IEEE 802.11p, the known standard for Vehicular Adhoc NETworks (VANETs), suffers from scalability issues and unbounded delay. In addition, the desire to use networks already in existence has created motivation for using cellular networks for vehicular applications. LTE-Advanced is one of the most promising access technologies in the wireless field, providing high data rate, low latency, and a large coverage area. Thus, LTE/LTE-A can be potential access technologies for supporting vehicular applications. Vehicular safety applications are based on broadcasting messages to neighboring vehicles. The vehicle location precision is crucial for safety applications. Thus, the freshness of the information (i.e. vehicle location) at the neighboring vehicles is very important. As LTE is an infrastructure-based network, all transmissions should pass through it. When the load of the network is high compared to the available resources, large delays may occur. The focus of this thesis is to propose solutions to make LTE suitable for vehicular safety applications. The first solution is to adapt the vehicular safety application to be suitable in LTE network. For this purpose, we propose an adaptation of the safety message generation rate. This adaptation uses a queueing model to compute the freshness of the information of vehicles at the destination, based on their message generation rates. It then adjusts the generation periods to provide a similar accuracy for all vehicles. The second approach is to modify the LTE and make it suitable for these kinds of applications. Thus, we proposed a scheduler for LTE which is suitable for vehicular safety applications. It considers the speed and location of the vehicles to allocate the resources to them for the transmission of safety messages. We also studied the message dissemination in the downlink, and proposed an efficient way to deliver the safety messages to the neighboring vehicles. Finally, we propose a scheme that uses both LTE-D2D and LTE-cellular communication for the transmission of safety messages. The centralized location information is used for Device-to-Device (D2D) pair discovery and resource allocation. The proposed scheme provides resource efficiency by enabling the reuse of the resources by vehicles. We also study the effect of the awareness range and period of updating location information at the server on resource usage and accuracy of D2D pair detection.

The dissertation investigates communication quality issues in Vehicular Ad-hoc Network (VANET) using statistical analysis, experimental measurements, simulations and modelling. The Object of research is quality characteristics of Inter-Vehicle communication, which is based on IEEE 802.11p standard. The main objective of current research is to investigate Inter-Vehicle communication quality characteristics: packet loss and delay. Additionally propose a redundant safety message transmission method and create the confidence index concept and the calculation method. To reach these objectives following tasks have to be solved: define the boundary vehicular multi-hop transmission algorithms and investigate their performance for latency times defined in different use cases; analyze a packet loss caused by obstacles on the road and define approximation equations, for use in modelling tools; create the redundant packet transmission method for the lost safety message reduction; investigate the confidence index concept in a vehicular network and propose the confidence metrics calculation method; investigate the safe following distance dependency on road conditions and compare it to reliable communication distance. The dissertation consists of introduction, 4 chapters, conclusions and references. The introduction reveals the aim of the dissertation. The first chapter gives detailed overview of Inter-Vehicle communication environments and defines the main Inter-Vehicle communication... [to full text] / Disertacijoje nagrinėjama VANET ryšio kokybės problematika, analizei naudojant statistikos metodus, eksperimentinius tyrimus, modeliavimą ir simuliacijas. Tyrimų objektas yra ryšio tarp automobilių, kurio pagrindas IEEE 802.11p standartas, kokybės charakteristikos. Pagrindinis darbo tikslas – ištirti ryšio tarp automobilių kokybės charakteristikas: vėlinimus ir paketų praradimus. Papildomai pasiūlyti metodus ir algoritmus, mažinančius prarandamų saugos pranešimų skaičių. Pasiūlyti vairuotojo pasitikėjimo indekso koncepciją ir skaičiavimo metodus. Norint pasiekti šiuos tikslus, buvo spręsti sekantys uždaviniai: apibrėžti ribinius perdavimo grandine algoritmus ir ištirti jų efektyvumą perduodant pranešimus grandine; išanalizuoti duomenų paketų praradimus dėl kliūčių ir pateikti atitinkamus aproksimavimo algoritmus, tinkamus modeliavimams; sukurti dubliuotų saugos pranešimų perdavimo metodą, kuris leistų sumažinti prarandamų saugos pranešimų skaičių; sukurti vairuotojo pasitikėjimo indekso koncepciją ryšio tarp automobilių tinkle ir pasiūlyti pasitikėjimo indekso dedamųjų skaičiavimo metodus; ištirti saugaus važiavimo atstumo priklausomybę nuo kelio sąlygų ir palyginti ją su patikimo ryšio nuotolio išraiška. Disertaciją sudaro įvadas, 4 skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvade atskleidžiamas disertacijos tikslas. Pirmame skyriuje pateikiamas detalus ryšio tarp automobilių aplinkos savybių tyrimas. Yra... [toliau žr. visą tekstą]

