Dissertations / Theses on the topic 'CA Networks'

Les protocoles de communications à accès aléatoires sont des candidats prometteurs pour les futurs systèmes de communications sans fil dédiés aux applications machine à machine (M2M). Ces méthodes d’accès sont généralement basées sur des techniques d'accès aléatoires mettant en œuvre des concepts simples de sondage de canal et de report de la transmission pour réduire les collisions, tout en évitant l'utilisation d'ordonnanceurs complexes. Parmi les différents protocoles, Carrier sense multiple access/collision avoidance with a Request-To-Send/Clear-To-Send (CSMA/CA-RTS/CTS) est un protocole qui pourrait être adopté pour les scénarios de M2M. Cette approche est efficace pour éviter les collisions entre les paquets de données. Cependant dans le cas d’un réseau très dense, les performances sont dégradées à cause de la forte probabilité de collisions. Pour atténuer cet effet, les collisions entre les messages de contrôles RTS doivent être réduites. Cette thèse propose de résoudre ce problème en divisant le canal commun en sous-canaux pour transmettre les messages de contrôle de demande d’accès au canal ; le canal commun est utilisé dans son ensemble pour la transmission de données. L’ajout d’un degré de liberté pour le message de demande d’accès permet de réduire la probabilité de collision, et donc d’améliorer les performances du système notamment dans des scénarios avec des nombres importants de nœuds souhaitant communiquer. Dans ce travail, nous dérivons ainsi une solution complète de méthode d’accès en s'appuyant sur le CSMA / CA - RTS / CTS et en multiplexant une configuration multi-canal pour les messages RTS et un canal unique pour la transmission de données. Une version améliorée, basée sur l'ordonnancement des utilisateurs, est également étudiée. Un modèle analytique a été développé, analysé et validé par simulations. Celui-ci est une extension du modèle Bianchi. Les performances en termes de débit saturé, de temps de transmission et de la probabilité de rejet de paquets sont discutées. Enfin, les impacts liés à la prise en compte d’une couche physique de type multi porteuses sont discutés dans le dernier chapitre
Opportunistic protocols are promising candidates for future wireless systems dedicated to machine to machine (M2M) communication. Such protocols are usually based on a random access with simple techniques of medium sensing and deferring to reduce collisions while avoiding the use of complex schedulers. Among different protocols, Carrier sense multiple access/collision avoidance with a Request-To-Send/Clear-To-Send (CSMA/CA-RTS/CTS) is an opportunistic protocol which could be adopted for M2M scenarios. Such approach is efficient to avoid collisions between data packets but in a very dense network, the random access used to send the RTS suffers itself from a high probability of collision which degrades the performance. In order to mitigate this effect, RTS collisions should be reduced. This thesis proposes to address this issue by splitting the common channel in sub-channels for transmitting the RTS messages. While the common channel is used as a whole for data transmission. Multiple nodes can then contend in time and frequency for these RTS sub-channels, thereby reducing RTS collisions and increasing overall efficiency. In this work, we thus derive a complete protocol solution relying on CSMA/CA - RTS/CTS multiplexing a multi-channel configuration for RTS messages and a unique channel for data transmission. An enhanced version based on users scheduling is integrated as well. In this thesis, the proposed protocol is investigated from a joint PHY-MAC point of view. This strategy is shown to provide better system performance particularly for loaded networks. An accurate analytical model derived as a straightforward extension of the Bianchi model is analyzed and validated by simulations. Performance in terms of saturation throughput, transmission delay and packet drop probability is discussed

Generally, collisions between packets are undesired in wireless networks. We design this scheme, Cooperative Jamming in Wireless Networks (CJWN), to make use of collision to protect secret DATA packets from being sniffed by a nearby eavesdropper. We are intending to greatly increase the Packet Error Rate (PER) at the eavesdropper when the PER at the receiver is maintained at an acceptable level. This scheme is not intended to completely take the place of various encryption/decryption schemes which are working based on successfully received packets. Adding CJWN to the popular CSMA/CA adopted in IEEE 802.11 will add more security even the key for encryption/decryption is already exposed. Because the overhead of CJWN is very big, we do not suggest using it on every transmission. When some secret packets have a high requirement of confidentiality, CJWN is worth trying at the cost of throughput performance and power.

The Sardinian Bronze Age (Nuragic period) and the factors which created and maintained an island-wide identity as seen through the presence of its distinctive nuraghi have received considerable attention; however the amount of research directly related to the stone tools of the era has been relatively limited despite the wealth of knowledge it is capable of yielding. This thesis hopes to contribute to Sardinian archaeology through the study of ancient technology, specifically obsidian lithic technology, by combining typological information with source data gleaned from the use of X-ray fluorescence spectrometry (XRF). These data are integrated with statistical analyses breaking down the spatial distribution of nuraghi across the island through the use of distance-based methods, including k-means and kernel density analyses, which create a more comprehensive understanding of the island-wide political and social structure. This research will test the hypothesis that changes in the acquisition of obsidian raw materials were coupled with corresponding changes in how the obsidian was used. The results provide precedence for future work in Sardinia and create a model for integrating two types of analyses, sourcing and typological. By combining these results, it is possible to investigate how obsidian influenced the ancient economy as well as assess its cultural significance for people of the past.

The focus of this research is to investigate the effects of bursts of errors and packet collisions on the performance of the medium access control (MAC) portion of the IEEE 802.11 wireless local area network (LAN) protocol.An important ingredient in rapid expansion of wireless networks is the seamless transition between wired and wireless systems. The IEEE standards group in charge of developing the widely used IEEE 802.3 LAN standard has developed the IEEE 802.11 wireless LAN standard. IEEE 802.11 remains hidden from the upper levels of the network, thus allowing a seamless transition between networks. The foundation protocol for the IEEE 802.11 standard, known as Distributed Foundation Wireless Medium Access Control (DFWMAC), operates at the MAC level of the Data Link Layer. The protocol bases its access control mechanism on a principle called Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), which is an adaptation of the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol used by IEEE 802.3 standard. The collision avoidance scheme in CSMA/CA allows data packets to be transferred via the wireless medium with lower probability of packet collision. In a slotted multi-access wireless system, performance parameters are affected by the bit error rates on the communication channel. These errors occur as a result of noise introduced by the radio channel or data packet collisions. Collisions occur when two or more stations select the same time slot to transmit their data, thus causing corruption in data packets. In this research, a simulation model coded in Microsoft's Visual Basic programming environment is utilized to investigate the effects of bit errors and packet collisions on performance in CSMA/CA. Performance parameters used in this study include throughput, medium utilization, collisions and station data queue lengths. In the simulation model, error bursts in the communication channel are modeled using a simple Gilbert model with two states, good (G) and bad (B). State G is error free, thus errors can only occur while the model is in state B. Collisions are simulated by two or more stations starting to transmit data packets in the same time slot. Therefore, as the number of stations increases, more and more stations compete for the medium, resulting in an increase in the number of collisions. Collisions are also increased by the amount of traffic that each station introduces into the system. Station load is defined here as the number of data packets per unit time that are released by the higher network protocol layers.The results in Chapter 5 demonstrate that higher network throughput can be achieved when the aggregate load on the network is distributed. For example, 30 stations offering 20 kilobits per second (kbps) of load for a total of 600 kpbs, results in a network throughput of 585 kbps. However, three stations offering 200 kbps of load for a total of 600 kbps offered load, results in a network throughput of 486 kbps. The distributed load is serviced at a 17 percent higher rate. However, once the network becomes saturated at above 40 stations for this model, collisions will more than offset the performance gains produced by the distribution of load.Furthermore, reducing the packet size by 50 percent under an approximately 19.5 percent packet error rate results in a 12 percent gain in throughput. This is primarily due to higher utilization of the network by shorter packets. However, as the packet error rate is reduced, the performance gap between the two packet sizes is reduced. Once the errors are removed completely from the communications channel, the longer packets produce a higher throughput than the shorter packets.
Master of Science

Caspases are important players in programmed cell death. Normal activities of caspases are critical for the cell life cycle and dysfunction of caspases may lead to the development of cancer and neurodegenerative diseases. They have become a popular target for drug design against abnormal cell death. In this study, the recognition of P5 position in substrates by caspase-3, -6 and -7 has been investigated by kinetics, modeling and crystallography. Crystal structures of caspase-3 and -7 in complexes with substrate analog inhibitor Ac-LDESD-CHO have been determined at resolutions of 1.61 and 2.45 Å, respectively, while a model of caspase-6/LDESD is constructed. Enzymatic study and structural analysis have revealed that Caspase-3 and -6 recognize P5 in pentapeptides, while caspase-7 lacks P5-binding residues. D-arginine dehydrogenase catalyzes the flavin-dependent oxidative deamination of D-amino acids to the corresponding imino acids and ammonia. The X-ray crystal structures of DADH and its complexes with several imino acids were determined at 1.03-1.30 Å resolution. The DADH crystal structure comprises a product-free conformation and a product-bound conformation. A flexible loop near the active site forms an “active site lid” and may play an essential role in substrate recognition. The DADH Glu87 forms an ionic interaction with the side chain of iminoarginine, suggesting its importance for DADH preference of positively charged D-amino acids. Comparison of the kinetic data of DADH activity on different D-amino acids and the crystal structures demonstrated that this enzyme is characterized by relatively broad substrate specificity, being able to oxidize positively charged and large hydrophobic D-amino acids bound within a flask-like cavity. Understanding biology at the system level has gained much more attention recently due to the rapid development in genome sequencing and high-throughput measurements. Current simulation methods include deterministic method and stochastic method. Both have their own advantages and disadvantages. Our group has developed a deterministic-stochastic crossover algorithm for simulating biochemical networks. Simulation studies have been performed on biological systems like auto-regulatory gene network and glycolysis system. The new system retains the high efficiency of deterministic method while still reflects the random fluctuations at lower concentration.

This thesis is concerned with the development of new mathematical models for the IEEE 802.11??s access mechanisms, with a particular focus on DCF and EDCA. Accurate mathematical models for the DCF and EDCA access mechanisms provide many benefits, such as improved performance analysis, easier network capacity planning, and robust network design. A feature that permeates the work presented in this thesis is the application of our new models to network environments where both saturated and non-saturated traffic sources are present. The scenario in which multiple traffic sources are present is more technically challenging, but provides for a more realistic setting. Our first contribution is the development of a new Markov model for non-saturated DCF in order to predict the network throughput. This model takes into account several details of the protocol that have been hitherto neglected. In addition, we apply a novel treatment of the packet service time within our model. We show how the inclusion of these effects provides more accurate predictions of network throughput than earlier works. Our second contribution is the development of a new analytical model for EDCA, again in order to predict network throughput. Our new EDCA model is based on a replacement of the normal AIFS parameter of EDCA with a new parameter more closely associated with DCF. This novel procedure allows EDCA to be viewed as a modified multi-mode version of DCF. Our third contribution is the simultaneous application of our new Markov models to both the non-saturated and the saturated regime. Hitherto, network throughput predictions for these regimes have required completely separate mathematical models. The convergence property of our model in the two regimes provides a new method to estimate the network capacity of the network. Our fourth contribution relates to predictions for the multimedia capacity of 802.11 networks. Our multimedia capacity analysis, which is based on modifications to our Markov model, is new in that it can be applied to a broad range of quality of service requirements. Finally, we highlight the use of our analysis in the context of emerging location-enabled networks.

