Η εργασία που ακολουθεί έχει ως σκοπό την μοντελοποίηση ενός ασύρματου καναλιού σε εσωτερικό χώρο. Πιο συγκεκριμένα θα προσπαθήσουμε να βρούμε την κατανομή της ισχύος εντός του χώρου θεωρώντας πως έχουμε εκπομπή ηλεκτρομαγνητικής ακτινοβολίας από δίκτυο wifi που εκπέμπει στα 2.4 GHz. Προκειμένου να μοντελοποιήσουμε το ασύρματο κανάλι μας είμαστε υποχρεωμένοι να γνωρίζουμε τα σημαντικότερα φαινόμενα που λαμβάνουν χώρα κατά την ασύρματη διάδοση, αυτά παρουσιάζονται στο κεφάλαιο 1. Επιπλέον μιας και αναφερόμαστε σε δίκτυα wifi θεωρείται αναγκαίο να καταγράψουμε τα σημαντικότερα χαρακτηριστικά αυτής της τεχνολογίας κάτι που γίνεται στο κεφάλαιο 2 αυτής της διπλωματικής εργασίας. Στη συνέχεια στο κεφάλαιο 3 παρουσιάζονται τα σημαντικότερα μοντέλα εσωτερικού χώρου για την εύρεση της μέσης ισχύς της ηλεκτρομαγνητικής ακτινοβολίας συναρτήσει της απόστασης ,ενώ τέλος στο κεφάλαιο 4 γίνεται η προσπάθεια για την μοντελοποίηση του ασύρματου καναλιού χρησιμοποιώντας τη θεωρία των Rayleigh και Rician διαλείψεων. / The work that follows is intended to model a wireless channel to the inner space . In particular we will try to find the distribution of power within the area that we are considering emission of electromagnetic radiation from wifi network emitting at 2.4 GHz. In order to model the wireless channel we have to know the important events that occur during wireless propagation ,these are presented in Chapter 1. Moreover since referring to wifi networks is considered necessary to record the important features of this technology which is in Chapter 2 of this thesis . Then in Chapter 3 presents the major indoor models to find the average power of electromagnetic radiation as a function of distance, and finally in Chapter 4 is the attempt to model the wireless channel using the theory of Rayleigh and Rician misfire .

Τα τελευταία χρόνια ο όγκος των δεδομένων που διακινείται μέσω δικτυακών συστημάτων είναι συνεχώς αυξανόμενος με την επιτακτική ανάγκη για αξιόπιστη επικοινωνία. Παρόλο που η εξέλιξη της τεχνολογίας επιτρέπει μεγαλύτερη ανοχή σε παρεμβολές στο τηλεπικοινωνιακό κανάλι, ο υψηλότερος ρυθμός δεδομένων προκαλεί παραμορφώσεις στο σήμα και κάνει το τηλεπικοινωνιακό σύστημα πιο επιρρεπές στον θόρυβο. Παράδειγμα τέτοιων συστημάτων αποτελούν εφαρμογές ασύρματων δικτύων όπως τα συστήματα κινητής τηλεφωνίας, οι δορυφορικές επικοινωνίες, ασύρματα τοπικά δίκτυα WiFi καθώς και ενσύρματων επικοινωνιών (ενσύρματα Modem). Η παρούσα διπλωματική επικεντρώνεται στα πρότυπα 802.11 που αφορούν ασύρματα τοπικά δίκτυα και πιο συγκεκριμένα στο πρόσφατο 802.11ac ώστε να τεθούν συγκεκριμένα κριτήρια απόδοσης. Αφενός γίνεται σχεδιασμός και υλοποίηση ενός αποκωδικοποιητή σύμφωνου με το πρότυπο λαμβάνοντας υπόψη περιορισμούς χρονισμού αλλά και επιφάνειας και επαλήθευση αυτών μέσω τεχνολογιών FPGA και ASIC. Αφετέρου μελετώνται διαφορετικές αρχιτεκτονικές υλοποίησης του αλγορίθμου (πχ high radix) και εξετάζονται τα πιθανά σχεδιαστικά trade-off. Εξετάζονται μέθοδοι αύξησης του throughput αλλά και θέματα απόδοσης που αφορούν την ικανότητα διόρθωσης λαθών. / In recent years the volume of data handled by network systems is growing with the need for reliable communication . Although the evolution of technology allows greater tolerance to interference in the telecommunication channel , higher data rate causes distortion to the signal and makes the telecommunication system more susceptible to noise. Examples of such systems are applications of wireless networks such as cellular systems , satellite communications , wireless local area networks WiFi and wired communications ( wired Modem). This thesis focuses on the 802.11 standards regarding wireless LANs and in particular in recent 802.11ac to put specific performance criteria. First is design and implementation of a decoder conforming to the model taking into account timing and surface constraints and verification technologies through FPGA and ASIC. Secondly, different architectures of the algorithm ( eg high radix) are studied and the possible design trade-off is examined. Methods of increasing the throughput and performance issues relating to error correction capability are examined.

