Abstract

Part 6: New Testing Methods; International audience; In this paper, we focus on Mobile Ad-hoc Networks (MANETs) with non-uniform node density distribution such as Vehicular Ad-hoc Networks (VANETs) and Delay Tolerant Networks (DTNs), and propose a technique for protocol testing and performance evaluation. In such MANETs, node density varies depending on locations and time, and it dynamically changes every moment. In the proposed method, we designate node density distributions and their dynamic variations in a target area. Then, we construct a graph called TestEnvGraph where all node density distributions are treated as its nodes and they are connected by edges whose weights denote differences of two node density distributions. We specify a set of edges to be tested in the graph, formulate a problem for efficiently reproducing all the given node density distributions and their dynamic variations as a rural postman problem, find its solution and use it as the order of reproduction of designated node density distributions and their variations. Protocol testing is carried out by reproducing node density distributions in the derived order. We have designed and developed a method and its tool for mobility generation on MANETs, which can reproduce any designated node density distribution and its dynamic variations in a target area. From our experiments for a VANET protocol, we have shown that our method can give a similar trend in network throughput and packet loss rates compared with realistic trace based protocol testing. Document type: Part of book or chapter of book

Abstract

Vehicle-to-vehicle communications (V2V) is a promising technique for Advanced Driver Assistance Systems to increase traffic safety and efficiency. A proposed system is the Congestion Assistant, which supports drivers when approaching and driving in traffic congestion. Studies have shown great potential for such systems to reduce the impact of congestion, even at low penetration. However, these studies assumed complete and instantaneous knowledge regarding position and velocity of vehicles ahead. This paper refines and analyses the TrafficFilter, designed to supply the required information to the Congestion Assistant. Vehicles collaboratively build a so-called TrafficMap, providing over-the-horizon awareness. To this end, an improvement to the Slotted 1-Persistence Flooding called microSlotted 1-Persistence Flooding is proposed and evaluated. In a simulation study the TrafficFilter is found to be a viable system to build over-the-horizon awareness for future Advanced Driver Assistance Systems like the Congestion Assistant, without triggering the phenomenon known as Broadcast Storm.

Abstract

Rede Ad hoc Veicular (VANET) é um subconjunto singular das redes ad hoc móveis (MANET), com o diferencial de que os nós são veículos providos de tecnologia própria de comunicação e que interagem para formar redes espontâneas, valendo-se de pouca ou nenhuma infraestrutura estabelecida previamente. VANETs admitem a integração de diferentes tecnologias sem fio na pretensão de mitigar adversidades, agregar segurança e eficiência ao tráfego. Na disseminação de dados, um salto único é suficiente para orientar os elementos ao alcance do sinal de rádio, e nós intermediários sustentam a comunicação aos demais, em encaminhamento multihop. Amparados em dispositivos embarcados, os veículos produzem registros, detectam sinais, trocam advertências e métricas. Avaliações dessas informações permitem ao condutor decisões ou reações antecipadas em situações adversas, a exemplo dos acidentes ou congestionamentos. Nesse contexto, a execução deste trabalho trata questões para elaborar estratégias adaptativas inteligentes de disseminação de dados, uma vez que as mesmas se consolidam como lastros da comunicação em VANET com condições adversas de operação. A abordagem proposta se utiliza de sistemas fuzzy para a detecção de congestionamento, com o propósito de agregar autonomia e adaptar a estratégia de disseminação às condições de tráfego identificadas. A convergência nos desenvolvimentos realizados se reflete na estratégia eFIRST, uma solução robusta para a detecção autônoma da condição atual de congestionamento que resguarda a disseminação adaptativa de alertas e abranda o problema da interrupção no tráfego. A abordagem se sustenta apenas na comunicação entre veículos e nos registros de identificação da vizinhança local, agregados em uma estratégia fuzzy e no ajuste adaptativo da potência do sinal de transmissão. Em conformidade com as tendências de condução e com os sistemas inteligentes, este desenvolvimento contribui com subsídios para ratificar a aproximação fuzzy como estratégia adaptativa às flutuações na densidade veicular, em diferentes cenários e regimes de tráfego. As avaliações comparativas do eFIRST respaldam concluir que a estratégia oportuniza o equilíbrio otimizado das perdas, colisões e cobertura, com superior alcance de propagação e redução dos congestionamentos. Vehicular Ad hoc Network (VANET) is a unique subset of mobile ad hoc networks (MANET), with the difference that nodes are vehicles provided with their own communication technology and interact to form spontaneous networks, with little or no infrastructure previously established. VANETs support the integration of different wireless technologies in order to mitigate adversities, add security and efficiency to traffic. In the data dissemination, a single hop is sufficient to guide the elements within reach of the radio signal, and intermediary nodes support the communication with the others in multihop routing. Supported by embedded devices, vehicles produce records, detect signals, exchange warnings and metrics. Assessments of this information allow the driver to make decisions or react beforehand in adverse situations, such as accidents or traffic congestions. From the observations in this context, this work deals with questions to elaborate intelligent adaptive strategies in data dissemination, since they consolidate themselves as ballast communication in VANET with adverse operating conditions. The proposed approach uses fuzzy systems to detect traffic congestion, with the purpose of aggregating autonomy and adapting the dissemination strategy to the identified traffic conditions. The convergence in the developments performed is reflected in the eFIRST strategy, a robust solution for the autonomous detection of the current traffic congestion condition that protects the adaptive dissemination of alerts and reduces the problem of the interruption in the traffic. The approach is supported only by communication between vehicles and in local neighborhood identification records, aggregated in a fuzzy strategy and in the adaptive adjustment of transmission signal power. In accordance with the driving trends and with the intelligent systems, this development contributes with assistance for ratify the fuzzy approach as an adaptive strategy to fluctuations in vehicular density in different scenarios and traffic regimes. Comparative evaluations of eFIRST support the conclusion that the strategy favors the optimal balance of losses, collisions and coverage, with a greater range of propagation and reduction of congestion.

