Dans les systèmes de communications sans fil, la transmission de grandes quantités d'information et à faible coût énergétique sont les deux principales questions qui n'ont jamais cessé d'attirer l'attention de la communauté scientifique au cours de la dernière décennie. Récemment, il a été démontré que la communication coopérative est une technique intéressante notamment parce qu'elle permet d'exploiter la diversité spatiale dans le canal sans fil. Cette technique assure une communication robuste et fiable, une meilleure qualité de service (QoS) et rend le concept de coopération prometteur pour les futurs générations de systèmes cellulaires. Typiquement, les QoS sont le taux d'erreurs paquet, le débit et le délai. Ces métriques sont impactées par le délai, induit par les mécanismes de retransmission Hybrid-Automatic Repeat-Request (HARQ) inhérents à la réception d'un paquet erroné et qui a un retard sur la QoS demandée. En revanche, les mécanismes HARQ créent une diversité temporelle. Par conséquent, l'adoption conjointe de la communication coopérative et des protocoles HARQ pourrait s'avérer avantageux pour la conception de schémas cross-layer. Nous proposons tout d'abord une stratégie de maximisation de débit total dans un réseau cellulaire hétérogène. Nous introduisons un algorithme qui alloue la puissance optimale à la station de base (BS) et aux relais, qui à chaque utilisateur attribue de manière optimale les sous-porteuses et les relais. Nous calculons le débit maximal atteignable ainsi que le taux d'utilisateurs sans ressources dans le réseau lorsque le nombre d'utilisateurs actifs varie. Nous comparons les performances de notre algorithme à ceux de la littérature existante, et montrons qu'un gain significatif est atteint sur la capacité globale. Dans un second temps, nous analysons théoriquement le taux d'erreurs paquet, le délai ainsi que l'efficacité de débit des réseaux HARQ coopératifs, dans le canal à évanouissements par blocs. Dans le cas des canaux à évanouissement lents, le délai moyen du mécanisme HARQ n'est pas pertinent à cause de la non-ergodicité du processus. Ainsi, nous nous intéressons plutôt à la probabilité de coupure de délai en présence d'évanouissements lents. La probabilité de coupure de délai est de première importance pour les applications sensibles au délai. Nous proposons une forme analytique de la probabilité de coupure permettant de se passer de longues simulations. Dans la suite de notre travail, nous analysons théoriquement l'efficacité énergétique (bits/joule) dans les réseaux HARQ coopératifs. Nous résolvons ensuite un problème de minimisation de l'énergie dans les réseaux coopératifs en liaison descendante. Dans ce problème, chaque utilisateur possède une contrainte de délai moyen à satisfaire de telle sorte que la contrainte sur la puissance totale du système soit respectée. L'algorithme de minimisation permet d'attribuer à chaque utilisateur la station-relai optimale et sa puissance ainsi que la puissance optimale de la BS afin de satisfaire les contraintes de délai. Les simulations montrent qu'en termes de consommation d'énergie, les techniques assistées par relais prédominent nettement les transmissions directes, dans tout système limité en délai. En conclusion, les travaux proposés dans cette thèse peuvent promettre d'établir des règles fiables pour l'ingénierie et la conception des futures générations de systèmes cellulaires énergétiquement efficaces. / In wireless systems, transmitting large amounts of information with low energetic cost are two main issues that have never stopped drawing the attention of the scientific community during the past decade. Later, it has been shown that cooperative communication is an appealing technique that exploits spatial diversity in wireless channel. Therefore, this technique certainly promises a robust and reliable communications, higher quality-of-service (QoS) and makes the cooperation concept attractive for future cellular systems. Typically, the QoS requirements are the packet error rate, throughput and delay. These metrics are affected by the delay, where each erroneous packet is retransmitted several times according to Hybrid-Automatic Repeat-Request (HARQ) mechanism inducing a delay on the demanded QoS but a temporal diversity is created. Therefore, adopting jointly cooperative communications and HARQ mechanisms could be beneficial for designing cross-layer schemes. First, a new rate maximization strategy, under heterogeneous data rate constraints among users is proposed. We propose an algorithm that allocates the optimal power at the base station (BS) and relays, assigns subcarriers and selects relays. The achievable data rate is investigated as well as the average starvation rate in the network when the load, i.e. the number of active users in the network, is increasing. It showed a significant gain in terms of global capacity compared to literature. Second, in block fading channel, theoretical analyses of the packet error rate, delay and throughput efficiency in relayassisted HARQ networks are provided. In slow fading channels, the average delay of HARQ mechanisms w.r.t. the fading states is not relevant due to the non-ergodic process of the fading channel. The delay outage is hence invoked to deal with the slow fading channel and is defined as the probability that the average delay w.r.t. AWGN channel exceeds a predefined threshold. This criterion has never been studied in literature, although being of importance for delay sensitive applications in slow fading channels. Then, an analytical form of the delay outage probability is proposed which might be useful to avoid lengthy simulations. These analyses consider a finite packet length and a given modulation and coding scheme (MCS) which leads to study the performance of practical systems. Third, a theoretical analysis of the energy efficiency (bits/joule) in relay-assisted HARQ networks is provided. Based on this analysis, an energy minimization problem in multiuser relayassisted downlink cellular networks is investigated. Each user has an average delay constraint to be satisfied such that a total power constraint in the system is respected. The BS is assumed to have only knowledge about the average channel statistics but no instantaneous channel state information (CSI). Finally, an algorithm that jointly allocates the optimal power at BS, the relay stations and selects the optimal relay in order to satisfy the delay constrains of users is proposed. The simulations show the improvement in terms of energy consumption of relay-assisted techniques compared to nonaided transmission in delay-constrained systems. Hence, the work proposed in this thesis can give useful insights for engineering rules in the design of the next generation energyefficient cellular systems.

