Diploma thesis deals with usage of artificial coordinate systems used for localization of a station on the internet and prediction of delay between the stations. There are described and compared basic properties of centralized and decentralized algorithms providing station localization on the internet and RTT prediction. More in depth are presented main representatives of both types of algorithms such as GNP, IDMAPS or Lighthouse. Central part of thesis is aimed at getting to know Vivaldi distributed algorithm. Basic principle of the algorithm for constant and variable time step, using two dimensional coordinate system with 3rd parameter height, is here outlined. Further more implementation of this algorithm as a library Vivaldi-lib in the environment of Java is implemented. Part of the thesis are simulations of behaviour of this algorithm for both variations realized on artificial networks and data obtained from PlanetLab experimental network, using simulation created program VIVALDIMONITOR.

Internet of Things changes our world with everything we have around us, our everyday things will be connected to the Internet. According to experts, in two years there will be up to 29 billion devices connected to the Internet. With all of the information that is produced it is important to keep the communication secure, otherwise there can be serious problems in the future. Therefore the objective with this study has been to investigate the area of jamming attacks on wireless communication for Internet of Things, more specifically on LoRa and WiFi technologies. This was made by a literature study to research about Internet of Things, the industrial side of it, the two communication technologies and wireless jamming of them. Additionally to this a small scale test bed system consisting of two LoRa nodes (an Arduino and a LoRa gateway), two WiFi nodes (a laptop and router) and a software defined radio frequency jammer (a HackRF One) were set up. Jamming was performed on the system and evaluated form the perspective of a typical industrial Internet of Things scenario. The testing on the system was done by measuring the received signal strength index, round trip time for a message and packet losses. The study showed that the WiFi communication broke down completely while the LoRa communication stood strong up to the jammer. This concluded that LoRa communication is secure for a typical Internet of Things scenario, from this particular jamming device, or a similar one.

De nombreux développements sont actuellement en cours dans le réseau Internet, particulièrement sur la gestion de la QoS et sur l'intégration des différents services. Les aspects portant sur l'amélioration des performances des flux élastiques ont été quelque peu négligés par la communauté scientifique. Le travail effectué porte sur l'évaluation et l'amélioration des performances des flux élastiques. Plus exactement, nos études mettent en avant l'importance d'assurer une bonne qualité de service à ce type de trafic. Deux architectures de QoS ont été proposées. La première architecture est basée sur la classification et le contrôle d'admission appliqués sur les deux types de flux TCP: courts et longs. La classification des flux nous permet d'avoir un système plus prévisible et plus facile à dimensionner puisque les flux d'un agrégat parviennent à partager équitablement la bande passante qui leur est allouée au sein d'une même classe. Le contrôle d'admission prend en compte la caractérisation en flux longs et flux courts ainsi que les contraintes de QoS propres à chaque type de flux. Un modèle analytique ainsi que des simulations ont été réalisés afin d'évaluer les avantages de l'architecture proposée et d'analyser l'impact des seuils d'admission. Il est important de signaler que, outre l'amélioration des performances dans les cas étudiés, l'approche proposée fournit un outil de dimensionnement du réseau permettant d'atteindre, pour une structure de trafic donnée, les mesures de performances attendues. La deuxième architecture est basée sur le traitement préférentiel. Ce dernier est appliqué aux premiers paquets de chaque connexion favorisant ainsi les connexions courtes. Nous comptons sur l'architecture DiffServ pour classifier les flux aux bordures d'un réseau. Plus spécifiquement, nous maintenons la longueur (en paquets) de chaque flux actif aux routeurs de bordures et l'employons pour classifier les paquets entrants. Cette architecture a la particularité de ne pas nécessiter le maintien en mémoire d'un état par flux au coeur du réseau. Dans ce dernier, nous utilisons la politique de gestion de file d'attente RED avec des seuils différents pour les deux types de classes. Ceci nous permet de réduire le taux de pertes éprouvé par les paquets des flux courts. Nous montrons, à travers des analyses et des simulations que notre modèle peut réaliser une meilleure équité et un temps de réponse plus petit pour les flux courts que les modèles sans traitement préférentiel.