Abstract

Mestrado em Engenharia de Computadores e Telemática Vehicular networks, also known as VANETs, are an ad-hoc network formed by vehicles and road-side units. Nowadays they have been attracting big interest both from researchers as from the automotive industry. With the upcoming of automotive specific operating systems and self-driving cars, the use of applications on vehicles and the integration with common mobile devices is becoming a big part of VANETs. Although many advances have been made on this field, there is still a big discrepancy between the communication layer services provided by VANETs and the user level services, namely those accessible through mobile applications on other networks and technologies. Users and developers are accustomed to user-to-user or user-tobusiness communication without explicit concerns related with the available communication transport layer. Such is not possible in VANETs since people may use more than one vehicle. However, to send a message to a specific user in these networks, there is a need to know the ID of the vehicle where the user is, meaning that there is a lack of services that map each individual user to VANETs endpoint (vehicle identification). This dissertation work proposes VANESS, a naming service as a resource to support user-to-user communication within a heterogeneous scenario comprising typical ISP scenario and VANETs focused on mobile devices. The proposed system is able to map the user to an end point either locally (i.e. there is not internet connection at all), online (i.e. system is not in a vehicular network but has direct internet connection) and using a gateway (i.e. the system is in a vehicular network where some of the nodes have internet access and will act as a gateway). VANESS was fully implemented on android OS with results proving his viability, and partially on iOS showing its multiplatform capabilities. As redes veiculares, também conhecidas por VANETs, são redes ad-hoc formadas por veículos e road-site units. Hoje em dia estas redes têm atraído bastante interesse tanto por parte de investigadores como da indústria automóvel. Com o aparecimento de sistemas operativos especificamente dedicados a automóveis e carros de condução autónoma, o uso de aplicações em veículos e a integração com dipositivos móveis está-se a tornar uma parte cada vez maior nas VANETs. Apesar dos grandes avanços tecnológicos realizados nesta área, ainda existe uma grande discrepância entre os serviços de camada de comunicação disponibilizados pelas VANETs e os serviços ao nível do utilizador, nomeadamente aqueles acessíveis a partir de aplicações móveis noutras redes e tecnologias. Os utilizadores e programadores estão habituados a interações utilizador-utilizador ou utilizadorempresa sem preocupações explícitas sobre a camada de transporte em causa. Isto não é possível em redes VANETs, uma vez que cada pessoa pode usar vários veículos. No entanto, uma mensagem para ser enviada para um utilizador específico através destas redes precisa do indentificador do veículo onde tal utilizador está, ou seja, existe uma falta de serviços que mapeiem cada utilizador individual a nós na VANET (identificação do veículo). O trabalho desta dissertação propõe o sistema VANESS, um serviço de nomes (naming service) disponibilizado como um recurso para suporte a comunicação utilizador-a-utilizador num cenário heterogéneo englobando o típico ISP e VANETs focadas em dispositivos móveis. O sistema proposto é capaz de mapear um utilizador a um veículo tanto localmente (i.e. não existe ligação à internet), online (i.e. o sistema não está numa rede veicular mas tem acesso direto à internet) e usando um gateway (i.e. o sistema está numa rede veicular onde algum nó tem acesso à internet e irá servir como gateway). VANESS foi integralmente implementado em Android OS, onde os resultados dos testes mostram que é um sistema viável, e parcialmente em iOS mostrando a sua capacidade para multi-plataformas.