The Eel River watershed has a high concentration of slow-moving landslides, or earthflows, due to argillaceous mélange bedrock and high tectonic uplift. Earthflows within this area are highly dissected by ephemeral channels, or gullies. Despite the pervasiveness of gullying in this area, the role of fluvial systems in relation to earthflows and varying uplift is poorly understood. To understand the role of earthflows and tectonics in dictating channel processes, we investigate channels in areas of differential uplift and mass failure activity. Channel networks are connected and continuous in catchments without earthflows, and disconnected and prone to bank failure on earthflow surfaces. Gully profiles are influenced BY earthflow undulations, which attenuate with fluvial incision after earthflows cease activity. We find notable differences in fluvial dissection between areas of high and low landslide activity. We find that mass wasting and local bedrock have a strong influence on formation and organization of channels.

L’amélioration de la qualité et de l’efficacité en santé est un réel enjeu sociétal. Elle implique la surveillance continue des paramètres vitaux ou de l’état mental du sujet. Les champs d’applications sont vastes : l’application la plus importante est la surveillance des patients à distance. Les avancées en micro-électronique, capteurs et réseaux sans-fil permettent aujourd’hui le développement de systèmes ambulatoires performants pour le monitoring de paramètres physiologiques, capables de prendre en compte d’importantes contraintes techniques : forte intégration pour la réduction de la taille et faible consommation pour une plus grande autonomie [1]. Cependant, la conception de ce type de réseaux de capteurs médicaux WBANs (Wireles Body Area Networks) se heurte à un certain nombre de difficultés techniques, provenant des contraintes imposées par les capacités réduites des capteurs individuels : basse puissance, énergie limitée et faible capacité de stockage. Ces difficultés requièrent des solutions différentes, encore très embryonnaires, selon l’application visée (monitoring à but médical). La forte mobilité et le changement rapide de la topologie du réseau dévoilent un verrou scientifique et social. En outre, l’interférence de différents capteurs constituant le WBAN augmente la difficulté de la mise en place de ce type de réseaux. De nombreuses solutions dans la littérature ont été étudiées, comme nous allons illustrer dans ce manuscrit, néanmoins elles restent limitées. Nous nous intéresserons tout particulièrement à la gestion des interférences Intra- et Inter-WBAN, leur impacte sur la fiabilité des transmissions (des liens) et la durée de vie de ce type de réseaux. Plus précisément, nous abordons ces problématiques en se basant sur des modélisations théoriques et analytiques et avec une conception pratique des solutions proposées. Afin d’atteindre les objectifs cités ci-dessous, nous abordons quatre solutions : • Une gestion des interférences intra-WBAN • Une gestion coopérative des interférences Inter-WBAN • Une gestion non coopérative des interférences, Inter-WBAN • Une gestion des interférences WBAN dans un contexte IoT Dans la première partie de cette thèse et afin de répondre en partie aux problèmes de gestion des interférences Intra-WBAN. Nous présentons deux mécanismes pour le WBAN : (a) CFTIM qui alloue dynamiquement des slots et des canaux dit- stables (avec un taux d’interférences le bas possible dans le temps) pour réduire les interférences intra-WBAN. (b) IAA ajuste dynamiquement la taille du superframe et limite le nombre de canaux à 2 pour abaisser les interférences Intra-WBAN et ainsi économiser l’énergie. Une validation avec un model probabiliste est proposé afin de valider théoriquement l’efficacité de notre solution. Les résultats de la simulation démontrent l’efficacité du CFTIM et de l’IAA en termes de réduction de la probabilité d’interférence, l’extension de la durée de vie du réseau et l’amélioration du débit et de la fiabilité des transmissions. Notre seconde contribution, propose une gestion coopératives des interférences Inter-WBAN en utilisant des codes orthogonaux. Motivé par un approvisionnement temporel distribué basé sur la norme [2] IEEE 802.15.6, nous proposons deux solutions. (a) DTRC qui fournit à chaque WBAN les connaissances sur les superframes qui se chevauchent. Le second, (b) OCAIM qui attribue des codes orthogonaux aux capteurs appartenant à deux listes de groupe de capteur en interférences de deux WBAN différents (SIL). Les résultats démontrent qu’OCAIM diminue les interférences, améliore le débit et préserve la ressources énergétiques. La troisième partie nous a permis d’aborder la gestion des interférences, mais cette fois ci d’une manière non-coopérative en se basant sur l’affectation couple Slot/Canal. Plus précisément, nous proposons deux schémas basés sur les carrés latins. (...)
A Wireless Body Area Network (WBAN) is a short-range network that consists of a coordinator (Crd) and a collection of low-power sensors that can be implanted in or attached to the human body. Basically, WBANs can provide real-time patient monitoring and serve in various applications such as ubiquitous health-care, consumer electronics, military, sports, etc. [1]. As the license-free 2.4 GHz ISM band is widely used among WBANs and across other wireless technologies, the fundamental problem is to mitigate the resulting co-channel interference. Other serious problems are to extend the network lifetime and to ensure reliable transmission within WBANs, which is an urgent requirement for health-care applications. Therefore, in this thesis, we conduct a systematic research on a few number of research problems related to radio co-channel interference, energy consumption, and network reliability. Specifically, we address the following problems ranging from theoretical modeling and analysis to practical protocol design: • Intra-WBAN interference mitigation and avoidance • Cooperative inter-WBAN interference mitigation and avoidance • Non-cooperative inter-WBAN interference mitigation and avoidance • Interference mitigation and avoidance in WBANs with IoT Firstly, to mitigate the intra-WBAN interference, we present two mechanisms for a WBAN. The first is called CSMA to Flexible TDMA combination for Interference Mitigation, namely, CFTIM, which dynamically allocates time-slots and stable channels to lower the intra-WBAN interference. The second is called Interference Avoidance Algorithm, namely IAA that dynamically adjusts the superframe length and limits the number of channels to 2 to lower the intra-WBAN interference and save energy. Theoretically, we derive a probabilistic model that proves the SINR outage probability is lowered. Simulation results demonstrate the effectiveness and the efficiency of CFTIM and IAA in terms of lowering the probability of interference, extending network lifetime, improving throughput and reliability. Secondly, we address the problem of interference among cooperative WBANs through using orthogonal codes. Motivated by distributed time provisioning supported in IEEE 802.15.6 standard [2], we propose two schemes. The first is called Distributed Time Correlation Reference, namely, DTRC that provides each WBAN with the knowledge about which superframes overlap with each other. The second is called Orthogonal Code Allocation Algorithm for Interference Mitigation, namely, OCAIM, that allocates orthogonal codes to interfering sensors belonging to sensor interference lists (SILs), which are generated based on the exchange of power-based information among WBANs. Mathematically, we derive the successful and collision probabilities of frames transmissions. Extensive simulations are conducted and the results demonstrate that OCAIM can diminish the interference, improve the throughput and save the power resource. Thirdly, we address the problem of co-channel interference among non-cooperative WBANs through time-slot and channel hopping. Specifically, we propose two schemes that are based on Latin rectangles. The first is called Distributed Algorithm for Interference mitigation using Latin rectangles, namely, DAIL that allocates a single channel to a timeslot combination to each sensor to diminish inter-WBAN interference and to yield better schedules of the medium access within each WBAN. The second is called Channel Hopping for Interference Mitigation, namely, CHIM, which generates a predictable interference free transmission schedule for all sensors within a WBAN. CHIM applies the channel switching only when a sensor experiences interference to save the power resource. Furthermore, we present an analytical model that derives bounds on collision probability and throughput for sensors transmissions. (...)

Providing access to telecommunication services in rural areas is of paramount importance for the development of any country. Since the cost is the main inhibiting factor, any technical solution for access in sparsely populated rural areas has to be reliable, efficient, and deployable at low-cost. This thesis studies the utilization of Multihop Wireless Networks (MWN) as an appealing alternative for rural communication. MWN are designed with a self-configuring capability and can adapt to the addition or removal of network radio units (nodes). This makes them simple to install, allowing unskilled users to set up the network quickly. To increase the performance and cost-efficiency, this thesis focuses on the use of Advanced Antenna Systems (AAS) in rural access networks. AAS promise to increase the overall capacity in MWN, improving the link quality while suppressing or reducing the multiple access interference. To effectively exploit the capabilities of AAS, a proper design of Medium Access Control (MAC) protocols is needed. Hence, the results of system level studies into MAC protocols and AAS are presented in this thesis. Two different MAC protocols are examined: Spatial Time Division Multiple Access (STDMA) and Carrier Sense Multiple Access Collision Avoidance (CSMA/CA) with handshaking. The effects of utilizing advanced antennas on the end-to-end network throughput and packet delay are analyzed with routing, power control and adaptive transmission data rate control separately and in combination. Many of the STDMA-related research questions addressed in this thesis are posed as nonlinear optimization problems that are solved by the technique called "column generation" to create the transmission schedule using AAS. However, as finding the optimal solution is computationally expensive, we also introduce low-complexity algorithms that, while simpler, yield reasonable results close to the optimal solution. Although STDMA has been found to be very efficient and fair, one potential drawback is that it may adapt slower than a distributed approach like CSMA/CA to network changes produced e.g. by traffic variations and time-variant channel conditions. In CSMA/CA, nodes make their own decisions based on partial network information and the handshaking procedure allows the use of AAS at the transmitter and the receiver. How to effectively use AAS in CSMA/CA with handshaking is addressed in this thesis. Different beam selection policies using switched beam antenna systems are investigated. Finally, we demonstrate how the proposed techniques can be applied in a rural access scenario in Nicaragua. The result of a user-deployed MWN for Internet access shows that the supported aggregated end-to-end rate is higher than an Asymmetric Digital Subscriber Line (ADSL) connection.
QC 20100908

The survival and success of religious reform groups in the late medieval period was often due to the efforts of an ecclesiastical patron, a powerful and often wealthy individual who exerted their influence on behalf of the group or their leaders and spokesmen. This thesis uses the wealth of documentation available on the Spiritual Franciscans to explore the origin, development and wider effect of the relationships between the most powerful ecclesiastical patrons of the reformers and their clients, spokesmen for the Italian Spirituals at the papal court who were taken into the patrons’ households for years or even decades. During that time, the political fortunes of the different groups of Spiritual Franciscans fluctuated dramatically: in only a handful of years they went from hopeful expectation at the Council of Vienne c. 1311 to heresy trials, imprisoned spokesmen and friars burned at the stake c.1317-1318. Using testaments from the patrons’ families and the patrons themselves, the thesis explores the possible reasons for the patrons’ initial attraction to their Spiritual Franciscan clients. Letters, chronicles and exegetical texts written by the clients during and after their time in the patrons’ households are examined along with papal registers and other narrative and epistolary sources to develop models of the nature and progression of the patronage relationship, and how it survived in the face of periods of intense disapproval and harassment from the papacy, other prelates and some members of the Franciscan hierarchy. After establishing a framework for the progression of the patronage relationship, evidence of art patronage and other religious and patronage interests that the patrons and clients shared is used to develop a deeper understanding of how the patrons’ choice to involve themselves with the Spiritual Franciscans positively or negatively affected others in their orbit, especially their other clients.