Denna rapport syftar till att beskriva arbetet kring att kunna detektera närvaro i ett rum medhjälp av så enkla sensorer som möjligt, kopplade till en Arduino. Samtidigt som detta skerså används också systemet till att med samma sensorer visa klimatet i rummet. Läsaren fåren inblick i problematiken med att detektera människor samt inom funktionen av de valdasensorerna. Utöver detta studeras energiförbrukningen i systemet. Rapportenmynnar ut i enslutsats där en procentuell chans för närvaro presenteras via en internetuppkoppling medhjälp av en omfattande testning av sensorernas beteende.

Submitted by Jesiel Ferreira Gomes (jesielgomes@ufcg.edu.br) on 2018-05-02T23:31:51Z No. of bitstreams: 1 GREGORY ARTHUR DE ALMEIDA CARLOS – TESE (PPGEE) 2016.pdf: 26196429 bytes, checksum: b0f539b04f91868561f613e31cebcc23 (MD5) / Made available in DSpace on 2018-05-02T23:31:51Z (GMT). No. of bitstreams: 1 GREGORY ARTHUR DE ALMEIDA CARLOS – TESE (PPGEE) 2016.pdf: 26196429 bytes, checksum: b0f539b04f91868561f613e31cebcc23 (MD5) Previous issue date: 2016-05-25 / Capes / Neste documento, s~ao propostas topologias de conversores que utilizam estruturas trifásicas, a três ou quatro fi os, alimentando equipamentos (motores ou transformadores) com terminais dispostos a enrolamentos abertos ou com conexão em estrela (Y ). Dentre os equipamentos mencionados tem-se: i) restaurador dinâmico de tensão (DVR), ii) ltro ativo de potência (APF) paralelo, iii) fi ltro ativo de potência (APF) série, iv) sistema de acionamento CA-CC-CA série/paralelo e v) sistema baseados em conversores com braços de dois e três-níveis. Para cada topologia estudada, são abordados os seguintes pontos: modelagem da con figuração, estratégias PWM, estratégia de controle. Também é realizado um estudo comparativo entre as topologias propostas e algumas convencionais, avaliando seus desempenhos atrav es de algumas guras de m erito as quais englobam distorções harmônicas das tensões e correntes, estimativa de perdas nos conversores e níveis de tensão no barramento CC. Resultados de simulação e experimentais são apresentados para fins de validação. / This document reports studies on converter topologies applied in three-phase, four-wire or three-wire, systems feeding open-end winding (OEW) equipment or Wye-connected equipment. Such equipment are considered in this work as induction motors or transformers. The devices associated with these equipment are: i) dynamic voltage restorer (DVR), ii) Shunt Active Power Filter (Shunt-APF), iii) Series Active Power Filter (Series-FAP), iv) AC-DCAC series/parallel motor drive, v) Systems with converters based on two- and three-level leg connections. Each studied topology presents its con guration model, PWM strategy, control strategy. Comparative studies considering proposed and some conventional topologies are presented highlighting the harmonic distortion for the voltages and currents, semiconductor losses estimation, dc-link voltage ratings, etc. Simulation and Experimental results are presented for validation purposes. Keywords: Dynamic voltage restorer, shunt active power lter, series active power lter, ac-dc-ac motor drive system, series-connected conveters, parallel-connected converters, converters based on two- and three-level leg connections.