Location techniques that satisfy the requirements of advanced Location-Based Services (LBS) in environments where GPS fails are needed, therefore accurate indoor positioning is becoming increasingly important. This PhD Thesis is devoted to the research on location of mobile devices employing WLAN (IEEE 802.11). The use of this kind of wireless networks infrastructures for positioning enables a powerful synergy between communications and location and allows solutions with good performances at moderated costs. However the adopted WLAN location methods suffer from important limitations that prevents from applying them to some fields that need more flexible and robust solutions. The main objective of this PhD is exploring precise WLAN location methods that allow overcoming these limitations. The researched methods here are based on measuring the Time Of Arrival (TOA), which is the time that takes the signal propagating from the transmitter to the receiver. TOA-based location works in two stages: ranging and positioning. The ranging consists of estimating the distances between the targeted terminal and several WLAN access points, each distance obtained measuring the TOA and then multiplying it by the speed of the WLAN signal. After that, the positioning takes as inputs the estimated distances and the known coordinates of the involved access points and calculates the position of the terminal by means of a trilateration or tracking algorithm. The key problem is that the characteristics of the IEEE 802.11 protocols difficult to perform accurate TOA measurements. The main challenge that faces the research work reported here is demonstrating the feasibility of achieving this while keeping the modifications over standard WLAN consumer equipment at minimum. The objective of this work can be understood as exploring the current limits of TOA-based methods over WLAN, making contributions that form a complete TOA-based location method that goes a step forward with respect to the other existing proposals. First, research on TOA-based ranging -the key component of TOA-based location methods- is reported. The general adopted approach consists of performing Round Trip Time (RTT) measurements employing IEEE 802.11 MAC frames, taking the maximum advantage of the combination of IEEE 802.11 protocol and WLAN consumer devices mechanisms. After that, the performed research on trilateration/tracking -the second stage of TOA-based location methods- is explained. Finally some performed studies about the achieved location method are presented. Lloc i data Signatura / Actualment existeix la necessitat de disposar de tècniques de localització que satisfacin els requeriments de serveis avançats basats en localització en entorns on GPS no està disponible, de manera que el posicionament precís en interiors d’edificis és cada vegada més important. Aquesta tesi doctoral està dedicada a la investigació sobre la localització de dispositius mòbils que utilitzen WLAN (IEEE 802.11). L'ús d'aquest tipus de xarxes sense fils per al posicionament permet una profitosa sinèrgia entre les comunicacions i la localització i permet solucions amb un bon rendiment a un cost moderat. No obstant això, els mètodes basats WLAN proposats fins el moment pateixen de limitacions importants que impedeix la seva aplicació a alguns camps que requereixen solucions més flexibles i robustes. L'objectiu principal d'aquesta tesi és explorar mètodes de localització precisa WLAN que permetin superar aquestes limitacions. Els mètodes que s’han investigat durant la tesi es basen en la mesura del time of arrival (TOA), que és el temps que tarda el senyal en propagar-se des del transmissor fins al receptor. En les tècniques de posicionament basades en TOA s’hi poden diferenciar dues fases: ranging i posicionament. El ranging consisteix en l’estimació de distàncies entre el terminal a localitzar i diversos punts d'accés WLAN; cada estimació de distància s’obté mesurant el TOA i multiplicant-lo després per la velocitat de propagació del senyal IEEE 802.11. Un cop fet això, el posicionament pren com a inputs les distàncies estimades per a, conegudes les coordenades dels punts d'accés involucrats, calcular la posició del terminal per mitjà d'un algoritme de tracking o trilateració. El problema clau és que les característiques dels protocols IEEE 802.11 a dia d’avui fan difícil la realització de mesures precises de TOA d’una manera senzilla. El principal repte que afronta el present treball de recerca és demostrar la viabilitat d’això darrer, minimitzant en la major mesura possible les modificacions sobre els equips WLAN comercials. L'objectiu d'aquest treball pot ser entesa com l'exploració dels límits actuals dels mètodes de posicionament basats en TOA sobre WLAN, realitzant contribucions que conformen un mètode complet de localització basat en TOA que pretén anar un pas endavant respecte a les propostes existents. En primer lloc, la investigació sobre ranging basat en TOA -el component clau dels mètode de localització TOA- és explicada en detall. El mètode general adoptat per a calcular el TOA consisteix en la mesura del temps d'anada i tornada del senyal, round trip time (RTT), utilitzant trames MAC IEEE 802.11 per tal de treure el màxim profit de la combinació del protocol IEEE 802.11 i els mecanismes dels dispositius WLAN comercials. Després d'això, es detalla la investigació realitzada sobre trilateració i tracking, la segona etapa dels mètodes de localització basats en TOA. Finalment es descriuen alguns estudis realitzats sobre les prestacions, possibles millores i encaix en futurs estàndars del mètode de localització explorat.

