Power control and scheduling for wireless data communications

Master'sMASTER OF ENGINEERIN

Provision Quality-of-Service Controlled Content Distribution in Vehicular Ad Hoc Networks

By equipping vehicles with the on-board wireless facility, the newly emerged vehicular networking targets to provision the broadband serves to vehicles. As such, a variety of novel and exciting applications can be provided to vehicular users to enhance their road safety and travel comfort, and finally raise a complete change to their on-road life. As the content distribution and media/video streaming, such as Youtube, Netflix, nowadays have become the most popular Internet applications, to enable the efficient content distribution and audio/video streaming services is thus of the paramount importance to the success of the vehicular networking. This, however, is fraught with fundamental challenges due to the distinguished natures of vehicular networking. On one hand, the vehicular communication is challenged by the spotty and volatile wireless connections caused by the high mobility of vehicles. This makes the download performance of connections very unstable and dramatically change over time, which directly threats to the on-top media applications. On the other hand, a vehicular network typically involves an extremely large-scale node population (e.g., hundreds or thousandths of vehicles in a region) with intense spatial and temporal variations across the network geometry at different times. This dictates any designs to be scalable and fully distributed which should not only be resilient to the network dynamics, but also provide the guaranteed quality-of-service (QoS) to users. The purpose of this dissertation is to address the challenges of the vehicular networking imposed by its intrinsic dynamic and large-scale natures, and build the efficient, scalable and, more importantly, practical systems to enable the cost-effective and QoS guaranteed content distribution and media streaming services to vehicular users. Note that to effective- ly deliver the content from the remote Internet to in-motion vehicles, it typically involves three parts as: 1.) an infrastructure grid of gateways which behave as the data depots or injection points of Internet contents and services to vehicles, 2.) protocol at gateways which schedules the bandwidth resource at gateways and coordinates the parallel transmissions to different vehicles, and 3.) the end-system control mechanism at receivers which adapts the receiver’s content download/playback strategy based on the available network throughput to provide users with the desired service experience. With above three parts in mind, the entire research work in this dissertation casts a systematic view to address each part in one topic with: 1.) design of large-scale cost-effective content distribution infrastructure, 2.) MAC (media access control) performance evaluation and channel time scheduling, and 3.) receiver adaptation and adaptive playout in dynamic download environment. In specific, in the first topic, we propose a practical solution to form a large-scale and cost-effective content distribution infrastructure in the city. We argue that a large-scale infrastructure with the dedicated resources, including storage, computing and communication capacity, is necessary for the vehicular network to become an alternative of 3G/4G cellular network as the dominating approach of ubiquitous content distribution and data services to vehicles. On addressing this issue, we propose a fully distributed scheme to form a large-scale infrastructure by the contributions of individual entities in the city, such as grocery stores, movie theaters, etc. That is to say, the installation and maintenance costs are shared by many individuals. In this topic, we explain the design rationale on how to motivate individuals to contribute, and specify the detailed design of the system, which is embodied with distributed protocols and performance evaluation. The second topic investigates on the MAC throughput performance of the vehicle-to- infrastructure (V2I) communications when vehicles drive through RSUs, namely drive-thru Internet. Note that with a large-scale population of fast-motion nodes contending the chan- nel for transmissions, the MAC performance determines the achievable nodal throughput and is crucial to the on-top applications. In this topic, using a simple yet accurate Marko- vian model, we first show the impacts of mobility (characterized by node velocity and moving directions) on the nodal and system throughput performance, respectively. Based on this analysis, we then propose three enhancement schemes to timely adjust the MAC parameters in tune with the vehicle mobility to achieve the maximal the system throughput. The last topic investigates on the end-system design to deliver the user desired media streaming services in the vehicular environment. In specific, the vehicular communications are notoriously known for the intermittent connectivity and dramatically varying throughput. Video streaming on top of vehicular networks therefore inevitably suffers from the severe network dynamics, resulting in the frequent jerkiness or even freezing video playback. To address this issue, an analytical model is first developed to unveil the impacts of network dynamics on the resultant video performance to users in terms of video start-up delay and smoothness of playback. Based on the analysis, the adaptive playout buffer mechanism is developed to adapt the video playback strategy at receivers towards the user-defined video quality. The proposals developed in the three topics are validated with the extensive and high fidelity simulations. We believe that our analysis developed in the dissertation can provide insightful lights on understanding the fundamental performance of the vehicular content distribution networks from the aspects of session-level download performance in urban vehicular networks (topic 1), MAC throughput performance (topic 2), and user perceived media quality (topic 3). The protocols developed in the three topics, respectively, offer practical and efficient solutions to build and optimize the vehicular content distribution networks