Submitted by Danielle Karla Martins Silva (danielle.martins@ufpe.br) on 2015-03-06T14:20:34Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Borba-Tese.pdf: 1333179 bytes, checksum: 96c554cc5271892d1ae4d75b520d7c24 (MD5) / Made available in DSpace on 2015-03-06T14:20:34Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Borba-Tese.pdf: 1333179 bytes, checksum: 96c554cc5271892d1ae4d75b520d7c24 (MD5) Previous issue date: 2012 / CNPq; FACEPE / Atrav es da utiliza c~ao de uma teoria de campo escalar representada no espa co dos momentos, vamos estudar os efeitos do tamanho nito no comportamento cr tico de sistemas competitivos m-axiais com d dimens~oes em uma geometria cujas superf cies delimitadoras s~ao placas planas e paralelas. Tais placas s~ao de extens~ao in nita e s~ao separadas por uma dist^ancia L. O par^ametro de ordem estar a sujeito a condi c~oes de contorno peri odicas ou antiperi odicas ao longo das duas superf cies. Ambas as formula c~oes com campos massivos e n~ao-massivos ser~ao aplicadas a m de obter os expoentes cr ticos respectivamente nos limites de escalamento ultravioleta e infravermelho, que s~ao necess arios a descri c~ao das regi~oes de escala presentes em sistemas com tamanho nito. Come caremos analisando sistemas sem competi c~ao (m = 0). Vamos introduzir uma nova descri c~ao para os regimes de \crossover" dimensional usuais relacionados com as regi~oes de escala. Desde que evitemos esse \crossover", caracterizado apenas por valores pequenos de L, calcularemos os expoentes e perturbativamente at e as respectivas ordens de dois e tr^es loops e veremos que eles s~ao id^enticos aos de um sistema in nito (L ! 1). Em seguida, vamos estender o nosso m etodo de an alise do tamanho nito para sistemas competitivos m-axiais no ponto cr tico de Lifshitz. Em uma abordagem inicial, consideraremos nita uma das dire c~oes ao longo do subespa co sem competi c~ao e observaremos um comportamento semelhante com rela c~ao ao \crossover" dimensional de sistemas n~ao-competitivos. Para L su cientemente grande, calcularemos os expoentes cr ticos L2, L2, L4 e L4 at e ordens de pelo menos dois loops com aux lio de uma aproxima c~ao especial para a regulariza c~ao das integrais de Feynman. Tais expoentes ser~ao id^enticos aos do sistema in nito. O pr oximo passo consiste em tornar nita a dire c~ao ao longo do eixo de competi c~ao em um sistema uniaxial (m = 1). Utilizaremos nessa con gura c~ao uma nova representa c~ao para as integrais de Feynman e, evitando a regi~ao de \crossover", calcularemos de forma exata at e ordens de dois loops os expoentes L2 e L2. Os nossos resultados ser~ao comparados com os expoentes obtidos por m etodos aproximados e por simula c~oes de Monte Carlo presentes na literatura.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-08-31T14:14:14Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação-Mariana-Gonçalves.pdf: 2227483 bytes, checksum: b7d8c5a2d8b5413ba4b7deb0487b279f (MD5) / Made available in DSpace on 2017-08-31T14:14:14Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação-Mariana-Gonçalves.pdf: 2227483 bytes, checksum: b7d8c5a2d8b5413ba4b7deb0487b279f (MD5) Previous issue date: 2016-02-26 / CNPQ / Gesture is a form of non-verbal communication using various body parts, mostly hand and face. It is the oldest method of communication used by humans becoming essential. By existing for a long time, the use of gestures is natural in interaction between humans, which means that its use does not cause awkwardness between people. Since the rise of technologies such as the computer, scientists have been looking for the best ways to enable the interaction of man with these machines. The gestures are presented as an valuable option because they are common to human beings and simple to be realized. Several devices began to be developed in order to be able to identify sets of gestures made by people and enabling, thus, new interactions. These sets of gestures tend to be generated by scientists themselves, by test users or even movies, are sometimes used as a means to inspire researchers. However, it is important to note that do not necessarily gestures are the best alternative to human-computer interaction. Science