In this thesis, we propose a new protocol named Layered TCP with RTT Compensation (LTCP-RC, for short). LTCP-RC is a simple modification to the congestion window response of the high-speed protocol, Layered TCP (LTCP). In networks characterized by large link delays and high RTTs, LTCP-RC makes the LTCP protocol more scalable. Ack-clocked schemes, similar to TCP, suffer performance problems like long convergence time and throughput degradation, when RTT experienced by the flow increases. Also, when flows with different RTTs compete, the problem of unfairness among competing flows becomes worse in the case of high-speed protocols. LTCP-RC uses an RTT Compensation technique in order to solve these problems. This thesis presents a general framework to decide the function for RTT Compensation factor and two particular design choices are analyzed in detail. The first algorithm uses a fixed function based on the minimum RTT observed by the flow. The second algorithm uses an adaptive scheme which regulates itself according to the dynamic network conditions. Evaluation of the performance of these schemes is done using analysis and ns-2 simulations. LTCP-RC exhibits significant performance improvement in terms of reduced convergence time, low drop rates, increased utilization in presence of links with channel errors and good fairness properties between the flows,. The scheme is simple to understand, easy to implement on the TCP/IP stack and does not require any additional support from the network resources. The choice of parameters can be influenced to tune the RTT unfairness of the scheme, which is not possible in TCP or other high-speed protocols. The flexible nature of the analysis framework has laid the ground work for the development of new schemes, which can improve the performance of the window based protocols in high delay and heterogeneous networks.

The RTT80 cone beam x-ray computed tomography system, developed by Rapiscan Systems Ltd, uses switched x-ray sources and fixed offset detector rings to remove the time consuming mechanical rotations of earlier imaging systems. This system produces three-dimensional images in real time. A Geant4 Monte Carlo simulation has been developed to investigate scattered radiation in the uncollimated detector machine, showing high levels of scatter behind highly attenuating objects. A new scatter correction method is proposed which estimates scatter to each detector, in each projection, from 1cm³ voxels of the computerised object. The scatter distributions from different materials are pre-determined using a Geant4 Monte Carlo simulation. The intensity of scatter from each voxel is based on measured data. The method is applied to two simulated test objects, a water box simulated with a monoenergetic input spectrum and a test suitcase simulated with a polyenergetic spectrum. The test suitcase is broken down into separate components to analyse the method further. The results show that the method performs well for low attenuating objects, but the results are sensitive to the intensity values. However, the method provides a good basis for a scatter correction method.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-12T13:37:34Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Master_Dissertation___Performance_Measurements_and_Analysis_of_Bluetooth_Low_Energy (8).pdf: 8669109 bytes, checksum: cb0af886f0cdc7babced229049a33535 (MD5) / Made available in DSpace on 2017-07-12T13:37:34Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Master_Dissertation___Performance_Measurements_and_Analysis_of_Bluetooth_Low_Energy (8).pdf: 8669109 bytes, checksum: cb0af886f0cdc7babced229049a33535 (MD5) Previous issue date: 2016-05-17 / The Internet of Things (IoT) paradigm has been rapidly gaining ground in the academic and industry communities as one of the most important emerging technologies. Some wireless communication technologies such as Bluetooth Low Energy (BLE) have been pointed as key technologies that will drive IoT applications. In order to leverage the BLE technology in IoT applications and identify the niche of applications this technology is more suitable, it is essential we have a deep understanding regarding some features such as link capacity, data transfer delay, connection establishment latency, and power consumption. This work evaluates the networking capabilities from BLE in scenarios of data transfer and connection establishment. The metrics maximum throughput, one-way delay, round-trip time, and connection establishment latency are evaluated through experimental measurements and we investigate how some factors (e.g. connection interval, pairing, packet size) impact on these metrics. Finally, this work proposes analytical models for the metrics investigated. / O paradigma da Internet das Coisas (Internet of Things - IoT) tem recebido grande destaque tanto das comunidades científicas como da indústria nos últimos anos. Algumas tecnologias de comunicação sem fio como Bluetooth Low Energy (BLE) tem sido apontadas como tecnologias que terão um papel fundamental na concepção de aplicativos de IoT. Um entendimento profundo de algumas características da tecnologia, como vazão e atraso na transmissão de dados, latência no estabelecimento de conexão e consumo de energia, é essencial para explorar ao máximo a tecnologia em cenários de IoT e identificar o nicho de aplicação onde esta tecnologia é mais aplicável. Este trabalho apresenta uma avaliação de desempenho da tecnologia BLE em cenários de transmissão de dados e estabelecimento de conexão. As métricas vazão máxima, atraso fim-a-fim, atraso ida-e-volta (Round-Trip Time - RTT) e latência de estabelecimento de conexão são avaliadas através de experimentos. Este trabalho também investiga como alguns fatores, como intervalo de conexão, encriptação de link e tamanho de pacote, impactam nas métricas avaliadas. Por fim, este trabalho apresenta modelos analíticos para as métricas investigadas.

