5 research outputs found
Computer simulations of VANETs using realistic city topologies
Researchers in vehicular ad hoc networks (VANETs) commonly use simulation
to test new algorithms and techniques. This is the case because of the high cost and labor
involved in deploying and testing vehicles in real outdoor scenarios. However, when determining
the factors that should be taken into account in these simulations, some factors such
as realistic road topologies and presence of obstacles are rarely addressed. In this paper,
we first evaluate the packet error rate (PER) through actual measurements in an outdoor
road scenario, and deduce a close model of the PER for VANETs. Secondly, we introduce a
topology-based visibility scheme such that road dimension and geometry can be accounted
for, in addition to line-of-sight. We then combine these factors to determine when warning
messages (i.e., messages that warn drivers of danger and hazards) are successfully received
in a VANET. Through extensive simulations using different road topologies, city maps, and
visibility schemes, we show these factors can impact warning message dissemination time
and packet delivery rate.This work was partially supported by the Ministerio de Educacion y Ciencia, Spain, under Grant TIN2011-27543-C03-01, and by the Diputacion General de Aragon, under Grant "subvenciones destinadas a la formacion y contratacion de personal investigador".MartĂnez, FJ.; Fogue, M.; Toh, C.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). Computer simulations of VANETs using realistic city topologies. Wireless Personal Communications. 69(2):639-663. https://doi.org/10.1007/s11277-012-0594-6S639663692Martinez F. J., Toh C.-K., Cano J.-C., Calafate C. T., Manzoni P. (2011) A survey and comparative study of simulators for vehicular ad hoc networks (VANETs). Wireless Communications and Mobile Computing Journal 11(7): 813–828Toh C.-K. (2001) Ad hoc mobile wireless networks: Protocols and systems. Prentice Hall, Englewood Cliffs, NJIEEE 802.11 Working Group. (2010). IEEE standard for information technology—telecommunications and information exchange between systems—local and metropolitan area networks—Specific requirements—Part 11: Wireless LAN medium access control (MAC) and physical layer (PHY) specifications amendment 6: Wireless Access in Vehicular Environments.Sommer, C., Eckhoff, D., German, R., & Dressler F. (2011). A computationally inexpensive empirical model of IEEE 802.11p radio shadowing in urban environments. In Eighth international conference on wireless on-demand network systems and services (WONS), pp. 84–90.Bohm, A., Lidstrom, K., Jonsson, M., & Larsson, T. (2010). Evaluating CALM M5-based vehicle-to-vehicle communication in various road settings through field trials. In Proceedings of the 35th IEEE conference on local computer networks (LCN’10), Denver, Colorado, USA, pp. 613–620.Martinez, F. J., Fogue, M., Coll, M., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2010). Assessing the impact of a realistic radio propagation model on VANET scenarios using real maps. In 9th IEEE international symposium on network computing and applications (NCA), Boston, USA, pp. 132–139.Fall, K., & Varadhan, K. (2000). “ns notes and documents,” The VINT project. UC Berkeley, LBL, USC/ISI, and Xerox PARC, February 2000. Available at http://www.isi.edu/nsnam/ns/ns-documentation.html .Marinoni, S., & Kari, H. H. (2006). Ad hoc routing protocol performance in a realistic environment. In Proceedings of the international conference on networking, international conference on systems and international conference on mobile communications and learning technologies (ICN/ICONS/MCL 2006), Washington, DC, USA.Mahajan, A., Potnis, N., Gopalan, K., & Wang, A. (2007). Modeling VANET deployment in urban settings. In International workshop on modeling analysis and simulation of wireless and mobile systems (MSWiM 2007), Crete Island, Greece.Suriyapaiboonwattana, K., Pornavalai, C., & Chakraborty, G. (2009). An adaptive alert message dissemination protocol for VANET to improve road safety. In IEEE intlernational conference on fuzzy systems, 2009. FUZZ-IEEE 2009, pp. 1639–1644.Bako, B., Schoch, E., Kargl, F., & Weber, M. (2008). Optimized position based gossiping in VANETs. In Vehicular technology conference, 2008. VTC 2008-Fall. IEEE 68th, pp. 1–5.Martinez, F. J., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2008). Citymob: A mobility model pattern generator for VANETs. In IEEE vehicular networks and applications workshop (Vehi-Mobi, held with ICC), Beijing, China.Torrent-Moreno, M., Santi, P., & Hartenstein, H. (2007). Inter-vehicle communications: Assessing information dissemination under safety constraints. In Proceedings of the 4th annual conference on wireless on demand network systems and services (WONS), Oberguyrgl, Austria.Martinez, F. J., Toh, C.