Vehicular ad hoc networks (VANETs) are a subclass of mobile ad hoc networks (MANETs) in which the mobile nodes are vehicles; these vehicles are autonomous systems connected by wireless communication on a peer-to-peer basis. They are self-organized, self-configured and self-controlled infrastructure-less networks. This kind of network has the advantage of being able to be set-up and deployed anywhere and anytime because it has no infrastructure set-up and no central administration. Distributing information between these vehicles over long ranges in such networks, however, is a very challenging task, since sharing information always has a risk attached to it especially when the information is confidential. The disclosure of such information to anyone else other than the intended parties could be extremely damaging, particularly in military applications where controlling the dissemination of messages is essential. This thesis therefore provides a review of the issue of security in VANET and MANET; it also surveys existing solutions for dissemination control. It highlights a particular area not adequately addressed until now: controlling information flow in VANETs. This thesis contributes a policy-based framework to control the dissemination of messages communicated between nodes in order to ensure that message remains confidential not only during transmission, but also after it has been communicated to another peer, and to keep the message contents private to an originator-defined subset of nodes in the VANET. This thesis presents a novel framework to control data dissemination in vehicle ad hoc networks in which policies are attached to messages as they are sent between peers. This is done by automatically attaching policies along with messages to specify how the information can be used by the receiver, so as to prevent disclosure of the messages other than consistent with the requirements of the originator. These requirements are represented as a set of policy rules that explicitly instructs recipients how the information contained in messages can be disseminated to other nodes in order to avoid unintended disclosure. This thesis describes the data dissemination policy language used in this work; and further describes the policy rules in order to be a suitable and understandable language for the framework to ensure the confidentiality requirement of the originator. This thesis also contributes a policy conflict resolution that allows the originator to be asked for up-to-date policies and preferences. The framework was evaluated using the Network Simulator (NS-2) to provide and check whether the privacy and confidentiality of the originators’ messages were met. A policy-based agent protocol and a new packet structure were implemented in this work to manage and enforce the policies attached to packets at every node in the VANET. Some case studies are presented in this thesis to show how data dissemination can be controlled based on the policy of the originator. The results of these case studies show the feasibility of our research to control the data dissemination between nodes in VANETs. NS-2 is also used to test the performance of the proposed policy-based agent protocol and demonstrate its effectiveness using various network performance metrics (average delay and overhead).

Denna rapport behandlar prestandaproblem i den nyligen standardiserade Mesh kommunikationsstandarden (IEEE 802.11s). I denna rapport, undersöker och förbättra vi ett förhållande som resulterar i reduktion av genomströmningen i en kedja av noder topologi. IEEE802.11s är mycket lovande med många fördelar för både IoT-systemen och trådlösa nätverk i båda hemmet och arbete.Vi arbetar med frågan om orättvisa när CSMA/CA tillämpas, vilket orsakar genomströmningsreduktion på grund av paketförluster och indikerar svältning. Vi analyserar konsekvenserna av Collision Avoidance (CA) mekanism och föreslår en ersättning för CA som är både rättvist och samtidigt kan upprätthålla undvikande av kollisioner. Vi implementera detta i en simulator och resultatet visar på betydligt högre end-to-end-genomströmning än standard CSMA/CA och inga paketförluster på grund av buffertspill.
This thesis rapport deals with the performance issues of the newly standardized Wireless mesh protocol (IEEE 802.11s). In this thesis, we work on improving the conditions that results in throughput degradation in a chain of nodes topology. The mesh standard is very promising with many advantages for both IoT systems and home wireless networks.We work on the issue of unfairness when CSMA/CA is applied, which causes throughput degradation due to packet loss and indicates starvation. We analyze the implication of the Collision Avoidance (CA) mechanism and propose a replacement for the CA that is both fair and able to maintain collision avoidance. We implement this in a simulator and the result shows significantly higher end-to-end throughput compared to the original CSMA/CA and no packet loss due to buffer overflow.

Ca²⁺ is an important part of many short-term signalling pathways in both plants and animals. As [Ca²⁺]_cyt levels are under circadian control, it is possible that Ca²⁺ is also used as a component in the circadian signalling pathway. In this thesis, I have tried to position circadian [Ca²⁺]_cyt oscillations in the circadian signalling pathway of Arabidopsis thaliana using a range of genetic and pharmacological tools. Three main approaches were used: the measurement of circadian [Ca²⁺]_cyt oscillations in circadian clock mutants, the use of drugs related to nitric oxide signalling and the overexpression of Ca²⁺-binding proteins. Using photoreceptors mutants, I show that PHYTOCHROMES and CRYPTOCHROMES modulate the [Ca²⁺]_cyt basal levels independently of the circadian clock. Using lines misexpressing components of the circadian oscillator, I show that circadian [Ca²⁺]_cyt oscillations are controlled by a CCA1/LHY/TOC1 (CIRCADIAN CLOCK ASSOCIATED 1/ LATE ELONGATED HYPOCOTYL/ TIMING OF CAB 1) containing oscillator. However, this oscillator is not the same as the one that controls rhythms of CHLOROPHYL A/B BINDING PROTEIN2 (CAB2) promoter activity as its components are used differently. Pharmacological tools suggest that, while cyclic-ADP ribose (cADPR) may set the pace of the circadian clock, nitric oxide (NO) does not. In short-term Ca²⁺ signalling, NO regulates [Ca ²⁺]_cyt levels through cADPR but not in circadian clock signalling. A separation between short-term and circadian signalling is also suggested by the absence of effects of overexpression of Ca²⁺-binding proteins in circadian [Ca²⁺]_cyt oscillations. The role of circadian [Ca²⁺]cyt oscillations remain unknown but they may be an input to the clock and be part of the photoperiodic pathway controlling the transition to reproductive growth.

Initially, a systematic characterisation of all the possible ways in which two communicating pairs of nodes can interfere with each other is made. Using this as a building block and assuming independence of the stations, an estimate for the network throughput can be derived. The latter proves to be quite accurate for symmetric networks and manages to follow the performance trends in an arbitrary network. Following this, a more detailed Markovian-based mathematical model is proposed for the analysis of the hidden node case. This approach does not rely on common assumptions, such as renewal theory and node synchronisation, and is highly accurate, independently of the system parameters, unlike prior methods. Moreover, the usual decoupling approximation is not adopted; on the contrary, a joint view of the competing stations is taken into consideration. The model is firstly developed based on the assumption that the network stations employ a constant contention window for their backoff process. However, later in the thesis this assumption is relaxed, and performance curves are derived for the case when the stations employ the Binary Exponential Backoff Scheme, as is the case in practice. The Markovian state space is kept relatively small by employing an iterative technique that computes the unknown distributions. The adoption of this technique makes the analysis computationally efficient.

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The National Training Center (NTC) located at Fort Irwin, California provides the U.S. Army sole replication of a desert combat environment. The NTC provides U.S. Army brigade size heavy forces both realistic training scenarios and an accurate record of mission execution. The primary emphasis of this research is to develop the methodology for modeling both data encapsulation and transmission via a fiber optic cable for the NTC. To capitalize on technological advances, the NTC requires a relational database for data encapsulation. The database structure in this effort efficiently stores Range Data Management System (RDMS) and Observer/Controller (OC) data input. The NTC also requires a mathematical modeling (network) tool with the capability of flexible analysis of a modular fiber optic cable system. The NTC Route Optimizer program developed in this effort provides a tool for rapid manipulation of design factors with immediate graphical and numerical feedback. Additionally, the reader is given methods to design future upgrades to the database and change specifications of the fiber optic cable system. This allows the reader to manipulate technology for specific goals instead of receiving transparent improvements that are disconnected

The master thesis is a prototyping project of a wireless body area network (WBANs) for patient monitoring in hospitals. The goal of this project was to study various technologies suitable for wireless body area networks, complete a requirement analysis, design a WBAN suitable to achieve the requirements and to test and evaluate the system against the requirements. Seven sensor end nodes are chosen to monitor seven vital signs for patient monitoring. After studying different technologies suitable for WBANs, IEEE 802.15.4j was chosen because it communicates in a special allocation of medical spectrum of 2360 to 2400MHz. A coordinator or master will be the center of the network using a star topology. Due to certain limitations in the firmware of the NXP FRDMKW40Z, IEEE 802.15.4j had to be dropped and IEEE 802.15.4 was the final chosen technology because the only difference between IEEE 802.15.4j and IEEE802.15.4 is the difference in the physical layer, while the developed application remains the same, making the shift back to IEEE802.15.4j, in the future, simple. There have been several projects working on the same idea with IEEE 802.15.4, but they do not combine multiple sensors to form a network and the total throughput requirements for this thesis project are much higher. The beacon mode and the non-beacon mode of IEEE 802.15.4 are studied. Non beacon mode is unpredictable due to the use of carrier sense multiple access with collision avoidance (CSMA/CA) to access the medium. When multiple end nodes compete to get access to the medium, unreliability is introduced into the system. In the beacon mode, because of the slotted CSMA access of sixteen equally spaced time slots for communication, there is a restriction of the size of a time slot and thus, the high throughput requirement of the system is not met. The solution proposed in the thesis project is to develop a custom time slot system in the non-beacon mode, where each end node is granted a reserved time slot of a specific length as required by the end node. There is a timer mechanism which makes sure that the time slots for each device maintain the time limit on the time slot, on the side of the main master/coordinator of the network and on the side of the end node. The protocol for an end node to join a personal area network (PAN) is called as the association process. The association process enables the end node to be a part of a PAN to exchange its sensor data. Traditionally, in IEEE 802.15.4, the end nodes scan the sixteen IEEE 802.15.4 channels and when an appropriate coordinator is found, the end node initiates the association process with the coordinator. The solution proposed for the formation of the network by the association process is to use two different technologies. The end nodes and the coordinator exchange information using near field communication (NFC) technology by a simple tapping mechanism. The end node has an active NFC tag while the coordinator has an NFC reader. During the tap between the two devices, first the coordinator reads the end node data from the active tag. This data is required to form the custom time slot. Next the coordinator writes all association information into the active tag. After the NFC data exchange is done, the end node initiates the traditional IEEE 802.15.4 association protocol to join the coordinator’s PAN. Similarly after seven end nodes are associated to the coordinator, the network begins to function. All the end nodes communicate their data to the coordinator. The coordinator collects all the sensor data from the seven end nodes and may send the cumulative sensor data to the backend database servers which may be viewed by the medical authorities, this part is not included in the current version of the project. Several tests are run on this system to evaluate the requirements of latency, throughput and quality of service with two different ranges of 20cm and 250cm. The latency of association between the coordinator and end node is 632ms. The required throughput is met by the network. The packet delivery rate of the system is always above 99%. The graphs for packet delivery rates for all the sensors with a range of 20cm and 250 cm are shown in the appendices. The probabilities for the packet delivery rates greater than 90%, 99%, 99.9% and 99.99% are also graphically shown using a normal distribution in the appendices.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ)
This work proposes a topology of isolated microgrids with hybrid network (part in DC and part in AC) of electric power distribution. This topology can serve as an alternative model to the conventional AC distribution network model for the electrical service of isolated communities. The topology consists of using a main system of DC power distribution and subsystems with an AC distribution. DC/AC converters are strategically distributed along the DC main network, forming AC subsystems, in order to serve a certain number of consumers with AC loads. Although there are loads that can be fed in DC, this is not a reality for household loads, which are basically AC powered. Thus, the interest of this work is to evaluate the possible advantages of this topology over the conventional microrredes with distribution network in low voltage in AC. In this contexto, the analysis parameters to be studied are: the increasing the extension of the distribution network without the need to use transformers, electric conductors with larger cross sections or distributed generation; the efficiency in the distribution of energy, evaluating the losses, and the reduction of implantation and operation costs. In order to compare the microgrid with hybrid distribution network, an isolated microgrid with purely CA distribution network was adopted as reference: the microgrid with solar-wind generation of Lençóis Island, located in the northeast of Brazil, which has been in operation since July 2008.
Este trabalho propõe uma topologia de microrredes isoladas com rede híbrida (parte em CC e parte em CA) de distribuição de energia elétrica. Essa topologia pode servir como modelo alternativo ao modelo convencional de rede de distribuição de energia totalmente em CA para o atendimento elétrico de comunidades isoladas. A topologia consiste em utilizar um sistema tronco de distribuição de energia em CC e de subsistemas com distribuição CA. Conversores CC/CA são distribuídos estrategicamente ao longo da rede tronco CC, formando subsistemas CA, com a finalidade de atender determinado número de consumidores com carga em CA. Apesar de existirem cargas que podem ser alimentadas em CC, essa não é uma realidade para as cargas de uso doméstico, que basicamente são alimentadas em CA. Assim, o interesse deste trabalho é avaliar as possíveis vantagens dessa topologia sobre as convencionais microrredes com rede de distribuição em baixa tensão em CA. Neste contexto, os parâmetros de análise a serem estudados são o aumento da extensão da rede de distribuição sem a necessidade de se utilizar transformadores, condutores elétricos com seções transversais maiores ou geração distribuída; a eficiência na distribuição de energia, avaliando as perdas, e a redução de custos de implantação e operação. Para se comparar a microrrede com rede de distribuição híbrida, adotouse como referência uma microrrede isolada com rede de distribuição somente CA: a microrrede com geração eólica-solar da Ilha de Lençóis está localizada no nordeste do Brasil, a qual está em operação desde julho de 2008.