Abstract

International audience; In this body of work, we are interested in road safety applications such as advanced driver assistance systems, based on Vehicular Ad Hoc Networks (VANETs). One of the particular characteristics of this kind of networks is the continuous sharing of safety information by its nodes. Since this kind of information is time sensitive, a node cannot spend much time to verify its validity with an authority. However, the presence of malicious and selfish nodes in VANETs corrupts exchanged data, and lowers the overall data reception ratio in the network. To tackle this, we propose a new incentive model with exclusion for malicious nodes called VIME. VIME is inspired from the signaling theory from economics. It is based on managing a credit count that each node receives at the initialization of the application. Straightforwardly, VIME is based on two pillars. On the one hand, a node pays an appropriate cost for each sent message, which is seen by the receivers as a guarantee from the source about the truthfulness of the information. On the other hand, nodes get rewarded for cooperating in the network. The proposed economic model allows computing the amounts to be paid and those to be awarded in order to fight selfish and malicious nodes. We validate our approach via simulations. We show that VIME is able to detect and evict gradually all malicious nodes in the network, and decreases the ratio of corrupted and false sent data until reaching zero. Moreover, it has a positive impact on the participation of selfish nodes, as our approach increases the average ratio of sent data as to equal the ideal case's percentage, when no selfish node is present.

Abstract

Wireless vehicular networks are to be deployed in both Europe and the USA within upcoming years. Such networks introduce a new promising source of information about vehicular environments to be used by cooperative advanced driver assistance systems (ADAS). However, development and evaluation of such cooperative ADAS is still challenging. Hence, we introduce a novel methodology for their development and evaluation processes. It is applied to evaluate the fulfillment of requirements on position accuracy information within exchanged messages. Such requirements are only roughly defined and not sufficiently evaluated in field tests. This holds especially for Global Navigation Satellite Systems (GNSS) optimized for maximum integrity of obtained positions. Such configuration is required to increase robustness and reliability of safety critical ADAS. We find that pure GNSS-based positioning cannot fulfill position accuracy requirements of studied ADAS in most test cases.

Abstract

TRA 2018, 7th Transport Research Arena, Vienne, AUTRICHE, 16-/04/2018 - 19/04/2018; The Vehicular Ad-Hoc Network (VANET) paradigm offers the opportunity of extending Intelligent Transport System (ITS) by supporting its applications through vehicle-to-vehicle communications, notably in the areas where the infrastructure is inexistent, in failure, or overloaded. However, the complexity induced by ad hoc network management raises many challenges that have to be solved such as the sharing of bandwidth resources, the limitations on the duration of the connections between the vehicles, and the application-specific quality of service (QoS) requirements. Recently, the Chain-Branch-Leaf clustering scheme (CBL) has been proposed for vehicle-to-vehicle ad hoc routing that combines the information of road configuration, vehicle mobility, and link quality in order to build an efficient clustering connecting the entire VANET through a flexible backbone. This work presents a comparative study between the native Multipoint relaying clustering used in the Optimized Link State Routing (OLSR) and CBL scheme. The results show that CBL reduces significantly the routing traffic overhead compared to native OLSR, thus freeing up more bandwidth for ITS applications and reducing the IP delays for peer-to-peer applications.