A Survey of Smart Parking Solutions

International audienceConsidering the increase of urban population and traffic congestion, smart parking is always a strategic issue to work on, not only in the research field but also from economic interests. Thanks to information and communication technology evolution, drivers can more efficiently find satisfying parking spaces with smart parking services. The existing and ongoing works on smart parking are complicated and transdisciplinary. While deploying a smart parking system, cities, as well as urban engineers, need to spend a very long time to survey and inspect all the possibilities. Moreover, many varied works involve multiple disciplines, which are closely linked and inseparable. To give a clear overview, we introduce a smart parking ecosystem and propose a comprehensive and thoughtful classification by identifying their functionalities and problematic focuses. We go through the literature over the period of 2000-2016 on parking solutions as they were applied to smart parking development and evolution, and propose three macro-themes: information collection, system deployment, and service dissemination. In each macro-theme, we explain and synthesize the main methodologies used in the existing works and summarize their common goals and visions to solve current parking difficulties. Lastly, we give our engineering insights and show some challenges and open issues. Our survey gives an exhaustive study and a prospect in a multidisciplinary approach. Besides, the main findings of the current state-of-the-art throw out recommendations for future research on smart cities and the Internet architecture

Distribuição de conteúdos em redes veiculares usando mecanismos de comunicação tolerantes ao atraso

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe last couple of decades have been the stage for the introduction of new telecommunication networks. It is expected that in the future all types of vehicles, such as cars, buses and trucks have the ability to intercommunicate and form a vehicular network. Vehicular networks display particularities when compared to other networks due to their continuous node mobility and their wide geographical dispersion, leading to a permanent network fragmentation. Therefore, the main challenges that this type of network entails relate to the intermittent connectivity and the long and variable delay in information delivery. To address the problems related to the intermittent connectivity, a new concept was introduced – Delay Tolerant Network (DTN). This architecture is built on a Store-Carry-and-Forward (SCF) mechanism in order to assure the delivery of information when there is no end-to-end path defined. Vehicular networks support a multiplicity of services, including the transportation of non-urgent information. Therefore, it is possible to conclude that the use of a DTN for the dissemination of non-urgent information is able to surpass the aforementioned challenges. The work developed focused on the use of DTNs for the dissemination of non-urgent information. This information is originated in the network service provider and should be available on mobile network terminals during a limited period of time. In order to do so, four different strategies were deployed: Random, Least Number of Hops First (LNHF), Local Rarest Bundle First (LRBF) e Local Rarest Generation First (LRGF). All of these strategies have a common goal: to disseminate content into the network in the shortest period of time and minimizing network congestion. This work also contemplates the analysis and implementation of techniques that reduce network congestion. The design, implementation and validation of the proposed strategies was divided into three stages. The first stage focused on creating a Matlab emulator for the fast implementation and strategy validation. This stage resulted in the four strategies that were afterwards implemented in the DTNs software Helix – developed in a partnership between Instituto de Telecomunicac¸˜oes (IT) and Veniam R , which are responsible for the largest operating vehicular network worldwide that is located in Oporto city. The strategies were later evaluated on an emulator that was built for the largescale testing of DTN. Both emulators account for vehicular mobility based on information previously collected from the real platform. Finally, the strategy that presented the best overall performance was tested on a real platform – in a lab environment – for concept and operability demonstration. It is possible to conclude that two of the implemented strategies (LRBF and LRGF) can be deployed in the real network and guarantee a significant delivery rate. The LRBF strategy has the best performance in terms of delivery. However, it needs to add a significant overhead to the network in order to work. In the future, tests of scalability should be conducted in a real environment in order to confirm the emulator results. The real implementation of the strategies should be accompanied by the introduction of new types of services for content distribution.Nas últimas décadas tem-se assistido à introdução de novas redes de telecomunicações. Entre estas destacam-se as redes veiculares constituídas por todo o tipo de veículos com capacidades de intercomunicação. As redes veiculares têm especificidades singulares face a outro tipo de redes devido à constante mobilidade dos nós e à sua elevada dispersão geográfica. Os principais desafios introduzidos por este tipo de redes prendem-se com a conectividade intermitente e o atraso longo e variado na entrega da informação. Por forma a fazer face aos problemas relacionados com a conectividade intermitente, introduziu-se um novo conceito intitulado de Delay Tolerant Network (DTN). Esta arquitetura assenta num mecanismo de StoreCarry-and-Forward (SCF) por forma a garantir a entrega de informação em situações onde não existe um caminho estabelecido fim-a-fim. As redes veiculares suportam uma multiplicidade de serviços, nos quais se inclui o transporte de informação não-urgente. Desta forma, a utilização de uma DTN para a difusão de informação não-urgente permite ultrapassar os desafios identificados anteriormente. O trabalho realizado foca-se na utilização de DTNs para a disseminação de informação não-urgente. Por forma a operacionalizar esta premissa foram implementadas quatro estratégias distintas: Random, Least Number of Hops First (LNHF), Local Rarest Bundle First (LRBF) e Local Rarest Generation First (LRGF). Todas estas estratégias tem um objetivo comum: disseminar um conteúdo na rede no menor tempo possível minimizando ao máximo o congestionamento da rede. Foram também implementadas e estudadas técnicas para minimizar o congestionamento do meio. A metodologia de desenho, implementação e validação das estratégias propostas foi desenvolvida em três fases. A primeira focou-se na criação de um emulador Matlab para a implementação rápida e validação das estratégias. Dessa primeira fase resultaram quatro estratégias que foram posteriormente implementadas no software de DTNs Helix desenvolvido através de uma parceria entre o Instituto de Telecomunicações (IT) e a Veniam R (responsáveis pela maior rede veicular em operação a nível mundial localizada na cidade do Porto). As estratégias foram depois avaliadas num emulador construído para fazer testes de grande escala. Ambos os emuladores introduzem a mobilidade dos veículos com base em informação recolhida previamente da plataforma real. Por fim a estratégia que apresentou o melhor desempenho foi introduzida e testada numa plataforma real para demonstração de conceito e operacionalidade. Conclui-se que duas das estratégias implementadas (LRBF and LRGF) são passíveis de utilização na rede real garantido uma taxa de entrega significativa. A estratégia LRBF apresentou o melhor desempenho em termos de entrega, no entanto, necessita de adicionar um overhead considerável na rede para funcionar. No futuro devem ser realizados testes de escalabilidade em ambiente real por forma a confirmar os resultados obtidos em ambiente de emulação e real em pequena escala. A implementação real das estratégias deve ser acompanhada pela introdução de novos tipos de serviços para distribuição de conteúdos