Dans ce travail de thèse, nous présentons nos travaux qui portent sur l’identification des cibles en général par un radar Ultra-Large Bande (ULB) et en particulier l’identification des cibles dont la surface équivalente radar est faible telles que les piétons et les cyclistes. Ce travail se décompose en deux parties principales, la détection et la reconnaissance. Dans la première approche du processus de détection, nous avons proposé et étudié un détecteur de radar ULB robuste qui fonctionne avec des données radar 1-D (A-scan) à une dimension. Il exploite la combinaison des statistiques d’ordres supérieurs et du détecteur de seuil automatique connu sous le nom de CA-CFAR pour Cell-Averaging Constant False Alarm Rate. Cette combinaison est effectuée en appliquant d’abord le HOS sur le signal reçu afin de supprimer une grande partie du bruit. Puis, après avoir éliminé le bruit du signal radar reçu, nous implémentons le détecteur de seuil automatique CA-CFAR. Ainsi, cette combinaison permet de disposer d’un détecteur de radar ULB à seuil automatique robuste. Afin d’améliorer le taux de détection et aller plus loin dans le traitement, nous avons évalué l’approche des données radar 2-D (B-Scan) à deux dimensions. Dans un premier temps, nous avons proposé une nouvelle méthode de suppression du bruit, qui fonctionne sur des données B-Scan. Il s’agit d’une combinaison de WSD et de HOS. Pour évaluer les performances de cette méthode, nous avons fait une étude comparative avec d’autres techniques de suppression du bruit telles que l’analyse en composantes principales, la décomposition en valeurs singulières, la WSD, et la HOS. Les rapports signal à bruit -SNR- des résultats finaux montrent que les performances de la combinaison WSD et HOS sont meilleures que celles des autres méthodes rencontrées dans la littérature. A la phase de reconnaissance, nous avons exploité les données des deux approches à 1-D et à 2-D obtenues à partir du procédé de détection. Dans la première approche à 1-D, les techniques SVM et le DBN sont utilisées et évaluées pour identifier la cible en se basant sur la signature radar. Les résultats obtenus montrent que la technique SVM donne de bonnes performances pour le système proposé où le taux de reconnaissance global moyen atteint 96,24%, soit respectivement 96,23%, 95,25% et 97,23% pour le cycliste, le piéton et la voiture. Dans la seconde approche à 1-D, les performances de différents types d’architectures DBN composées de différentes couches ont été évaluées et comparées. Nous avons constaté que l’architecture du réseau DBN avec quatre couches cachées est meilleure et la précision totale moyenne peut atteindre 97,80%. Ce résultat montre que les performances obtenues avec le DBN sont meilleures que celles obtenues avec le SVM (96,24%) pour ce système de reconnaissance de cible utilisant un radar ULB. Dans l’approche bidimensionnelle, le réseau de neurones convolutifs a été utilisé et évalué. Nous avons proposé trois architectures de CNN. La première est le modèle modifié d’Alexnet, la seconde est une architecture avec les couches de convolution arborescentes et une couche entièrement connectée, et la troisième est une architecture avec les cinq couches de convolution et deux couches entièrement connectées. Après comparaison et évaluation des performances de ces trois architectures proposées nous avons constaté que la troisième architecture offre de bonnes performances par rapport aux autres propositions avec une précision totale moyenne qui peut atteindre 99,59%. Enfin, nous avons effectué une étude comparative des performances obtenues avec le CNN, DBN et SVM. Les résultats montrent que CNN a les meilleures performances en termes de précision par rapport à DBN et SVM. Cela signifie que l’utilisation de CNN dans les données radar bidimensionnels permet de classer correctement les cibles radar ULB notamment pour les cibles à faible SER et SNR telles que les cyclistes ou les piétons
In this thesis work, we focused on the study and development of a system identification using UWB-Ultra-Wide-Band short range radar to detect the objects and particularly the vulnerable road users (VRUs) that have low RCS-Radar Cross Section- such as cyclist and pedestrian. This work is composed of two stages i.e. detection and recognition. In the first approach of detection stage, we have proposed and studied a robust UWB radar detector that works on one dimension 1-D radar data ( A-scan). It relies on a combination of Higher Order Statistics (HOS) and the well-known CA-CFAR (Cell-Averaging Constant False Alarm Rate) detector. This combination is performed by firstly applying the HOS to the received radar signal in order to suppress the noise. After eliminating the noise of the received radar signal, we apply the CA-CFAR detector. By doing this combination, we finally have an UWB radar detector which is robust against the noise and works with the adaptive threshold. In order to enhance the detection performance, we have evaluated the approach of using two dimensions 2-D (B-Scan) radar data. In this 2-D radar approach, we proposed a new method of noise suppression, which works on this B-Scan data. The proposed method is a combination of WSD (Wavelet Shrinkage Denoising) and HOS. To evaluate the performance of this method, we performed a comparative study with the other noise removal methods in literature including Principal Component Analysis (PCA), Singular Value Decomposition (SVD), WSD and HOS. The Signal-to-Noise Ratio (SNR) of the final result has been computed to compare the effectiveness of individual noise removal techniques. It is observed that a combination of WSD and HOS has better capability to remove the noise compared to that of the other applied techniques in the literature; especially it is found that it allows to distinguish efficiency the pedestrian and cyclist over the noise and clutters whereas other techniques are not showing significant result. In the recognition phase, we have exploited the data from the two approaches 1-D and 2-D, obtained from the detection method. In the first 1-D approach, Support Vector Machines (SVM) and Deep Belief Networks (DBN) have been used and evaluated to identify the target based on the radar signature. The results show that the SVM gives good performances for the proposed system where the total recognition accuracy rate could achieve up to 96,24%. In the second approach of this 1-D radar data, the performance of several DBN architectures compose of different layers have been evaluated and compared. We realised that the DBN architecture with four hidden layers performs better than those of with two or three hidden layers. The results show also that this architecture achieves up to 97.80% of accuracy. This result also proves that the performance of DBN is better than that of SVM (96.24%) in the case of UWB radar target recognition system using 1-D radar signature. In the 2-D approach, the Convolutional Neural Network (CNN) has been exploited and evaluated. In this work, we have proposed and investigated three CNN architectures. The first architecture is the modified of Alexnet model, the second is an architecture with three convolutional layers and one fully connected layer, and the third is an architecture with five convolutional layers and two fully connected layers. The performance of these proposed architectures have been evaluated and compared. We found that the third architecture has a good performance where it achieves up to 99.59% of accuracy. Finally, we compared the performances obtained using CNN, DBN and SVM. The results show that CNN gives a better result in terms of accuracy compared to that of DBN and SVM. It allows to classify correctly the UWB radar targets like cyclist and pedestrian

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Today's highly eletricity dependent society together with the scarcity of conventional energy sources and magnitude of environmental problems brought by them, has raised the level of importance of renewable energy sources such as photovoltaic energy. However, it is necessary to develop new techniques of PV panel production and electronic converters required in their use, as well as the dissemination of such technologies in Brazil. This work contributes to the systematic design of an inverter for photovoltaic systems connected to the mains. The key techniques needed to control these systems are described and analyzed within a common base. Furthermore, this paper describes the hardware design of an inverter for connecting PV panels to the AC mains, allowing an overview of all the steps required for the design of a PV inverter. A new methodology for the design of current controllers for current injection into the grid is presented and the advantages of the proportional resonant controller are shown. This work resulted in a functional inverter with commercially viable features, a total current harmonic distortion of 2.03%, maximum power point operation and in conformance to international regulatory standards.
A dependência quase que imperativa da sociedade atual à energia elétrica aliada à escassez das fontes de energia convencionais e à magnitude dos problemas socioambientais trazidos por elas, tem elevado o nível de importância de fontes renováveis de energia, tais como a fotovoltaica. Entretanto, ainda é necessário o desenvolvimento de novas técnicas de produção de painéis FV e dos conversores eletrônicos necessários ao seu uso, bem como a disseminação dessas tecnologias no Brasil. Este trabalho contribui com a sistematização do projeto de um inversor para sistemas fotovoltaicos conectados à rede CA. São descritas e analisadas, dentro de uma base comum, as principais técnicas de controle necessárias a estes sistemas. Além disso, esse trabalho descreve o projeto de hardware de um inversor para conexão entre painéis FV e a rede CA, possibilitando uma visão global de todas as etapas necessárias para o projeto de um inversor fotovoltaico. É apresentada uma nova metodologia para o projeto dos controladores da corrente injetada na rede e mostra-se as vantagens do controlador proporcional ressonante. Tem-se como resultado um inversor funcional, com características comercialmente viáveis, com uma taxa de distorção harmônica de corrente de 2,03%, funcionamento no ponto de máxima potência e adequado às normas regulatórias internacionais.