Disertacijoje nagrinėjama VANET ryšio kokybės problematika, analizei naudojant statistikos metodus, eksperimentinius tyrimus, modeliavimą ir simuliacijas. Tyrimų objektas yra ryšio tarp automobilių, kurio pagrindas IEEE 802.11p standartas, kokybės charakteristikos. Pagrindinis darbo tikslas – ištirti ryšio tarp automobilių kokybės charakteristikas: vėlinimus ir paketų praradimus. Papildomai pasiūlyti metodus ir algoritmus, mažinančius prarandamų saugos pranešimų skaičių. Pasiūlyti vairuotojo pasitikėjimo indekso koncepciją ir skaičiavimo metodus. Norint pasiekti šiuos tikslus, buvo spręsti sekantys uždaviniai: apibrėžti ribinius perdavimo grandine algoritmus ir ištirti jų efektyvumą perduodant pranešimus grandine; išanalizuoti duomenų paketų praradimus dėl kliūčių ir pateikti atitinkamus aproksimavimo algoritmus, tinkamus modeliavimams; sukurti dubliuotų saugos pranešimų perdavimo metodą, kuris leistų sumažinti prarandamų saugos pranešimų skaičių; sukurti vairuotojo pasitikėjimo indekso koncepciją ryšio tarp automobilių tinkle ir pasiūlyti pasitikėjimo indekso dedamųjų skaičiavimo metodus; ištirti saugaus važiavimo atstumo priklausomybę nuo kelio sąlygų ir palyginti ją su patikimo ryšio nuotolio išraiška. Disertaciją sudaro įvadas, 4 skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvade atskleidžiamas disertacijos tikslas. Pirmame skyriuje pateikiamas detalus ryšio tarp automobilių aplinkos savybių tyrimas. Yra... [toliau žr. visą tekstą] / The dissertation investigates communication quality issues in Vehicular Ad-hoc Network (VANET) using statistical analysis, experimental measurements, simulations and modelling. The Object of research is quality characteristics of Inter-Vehicle communication, which is based on IEEE 802.11p standard. The main objective of current research is to investigate Inter-Vehicle communication quality characteristics: packet loss and delay. Additionally propose a redundant safety message transmission method and create the confidence index concept and the calculation method. To reach these objectives following tasks have to be solved: define the boundary vehicular multi-hop transmission algorithms and investigate their performance for latency times defined in different use cases; analyze a packet loss caused by obstacles on the road and define approximation equations, for use in modelling tools; create the redundant packet transmission method for the lost safety message reduction; investigate the confidence index concept in a vehicular network and propose the confidence metrics calculation method; investigate the safe following distance dependency on road conditions and compare it to reliable communication distance. The dissertation consists of introduction, 4 chapters, conclusions and references. The introduction reveals the aim of the dissertation. The first chapter gives detailed overview of Inter-Vehicle communication environments and defines the main Inter-Vehicle communication... [to full text]

<p>Behavior change is not a product of knowledge alone but by the other constructs within the Theory of Planned Behavior (TPB). This includes attitude, subjective norms, and perceived behavioral control. In order to ensure positive change in food safety behavior, researchers should explore the current situation before providing the necessary resources for consumers. This can be done through consumer needs assessments which explore practices, perceptions, demographics, and more. Along with that, major health events like the COVID-19 pandemic can increase risk perceptions of consumers which may lead them to follow safe (washing hands with soap and water) and unsafe food handling behaviors (washing fruits and vegetables with soap). Information spreads quicker during this digital age and this can cause consumers to follow certain behaviors. To assess information being spread, chapter 2 includes a study assessing COVID-19-related food safety information on YouTube early on in the pandemic. Chapter 3 and 4 contain longitudinal studies that used surveys and focus groups to assess consumer food handling practices and risk perceptions throughout the pandemic. Another factor is the type of food being handled. Consumers are not aware that certain foods like pet food (Ch. 5) and raw wheat flour (Ch. 6) can cause foodborne illness. Thus, they may not be handling these types of products as carefully. It is important to communicate that these foods can also cause foodborne illness. In the case of raw wheat flour, while commercial brands provide food safety messages on the packaging, consumers have a hard time finding and understanding the messages. All the studies within this dissertation explored multiple elements that can fall under the different constructs of the TPB in the context of the different factors that affect food safety behaviors. For example, previous studies have found that risk perception may fall under the construct of attitude because human perceptions can influence how a person feels about the situation. The objective of this dissertation is to explore different consumer food safety needs and explore how the elements within the needs assessments feeds into the TPB. With this information, researchers can advance the use of the TPB and researchers and food safety educators can ensure positive behavior change through the TPB.</p>