Abstract

In vehicular ad hoc networks (VANETs), successful delivery of GeoUnicast and GeoBroadcast packets depends on scenario-specific aspects like vehicle density, distribution of vehicles on the road and type of the environment (e.g., urban, rural). These aspects can significantly influence the reliability of the connection between communication parties making traditional ITS-G5 based ad hoc networks unreliable. The absence of communication partners in range, long transmission distances, non-line-of-sight (NLOS) conditions are just a few examples that could hinder ITS-G5 transmissions. In this paper, we propose a Hybrid Policy-based Network Selection Algorithm that uses LTE to strengthen and complement ITS-G5 under critical conditions in which successful transmission over the ad hoc network is highly unlikely. The main objective is to use as less LTE transmissions as possible whilst maintaining high Packet Delivery Ratio (PDR) within defined delay constraints. The results, which are derived from extensive simulation campaigns, show a clear advantage of using the hybrid scheme over solely ITS-G5 or LTE. Document type: Conference object

Abstract

High-precision and lane selective position estimation is of fundamental importance for prospective advanced driver assistance systems (ADAS) and automated driving functions, as well as for traffic information and management processes in intelligent transportation systems (ITS). User and vehicle positioning is usually based on Global Navigation Satellite System (GNSS), which, as stand-alone positioning, does not meet the necessary requirements in terms of accuracy. Furthermore, the rise of connected driving offers various possibilities to enhance GNSS positioning by applying cooperative positioning (CP) methods. Utilizing only low-cost sensors, especially in urban environments, GNSS CP faces several demanding challenges. Therefore, this contribution presents an empirical study on how Vehicle-to-Everything (V2X) technologies can aid GNSS position estimation in urban environments, with the focus being solely on positioning performance instead of multi-sensor data fusion. The performance of CP utilizing common positioning approaches as well as CP integration in state-of-the-art Vehicular Ad-hoc Networks (VANET) is displayed and discussed. Additionally, a measurement campaign, providing a representational foundation for validating multiple CP methods using only consumer level and low-cost GNSS receivers, as well as commercially available IEEE 802.11p V2X communication modules in a typical urban environment is presented. Evaluating the algorithm&rsquo s performance, it is shown that CP approaches are less accurate compared to single positioning in the given environment. In order to investigate error influences, a skyview modelling seeking to identify non-line-of-sight (NLoS) effects using a 3D building model was performed. We found the position estimates to be less accurate in areas which are affected by NLoS effects such as multipath reception. Due to covariance propagation, the accuracy of CP approaches is decreased, calling for strategies for multipath detection and mitigation. In summary, this contribution will provide insights on integration, implementation strategies and accuracy performances, as well as drawbacks for local area, low-cost GNSS CP in urban environments. Document type: Article

Abstract

Wireless vehicular ad-hoc networks comprised solely of city taxis are investigated for their ability to deliver data across an urban environment. Openly available taxi trace datasets for Rome (Italy) and San Francisco (USA) are combined with respective building footprint and road network topology data from OpenStreetMap, to generate a realistic systems level model of a taxi V2V network. Analysis of LOS and NOLOS constraints on wireless transmission range suggests a minimum threshold of 50m is applicable to ensure LOS in over 90% of cases. Variations in taxi location sampling frequency and filtering techniques for the taxi trace datasets are also investigated. Overall vehicular network performance is computed for an all-to-one transmission scenario for both cities with varying taxi fleet size. Results suggest a non-linear relationship between increases in taxi fleet sizes and the reduction of end-to-end delay; doubling taxi fleet size (using a randomised data folding technique) reduces end-to-end delay by a factor of 0.6–0.7. However, doubling the fleet does not increase the fraction of delivered source messages, which saturates at 0.67–0.71 in most simulations. Finally it appears that taxi networks for delivering messages across urban environments are limited more by their routing than by the number of possible V2V exchanges. In a simulated one-to-all continuous V2V broadcast scenario, over 90% of the taxis within the fleet receive the source message within one hour of the original taxi passing the source node.