-K., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2009). Realistic radio propagation models (RPMs) for VANET simulations. In IEEE wireless communications and networking conference (WCNC), Budapest, Hungary.Martinez, F. J., Toh, C.-K., Cano, J.-C., Calafate, C. T., & Manzoni, P. (2010). A street broadcast reduction scheme (SBR) to mitigate the broadcast storm problem in VANETs. Wireless personal communications, pp. 1–14. doi: 10.1007/s11277-010-9989-4Ni, S.-Y., Tseng, Y.-C., Chen, Y.-S., & Sheu, J.-P. (1999). The broadcast storm problem in a mobile ad hoc network. In ACM/IEEE international conference on mobile computing and networking (MobiCom 1999), Seattle Washington.Krajzewicz, D., & Rossel, C. (2007). “Simulation of urban mobility (SUMO),” Centre for Applied Informatics (ZAIK) and the Institute of Transport Research at the German Aerospace Centre. Available at http://sumo.sourceforge.net/index.shtml .OpenStreetMap Team. (2009). OpenStreetMap, collaborative project to create a free editable map of the world. Available at http://www.openstreetmap.org .U.S. Census Bureau. (2009). TIGER, topologically integrated geographic encoding and referencing. Available at http://www.census.gov/geo/www/tiger .Krauss S., Wagner P., Gawron C. (1997) Metastable states in a microscopic model of traffic flow. Physical Review E 55(5): 5597–5602Krajzewicz, D., Hertkorn, G., Rossel, C., & Wagner, P. (2002). SUMO (Simulation of Urban MObility)—An open-source traffic simulation. In Proceedings of the 4th middle east symposium on simulation and modelling (MESM2002), Sharjah, United Arab Emirates, pp. 183–187
Etude et réalisation d'un système de communications par lumière visible (VLC/LiFi). Application au domaine automobile.
The scientific problematic of this PhD is centered on the usage of Visible LightCommunications (VLC) in automotive applications. By enabling wireless communication amongvehicles and also with the traffic infrastructure, the safety and efficiency of the transportation canbe substantially increased. Considering the numerous advantages of the VLC technologyencouraged the study of its appropriateness for the envisioned automotive applications, as analternative and/or a complement for the traditional radio frequency based communications.In order to conduct this research, a low-cost VLC system for automotive application wasdeveloped. The proposed system aims to ensure a highly robust communication between a LEDbasedVLC emitter and an on-vehicle VLC receiver. For the study of vehicle to vehicle (V2V)communication, the emitter was developed based on a vehicle backlight whereas for the study ofinfrastructure to vehicle (I2V) communication, the emitter was developed based on a traffic light.Considering the VLC receiver, a central problem in this area is the design of a suitable sensorable to enhance the conditioning of the signal and to avoid disturbances due to the environmentalconditions, issues that are addressed in the thesis. The performances of a cooperative drivingsystem integrating the two components were evaluated as well.The experimental validation of the VLC system was performed in various conditions andscenarios. The results confirmed the performances of the proposed system and demonstrated thatVLC can be a viable technology for the considered applications. Furthermore, the results areencouraging towards the continuations of the work in this domain.La problématique scientifique de cette thèse est centrée sur le développement decommunications par lumière visible (Visible Light Communications - VLC) dans lesapplications automobiles. En permettant la communication sans fil entre les véhicules, ou entreles véhicules et l’infrastructure routière, la sécurité et l'efficacité du transport peuvent êtreconsidérablement améliorées. Compte tenu des nombreux avantages de la technologie VLC,cette solution se présente comme une excellente alternative ou un complément pour lescommunications actuelles plutôt basées sur les technologies radio-fréquences traditionnelles.Pour réaliser ces travaux de recherche, un système VLC à faible coût pour applicationautomobile a été développé. Le système proposé vise à assurer une communication très robusteentre un émetteur VLC à base de LED et un récepteur VLC monté sur un véhicule. Pour l'étudedes communications véhicule à véhicule (V2V), l'émetteur a été développé sur la base d’un pharearrière rouge de voiture, tandis que pour l'étude des communications de l'infrastructure auvéhicule (I2V), l'émetteur a été développé sur la base d'un feu de circulation. Considérant lerécepteur VLC, le problème principal réside autour d’un capteur approprié, en mesured'améliorer le conditionnement du signal et de limiter les perturbations dues des conditionsenvironnementales. Ces différents points sont abordés dans la thèse, d’un point de vue simulationmais également réalisation du prototype.La validation expérimentale du système VLC a été réalisée dans différentes conditions etscénarii. Les résultats démontrent que la VLC peut être une technologie viable pour lesapplications envisagées