While GPS long has been an industry standard for localization of an entity or person anywhere in the world, it loses much of its accuracy and value when used indoors. To enable services such as indoor navigation, other methods must be used. A new standard of the Wi-Fi protocol, IEEE 802.11mc (Wi-Fi RTT), enables distance estimation between the transmitter and the receiver based on the Round-Trip Time (RTT) delay of the signal. Using these distance estimations and the known locations of the transmitting Access Points (APs), an estimation of the receiver’s location can be determined. In this thesis, a smartphone Wi-Fi RTT based Indoor Positioning System (IPS) is presented using an Unscented Kalman Filter (UKF). The UKF using only RTT based distance estimations as input, is established as a baseline implementation. Two extensions are then presented to improve the positioning performance; 1) a dead reckoning algorithm using smartphone sensors part of the Inertial Measurement Unit (IMU) as an additional input to the UKF, and 2) a method to detect and adjust distance measurements that have been made in Non-Line-of-Sight (NLoS) conditions. The implemented IPS is evaluated in an office environment in both favorable situations (plenty of Line-of-Sight conditions) and sub-optimal situations (dominant NLoS conditions). Using both extensions, meter level accuracy is achieved in both cases as well as a 90th percentile error of less than 2 meters.

Rett syndrome (RTT), a severe neurodevelopmental disorder, affects females resulting from loss-of-function mutations in the X-linked transcription factor methyl-CpG-binding protein 2 (MECP2). RTT patients show severe verbal, motor, respiratory, and intellectual impairments. We studied two forms of activity-dependent plasticity in Mecp2 mutant mice to better understand the loss of MECP2 function in neuronal circuit and sensory processing. Sensory deprivation was applied by trimming one whisker to 3 mm to study long-term cortical plasticity in Mecp2-/y mice. Intrinsic optical signaling (IOS) imaging showed the neuronal response to wiggling a non-trimmed was consistent from day 0 to 14 but reduced for the trimmed whisker by 49.0 ± 4.3% in wild type (WT) and 22.7 ± 4.6% (p=0.0135) in RTT mice. Primary hindlimb (HL) somatosensory cortical responses to vibratory stimulation were assessed by IOS and intracortical local field potential (LFP). Responses were assessed before, during and, after 1 hour of repeated HL vibratory stimulation (100Hz,1sec, ISI 6 sec) in symptomatic male (4-6 week), female (10-12 month) and pre-symptomatic young female (4 week) RTT model mice. After 1-hour, cortical responses to test vibrations were reduced by approximately 40% in RTT and WT mice as assessed by both methods. Recovery of the IOS responses (1 sec vibration at 100Hz) and LFP (300µm below pia, 7 stimuli, 100mse ISI) were tested at 15 min intervals for 1 hour after ceasing the repeated stimulation. Reduced responses persisted for at least 60 min in WT but recovered to 90-100% of normal within 15-30 min in RTT. Analysis of the LFP responses within the test train indicated that the reduced cortical sensitivity during and after continuous stimulation resulted primarily from an increase in adaptation during the 7-stimulus test train rather than a reduction in the response to a single vibratory stimulus in all groups. Retention of this increased STA is the primary cause of the persistently reduced tactile response in young WT female mice, while in RTT mice the rapid recovery of tactile sensitivity was due to the return of STA to lower, baseline levels. Male RTT mice exhibited a marked increased excitability to the first stimulus in the test train resulting in hypersensitivity to a single vibration by 45 minutes. Old females exhibited the same pattern of adaptation and recovery but retention of adaptation was less pronounced in both WT and RTT compared to younger animals suggesting an age-dependent reduction in neural plasticity may mask deficits specific to RTT. Recording sciatic nerve sensory afferent activity did not reveal any STA, persistent adaptation or sensitization of peripheral afferent endings in any groups. I propose persistent sensory adaptation mediated by increased short-term adaptation may reflect enhanced feedback by inhibitory elements of circuits within the sensory pathway. The rapid recovery of responsiveness in young female RTT mice may therefore reflect a deficit in the capacity for activity dependent plasticity to consolidate and thus could provide a platform to understand the causes of learning and cognitive deficits in RTT patients. / Graduate

In this thesis I focus on finding the position of computers on the Internet. This need for locating computers originated in the last several years through the creation of overlay networks. For this activity there are many algorithms. This paper describes the King method that estimated the distance between communicating stations by using the domain name system. The aim of this work is to verify the accuracy of the King method in experimental PlanetLab network. This network provides access for more than 1000 stations worldwide.