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Téléchargement de Contenus dans les réseaux véhiculaires

L’évolution des systèmes de communications sans fil a permis d’envisager de très nombreuses applications pour les systèmes de transport intelligents (ITS). Elles peuvent ou non utiliser une infrastructure et iront de la sécurité routière aux applications de confort du conducteur ou aux jeux en réseaux. La mise à jour de cartes constitue de notre point de vue une application représentative dans la mesure où ce n’est pas une application de sécurité en tant que telle, mais qu’en revanche elle peut contribuer à réduire les embouteillages en améliorant l’efficacité dans la prise de décisions des conducteurs. Elle possède des caractéristiques facilement identifiables : volume élevé de données, faible contrainte de délai, possibilité de mise en œuvre par des communications d’infrastructure à véhicule, entre véhicules, et hybrides. L’objectif est que les contenus soient téléchargés intégralement par tous les véhicules en un temps minimal, en utilisant le moins de ressources possible et au moindre coût. Les solutions qui sont apparues comme les plus adaptées ont concerné l’utilisation de solutions 802.11p avec ou sans infrastructure. Dans le cas de solutions avec infrastructure, un certain nombre de points d’accès diffuseront des informations avec des zones de couverture le plus souvent disjointes. Vu les tailles de zone retenues et/ou le débit consacré à ce type d’applications, le passage devant un seul point d’accès ne suffira pas à télécharger de telles cartes. Il s’agit alors de définir des stratégies de diffusion d’information. Une première étude a consisté à comparer une stratégie unicast à du broadcast/multicast. Cette dernière se révèle largement meilleure. Une combinaison de ces principes n’améliore pas les performances du système, car le débit consacré à la transmission unicast ne compense pas le débit non utilisé par le broadcast. Le problème provient des doublons reçus par les véhicules en passant auprès de plusieurs points d’accès consécutifs. Afin d’atténuer le phénomène des doublons, nous avons eu recours au Codage Réseau linéaire pseudo-aléatoire. L’idée est que le point d’accès diffuse des combinaisons linéaires de morceaux de fichiers. Le grand nombre de ces combinaisons linéaires réduit de façon significative ce phénomène. De façon complémentaire, nous avons étudié l’utilisation de communications ad-hoc pour combler les morceaux de fichier manquants, en particulier dans le cas d’absence d’infrastructure. Nous avons vérifié que l’on pouvait atteindre de bons résultats dans ce contexte en fonction de la diversité des morceaux de fichiers appartenant aux véhicules rencontrés. ABSTRACT : The evolution of wireless communications systems have enabled to consider many applications for Intelligent Transportation Systems (ITS). They may or may not use the infrastructure. They will consider from the traffic safety applications up to the driver’s comfort or network games. The map updates are, from our point of view, a representative application but in the other hand it can help to reduce congestion in improving efficiency in decision making. It has well-defined characteristics : high volume of data, low delay constraint, possibility of implementation of infrastructure-to-vehicle communications, between vehicles and hybrids. The objective is that the contents are fully downloaded by all vehicles in minimum time, using fewer resources and lower costs. The solutions that have emerged as the most suitable concerned the use of the technology 802.11p with or without infrastructure. In the case of solutions with infrastructure, a number of access points broadcast information with coverage areas most often disjointed. Given the size of area used and/or flow devoted to this type of applications, the transition to a single access point is not enough to download these maps. It is then to define strategies of information dissemination. A first study was to compare a unicast strategy face to broadcast/multicast strategy. The latter appears largely improved. A combination of these principles does not improve system performance, because the flow devoted to unicast transmission does not compensate for the flow not used by the broadcast. The problem is duplicate chunks received by vehicles passing from several consecutive access points. To mitigate the phenomenon of duplication, we used the linear network coding pseudorandom. The idea is that the access point broadcasts linear combinations of chunks of files. The large number of these linear combinations significantly reduces this phenomenon. In a complementary manner, we investigated the use of ad hoc communications to fill the missing chunks of file, particularly in the absence of infrastructure. We verified that we could achieve good results in this context based on the diversity of chunks of files which are owned by the encountered vehicles

