Modelling and Delay Analysis of Intermittently Connected Roadside Communication Networks

During the past decade, consumers all over the world have been showing an incremental interest in vehicular technology. The world’s leading vehicle manufacturers have been and are still engaged in continuous competitions to present for today’s sophisticated drivers, vehicles that gratify their demands. This has lead to an outstanding advancement and development of the vehicular manufacturing industry and has primarily contributed to the augmentation of the twenty first century’s vehicle with an appealing and intelligent personality. Particularly, the marriage of information technology to the transport infrastructure gave birth to a novel communication paradigm known as Vehicular Networking. More precisely, being equipped with computerized modules and wireless communication devices, the majority of today’s vehicles qualify to act as typical mobile network nodes that are able to communicate with each other. In addition, these vehicles can as well communicate with other wireless units such as routers, access points, base stations and data posts that are arbitrarily deployed at fixed locations along roadways. These fixed units are referred to as Stationary Roadside Units (SRUs). As a result, ephemeral and self-organized networks can be formed. Such networks are known as Vehicular Networks and constitute the core of the latitudinarian Intelligent Transportation System (ITS) that embraces a wide variety of applications including but not limited to: traffic management, passenger and road safety, environment monitoring and road surveillance, hot-spot guidance, on the fly Internet access, remote region connectivity, information sharing and dissemination, peer-to-peer services and so forth. This thesis presents an in-depth investigation on the possibility of exploiting mobile vehicles to establish connectivity between isolated SRUs. A network of intercommunicating SRUs is referred to as an Intermittently Connected Roadside Communication Network (ICRCN). While inter-vehicular communication as well as vehicle-to-SRU communication has been widely studied in the open literature, the inter-SRU communication has received very little attention. In this thesis, not only do we focus on inter-SRU connectivity establishment through the transport infrastructure but also on the objective of achieving delay-minimal data delivery from a source SRU to a destination SRU in. This delivery process is highly dependent on the vehicular traffic behaviour and more precisely on the arrival times of vehicles to the source SRU as well as these vehicles’ speeds. Vehicle arrival times and speeds are, in turn, highly random and are not available a priori. Under such conditions, the realization of the delay-minimal data delivery objective becomes remarkably challenging. This is especially true since, upon the arrival of vehicles, the source SRU acts on the spur of the moment and evaluates the suitability of the arriving vehicles. Data bundles are only released to those vehicles that contribute the most to the minimization of the average bundle end-to-end delivery delays. Throughout this thesis, several schemes are developed for this purpose. These schemes differ in their enclosed vehicle selection criterion as well as the adopted bundle release mechanism. Queueing models are developed for the purpose of capturing and describing the source SRU’s behaviour as well as the contents of its buffer and the experienced average bundle queueing delay under each of theses schemes. In addition, several mathematical frameworks are established for the purpose of evaluating the average bundle transit delay. Extensive simulations are conducted to validate the developed models and mathematical analyses

Analysis of Security Overhead in Broadcast V2V Communications

This paper concerns security issues for broadcast vehicle to vehicle (V2V) messages carrying vehicle status information ((location, heading, speed, etc.). These are often consumed by safety-related applications that e.g. augment situational awareness, issue alerts, recommend courses of action, and even trigger autonomous action. Consequently, the messages need to be both trustworthy and timely. We explore the impact of authenticity and integrity protection mechanisms on message latency using a model based on queuing theory. In conditions of high traffic density such as found in busy city centres, even the latency requirement of 100ms for first generation V2V applications was found to be challenging. Our main objective was to compare the performance overhead of the standard, PKC-based, message authenticity and integrity protection mechanism with that of an alternative scheme, TESLA, which uses symmetric-key cryptography combine with hash chains. This type of scheme has been dismissed in the past due to sup-posed high latency, but we found that in high traffic density conditions it outperformed the PKC-based scheme. without invoking congestion management measures. Perhaps the most significant observation from a security perspective is that denial of service attacks appear very easy to carry out and hard to defend against. This merits attention from the research and practitioner communities and is a topic we intend to address in the future

Performance of management solutions and cooperation approaches for vehicular delay-tolerant networks