The aim of this thesis is to analyse the mutual impact which social relations and entrepreneurship had in relation to the success of four actors in a rural area in northern Sweden at the beginning of the nineteenth century. Many Swedish scholars have studied the process of social differentiation, before the industrial revolution. However, we still know very little about the forces behind this process, why some peasant households became more successful than others, especially during the first half of the nineteenth century when the economic differences were increasing. To grasp this process, the notion of social position has been used as a tool to grade the population on a scale from low- to high-ranked households in an economic and political sense. The fact that households were more or less successful turns our attention to the ability among individuals and households to change their social position. A theoretical concept chosen to investigate such change is the notion of entrepreneur, which implies a focus on the actor working for personal profit in a changing economic world. The main question has been how important social relations connected to entrepreneurship are in order to promote success among peasant households in the pre-industrial society. The empirical investigation has been conducted on two different levels. The first level is a structural study analysing the physical landscape of the court district of Rödön, the economic stratification and the political activity of the population in the area and, finally, their economic behaviours as peasants and rural businessmen. The second is a qualitative study emphasising on four individual actors: the businessman Per Wikström in the town of Östersund and three of the most successful peasant households in the region. The four case studies reveal that the rural elite had a pragmatic and dynamic approach to choosing social relations outside the family. Many acquaintances grew persistent and embedded in family or kinship relations, whereas others were short-lived or sacrificed for a calculated economic gain.

Malta hat in der Geschichte durch seine günstige Lage mitten im Mittelmeer eine bedeutende Rolle bespielt. Die Phönizier, ein Seefahrervolk, das ursprünglich von der heutigen Libanonküste stammt, haben die Insel für ihre Zwecke strategisch und wirtschaftlich genutzt. Diese Dissertation beschäftigt sich mit der phönizischen Epoche auf Malta. Im Besonderen wird der Zeitraum zwischen 1000 und 500 v. Chr. untersucht. Die Arbeit fokussiert sich auf das Keramikrepertoire und die Kleinfunde, die in den Zeitraum eingeordnet werden. Das erste Kapitel befasst sich mit der aktuellen Forschungsliteratur rund um die Phönizier. Identität, Sprache und Herkunft der Bewohner der heutigen Libanonküste stehen hierbei besonders im Vordergrund. Das darauffolgende Kapitel leitet zur aktuellen Forschungsgeschichte zu den Phöniziern auf Malta über. Fragen nach der Chronologie, des Keramikrepertoires, des Heiligtums Tas-Silġ und nach der einstigen phönizischen Siedlung werden unter anderem behandelt. Der Hauptteil der Studie befasst sich mit der systematischen Bearbeitung der Keramik und der Kleinfunde. Eine Formenanalyse von jeder Form wird sowohl bei der Keramik als auch bei den Kleinfunden durchgeführt. Insgesamt wurden 680 Objekte in der Studie untersucht. 554 Keramikobjekte und 126 Kleinfunde. Der Schlussteil befasst sich mit den Ergebnissen der Studie. Insbesondere wird die Hypothese hervorgehoben, die besagt, dass ein „Inselnetzwerk“ zwischen den Phöniziern geknüpft wurde, die schon früh Sizilien, Sardinien, Nordafrika und Malta besiedelten. Um diese These besser zu belegen, werden Vergleichsmodelle zu Handelsnetzwerken aus der Antike und aus dem Mittelalter herangezogen.
Malta played an important role in history because of its specific location right in the middle of the Mediterranean Sea. The Phoenicians, a seafaring nation who is originated at today’s Lebanon coast, did use the island for strategic and economic purpose. That dissertation deals with the Phoenician epoch on Malta. In special analyzing focus stands the period between 1000 and 500 B.C. The study focuses the ceramic repertoire and the small finds which are classified into that period. The first chapter consider the current research literature concerning the Phoenicians. Identity, language and the origin of the inhabitants of the nowadays Lebanon coast are in special interest. The next chapter is leading to the research literature concerning the Phoenicians on Malta. Amongst others it deals with questions about chronology, the ceramic repertoire, the sanctuary of Tas-Silġ and the erstwhile phoenician settlement. The main chapter of this study considers a systematic analysis of the ceramic and the small finds. An analysis of every specific shape of the ceramic items and the small finds is made. 680 objects have been observed in total. 554 ceramic objects and 126 small finds. The last chapter deals with the results of the study. Especially emphasized is the hypothesis, that the early phoenician settlers were creating an “island-network” between Sicily, Sardinia, North Africa and Malta. For proving this thesis much better, comparison models were used which comes from the antiquity and from the middle ages.

The internet is one of the most widely used mediums for communication in modern society and it has become an everyday necessity for many. It is therefore of utmost importance that it remains as secure as possible. SSL and TLS are the backbones of internet security and an integral part of these technologies are the certificates used. Certificate authorities (CAs) can issue certificates that validate that domains are who they claim to be. If a user trusts a CA they can in turn also trust domains that have been validated by them. CAs can in turn trust other CAs and this, in turn, creates a chain of trust called a certificate chain. In this thesis, the structure of these certificate chains is analysed and a longitudinal dataset is created. The analysis looks at how the certificate chains have changed over time and puts extra focus on the domains of big tech companies. The dataset created can also be used for further analysis in the future and will be a useful tool in the examination of historical certificate chains. Our findings show that the certificate chains of the domains studied do change over time; both their structure and the lengths of them vary noticeably. Most of the observed domains show a decrease in average chain length between the years of 2013 and 2020 and the structure of the chains vary significantly over the years.

The objective of this thesis is to get familiar with wireless sensor networks technologies and with standard IEEE 802.15.4. and communication principle in wireless sensor networks built on this standard. Main goal of this project is to design a packet analyzer, which is capable to catch data on chosen channel and this data is able to analyze. Part of this project is production of necessary microcontroller software equipment. Another output of this project is do a research of available packet analyzers on market and compare them with analyzer build by this thesis.

Uma série de equipamentos de eletrônica de potência é ligada à rede de corrente alternada através de transformadores, que exercem as funções de isolamento galvânico, elevação/abaixamento de tensão, etc. Estes transformadores podem sofrer saturação em condições transitórias (inrush) ou quando o conversor ligado a ele impõe valor médio não nulo de tensão. O problema é normalmente sanado nas malhas de controle do conversor, no entanto o ajuste destas malhas em ambiente de simulação computacional requer um modelo que represente adequadamente a característica de saturação do núcleo ferromagnético. Este trabalho apresenta um modelo de simulação computacional adequado para transformadores operando em saturação intensa, visando aplicações em projetos de equipamentos de eletrônica de potência com transformador monofásico alimentado por inversor. Além disso, é demonstrado um método experimental de obtenção da característica de saturação do núcleo, sem necessidade das suas características construtivas. Resultados de simulação obtidos são comparados com resultados experimentais para validação do modelo e método.
Several power electronics based equipments are connected to the alternating current network through transformers, which perform galvanic insulation, voltage increasing/lowering, etc. These transformers may experience saturation under transitory conditions (inrush), or when its converter imposes non-zero average voltage. Such problem is commonly treated in the converter\'s control loops, but the tuning of these loops in a computer simulation environment requires a transformer model that represents adequately the ferromagnetic core saturation effect. The current work proposes a computer simulation model that adequately describes the operation of the transformer at deep saturation, suitable for design of power electronics applications with single phase transformers connected to power inverter. Additionally, an experimental method for determining its core saturation characteristic is demonstrated. This method does not require previous knowledge of the core\'s constructive parameters. Simulation and experimental results are presented to confirm the validity of the model and the method.

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A proposta dessa Tese é o projeto e desenvolvimento de um sistema de fornecimento de energia elétrica conectada à rede sem a utilização de circuitos eletrônicos complexos. O sistema eletroeletrônico convencional utiliza um inversor de frequência que transfere a potência ativa do nível de tensão e corrente CC para o nível compatível com a rede elétrica CA em frequência, tensão e sincronismo de fases. Já o desenvolvimento do projeto teve como parte experimental a utilização de indutores adequados com valores variáveis de 200 mH a 500 mH entre os painéis fotovoltaicos e a rede convencional. A tensão e a corrente máxima de CC foi de 29,6 V e a máxima possível foi de 20 amperes. Utilizou-se do princípio do casamento de impedâncias entre o painel fotovoltaico e o sistema de fornecimento de energia CA. Assim o painel fotovoltaico fornece somente potência ativa para a rede não interferindo no sincronismo. Na onda de tensão e corrente CA há uma pequena alteração no nível CA em relação a simetria do eixo dos tempos, dentro dos limites previstos para a rede convencional de energia. Logo evidencia-se o fornecimento de potência ativa para a rede CA. Os resultados obtidos permitiram inserção na rede de cerca de 10% da potência ativa dos painéis fotovoltaicos, com a otimização dos valores dos indutores, ocorrendo a transferência de potência ativa dos painéis fotovoltaicos para a rede convencional de energia CA.
The purpose of this thesis is the design and development of a delivery system of electricity connected to the network without the use of complex electronic circuits. The electronics system uses a frequency inverter that transfers the active power level voltage and DC current to the level compatible with the mains AC frequency, voltage and phase synchronization. But the project was to develop experimental part the use of suitable inductors with variable values of 200 mH to 500 mH between the PV panels and the conventional network. The maximum current was 20 amperes. We used the principle of impedance matching between the photovoltaic panel and the power supply system CA. So the photovoltaic panel supplies only active power to the grid not interfering with the timing. In the wave of AC voltage and current for a small change in CA level against the symmetry axis of time. Logo is evident in the supply of active power to the grid CA. The results allowed inclusion in the network of about 10% of the active power of photovoltaic panels by optimizing the values of the inductors for the occurrence of power transfer of conventional photovoltaic panels for energy occurs CA.

This thesis is concerned the technology with technologies of transfer through wireless devices. It is about possibilities of optimization of transfer in wireless net, especially of the reduction of interference influence. The first part is about theory and the standards development of wireless technology. There are methods and principles used in wireless technologies. The second part is a practical measuring and testing of an internal wireless net, with the emphasis being on the source of interference influence. Measuring was focused on interference between access points and was not about meteorological influence. It continues with theory and testing of interference of the microwave oven in our wireless net. Then, it is a practical demonstration of interference in an external environment. There are practical examples of interference between different providers’ nets on the same area and solutions to prevent or to cancel this interference. In next part of work the wireless net is parsed and described in a given territory. Here is described the way how to precede the reciprocal interference and eventually how this mutual disturbance suppress. Consequently, our net is optimized for customer growth and for today’s options of newer and more powerful components for wireless transfer. Finally there are two laboratory tasks. The first one is about practical measuring and testing of wireless net’s parameters and the second one is about simulation of wireless networks in the Opnet program.