Dynamic power allocation and routing for satellite and wireless networks with time varying channels

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2004.Includes bibliographical references (p. 283-295).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Satellite and wireless networks operate over time varying channels that depend on attenuation conditions, power allocation decisions, and inter-channel interference. In order to reliably integrate these systems into a high speed data network and meet the increasing demand for high throughput and low delay, it is necessary to develop efficient network layer strategies that fully utilize the physical layer capabilities of each network element. In this thesis, we develop the notion of network layer capacity and describe capacity achieving power allocation and routing algorithms for general networks with wireless links and adaptive transmission rates. Fundamental issues of delay, throughput optimality, fairness, implementation complexity, and robustness to time varying channel conditions and changing user demands are discussed. Analysis is performed at the packet level and fully considers the queueing dynamics in systems with arbitrary, potentially bursty, arrival processes. Applications of this research are examined for the specific cases of satellite networks and ad-hoc wireless networks. Indeed, in Chapter 3 we consider a multi-beam satellite downlink and develop a dynamic power allocation algorithm that allocates power to each link in reaction to queue backlog and current channel conditions. The algorithm operates without knowledge of the arriving traffic or channel statistics, and is shown to achieve maximum throughput while maintaining average delay guarantees. At the end of Chapter 4, a crosslinked collection of such satellites is considered and a satellite separation principle is developed, demonstrating that joint optimal control can be implemented with separate algorithms for the downlinks and crosslinks.(cont.) Ad-hoc wireless networks are given special attention in Chapter 6. A simple cell- partitioned model for a mobile ad-hoc network with N users is constructed, and exact expressions for capacity and delay are derived. End-to-end delay is shown to be O(N), and hence grows large as the size of the network is increased. To reduce delay, a transmission protocol which sends redundant packet information over multiple paths is developed and shown to provide O(vN) delay at the cost of reducing throughput. A fundamental rate- delay tradeoff curve is established, and the given protocols for achieving O(N) and O(vN) delay are shown to operate on distinct boundary points of this curve. In Chapters 4 and 5 we consider optimal control for a general time-varying network. A cross-layer strategy is developed that stabilizes the network whenever possible, and makes fair decisions about which data to serve when inputs exceed capacity. The strategy is decoupled into separate algorithms for dynamic flow control, power allocation, and routing, and allows for each user to make greedy decisions independent of the actions of others. The combined strategy is shown to yield data rates that are arbitrarily close to the optimally fair operating point that is achieved when all network controllers are coordinated and have perfect knowledge of future events. The cost of approaching this fair operating point is an end-to-end delay increase for data that is served by the network.by Michael J. Neely.Ph.D