A wide range of daily-life applications supported by vehicular networks attracted the interest, not only from the research community, but also from governments and the automotive industry. For example, they can be used to enable services that assist drivers on the roads (e.g., road safety, traffic monitoring), to spread commercial and entertainment contents (e.g., publicity), or to enable communications on remote or rural regions where it is not possible to have a common network infrastructure. Nonetheless, the unique properties of vehicular networks raise several challenges that greatly impact the deployment of these networks. Most of the challenges faced by vehicular networks arise from the highly dynamic network topology, which leads to short and sporadic contact opportunities, disruption, variable node density, and intermittent connectivity. This situation makes data dissemination an interesting research topic within the vehicular networking area, which is addressed by this study. The work described along this thesis is motivated by the need to propose new solutions to deal with data dissemination problems in vehicular networking focusing on vehicular delay-tolerant networks (VDTNs). To guarantee the success of data dissemination in vehicular networks scenarios it is important to ensure that network nodes cooperate with each other. However, it is not possible to ensure a fully cooperative scenario. This situation makes vehicular networks suitable to the presence of selfish and misbehavior nodes, which may result in a significant decrease of the overall network performance. Thus, cooperative nodes may suffer from the overwhelming load of services from other nodes, which comprises their performance. Trying to solve some of these problems, this thesis presents several proposals and studies on the impact of cooperation, monitoring, and management strategies on the network performance of the VDTN architecture. The main goal of these proposals is to enhance the network performance. In particular, cooperation and management approaches are exploited to improve and optimize the use of network resources. It is demonstrated the performance gains attainable in a VDTN through both types of approaches, not only in terms of bundle delivery probability, but also in terms of wasted resources. The results and achievements observed on this research work are intended to contribute to the advance of the state-of-the-art on methods and strategies for overcome the challenges that arise from the unique characteristics and conceptual design of vehicular networks.O vasto número de aplicações e cenários suportados pelas redes veiculares faz com que estas atraiam o interesse não só da comunidade científica, mas também dos governos e da indústria automóvel. A título de exemplo, estas podem ser usadas para a implementação de serviços e aplicações que podem ajudar os condutores dos veículos a tomar decisões nas estradas, para a disseminação de conteúdos publicitários, ou ainda, para permitir que existam comunicações em zonas rurais ou remotas onde não é possível ter uma infraestrutura de rede convencional. Contudo, as propriedades únicas das redes veiculares fazem com que seja necessário ultrapassar um conjunto de desafios que têm grande impacto na sua aplicabilidade. A maioria dos desafios que as redes veiculares enfrentam advêm da grande mobilidade dos veículos e da topologia de rede que está em constante mutação. Esta situação faz com que este tipo de rede seja suscetível de disrupção, que as oportunidades de contacto sejam escassas e de curta duração, e que a ligação seja intermitente. Fruto destas adversidades, a disseminação dos dados torna-se um tópico de investigação bastante promissor na área das redes veiculares e por esta mesma razão é abordada neste trabalho de investigação. O trabalho descrito nesta tese é motivado pela necessidade de propor novas abordagens para lidar com os problemas inerentes à disseminação dos dados em ambientes veiculares. Para garantir o sucesso da disseminação dos dados em ambientes veiculares é importante que este tipo de redes garanta a cooperação entre os nós da rede. Contudo, neste tipo de ambientes não é possível garantir um cenário totalmente cooperativo. Este cenário faz com que as redes veiculares sejam suscetíveis à presença de nós não cooperativos que comprometem seriamente o desempenho global da rede. Por outro lado, os nós cooperativos podem ver o seu desempenho comprometido por causa da sobrecarga de serviços que poderão suportar. Para tentar resolver alguns destes problemas, esta tese apresenta várias propostas e estudos sobre o impacto de estratégias de cooperação, monitorização e gestão de rede no desempenho das redes veiculares com ligações intermitentes (Vehicular Delay-Tolerant Networks - VDTNs). O objetivo das propostas apresentadas nesta tese é melhorar o desempenho global da rede. Em particular, as estratégias de cooperação e gestão de rede são exploradas para melhorar e optimizar o uso dos recursos da rede. Ficou demonstrado que o uso deste tipo de estratégias e metodologias contribui para um aumento significativo do desempenho da rede, não só em termos de agregados de pacotes (“bundles”) entregues, mas também na diminuição do volume de recursos desperdiçados. Os resultados observados neste trabalho procuram contribuir para o avanço do estado da arte em métodos e estratégias que visam ultrapassar alguns dos desafios que advêm das propriedades e desenho conceptual das redes veiculares

Influence of various application types on the performance of LTE mobile networks

Modern mobile internet networks are becoming heavier and denser. Also it is not regularly planned, and becoming more heterogeneous. The explosive growth in the usage of smartphones poses numerous challenges for LTE cellular networks design and implementation. The performance of LTE networks with bursty and self-similar traffic has become a major challenge. Accurate modeling of the data generated by each connected wireless device is important for properly investigating the performance of LTE networks. This paper presents a mathematical model for LTE networks using queuing theory considering the influence of various application types. Using sporadic source traffic feeding to the queue of the evolved node B and with the exponential service time assumption, we construct a queuing model to estimate the performance of LTE networks. We use the performance model presented in this paper to study the influence of various application categories on the performance of LTE cellular networks. Also we validate our model with simulation using NS3 simulator with different scenarios