博士
國立臺灣大學
資訊工程學研究所
95
Recently, CAMA/CA-based wireless mesh networking technology has received much attention, because they can provide metropolitan-scale wireless broadband Internet access networks, and enable a cost-effective scalable deployment with less wired lines. A wireless mesh network consists of several mesh backhaul networks where any two mesh nodes in a mesh backhaul network communicate with each other by wireless radio in a multi-hop manner. Some mesh nodes also act as gateways for connecting the mesh backhaul network to the Internet. Each mesh node in a mesh backhaul network forms its own mesh client network, where its associated mobile users can use it as an access point to communicate with other users or access Internet services through the mesh backhaul network. With the diversity of applications evolved until today, in addition to traditional best effort applications, multimedia applications with different quality requirements will be available in the near future. In order to provide quality delivery to multimedia applications, it is imperative that wireless mesh networks have to support quality-of-service (QoS) so that their required resource can be guaranteed. Thus far, providing QoS in a CAMA/CA-based mesh backhaul network is still a challenge, due to the spatial contention among shared wireless medium. In this dissertation, we focus on the QoS routing problems in a mesh backhaul network with the following two aspects. (P1) QoS routing with bandwidth requirement. (P2) QoS routing with maximum bandwidth. On the other hand, in a CSMA/CA-based mesh client network, a performance anomaly problem will incur when there are multiple applications transmitted with different channel bit rates. The anomaly problem arises because the basic CSMA/CA channel access method guarantees that the long-term channel access probabilities of the mobile devices transmitting at different data rates are equivalent to one another, and hence the long-term channel occupancy time for those devices transmitting at a lower data rate will be larger than those devices transmitting at a higher rate. When one device transmitting at a lower data rate captures the channel, it will last for a long time and hence penalize the total throughput of those devices transmitting at a higher data rate. Since the problem will bring about great impact on the quality transmission in a mesh client network, the following problem is identified. (P3) A throughput optimization method when multi-rate traffic is presented. In this dissertation, one of objectives is to study the QoS routing problems in the CSMA/CA-based mesh backhaul network such that the required resource of multimedia applications can be attained. The other objective is to alleviate the impact of the performance anomaly in the CSMA/CA-based mesh client network by maximizing the total throughput. To evaluate their performance, extensive experiments shall be carried out.

碩士
國立暨南國際大學
電機工程學系
100
Wireless LANs have been part of our daily life thanks to the development of wireless technologies. However, the original design of IEEE 802.11 can not provide a good service in a large network. The new IEEE 802.11 standard defines EDCA for differentiated services, where each AC queue operates independently to contend for the wireless channel. When number of station increases, the collision probability increases dramatically. Furthermore, the lower priority ACs may starves at heavy load situations. In an infrastructure WLAN, the AP is the bottleneck for downlink packets because the AP needs to contend with numerous stations, resulting in asymmetric throughputs between downlink and uplink. In order to mitigate the above mentioned problems. In this thesis, we propose a new MAC architecture including the new queue management module and the super mode. In addition, a contention-free MAC is also investigated to provide a collision-free wireless access way instead of the traditional random access manner. By the scheduler of the queue management module, we can mix different AC packets for a given TXOP duration. With the super mode, the AP can grant the wireless channel without contention. Simulation results show that, the proposed system can balance the uplink and downlink traffic, reduces high collision probability, and improves the overall capacity.

This thesis investigates the design and development considerations to introduce through- put differentiation and management capabilities into the Medium Access Control (MAC) layer of IEEE 802.11 Wireless Local Area Network (WLAN) systems, while also maximizing overall throughput performance. The final control mechanism highlighted in this thesis requires only an initial user configuration to specify the required throughput differentiation and management rules prior to it operating in a fully autonomous manner. In order to maximize throughput performance the control mechanism is designed to seamlessly adjust the throughput differentiation and management rules to reflect the current network traffic load. Throughout this thesis, we discovered and identified the great difficultly that is inherent in trying to create a control mechanism that is capable of operating autonomously in a broad range of possible traffic load conditions. The difficulties faced stemmed primarily from the design philosophy of a fully self-contained control mechanism within the MAC layer of the AP alone, and employing a completely passive/non-intrusive decision making procedure. Furthermore the idiosyncrasies of TCP-based traffic required special attention which could have otherwise been avoided if cross layer interaction was permitted. The IEEE 802.11e MAC layer standard [1] is chosen to be the foundation for providing throughput management capabilities in a WLAN. In particular, the throughput management capability is provided using the IEEE 802.11e Enhanced Distributed Channel Access (EDCA). The EDCA mechanism supports service differentiation across 4 different Access Categories (AC). Each AC has specific tunable parameters associated to it, which affects the level of probabilistic medium access it obtains against other ACs. The implementation and control objective of tuning parameters within EDCA are left open in the IEEE 802.11e standard [1]. We describe the process of selecting appropriate settings for the tunable parameters associated with each AC such that a specified throughput proportion allocation can be achieved between each AC. The selection process is aided by an analytical model of IEEE 802.11e EDCA under saturation load conditions [2]. The model allows us to identify, when under saturation load conditions, the parameter combinations that achieves a required throughput proportion allocation amongst ACs and at the same time maximizes overall throughput performance. Based on this information, we define Control Scheme-1 that resides within the access point (AP) and, as required, notifies all stations in the WLAN what required parameters should be associated with each AC. Through this process, regardless of dynamically changing active station counts transmitting a particular AC traffic, we demonstrate the control scheme's ability to maintain a required throughput proportion allocation regime between ACs. We then proceed to specify throughput proportion allocations between Downlink (DL) and Uplink (UL) paths in a WLAN under saturation load. EDCA allows for differentiating the AP and wireless client stations through the use of independent tunable parameters specifically associated to the AP. We make use of this feature directly by describing an updated parameter selection process. Therefore based on the new selection of parameters, we describe the new Control Scheme-2 and demonstrate its ability to manage the WLAN. We then investigate a new objective of developing a control that can also operate in non-saturation load conditions. In doing this, we still aim to maintain, wherever possible, the requirements of managing the throughput proportion allocation between the DL and UL and its respective ACs, and all the while focussing on maximizing throughput performance. In order to achieve this goal, we divided the modification of Control Scheme-2 into two parts. The first being modifications required to handle non-saturation load conditions in DL and subsequently modifications required to handle non-saturation load conditions in UL. With both DL and UL modifications in place we verify that the completed control mechanism Control Scheme-3 is able to achieve the required performance results across a wide range of test case scenarios. In addition, we compare these performance results to that obtained when employing the standard reference implementation of IEEE 802.11e EDCA [1].
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2012

Ruan, Sichao.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves 62-65).
Abstracts in English and Chinese.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Multihop Ad Hoc Wireless Networks --- p.1
Chapter 1.1.1 --- Introduction to Multihop Ad Hoc Networks --- p.2
Chapter 1.1.2 --- Scalability of Ad Hoc Wireless Networks --- p.3
Chapter 1.2 --- Hidden Terminal Problem --- p.3
Chapter 1.3 --- Exposed Terminal Problem --- p.5
Chapter 1.4 --- Overview of the Thesis --- p.6
Chapter 2 --- Background --- p.8
Chapter 2.1 --- MAC Protocols for Wireless Networks --- p.8
Chapter 2.1.1 --- Aloha --- p.8
Chapter 2.1.2 --- CSMA/CA --- p.9
Chapter 2.1.3 --- IEEE 802.11 DCF Standard --- p.10
Chapter 2.2 --- Related Work --- p.12
Chapter 2.2.1 --- Schemes for Hidden Node Problem --- p.12
Chapter 2.2.2 --- Schemes for Exposed Node Problem --- p.13
Chapter 2.3 --- Tradeoff between Hidden and Exposed Nodes --- p.14
Chapter 2.4 --- The Effect of Carrier Sensing Range --- p.17
Chapter 3 --- Analysis on Carrier Sensing Range --- p.18
Chapter 3.1 --- Analysis Model --- p.18
Chapter 3.1.1 --- Terminal Configurations --- p.18
Chapter 3.1.2 --- Timing/Packet Parameters --- p.19
Chapter 3.1.3 --- Protocol Approximation --- p.20
Chapter 3.1.4 --- Throughput Measurement --- p.21
Chapter 3.2 --- Derivation of Throughput --- p.21
Chapter 3.2.1 --- Channel Modeling --- p.22
Chapter 3.2.2 --- Actual Transmission Rate --- p.24
Chapter 3.2.3 --- Case One --- p.24
Chapter 3.2.4 --- Case Two --- p.26
Chapter 3.2.5 --- Mathematical Form of Throughput --- p.28
Chapter 3.2.6 --- Analysis Results --- p.30
Chapter 3.3 --- Implications --- p.31
Chapter 3.3.1 --- Value of Sensing Range in CSMA/CA --- p.31
Chapter 3.3.2 --- Need for New MAC Protocols --- p.32
Chapter 4 --- MAC Protocols by Congestion Control --- p.34
Chapter 4.1 --- Motivations and Principles --- p.34
Chapter 4.1.1 --- Balancing Hidden and Exposed Nodes --- p.35
Chapter 4.1.2 --- Controlling Carrier Sensing Range --- p.36
Chapter 4.1.3 --- Non-homogenous Sensing Range --- p.36
Chapter 4.2 --- Algorithm Descriptions --- p.38
Chapter 4.2.1 --- Core Concept --- p.38
Chapter 4.2.2 --- LDMI Control Scheme --- p.40
Chapter 4.2.3 --- Tahoe Control Scheme --- p.41
Chapter 5 --- Simulation Analysis --- p.44
Chapter 5.1 --- Simulation Configurations --- p.44
Chapter 5.1.1 --- Geometric Burst Traffic Model --- p.45
Chapter 5.1.2 --- Network Topology --- p.46
Chapter 5.1.3 --- Simulation Parameters --- p.47
Chapter 5.2 --- Throughput Comparisons --- p.48
Chapter 5.3 --- Fairness Comparisons --- p.50
Chapter 5.3.1 --- Situation of Unfairness --- p.50
Chapter 5.3.2 --- Fairness Measurement --- p.52
Chapter 5.4 --- Convergence Comparisons --- p.54
Chapter 5.5 --- Summary of Performance Comparison --- p.55
Chapter 6 --- Conclusions --- p.56
Chapter A --- Categories of CSMA/CA --- p.58
Chapter A.1 --- 1-persistent CSMA/CA --- p.58
Chapter A.2 --- non-persistent CSMA/CA --- p.58
Chapter A.3 --- p-persistent CSMA/CA --- p.59
Chapter B --- Backoff Schemes --- p.60
Chapter B.1 --- Constant Window Backoff Scheme --- p.60
Chapter B.2 --- Geometric Backoff Scheme --- p.60
Chapter B.3 --- Binary Exponential Backoff Scheme --- p.61
Bibliography --- p.62

碩士
國立交通大學
電信工程研究所
103
In CSMS/CA-based, multi-hop, multi-rate wireless ad-hoc networks, we can balance the interplay of spatial reuse and transmission reliability by dynamicly tuning carrier-sensing threshold (Tcs) according to environmental situations in order to reach the maximum network capacity. Lower carrier-sensing thresholds generally lead to larger carrier-sensing ranges (dcs), which ensure higher transmission reliability. In this manner, we actually increase the transmission reliability by reducing packet collisions due to mitigated interference produced by concurrent transmissions. However, the total network capacity suffers because of too preservative channel access attempts. On the other hand, higher carrier-sensing thresholds usaually result in smaller carrier-sensing ranges, which encourage better spatial reuse yet transmission collisions will happen more frequently due to potentially increased interference. Therefore, it is important to make adequate adjustments of carrier-sensing thresholds according to environmental conditions in a CSMA/CA-based wireless network. In this thesis, we address the above issue by proposing an adaptive mechanism to dynamicly adjust carrier-sensing thresholds used by wireless nodes in a distributed manner within reasonable computation time. Simulation results show that our proposed algorithm outperforms other implemented carrier-sensing tuning approaches in terms of aggregate network capacity.