fiction movies (sci-fi) are one of the sources from which researchers extract ideas for new ways of interaction. The fact that they are being presented and followed around the world makes interactions found in sci-fi movies more accessible and easy to be accepted by the final public. Movies like Minority Report (1995) inspired and inspire many researchers in the search for a perfect interaction system, as the one shown in the film. Movies are a tool used by film producers to predict their own future visions that are harvested by researchers to be tested and, if produce good results, introduced in the market. By owning several sources of appearance, the hand gestures used in human-machine interactions, generally do not have a certain pattern. Each researcher and film producer gives the gesture interpretation what they believe to be the most appropriate. Thus, it is not difficult to find identical hand gestures generating distinct interactions. In this context, the work presented in this dissertation aims to collect and expose aspects to hand gestures found in science fiction films and papers published in scientific databases. For this, questions such as "Where does the gesture come from?", "What does it mean?", "How is it done?" and “What is it good for?” are answered through mappings that were performed using found hand gestures and sorting them into categories able to respond how hand gestures are being used either by researchers or by film producers. / O gesto é uma forma de comunicação não verbal utilizando várias partes do corpo, principalmente mãos e face. É o método mais antigo de comunicação utilizado pelos seres humanos tornando-se imprescindível. Por existir há muito tempo, o uso de gestos é natural na interação entre humanos, o que quer dizer que seu uso não provoca estranheza entre as pessoas. Desde o surgimento de tecnologias como o computador, cientistas têm procurado as melhores maneiras de possibilitar a interação do homem com essas máquinas. Os gestos se apresentaram como uma opção valiosa, pois são comuns aos seres humanos e simples de serem realizados. Diversos dispositivos começaram a ser desenvolvidos no intuito de conseguir identificar conjuntos de gestos realizados pelas pessoas e viabilizar, assim, novas interações. Esses conjuntos de gestos tendem a ser gerados pelos próprios cientistas, por usuários de teste ou até mesmo por filmes, utilizados por vezes como meio de inspirar os pesquisadores. No entanto, é importante salientar que não necessariamente gestos são a melhor alternativa na interação homem-computador. Filmes de ficção científica (sci-fi) são uma das fontes de onde pesquisadores extraem ideias para novos modos de interação. O fato de estarem sendo apresentadas e acompanhadas por todo o mundo torna as interações encontradas em filmes de sci-fi mais acessíveis e fáceis de serem aceitas pelo público final. Filmes como Minority Report (1995) inspiraram e inspiram muitos pesquisadores na busca de um sistema de perfeita interação, como mostrado no filme. O cinema é uma ferramenta utilizada pelos produtores de filmes para predizer suas próprias visões de futuro que são colhidas por pesquisadores para serem testadas e, se produzirem bons resultados, introduzidas no mercado. Por possuir diversas fontes de surgimento, os gestos de mão utilizados nas interações humano-máquina, geralmente, não possuem um padrão determinado. Cada pesquisador ou produtor de filme dá ao gesto a interpretação que acredita ser a mais adequada. Assim, não é difícil encontrar gestos de mão idênticos gerando interações distintas. Neste contexto, o trabalho apresentado nesta dissertação tem por objetivo coletar e expor aspectos relacionados a gestos de mão encontrados em filmes de ficção científica e em trabalhos publicados em bases de dados científicas. Para isso, perguntas como “de onde o gesto vem?”, “o que o gesto significa?”, “como o gesto é realizado?” e “para que o gesto é bom?” são respondidas através de mapeamentos que foram realizados utilizando os gestos de mão encontrados e classificando-os em categorias capazes de responder como os gestos de mão estão sendo utilizados seja por pesquisadores ou por produtores de cinema.