Comunicações sem fios confiáveis para aplicações veiculares
Doutoramento em Engenharia ElectrotécnicaIn the last decades the number of vehicles travelling in European road has
raised significantly. Unfortunately, this brought a very high number of road
accidents and consequently various injuries and fatalities. Even after the
introduction of passive safety systems, such as seat belts, airbags, and some
active safety systems, such as electronic brake system (ABS) and electronic
stabilization (ESP), the number of accidents is still too high. Approximately
eight per cent of the fatal accidents occur in motorways, in the Portuguese
case, the number of fatalities has remained constant in the first decade of the
21st century.
The evolution of wireless communications, along with the north-American and
European policies that reserve spectrum near the 5,9GHz band for safety
applications in the vehicular environment, has lead to the development of
several standards. Many of these applications are based on the possibility of
using a wireless communication system to warn drivers and passengers of
events occurring on the road that can put at risk their own safety. Some
examples of safety applications are the hard-brake warning, the wrong-way
warning and the accident warning.
This work aims to contribute in defining a communication protocol that
guarantees the timely dissemination of safety critical events, occurring in
scenarios with a high number of vehicles or in the neighbourhood of so called
motorway “blackspots”, to all vehicles in the zone of interest.
To ensure information integrity and user trust, the proposed system is based on
the motorway infrastructure, which will validate all events reported by the
vehicles with the usage of several means, such as video surveillance or other
sensors. The usage of motorway infrastructure that has full motorway coverage
using fixed stations also known as road side units, allows to have a global
vision of the interest zone, avoiding the problems associated to networks that
depend solely on vehicle to vehicle communication, generally total ad-hoc
networks. By using the infrastructure, it is possible to control medium access,
avoiding possible badly intended intrusions and also avoiding the phenomenon
known as alarm showers or broadcast storm that occur when all vehicles want
to simultaneously access the medium to warn others of a safety event.
The thesis presented in this document is that it is possible to guarantee in time
information about safety events, using an architecture where the road side units
are coordinated among themselves, and communicate with on board units (in
vehicles) that dynamically register and deregister from the system. An exhaustive and systematic state of the art of safety applications and related
research projects is done, followed by a study on the available wireless
communications standards that are able to support them. The set of standards
IEEE802.11p and ETSI-G5 was created for this purpose and is found to be the
more adequate, but care is taken to define a scenario where WAVE enabled
and non-enabled vehicles can coexist. The WAVE medium access control
protocol suffers from collision problems that do not guarantee a bounded delay,
therefore a new protocol (V-FTT) is proposed, based on the adaptation of the
Flexible Time Triggered protocol to the vehicular field. A theoretical analysis of
the V-FTT applied to WAVE and ETSI-G5 is done, including quantifying a real
scenario based on the A5 motorway from Lisbon to Cascais, one of the busiest
Portuguese motorways. We conclude the V-FTT protocol is feasible and
guarantees a bounded delay.Nas Ăşltimas dĂ©cadas tem-se assistido a um aumento do nĂşmero de veĂculos a
circular nas vias rodoviárias europeias, trazendo consigo um elevado número
de acidentes e como consequĂŞncia muitos feridos e vĂtimas mortais. Apesar da
introdução de sistemas de segurança passivos, tais como cintos de segurança,
airbags e de alguns sistemas de segurança activos, tais como o sistema
electrĂłnico de travagem (ABS) e o sistema electrĂłnico de estabilidade (ESP), o
nĂşmero de acidentes continua a ser demasiado elevado. Aproximadamente
oito por cento dos acidentes fatais na Europa ocorrem em auto-estradas, no
caso PortuguĂŞs, o nĂşmero de vĂtimas mortais tem-se mantido constante ao
longo da primeira década do século XXI.