A wireless sensor network consists of a number of sensor devices and coordinator(s) or sink(s). A coordinator collects the sensed data from the sensor devices for further processing. In such networks, sensor devices are generally powered by batteries. Since wireless transmission of packets consumes significant amount of energy, it is important for a network to adopt a medium access control (MAC) technology which is energy efficient and satisfies the communication performance requirements. Carrier sense multiple access with collision avoidance (CSMA/CA), which is a popular access technique because of its simplicity, flexibility and robustness, suffers poor throughput and energy inefficiency performance in wireless sensor networks. On the other hand, time division multiple access (TDMA) is a collision free and delay bounded access technique but suffers from the scalability problem. For this reason, this thesis focuses on design and analysis of hybrid channel access schemes which combine the strengths of both the CSMA/CA and TDMA schemes. In a hybrid CSMA/CA-TDMA scheme, the use of the CSMA/CA period and the TDMA period can be optimized to enhance the communication performance in the network. If such a hybrid channel access scheme is not designed properly, high congestion during the CSMA/CA period and wastage of bandwidth during the TDMA period result in poor communication performance in terms of throughput and energy efficiency. To address this issue, distributed and centralized channel access schemes are proposed to regulate the activities (such as transmitting, receiving, idling and going into low power mode) of the sensor devices. This regulation during the CSMA/CA period and allocation of TDMA slots reduce traffic congestion and thus improve the network performance. In this thesis work, time slot allocation methods in hybrid CSMA/CA-TDMA schemes are also proposed and analyzed to improve the network performance. Finally, such hybrid CSMA/CA-TDMA schemes are used in a cellular layout model for the multihop wireless sensor network to mitigate the hidden terminal collision problem.

碩士
國立臺北科技大學
電子工程系
107
In the previous study, [1] analyzed and simulated the throughput of DS CDMA/unslotted ALOHA networks with Markov Gaussian impulse noise. All previous research papers in CSMA/CA for power line communication (PLC) do not consider impulse noise in the physical (PHY) layer. The exception is [2], which considers CSMA/CA with Bernoulli-Gaussian impulse noise and do not consider queue effect in PLC. However, its impulse noise is memoryless. In this paper, we propose the throughput simulation of CSMA/CA with the Markov Gaussian impulse noise in PLC. The simulation results show that the throughput is higher due to the CSMA/CA mechanism compared to non-CDMA version of the previous ALOHA with Markov Gaussian impulse noise [1]. However, when the Gaussian noise/impulse noise ratio R is larger, the throughput decreases.

碩士
國立高雄第一科技大學
電腦與通訊工程所
97
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) of IEEE 802.11 is a common access method of media access control (MAC). When the number of nodes running CSMA protocol is increased, the package collision probability becomes larger. It also causes total throughput of the network worse. In this study, Time Division Multiple Access (TDMA) assigns a slot to each node. And it is able to arrange the transmission order among nodes, and there is no collision. However, in TDMA, when there are few transmitting nodes, it causes total throughput become low, due to poor slot utilization. To overcome the weakness of CSMA/CA and TDMA, we propose a protocol, which groups ad hoc nodes into non-overlapped spatial clusters. Within a cluster, each node runs both CSMA/CA and Spatial TDMA to improve total throughput. Among clusters, CSMA/CA and AODV are adopted. Finally, we analyze the protocol, which is the combination of CSMA/CA and Spatial TDMA, using ns2.

碩士
國立交通大學
電信工程研究所
106
With the arising of Internet of Things (IoT) applications and the fast growing of wireless devices, the Internet has become more and more crowded. How to deploy the resources effectively and make the best use of wireless channel is an essential yet non-trivial problem. Generally, increasing the spatial reuse will decrease the channel reliability simultaneously. In CSMA/CA-based wireless networks, adjusting physical carrier sensing threshold is an effective way to influence the spatial reuse factor. Increasing carrier sensing threshold typically encourages a better spatial reuse, which also means a better networks capacity. However, too many simultaneous transmissions will incur a higher packet collision probability. In this paper, we propose to combine the Simulated Annealing and Genetic Algorithm to obtain a global network-wise carrier sensing threshold for throughput improvement. Our simulation results validate the efficacy of the proposed tuning approach.

No
Supported by the IEEE 802.15.4 standard, embedded sensor networks have become popular and been widely deployed in recent years. The IEEE 802.15.4 medium access control (MAC) protocol is uniquely designed to meet the desirable requirements of the low end-to-end delay, low packet loss, and low power consumption in the low rate wireless personal areas networks (LR-WPANs). This paper develops an analytical model to quantify the key performance metrics of the MAC protocol in LR-WPANs with bursty ONOFF traffic. This study fills the gap in the literature by removing the assumptions of saturated traffic or nonbursty unsaturated traffic conditions, which are unable to capture the characteristics of bursty multimedia traffic in sensor networks. This analytical model can be used to derive the QoS performance metrics in terms of throughput and total delay. The accuracy of the model is verified through NS-2 (http://www.isi.edu/nsnam/ns/) simulation experiments. This model is adopted to investigate the performance of the MAC protocol in LR-WPANs under various traffic patterns, different loads, and various numbers of stations. Numerical results show that the traffic patterns and traffic burstiness have a significant impact on the delay performance of LR-WPANs.

This research aims to understand the different practices and strategies early career researchers and PhD students from the social sciences have in Social Networking Sites (SNSs) for science communication in one particular country: Brazil. Following this purpose, the central research question is which are the motives and rationale of the researchers for using social networking sites for science communication. Two sub-questions arise from this general research question: How do practices and strategies relate to the academic system of this country? And How do the traditional science communication practices translate into the use of Social Networking Sites (SNS)? This research is empirically oriented building up on case studies in Brazil. This study makes use of the adaptation that Van Dijck (2013) made of the Actor-Network Theory (ANT) and the review of affordances of social media platforms (Bucher & Helmond, 2016) to apply it to the study of social media as the theoretical approach. The methodological approach of this research is qualitative, using both interviews and netnography as research methods. The primary motivations for using different Social Networking Sites are all related to connectivity: communication with peers, to the public and research subjects, updating themselves about their research issue, dissemination of research, availability of papers, self-branding and participation in interest groups are the most mentioned. These motivations translate into cross-posting practices and integrated communication strategies -combining online and offline elements- on the different Social Networking Sites. These motivations translate into perceived affordances all related to social affordances, therefore, social capital processes: availability, scalability, visibility and multimediality. The academic system of the country has remained unchanged as it privileges traditional scholarly academic formats; therefore, early career researchers and PhD students from the social sciences only use the different Social Networking Sites (SNS) as a side aid but not as a primary means of communication. Social media is underused as a means of public science communication, even though these platforms offer a lot of advantages for pursuing such issue. Traditional science communication practices translate into the use of Social Networking Sites (SNSs). The most important issue that came out in this report was the fact that social affordances provided by Social Networking (SNSs) are still required to be endorsed by real life meeting to start further collaboration and the fact that English is the preferred language for such issues.

Programa doutoral em Engenharia Electrónica e de Computadores
Railway systems have progressively been developed since James Watt presented a technique of converting steam power into a circular movement back in 1763. With the novelty of steam engines at that time and the increasing of railway networks, railway industry quickly became an economic catalyst throughout the world due to the advantages of passenger and freight transport. In 1879, Siemens & Halske company introduced the world’s first electric train in the city of Berlin, consisting of a locomotive and three wagons, and supplied via an insulated third rail with 150 V direct current (DC). From that time, the world has begun to recognize the important transition from steam power to electric power, and the potential of the electrified railway as a mode of mass transport. Due to the plenty of fuel in the last century, Diesel trains were not only common, but they also dominated the railway sector for a few decades. Consequently, the development in the infrastructures of electric trains decelerated, and the path to having fully electrified trains was long enough. In this context, electric trains have introduced progressively, in which Diesel and electric power have been combined to create hybrid locomotives. However, and with the increased demand for transportation and the higher fuel prices in the last decades, electric trains can substantially offer lower operating costs and lower emissions compared with the Diesel-powered trains. Nowadays, most of the high-speed electric trains use alternating current (AC) power supply for their traction power systems, which provide better performance under long-distance power transmission than DC power supply. However, as the need for railway transportation increases due to more passengers and higher mobility requirements, more flexible and efficient traction systems are always needed. In Europe, AC traction power systems are mainly classified according to the voltage and frequency parameters (15 kV, 16.7 Hz) or (1×25 kV or 2×25 kV, 50 Hz). In all cases, railway operators have an absolute interest to run the electrified trains with the lowest possible operation and maintenance costs. In this context, power quality improvement at the three-phase power grid, associated with the AC electrified railway has drawn more attention in the last decades, especially after the evolution in the Power Electronics field. Subsequently, various solutions based on Power Electronics converters have been proposed to improve power quality in the electrified railway, e.g., the flexible AC transmission systems (FACTS). The rail power conditioner (RPC) is one of the FACTS devices that can be used to improve power quality by compensating harmonic contents, reactive power and negative sequence components of currents generated by the railway system. Among the other possible multilevel power converters, the modular multilevel converter (MMC) is an attractive solution for medium-voltage applications due to harmonics reduction, lower switching losses, and higher flexibility, scalability and reliability. Therefore, the MMC has been enhanced to be combined with the FACTS family. Taking into consideration the existing opportunities in the railway industry, not only in the development of the electric train itself, but also on the power quality improvement in the electrified railway, there is a strong investment in technological development for electrified railway systems. Therefore, this work presents a new topology of Power Electronics converter (RPC based on MMC) that compensates power quality problems associated with traction power systems, thus, reducing the operating costs of the electrified trains and increasing the power capacity of the electric traction grid. The main innovations of the RPC based on MMC are the integration of the MMC topology to operate as a railway power quality conditioner, benefiting from the advantages of the MMC in the traction power supply system. In this context, the research work proposed and developed in this Ph.D. thesis aimed to design, develop and validate a reduced-scale laboratory prototype of the RPC based on MMC, including all the necessary control algorithms and simulation models that are important to support the correct operation of the proposed system. Under simulation conditions, this work developed control algorithms for different RPC topologies, (full-bridge, half-bridge, three-wire, etc.) for demonstrating the general capabilities of the RPC system, and also for two different transformers connections (V/V and Scott). The most favorable RPC based on MMC topology (based on half-bridge MMC) was deeply and extensively simulated, namely employing predictive control approach. The experimental results obtained from a developed reduced-scale prototype confirm the validity of the presented control theory, as well as the power quality improvement capability of the proposed solution.
Os sistemas ferrovias foram progressivamente desenvolvidos desde que James Watt apresentou uma técnica de conversão da energia a vapor para um movimento circular em 1763. Com a novidade dos motores a vapor e a sua implementação nas redes ferroviárias, a indústria ferroviária rapidamente se tornou um catalisador econômico em todo o mundo devido às vantagens no transporte de passageiros e mercadorias. Em 1879, a empresa Siemens & Halske introduziu o primeiro comboio elétrico do mundo na cidade de Berlim, consistindo numa locomotiva com três vagões, alimentado por um terceiro trilho isolado alimentado com corrente contínua em 150 V (CC). A partir desse momento, o mundo começou a reconhecer a importante transição da energia a vapor para a energia elétrica e o potencial na ferrovia eletrificada como um meio de transporte de massa. Devido à abundância de combustível fóssil no século passado, os comboios a Diesel não eram apenas comuns, mas também dominaram o setor ferroviário. Consequentemente, o desenvolvimento das infraestruturas dos comboios elétricos desacelerou, e o caminho para haver comboios totalmente eletrificados tornou-se bastante longo. Nesse contexto, os comboios elétricos começaram a impor-se progressivamente, inicialmente pela combinação do motor Diesel e do motor elétrico, resultando numa locomotiva híbrida. No entanto, com o aumento da demanda pelo transporte, e com o aumento do preço dos combustíveis nas últimas décadas, os comboios elétricos afirmaram-se por poderem oferecer custos operacionais mais baixos, assim como melhor desempenho ambiental. Atualmente, a maioria dos comboios elétricos de alta velocidade utilizam sistema de tração em corrente alternada (CA), que oferece melhor desempenho na transmissão de energia a longa distância do que sistema de tração em corrente contínua CC. No entanto, o aumento do transporte ferroviário requer a melhoria da eficiência energética devido a haver mais passageiros e maiores requisitos de mobilidade. Na Europa, os sistemas de tração elétrica são classificados principalmente de acordo com os parâmetros de tensão e frequência (15 kV, 16,7 Hz) ou (1×25 kV ou 2×25 kV, 50 Hz). Em ambos os casos, os operadores ferroviários têm interesse absoluto em otimizar os custos. Nesse contexto, a melhoria da qualidade de energia elétrica na ferrovia suscitou mais atenção nas últimas décadas, principalmente pela introdução da eletrônica de potência. Posteriormente, várias soluções baseadas em conversores de eletrônica de potência foram propostas para melhorar a qualidade de energia elétrica na ferrovia, como por exemplo, os sistemas flexíveis de transmissão CA (FACTS – Flexible AC Transmission Systems). O condicionador ativo de potência ferroviário (RPC – Rail Power Conditioner) é um dos dispositivos FACTS que pode ser usado para melhorar a qualidade da energia elétrica, compensando o conteúdo harmônico, a potência reativa e os componentes de sequência negativa das correntes. Por outro lado, o conversor multinível modular (MMC – Modular Multilevel Converter) é uma solução atraente para aplicações de média tensão, devido à redução dos harmónicos e das perdas de comutação, e ao aumento da flexibilidade, confiabilidade e escalabilidade. Deste modo, o MMC foi aprimorado para ser integrado na família FACTS. Levando em consideração as oportunidades existentes no setor ferroviário, não apenas no desenvolvimento do próprio comboio elétrico, mas também na melhoria da qualidade de energia elétrica na ferrovia, existe um forte investimento no desenvolvimento tecnológico para os sistemas ferroviários eletrificados. Assim sendo, este trabalho apresenta uma nova topologia de conversor de eletrônica de potência (RPC baseado em MMC) que compensa os problemas de qualidade de energia elétrica associados aos sistemas de tração, reduzindo os custos operacionais dos comboios elétricos e otimizando a qualidade de energia da rede elétrica. As inovações principais do RPC baseado em MMC são a integração da topologia do MMC para operar como condicionador de qualidade de energia elétrica na ferrovia, beneficiando das vantagens do MMC. Neste contexto, o trabalho de investigação proposto e desenvolvido nesta tese apontou como objetivo projetar, desenvolver e validar um protótipo laboratorial em escala reduzida do RPC baseado em MMC, incluindo todos os algoritmos de controlo necessários e os modelos de simulação que são importantes para suportar a operação correta do sistema. Sob condições de simulação, este trabalho desenvolveu algoritmos de controlo para diferentes topologias do RPC (ponte completa, meia ponte, três fios, etc.), para demonstrar as capacidades gerais do sistema do RPC, e também para dois transformadores diferentes (V/V e Scott). O RPC mais favorável baseado na topologia do MMC (baseado no MMC de meia ponte) foi profunda e extensivamente simulado, nomeadamente utilizando uma abordagem de controlo preditivo. As simulações e os resultados experimentais confirmam a validade da teoria de controlo apresentada, bem como a capacidade de melhoria da qualidade de energia elétrica na solução proposta.
Fundação para a Ciência e a Tecnologia – FCT), which allowed me to continue my studies with the PD/BD/127815/2016 Ph.D. scholarship under the Innovation in Railway Systems and Technologies Doctoral Program – iRail.

