Sleep-Enabled Roadside Units for Motorway Vehicular Networks

In this paper, we introduce a number of generic sleep mechanisms for energy saving at the vehicular roadside units (RSUs). Since random sleep cycles (sleep cycles type-I) were already introduced before, we term the introduced mechanisms sleep cycles (type-II, III, IV, V, VI). Each sleep cycles type arranges the service and sleep sequences distinctively to yield various levels of energy savings and average packet delay. A generic analytic model for the roadside unit (RSU) with such sleep cycles is proposed using G/G/1/K G-vacation queuing, where real vehicular traffic profiles and packet size measurements are utilised. The performance evaluation reveals that with one of the proposed sleep cycles (type-IV), the RSU achieves 68% energy savings and 7.3 ms average packet delay over the day, resulting in respective improvements of 10% and 28% compared to the existing random sleep cycles. These improvements have been achieved under a very conservative operating delay bound for audio conferencing applications. However, modern compression and codecs, due to their leniency on Quality of Service (QoS), would potentially enable higher energy savings through the proposed sleep cycles

Energy Efficient Nano Servers Provisioning for Information Piece Delivery in a Vehicular Environment

In this paper, we propose energy efficient Information Piece Delivery (IPD) through Nano Servers (NSs) in a vehicular network. Information pieces may contain any data that needs to be communicated to a vehicle. The available power (renewable or non-renewable) for a NS is variable. As a result, the service rate of a NS varies linearly with the available energy within a given range. Our proposed system therefore exhibits energy aware rate adaptation (RA), which uses variable transmission energy. We have also developed another transmission energy saving method for comparison, where sleep cycles (SC) are employed. Both methods are compared against an acceptable download time. To reduce the operational energy, we first optimise the locations of the NSs by developing a mixed integer linear programming (MILP) model, which takes into account the hourly variation of the traffic. The model is validated through a Genetic Algorithm (GA1). Furthermore, to reduce the gross delay over the entire vehicular network, the available renewable energy (wind farm) is optimally allocated to each NS according to piece demand. This, in turn, also reduces the network carbon footprint. A Genetic Algorithm (GA2) is also developed to validate the MILP results associated with this system. Through transmission energy savings, RA and SC further reduce the NSs energy consumption by 19% and 18% respectively, however at the expense of higher download time. MILP model 4 (with RA) and model 5 (with SC) reduced the delay by 81% and 83% respectively, while minimising the carbon footprint by 96% and 98% respectively, compared to the initial MILP model

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 últimas décadas tem-se assistido a um aumento do número de veículos a circular nas vias rodoviárias europeias, trazendo consigo um elevado número de acidentes e como consequência muitos feridos e vítimas 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 electrónico de travagem (ABS) e o sistema electrónico de estabilidade (ESP), o número de acidentes continua a ser demasiado elevado. Aproximadamente oito por cento dos acidentes fatais na Europa ocorrem em auto-estradas, no caso Português, o número de vítimas mortais tem-se mantido constante ao longo da primeira década do século XXI. A evolução das comunicações sem fios, acompanhada de políticas europeias e norte-americanas no sentido de reservar frequências próximas 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 veículos para eventos ocorridos nas estradas que possam colocar em risco a sua segurança. Exemplos de aplicações de segurança crítica são o aviso de travagem brusca, o aviso de veículo em contra mão 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 crítica, que ocorram em cenários com um elevado número de veículos em zonas urbanas ou na vizinhança dos chamados “pontos negros” das auto-estradas, é disseminada com pontualidade por todos os veículos localizados na zona de interesse Por uma questão 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 veículos usando vários meios à 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 veículos, que são 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 veículos querem aceder simultaneamente ao meio para avisar os restantes da existência dum evento de segurança crítica. A tese apresentada neste documento defende que é possível garantir informação atempada sobre eventos que põem em risco a segurança dos veículos a partir de uma arquitectura de interligação entre as estações de comunicações fixas, coordenadas entre si, e unidades móveis (veículos) 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 disponíveis 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 são as que mais se adequam à finalidade desejada. Considera-se que o cenário de utilização é evolutivo, podendo coexistirem veículos que não dispõem de sistemas de comunicação com outros que suportam a norma WAVE. Dado que o protocolo de acesso ao meio proposto pela norma WAVE não garante um acesso determinístico 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