Large-scale, high-density Wi-Fi networks use hundreds of access points to serve thousands of closelypacked users within a large physical space (hundreds of thousands of square feet or more, such as in a stadium or arena). Because of their scale, these are complex and dynamic systems comprised of several layers and multiple components within each layer, and faults may be present in any one of these components. The problems that manifest from these faults are usually not network-wide and may be localized to a certain physical areas of the network. This makes these problems challenging to detect and diagnose; in most cases, only a small number of devices tend to be impacted by any given problem. However, many such problems may occur simultaneously in different areas of the network. Adding to the complexity is the dynamic nature of such networks, where the physical positions of radios (in end-user devices), human bodies, and other objects in the space are constantly changing, thereby creating a continually-changing RF environment. Taken together, these properties make problem diagnosis in large-scale, high-density Wi-Fi networks challenging. There are many existing techniques for diagnosing problems in Wi-Fi networks. Many of these approaches rely on data from only a single perspective of the network to diagnose problems, for example, either the client, the infrastructure (access points), or external Wi-Fi sensors that passively monitor the network. In addition, many of these approaches require the invasive modification of the network’s components in order to collect data, through techniques such as the installation of specialized software on clients, modifying the firmware on access points, or even physically installing specialized devices in the RF environment of the Wi-Fi network. Finally, many approaches rely on offline analysis of the collected instrumentation, in which case diagnosis cannot be done in real time (minutes or less). Many others require network connectivity for real-time diagnosis, in which case the device must be able to communicate using the Wi-Fi infrastructure (that may be experiencing a problem). As a result, many of these approaches are difficult to deploy in production networks (due to the high financial cost or maintenance effort required), and those that are deployed often fail to detect and diagnose problems that are localized to a small number of devices (10 or less) or problems that are only present for a short time (minutes or less). This dissertation takes a unique approach that contrasts with existing approaches in three key ways. First, we combine the Wi-Fi performance data from multiple layers of the Wi-Fi network and attempt to diagnose problems at all of these layers, rather than focusing on a single layer alone, and we introduce a fault model that includes faults that can occur across all layers of the system. Second, we require no invasive modification of the Wi-Fi network or its components in order collect data and perform problem diagnosis and mitigation. Third, we present an infrastructure-free approach to problem diagnosis that relies on Bluetooth communication with other devices nearby (peers) to perform diagnosis based on multiple perspectives of the Wi-Fi network. With this approach, our diagnosis algorithm is able to collect data from multiple network perspectives without relying on Wi-Fi infrastructure, which may be slow or unavailable. Our approach begins with the construction of an instrumentation and data-collection system to obtain Wi-Fi performance metrics from both the client and infrastructure perspectives of the network. We then build upon our instrumentation to determine when user-visible problems occur. We define a user-visible problem as a Wi-Fi-network-performance problem that causes users to disengage from using the network. Once we have detected a user-visible problem, we then proceed to diagnose the root cause of the problem as one of the faults in our fault model using an approach based on decision trees. Finally, based on the diagnosed fault, we apply an automated mitigation-strategy, which forces the device to associate with a different access point that will likely provide better performance. To validate our approach and demonstrate its real-world impact, we have conducted a number of studies to collect data in support of our approach from both a laboratory testbed and real-world production Wi-Fi networks. We used our instrumentation and data-collection system to obtain data from over 25 real-world, large-scale, high-density Wi-Fi networks located within collegiate and professional stadiums. Our diagnostic system was deployed in a real-world mobile video-streaming application used over the Wi-Fi networks in these stadiums. Using this data, we determined the thresholds for when a Wi-Fi performance problem becomes user visible, based on our study of when users disengage from using the video-streaming application in the face of buffering. In addition to obtaining real-world data, we have studied this phenomenon in a testbed for fault injection and diagnosis that has been deployed both in a lab environment and in an arena to collect data on the behavior of large-scale, high-density Wi-Fi networks and understand how best to diagnose problems. Using this testbed, we evaluated the performance of our problem-diagnosis approach in terms of its precision and recall on injected faults. We also evaluated the performance of our mitigation strategy on our testbed by injecting faults and verifying that the selected mitigation strategy successfully mitigated the problem caused by that fault. We found that our approach diagnoses the correct root cause of faults with high precision and recall (often above 90%) and can mitigate problems via alternative access-point selection in 100% of our test cases. While we have studied our approach in certain test environments and for video-streaming applications, we believe that our approach can be applied to any Wi-Fi network and many other applications outside of video streaming. Our work in this dissertation could be extended through the automated discovery of the parameters for our diagnosis and mitigation algorithms that provide the best performance in other Wi-Fi networks, along with further studies of how Wi-Fi performance problems manifest in other types of applications and under what conditions users disengage with those applications due to problems.