A evolução das comunicações sem fios, acompanhada de polĂticas europeias
e norte-americanas no sentido de reservar frequĂŞncias prĂłximas dos 5,9GHz
para aplicações de segurança no ambiente veicular, levou à especificação de
várias normas. A maior parte destas aplicações baseiam-se na possibilidade
de usar um sistema confiável de comunicação sem fios para alertar os
condutores e passageiros de veĂculos para eventos ocorridos nas estradas que
possam colocar em risco a sua segurança. Exemplos de aplicações de
segurança crĂtica sĂŁo o aviso de travagem brusca, o aviso de veĂculo em
contra mĂŁo e o aviso de acidente na estrada.
Este trabalho contribui para a definição de protocolos de comunicação capazes
de garantir que a informação sobre eventos relacionados com situações de
segurança crĂtica, que ocorram em cenários com um elevado nĂşmero de
veĂculos em zonas urbanas ou na vizinhança dos chamados “pontos negros”
das auto-estradas, Ă© disseminada com pontualidade por todos os veĂculos
localizados na zona de interesse Por uma questĂŁo da integridade das
comunicações e confiança dos condutores, o sistema proposto baseia-se na
infra-estrutura do concessionário da auto-estrada, que validará os eventos
reportados pelos veĂculos usando vários meios Ă sua disposição, como por
exemplo sistemas de videovigilância e outros sensores.
O uso de uma infra-estrutura de comunicações, que dispõe de cobertura
integral a partir de estações fixas, permite uma visão global da zona coberta,
evitando os problemas associados a redes baseadas apenas na comunicação
entre veĂculos, que sĂŁo em geral totalmente ad-hoc. O uso da infra-estrutura
permite, entre outras vantagens, controlar o acesso ao meio, evitando
simultaneamente intrusões de estranhos ao sistema e o fenómeno conhecido
como “chuva de alarmes” desencadeado quando todos os veĂculos querem
aceder simultaneamente ao meio para avisar os restantes da existĂŞncia dum
evento de segurança crĂtica. A tese apresentada neste documento defende que Ă© possĂvel garantir
informação atempada sobre eventos que põem em risco a segurança dos
veĂculos a partir de uma arquitectura de interligação entre as estações de
comunicações fixas, coordenadas entre si, e unidades mĂłveis (veĂculos) que
se registam e se desligam dinamicamente do sistema.
Nesta tese faz-se um levantamento exaustivo e sistemático das aplicações de
segurança abordando projectos de investigação relacionados, estudam-se as
tecnologias de comunicação sem fios disponĂveis e a sua possibilidade de
suportar aplicações de segurança rodoviária. Desta análise, conclui-se que a
norma norte americana WAVE/IEEE802.11p e a europeia ETSI-G5, criadas
especificamente para o efeito sĂŁo as que mais se adequam Ă finalidade
desejada.
Considera-se que o cenário de utilização é evolutivo, podendo coexistirem
veĂculos que nĂŁo dispõem de sistemas de comunicação com outros que
suportam a norma WAVE. Dado que o protocolo de acesso ao meio proposto
pela norma WAVE nĂŁo garante um acesso determinĂstico ao meio partilhado,
propõe-se um novo protocolo, o Vehicular Flexible Time-Triggered protocol (VFTT).
Faz-se a análise teórica da viabilidade do protocolo proposto para a norma
WAVE e respectiva norma europeia (ETSI-G5). Quantifica-se o protocolo VFTT
para um cenário real: a auto-estrada A5 Lisboa-Cascais, uma das autoestradas
portuguesas mais movimentadas. Conclui-se que o protocolo é viável
e garante um atraso restringido temporalmente