencia son múltiples, lo que justifica la cantidad y recursos de investigación que se están dedicando en los últimos años. En el desarrollo de esta Tesis, los esfuerzos se han centrado en el área de las Vehicular Ad-hoc Networks, una subclase de las Redes Vehiculares que se centra en las comunicaciones entre los vehículos, sin necesidad de que existan elementos de infraestructura. Con la intención de mejorar el proceso de diseminación de mensajes de alerta, imprescindibles para las aplicaciones relacionadas con la seguridad, se ha propuesto un esquema de difusión adaptativo, capaz de seleccionar automáticamente el mecanismo de difusión óptimo en función de la complejidad del mapa y de la densidad actual de vehículos. El principal objetivo es maximizar la efectividad en la difusión de mensajes, reduciendo al máximo el número de mensajes necesarios, evitando o mitigando las tormentas de difusión. Las propuestas actuales en el área de las VANETs, se centran principalmente en analizar escenarios con densidades típicas o promedio. Sin embargo, y debido a las características de este tipo de redes, a menudo se dan situaciones con densidades extremas (altas y bajas). Teniendo en cuenta los problemas que pueden ocasionar en el proceso de diseminación de los mensajes de emergencia, se han propuesto dos nuevos esquemas de difusión para bajas densidades: el \emph{Junction Store and Forward} (JSF) y el \emph{Neighbor Store and Forward} (NSF). Además, para situaciones de alta densidad de vehículos, se ha diseñado el \emph{Nearest Junction Located} (NJL), un esquema de diseminación que reduce notablemente el número de mensajes enviados, sin por ello perder prestaciones. Finalmente, hemos realizado una clasificacion de los esquemas de difusión para VANETs más importantes, analizando las características utilizadas en su diseño. Además hemos realizado una comparación de todos ellos, utilizando el mismo entorno de simulación y los mismos escenarios, permitiendo conocer cuál es el mejor esquema de diseminación a usar en cada momento