De nos jours, la voiture est devenue le mode de transport le plus utilisé, mais malheureusement, il est accompagné d’un certain nombre de problèmes (accidents, pollution, embouteillages, etc.), qui vont aller en s’aggravant avec l’augmentation prévue du nombre de voitures particulières, malgré les efforts très importants mis en œuvre pour tenter de les réduire ; le nombre de morts sur les routes demeure très important. Les réseaux sans fil de véhicules, appelés VANET, qui consistent de plusieurs véhicules mobiles sans infrastructure préexistante pour communiquer, font actuellement l’objet d'une attention accrue de la part des constructeurs et des chercheurs, afin d’améliorer la sécurité sur les routes ou encore les aides proposées aux conducteurs. Par exemple, ils peuvent avertir d’autres automobilistes que les routes sont glissantes ou qu’un accident vient de se produire. Dans VANET, les protocoles de diffusion (broadcast) jouent un rôle très important par rapport aux messages unicast, car ils sont conçus pour transmettre des messages de sécurité importants à tous les nœuds. Ces protocoles de diffusion ne sont pas fiables et ils souffrent de plusieurs problèmes, à savoir : (1) Tempête de diffusion (broadcast storm) ; (2) Nœud caché (hidden node) ; (3) Échec de la transmission. Ces problèmes doivent être résolus afin de fournir une diffusion fiable et rapide. L’objectif de notre recherche est de résoudre certains de ces problèmes, tout en assurant le meilleur compromis entre fiabilité, délai garanti, et débit garanti (Qualité de Service : QdS). Le travail de recherche de ce mémoire a porté sur le développement d’une nouvelle technique qui peut être utilisée pour gérer le droit d’accès aux médias (protocole de gestion des émissions), la gestion de grappe (cluster) et la communication. Ce protocole intègre l'approche de gestion centralisée des grappes stables et la transmission des données. Dans cette technique, le temps est divisé en cycles, chaque cycle est partagé entre les canaux de service et de contrôle, et divisé en deux parties. La première partie s’appuie sur TDMA (Time Division Multiple Access). La deuxième partie s’appuie sur CSMA/CA (Carrier Sense Multiple Access / Collision Avoidance) pour gérer l’accès au medium. En outre, notre protocole ajuste d’une manière adaptative le temps consommé dans la diffusion des messages de sécurité, ce qui permettra une amélioration de la capacité des canaux. Il est implanté dans la couche MAC (Medium Access Control), centralisé dans les têtes de grappes (CH, cluster-head) qui s’adaptent continuellement à la dynamique des véhicules. Ainsi, l’utilisation de ce protocole centralisé nous assure une consommation efficace d’intervalles de temps pour le nombre exact de véhicules actifs, y compris les nœuds/véhicules cachés; notre protocole assure également un délai limité pour les applications de sécurité, afin d’accéder au canal de communication, et il permet aussi de réduire le surplus (overhead) à l’aide d’une propagation dirigée de diffusion. / Nowadays, the car has become the most popular mode of transport, but unfortunately its use is accompanied by a number of problems (accidents, pollution, congestion, etc.). These problems will get worse with the increase in the number of passenger cars, despite very significant efforts made to reduce the number of road deaths, which is still very high. Wireless networks for vehicles called VANET (Vehicle Ad Hoc Networks), were developed when it became possible to connect several mobile vehicles without relying on pre existing communication infrastructures. These networks have currently become the subject of increased attention from manufacturers and researchers, due to their potential for improving road safety and/or offering assistance to drivers. They can, for example, alert other drivers that roads are slippery or that an accident has just occurred. In VANETs, broadcast protocols play a very important role compared to unicast protocols, since they are designed to communicate important safety messages to all nodes. Existing broadcast protocols are not reliable and suffer from several problems: (1) broadcast storms, (2) hidden nodes, and (3) transmission failures. These problems must solved if VANETs are to become reliable and able to disseminate messages rapidly. The aim of our research is to solve some of these problems while ensuring the best compromise among reliability, guaranteed transmission times and bandwidth (Quality of Service: QoS). The research in this thesis focuses on developing a new technique for managing medium access. This protocol incorporates the centralized management approach involving stable clusters. In this technique, time is divided into cycles; with each cycle being shared among the control and service channels, and is divided into two segments. The first is based on TDMA (Time Division Multiple Access) while the second is based on CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) to manage access to the medium. Furthermore, our protocol adaptively adjusts the time consumed in broadcasting safety messages, thereby improving channel capacity. It is implemented in the MAC (Medium Access Control), and centralized in stable cluster heads that are able to adapt to the dynamics of vehicles. This protocol provides a centralized and efficient use of time intervals for an exact number of active vehicles, including hidden nodes/vehicles. Our protocol also provides time intervals dedicated to security applications for providing access to communication channels, and also reduces overhead via directed diffusion of data. Keywords: Ad-hoc networks, VANET, Vehicle, Periodic Safety Messages, broadcast protocols, contention-free.

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