<p>This dissertation examines the impact of the expansion of renewable technology at both national and local level, through distinct essays. At the national level, the first paper analyzes the effects of economic and distributional impacts of climate mitigation policy, in the context of a developing country, to understand the interactions between the energy system and the macroeconomic environment. In the case of the local level, the second paper uses synthetic control method, to estimate the effect at the county level of utility scale wind in the development indicators for two counties in the U.S. </p> <p>The first paper assesses the economic and distributional impacts of Nicaragua’s commitments to limit future greenhouse gas emissions in the context of the Paris Agreement, known as the Nationally Determined Contributions (NDCs). The analysis relies on two distinct models. The first is a top-down approach based on a single-country computable general equilibrium (CGE) model, known as the Mitigation, Adaptation and New Technologies Applied General Equilibrium (MANAGE) Model. The second is a bottom-up approach based on the Open-Source energy Modeling System (OSeMOSYS), which is technology rich energy model. The combined model is calibrated to an updated social accounting matrix for Nicaragua, which disaggregates households into 20 representative types: 10 rural and 10 urban households. For the household disaggregation we have used information from the 2014 Living Standards Measurement Study (LSMS) for Nicaragua. Our analysis focuses on the distributional impacts of meeting the NDCs as well as additional scenarios—in a dynamic framework as the MANAGE model is a (recursive) dynamic model. The results show that a carbon tax has greatest potential for reduction in emissions, with modest impact in macro variables. An expansion of the renewable sources in the electricity matrix also leads to significant reduction in emissions. Only a carbon tax achieves a reduction in emissions consistent with keeping global warming below 2°C. Nicaragua’s NDC alone would not achieve the target and mitigation instruments are needed. An expansion of generation from renewable sources, does not lead to a scenario consistent with a 2°C pathway. </p> <p>The second paper measures the impact of wind generation on county level outcomes through the use of the Synthetic Control Method (SCM). SCM avoids the pitfalls of other methods such as input-output models and project level case studies that do not provide county level estimates. We find that the local per capita income effect of utility wind scale is 6 percent (translate into an increase of $1,511 in per capita income for 2019) for Benton County and 8 percent for White county in Indiana (an increase of $2,100 in per capita income for 2019). The per capita income effect measures the average impact, which includes the gains in rents from capital, land, and labor from wind power in these counties. Moreover, we find that most of the rents from wind power accrue to the owners of capital and labor. Even assuming the lowest projections of electricity prices and the highest reasonable cost we still find a 10 percent minimum rate of return to capital for both Benton and White counties’ wind power generators. Furthermore, we find that there are excess rents that could be taxed and redistributed at the county, state, or federal level without disincentivizing investment in wind power.</p>

The diploma thesis is focused on the building embedded demonstration application of the proprietary Low Complexity Ethernet module for industrial usage further called the LEN/LES 2. At the first, main used technologies such as MCU, or the lightweight IP stack is discussed, Consequently, there is detailed view on system hardware architecture proposed by hardware and software requirements. Then though part describes blocks of embedded system are in term of specific parts and hardware requirements to create universal board. Following chapters expresses first startup and known hardware bugs, LWIP implementation and MODBUS system implementation. The core of the system is the new released microcontroller an ADuCM4050 and the Low Complexity Ethernet MAC-PHY prototype block and much more dependent convenient peripherals of the MCU based application.