Green Vehicular Content Distribution Network

With environmental awareness becoming a global concern, content distribution has become popular in the context of modern city scenario with obvious concerns for ICT power consumption. The business world demands huge amounts of information exchange for advertisement and connectivity, which is an integral part of a smart city. In this thesis, a number of energy saving and performance improvement techniques are proposed for the content delivery scenario. These are: content cache location optimisation techniques for energy saving and transceiver load adaptive techniques that save energy while maintaining acceptable piece delay. With the recent advancement in Fog computing, nano-servers are introduced in the later part of the thesis for content delivery and process of user demands. Two techniques random sleep cycles and rate adaptation are proposed to save transmission energy. The quality of service in terms of piece delay and dropping probability are optimised by deploying renewable and non-renewable energy powered nano-servers (NS). Finally, mixed integer linear programming models (MILP) were developed alongside other optimisations methods like bisection, greedy and genetic algorithms which judiciously distribute renewable energy to the fog servers in order to minimise the piece delay and dropping probability in heavily loaded regions of the city area

Pervasive wireless sensors: A new monitoring tool for road traffic noise evaluation

Noise pollution is estimated to affect 170 million citizens in Europe, causing serious public health problems [1]. The World Health Organisation claims that at least one million healthy life years are lost per year in Europe due to road traffic noise [2]. Effective management of noise requires an understanding of its causes. This understanding is limited by traditional monitoring methods, which employ expensive equipment and are labour intensive. This paper presents the results of a comprehensive programme of correction and validation of a low-cost device referred to as an eMote for pervasive monitoring and is the first to quantify the accuracy of inexpensive noise systems that use microphones typically costing about one Euro. Pervasive wireless noise sensors (eMotes) were validated by co-location with precision sound level meters in controlled indoor, and at roadside outdoor environments. Strong linear relationships between the eMotes and the precision systems, across a noise range between 55 dBA and 94 dBA were observed and exhibited consistent bias compared to the precision measurement. Therefore, a generic, corrective relationship was derived and validated in three contrasting outdoor traffic noise environments, employing both short-term attended, and long-term unattended measurements, which were carried out during day and/or evening and/or night periods. The eMotes were shown to respond consistently to white and pink generated noise during the evaluation of the accuracy process, and the generic correction algorithm for white noise delivered better than 3 dBA accuracy in comparison to precision data at a one-minute averaging resolution. The correction algorithm improved the concordance correlation coefficient (ccc) and coefficient of determination (R2) of the eMote measurements against those of the precision instrument. Removal of short-duration, excessively loud events (e.g. sirens), which represented 2% of the total data, improved the ccc and R2 values further typically to 0.74 and 0.60 respectively, which is considered good, given the limitations of the experimental procedure. The research provides scientific evidence that whilst not acceptable for compliance monitoring to standards for noise exposure, the eMote is a valuable system to screen for excessive exposure; to understand the causes of traffic related noise in urban areas; to provide an indication of the spatial and temporal variation in noise levels and the knowledge to design appropriate solutions, in turn this will lead to more effective abatement. The continued monitoring allows the impact to be quantified giving confidence that intervention measures are worthwhile, delivering added value compared to current measurement methods

Analysis, simulation and testing of ITS applications based on wireless communication technologies

Intelligent Transportation Systems (ITS) aim to improve road transport safety and efficiency, to manage road networks in the interest of the society and to provide real time responses to events. In order to reach these goals, real time feedback to the drivers is expected through the integration of telecommunications, sensing and information technologies with transport engineering. Wireless communication technologies, that have been used in industrial applications for more than 30 years, play a crucial role in ITS, as based on the concept of multiple devices (on both vehicle and infrastructure side) interconnected in different ways. Connectivity, in tandem with sensing technologies, is fuelling the innovations that will inevitably lead to the next big opportunity for road transport: autonomous vehicles. Therefore, this study has investigated - through analysis, simulation and field testing – on applications based on wireless communication technologies meant to support both Data acquisition and Data diffusion as fundamental aspects/ phases in ITS, where data is widely individuated as being the key element

A Survey and Comparison of Low-Cost Sensing Technologies for Road Traffic Monitoring

Abstract This paper reviews low-cost vehicle and pedestrian detection methods and compares their accuracy. The main goal of this survey is to summarize the progress achieved to date and to help identify the sensing technologies that provide high detection accuracy and meet requirements related to cost and ease of installation. Special attention is paid to wireless battery-powered detectors of small dimensions that can be quickly and effortlessly installed alongside traffic lanes (on the side of a road or on a curb) without any additional supporting structures. The comparison of detection methods presented in this paper is based on results of experiments that were conducted with a variety of sensors in a wide range of configurations. During experiments various sensor sets were analyzed. It was shown that the detection accuracy can be significantly improved by fusing data from appropriately selected set of sensors. The experimental results reveal that accurate vehicle detection can be achieved by using sets of passive sensors. Application of active sensors was necessary to obtain satisfactory results in case of pedestrian detection

