The DVB-T-Based Positioning System and Single Frequency Network Offset Estimation

As position information becomes more and more important in many fields of technology it is advantageous to recognize it in scenarios where satellite-based systems fail. Such a case is the scenario inside buildings where attenuation of a signal is too high making it impossible to receive despite the availability of terrestrial services. A positioning system based on terrestrial broadcasting is presented in this paper. The aim is to create an automatic receiver enabling a multi--sensor positioning system to be built and resulting in increased availability and reliability of position information. This paper introduces a method that demonstrates how to design a signal detector capable of operating in a multipath scenario. Finally, the most restrictive problem of the positioning system is the unknown time offset setting of individual emitters that render this system useless. A solution to this problem is proposed and tested in a real scenario. The innovative methods and algorithms presented in this paper show, for the first time, how to automatically evaluate position using digital video broadcasting. The result of an experiment with a real digital video broadcasting network is presented

MAC layer assisted localization in wireless environments with multiple sensors and multiple emitters

Extreme emitter density (EED) RF environments, defined as 10k-100k emitters within a footprint of less than 1 km squared, are becoming increasingly common with the proliferation of personal devices containing myriad communication standards (e.g. WLAN, Bluetooth, 4G, etc). Attendees at concerts, sporting events, and other such large-scale events desire to be connected at all times, creating tremendous spectrum management challenges, especially in unlicensed frequencies such as 2.4 GHz, 5 GHz, or 900 MHz Industrial, Scientific, and Medical (ISM) bands. In licensed bands, there are often critical communication systems such as two-way radios for emergency personnel which must be free from interference. Identification and localization of a non-conforming or interfering Emitter of Interest (EoI) is important for these critical systems. In this dissertation, research is conducted to improve localization for these EED RF environments by exploiting side information available at the Medium Access Control (MAC) layer. The primary contributions of this research are: (1) A testbed in Bobby Dodd football stadium consisting of three spatially distributed, time-synchronized RF Sensor Nodes (RFSN) collecting and archiving complex baseband samples for algorithm development and validation. (2) A modeling framework and analytical results on the benefits of exploiting the structure of the MAC layer for associating physical layer measurements, such as Time Difference of Arrivals (TDoA), to emitters. (3) A three stage localization algorithm exploiting time between packets and a constrained geometry to shrink the error ellipse of the emitter position estimate. The results are expected to improve localization accuracy in wireless environments when multiple sensors observe multiple emitters using a known communications protocol within a constrained geometry.Ph.D

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

An analysis of regulatory frameworks for wireless communications, societal concerns and risk: the case of radio frequency (RF) allocation and licensing.

This thesis analyses how and why culture and geography influence the allocation and licensing of the radio frequency (RF) spectrum in different nations. Based on a broad study of 235 countries, an inter-disciplinary approach is used to explore regulatory frameworks and attitudes toward risk. In addition, detailed case studies of the UK, France, the US and Ecuador provide deeper insights into the main contrasting regulatory styles. Three alternative sociological theories are used to analyse and explain the results for both the in-depth and broad brush studies. The Cultural Theory of Mary Douglas and co-workers is first used to categorise countries in terms of perceptual filters. The empirical findings indicate some countries to be apparently exceptional in their behaviour. The theory of Bounded Rationality is used to investigate and explain these apparent irrationalities. Finally, Rational Field Theory shows how beliefs and values guide administrations in their RF regulation. A number of key factors are found to dominate and patterns emerge. The European RF harmonisation is unique. Following European unification, wireless regulation is divided into two major camps (the EU and the US), which differ in their risk concerns, approach to top-down mandated standards, allocation of RF spectrum to licence-exempt bands and type approval process. The adoption of cellular and TV standards around the world reflects geopolitical and colonial influence. The language of a country is a significant indicator of its analogue TV standard. Interestingly, the longitude of a country to a fair extent defines RF allocation: Africa and West Asia follow Europe, whereas the Americas approximate the US. RF regulation and risk tolerability differ between tropical and non-tropical climates. The collectivised/centralised versus the individualised/market-based rationalities result in different regulatory frameworks and contrasting societal and risk concerns. The success of the top-down European GSM and the bottom-up Wi-Fi standards reveal how the central- planning and market-based approaches have thrived. Attitudes to RF human hazards and spurious emissions levels reveal that the US, Canada and Japan are more tolerant of these risks than Europe. Australia, Canada, New Zealand, UK and USA encourage technological innovation. A practical benefit of this study is that it will give regulators more freedom to choose a rational RF licensing protocol, by better understanding the possibly self-imposed boundaries of cultural and geographical factors which are currently shaping allocation. Academically, there is utility in undertaking a cultural and geographic analysis of a topic that is mostly the domain of engineering, economic and legal analysts

D5.2 - Evaluation of Selected Measurement-based Techniques

Deliverable D5.2 del projecte FARAMIRPreprin