The main research objective of this study was to determine whether Wi-Fi affects customer's loyalty and how its impact differs depending on the type of restaurants: coffee shops, fast food restaurants, and casual dining restaurants. For the study I designed a primary field survey to collect data and performed multiple linear regression analysis to test the study hypotheses. Findings show that Wi-Fi service factors turned out to be significant for all types of restaurants for both attitudinal and behavioral loyalty. Wi-Fi service factors were more important for coffee shop loyalty than fast-food restaurants or casual dining restaurants. However, not all of the Wi-Fi usage factors were significant consistently. Furthermore, Wi-Fi service factors were much more important for coffee shop loyalty than fast food restaurants or casual dining restaurants. Findings are expected to assist hospitality marketers to utilize Wi-Fi service as a point of service towards their customers.

Indoor localization is the process of localizing people or objects inside a building in the same way GPS does in an outside environment. In recent years, researchers have successfully achieved improvement in indoor localization accuracy. Still there are many limitations to overcome in performing and achieving good accuracy in indoor localization. The interest in estimating the location of something inside a building with good accuracy is very strong. In this thesis we first propose an indoor localization technique relative to Wi-Fi access points along with a novel heuristic search based algorithm, named MuSLoc. Through simulation and comparative studies, we have shown that MuSLoc outperforms other indoor localization models without the help of fingerprinting or crowdsourcing about the environment. MuSLoc provides almost the same accuracy in LOS (Line of Sight) and NLOS (Non-Line of Sight) environments with regular infrastructure that has recently been provided by smart phones. This model doesn't require any additional hardware support in order to perform well. Further, we propose another indoor localization based Wi-Fi device tracker model, named MSTracker, which is able to track both moving and non-moving devices inside a building. This model is also free from specialized infrastructure and can perform well without any training data information. Through real time simulation and analysis we have shown that it performs more accurately than other available models. Through extensive simulations in a real time environment and analysis of performance comparatives with other available models, we have shown that both MuSLoc and MSTracker perform more accurately with COTS than any other method of indoor localization and tracking of objects inside a building. The complete package of MuSLoc and MSTracker can perform perfectly with recently available Wi-Fi modules and smartphones.

Main goals of this diploma thesis is to chart methods used to secure wireless internet networks a test those methods through attack on access point of wireless network with target to receive password to access this network and decryption of captured packets. For charting of types of security measures used for wireless network, I performed a series of measurements in field on different places in Czech Republic and Germany. Primary purpose of mesurements performed in Germany is caomparison of results from Germany with results from Czech Republic. Also, I tried to crack the security measures i controlled environment. Due to illegality of this experiment I used my own network and network that belongs o one of my friends who agreed with the experiment.In the end is the presentation of results of field measurements and cracking attempts along with some tips for network security.