Wireless Vehicular Communication Based Solution for Road Traffic Efficiency

Wireless vehicular communications is a cutting edge set of technologies driven by the vision of providing a suite of original applications, and supported by emerging standards such as IEEE 802.11p. In turn the popularity of these applications is one of the key factors, which will drive the uptake of these vehicular communications technologies and ultimately determine their market success. Applications for vehicular communications can be placed in three main categories - Traffic Safety, Traffic Efficiency and Value-added Services (e.g. Infotainment/Business). Our work focuses on the provision of traffic efficiency services as we believe they offer an immediate benefit and can be adopted quickly by a large number of potential users. Satellite navigation systems provide a ready made deployment platform for these types of services and have already proven popular (14.4 million portable satellite navigation systems sold in Western Europe in 2007). There is also an existing trend toward complementing satellite navigation-related technology with local area wireless communications (by 2013 34% of all portable navigation devices will feature wireless cards 2). Our emphasis is on an infrastructure-based approach as this allows early adopters of wireless enabled satellite navigation devices to receive useful services from day one, regardless of the penetration level of the technology. This thesis describes Smart City, a novel framework, which purposes the use of wireless communication to make city life greener and more efficient. A major contribution to this framework is the proposed intelligent traffic management module. A route management service, which is powered by a best route selection algorithm, is put forward as a prototypical traffic efficiency service for this module. The novel aspect is that the algorithm minimizes journey times and traffic congestion as well as fuel consumption and emissions. Testing has shown how the algorithm provides-shorter journey times, a reduction in fuel consumption and harmful emissions and also results in financial savings. We have proposed and implemented an infrastructure-based communication scheme that enables prioritization of services provided to vehicles

Smart streetlights: a feasibility study

The world's cities are growing. The effects of population growth and urbanisation mean that more people are living in cities than ever before, a trend set to continue. This urbanisation poses problems for the future. With a growing population comes more strain on local resources, increased traffic and congestion, and environmental decline, including more pollution, loss of green spaces, and the formation of urban heat islands. Thankfully, many of these stressors can be alleviated with better management and procedures, particularly in the context of road infrastructure. For example, with better traffic data, signalling can be smoothed to reduce congestion, parking can be made easier, and streetlights can be dimmed in real time to match real-world road usage. However, obtaining this information on a citywide scale is prohibitively expensive due to the high costs of labour and materials associated with installing sensor hardware. This study investigated the viability of a streetlight-integrated sensor system to affordably obtain traffic and environmental information. This investigation was conducted in two stages: 1) the development of a hardware prototype, and 2) evaluation of an evolved prototype system. In Stage 1 of the study, the development of the prototype sensor system was conducted over three design iterations. These iterations involved, in iteration 1, the live deployment of the prototype system in an urban setting to select and evaluate sensors for environmental monitoring, and in iterations 2 and 3, deployments on roads with live and controlled traffic to develop and test sensors for remote traffic detection. In the final iteration, which involved controlled passes of over 600 vehicle, 600 pedestrian, and 400 cyclist passes, the developed system that comprised passive-infrared motion detectors, lidar, and thermal sensors, could detect and count traffic from a streetlight-integrated configuration with 99%, 84%, and 70% accuracy, respectively. With the finalised sensor system design, Stage 1 showed that traffic and environmental sensing from a streetlight-integrated configuration was feasible and effective using on-board processing with commercially available and inexpensive components. In Stage 2, financial and social assessments of the developed sensor system were conducted to evaluate its viability and value in a community. An evaluation tool for simulating streetlight installations was created to measure the effects of implementing the smart streetlight system. The evaluation showed that the on-demand traffic-adaptive dimming enabled by the smart streetlight system was able to reduce the electrical and maintenance costs of lighting installations. As a result, a 'smart' LED streetlight system was shown to outperform conventional always-on streetlight configurations in terms of financial value within a period of five to 12 years, depending on the installation's local traffic characteristics. A survey regarding the public acceptance of smart streetlight systems was also conducted and assessed the factors that influenced support of its applications. In particular, the Australia-wide survey investigated applications around road traffic improvement, streetlight dimming, and walkability, and quantified participants' support through willingness-to-pay assessments to enable each application. Community support of smart road applications was generally found to be positive and welcomed, especially in areas with a high dependence on personal road transport, and from participants adversely affected by spill light in their homes. Overall, the findings of this study indicate that our cities, and roads in particular, can and should be made smarter. The technology currently exists and is becoming more affordable to allow communities of all sizes to implement smart streetlight systems for the betterment of city services, resource management, and civilian health and wellbeing. The sooner that these technologies are embraced, the sooner they can be adapted to the specific needs of the community and environment for a more sustainable and innovative future