The master’s thesis deals with development of the radio channel analyser operating in the unlicensed 2.4 GHz band according to IEEE 802.15.4 standard. The analyzer will contain two basic functions, namely energy detection of channels and analysation of selected channel. Detection of energy will be solved by selection between simple graph and text list on display. Based on information about the occupancy of channels the user can decide which channel would be set up. During the receiving of valid frame the source address, signal strength and signal quality will be stored. At the end the processor will show these data on display. For controlling the device will be installed two LEDs and four buttons.

This thesis deals with the design and implementation of system for recording and repeating of events for audio systems. The introductory part is devoted to the study of sound systems, their user interfaces and communication protocols that are used by audio systems. Hereafter the description of essential features of Mac OS X, as well as the characteristic of its user interface and principles of development on this platform, are given. The core of the thesis consists of the design of system for recording and repeating of events and the concept of events which specifies the reprezentation of events in the system and their subsequent processing. In~the end of the thesis is presented the implementation of the designed system for Mac OS X with respect to possible extensions of the system and its features.

The thesis describes the design of scheme for access system with user authentication via smart cards. The first chapter explains various types of identification items used for authentication of users and different types of readers and terminals, followed by chapter 2 with a deeper insight on smart cards with focus on their types, what internal structure and principle of communication with card readers are used, etc. with primary focus on Java cards. The third chapter describes Java Card cryptography - especially elliptic curve cryptography used on this platform. The fourth part focuses on PACE protocol with subsections dedicated to the individual parts of the protocol and its applicability to smart cards environment. Chapter 5 explains the proposed design of the authentication scheme elaborated in the thesis, including a detailed description of specific parts, their funcionality and exemplary usage in the created applications.

Real-time voice measurements were performed to assess whether there are significant problems with 802.11b wireless networks regarding real-time voice communication. We present an analysis of how the 802.11b MAC protocol and diverse environmental conditions affect the quality of real-time voice in terms of loss, delay, and jitter. We also reveal practical issues of wireless monitoring with passive sniffers for this type of analysis. The results obtained in our measurements show that in the majority of the experiments the quality was good, but under some circumstances the requirements for an acceptable voice communication were not met. / Realtidsröstmätningar gjordes för att testa om det finns problem med 802.11b trådlösa nätverk beträffande realtidsröstkommunikation. En analys presenteras av hur 802.11b MACs protokoll och olika tillstånd i omgivningen påverkar kvaliteten på realtidsrösten i form av förluster, fördröjningar och jitter. Även praktiska angelägenheter om trådlös övervakning med passiva sniffers visas. De erhållna resultaten visar att i en majoritet av fallen var kvaliteten acceptabel, men under vissa förhållanden blev inte kraven för röstkommunikation uppfyllda.

The theme of this diploma thesis is operating system OS X Server services by Apple. The thesis presents the possibility of their use for data sharing and communication among users of computer networks and examines the practical use of the information society. The opening chapter is an introduction of OS X Server. The second chapter deals with the progression of the system, its features, hardware selection, system requirements, support and overall evaluation. The third chapter is devoted to server services and their protocols. The fourth chapter presents the basic tools needed for server management and data protection. The essence of the work consists of the practical part, which provides services server uses based on the case study of a musical recording studio 3bees. Part of this thesis is also Research of the OS X Server deployment in the Czech Republic, which was organised by questionnaire survey. The survey focuses on the analysis of the environment and conditions in which the product is deployed and the most frequently used services.

This MSc Thesis focuses on principles, practical performability and security against four attacks used in contemporary local-area networks: CAM Table Overflow capable of capturing traffic in switched networks, ARP Man-in-the-Middle, whose target is to redirect or modify traffic and against two variants of VLAN Hopping attack allowing a hacker to send and capture data from VLANs he has no access to.

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