碩士
逢甲大學
資訊工程所
92
With the growth quickly of the wireless network technology, there are more and more existent network servies trending to adopt wireless network technology. The popularization of IEEE 802.11 Wireless LAN and IEEE 802.16 Wireless Broadband Network, all make the wireless network technology become more and more important, and there are many relative technologies and products appeared. Following Bluetooth’s rise and development, Wireless Personal Area Network (WAPN) also became popular. Therefore, one application of WPAN – Wireless Sensor Network, also start to be discuss widely. Wireless Sensor Network (WSN) make use of a large number of sensor nodes to dispose in a particular range, and every sensor node must to sense the special information in the area (ex:temperature, humidity, pressure,etc). Then, transmit the data through wireless transmission technology to a special equipment (Sink) to analyze to sensing data and to do corresponding actions. WSN is one application of WPAN, there is no definite specifications. Now, many WSN research use IEEE 802.15.4 to design, it characteristic includes low rate, low transit distance, low power, simple architecture, low cost, small size, etc. All characteristic are similar to the applications of WSN. In IEEE 802.15.4, packets maybe occur collision or packet loss when sensor nodes try to transit. WSN’s transmission characteristic is differ from general network. General network always have large number of packets to be transmit, but WSN transmissive interval is long (1 min, 5 min, even 1 hour.).therefore, the characteristic of collision problem maybe differ from general network. IEEE 802.15.4 make use of CSMA/CA to solve collision problem, the CSMA/CA algorithm is similar to IEEE 802.11, but not all the same. We called Slotted CSMA/CA algorithm. I will explain in this paper. Furthermore, in this paper, I will aim at IEEE 802.15.4 collision mechanism, and use program to simulate the operation of IEEE 802.15.4. Finally, Analyze and estimate the performance of Slotted CSMA/CA algorithm, and try to find out the Slotted CSMA/CA’s optimum BE parameter in simulation result.

碩士
大同大學
資訊經營學系(所)
106
In recent years, with the trend of Internet services, personal information is often disclosed and compromised on the Internet. In order to enhance information security with consideration of communication convenience, most websites and communication software support HTTPS connection. Nowadays more than 50% of Internet traffic has taken HTTPS encrypted communication protocol. Previous studies focused on encrypted network communication trying to identify software connection signature. Their disadvantage is that if the version of signature varies with the time, the original signature is no more valid. In addition, they did not consider the connection security. This study started from establishing a system to monitor network traffic by collecting various kinds of communication protocols （such as SSL or TLS）. It also checked the validity of certificates by their issuers and valid dates of the certificates. To analyze the access to websites through secure channel, we use HTTPS （SSL/TLS） and credential information to determine the security of the connection. We use the version of SSL or TLS and the site digital certificate such as CA voucher issuing unit and expiration date as conditions for judging the security of HTTPS connection. The experimental results summarized from 20 experiments reveal that the security of the internal HTTPS connection within the enterprise can be identified. Advantage of this approach includes that version updates of software do not affect the effectiveness of our method. It is suggested that research in the future could include identifications of other software to increase connection security.

碩士
國立臺北科技大學
電腦與通訊研究所
97
In this paper, we propose the effective analysis methodology to be applied to the monitoring network of synchronous under the IEEE 802.15.4 standard, we call it real-time wireless sensor network (RT-WSN) in this network that is build for the “real-time” specific application. We aim at the slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) of algorithm of channel access mechanism in IEEE 802.15.4 MAC layer to build the network model and analyze the average packet delay over RT-WSN based on probability theory. The proposed theoretical analysis was nearly consistent with the correct result of simulation and the experiment. The result shows that this slotted CSMA/CA cannot be effectively applied to RT-WSN since it cannot avoid the high packet collision in the saturation throughput conditions. When receiving 10 sensor nodes, the packet delay caused by packet collision is 6.29 times more than one ideal model. Hence, we propose the like Time Division Multiple Access (TDMA) to improve CSMA/CA in packet collision problem. With neighbor table, TDMA can record the network states and implement the dynamic network configuration. Our experimental results show that TDMA can own the characteristics of the stable and limited packet delay. Once the total traffic load is lower than maximum throughput, it can guarantee the packet transmission of real-time without considering the amount of sensor nodes in network. Moreover, compare with CSMA/CA in 10 sensor nodes conditions, 57 % of the maximum throughput is improved. Therefore, we can meet with the QoS requirement of packet delay in RT-WSN. In the end, we install a remote ECG monitoring system for an example of application situation in the sanatorium. We provide steady wireless transmission media for the front of this system and reach the purpose of real-time remote medical care.

Στην παρούσα εργασία η ενασχόλησή μας αφορούσε τη σύνθεση και τον χαρακτηρισμό βιοενεργών γυαλιών. Οι συνθέσεις που πραγματοποιήθηκαν ήταν καθαρής SiO2, μικτών γυαλιών SiO2–ΜΟ (Μ=Ca, Mg) αλλά επίσης και γυαλιών σύστασης SiO2 –CaΟ–P2O5. Πραγματοποιήθηκαν παρασκευές με διάφορα ποσοστά τροποποιητών (Ca, Mg). Μετά την παρασκευή των υλικών ακολούθησε ο φυσικοχημικός χαρακτηρισμός τους με διάφορες τεχνικές όπως: προσδιορισμός ειδικής επιφάνειας και όγκου πόρων (ΒΕΤ), ηλεκτρονική μικροσκοπία σάρωσης (SEM), θερμοσταθμική ανάλυση (TGA), περίθλαση ακτίνων Χ (XRD) και φασματοσκοπία απορρόφησης υπερύθρου (IR). Μετά ακολούθησε μελέτη της βιοενεργότητας με εμβάπτιση σε διάλυμα SBF. Τα αποτελέσματα έδειξαν ότι τα γυαλιά που παρασκευάστηκαν είχαν μεσοπορώδη δομή ενώ όσον αφορά τη βιοενεργότητα τα γυαλιά σύστασης SiO2–CaO and SiO2–CaΟ–P2O5 προκάλεσαν σχηματισμό απατίτη στην επιφάνειά τους.
In the present thesis our work was focused on the study of the synthesis and characterization of bioactive glasses. Pure SiO2 and mixed glasses composed of SiO2–ΜΟ (Μ=Ca, Mg) and SiO2–CaΟ–P2O5 were prepared using different amounts of modifiers (Ca, Mg). Next the prepared materials were characterized by using various techniques such as: BET, SEM, TGA, XRD and IR. Finally their bioactivity was studied in vitro after immersion in SBF solution. It was found that the prepared materials showed a mesoporous structure. Regarding the bioactivity glasses with compositions of SiO2–CaO and SiO2–CaΟ–P2O5 induced the formation of apatite layer on their surface.

Text in German with summaries in German and English
Includes bibliographical references (leaves 197-211)
Biblical studies in New Testament are generating considerable interest in the investigation of historical groups, for example by using prosopographic approaches. This thesis presents a new approach to reconstruct the early Christian network in Acts 1-12. We consider the social network analyses (SNA), critical spatiality and Proximal Point Analyses (PPA). Although these approaches show interesting results, they suffer from a global distance measure. Thus, we introduce a novel approach combining SNA and critical spatiality to analyse geographic and social distances. This method represents a valuable alternative to traditional theological tools for answering exegetical questions concerning the social network in Acts 1-12 offering ways for re-thinking and re-interpretation. The network represents the first fulfillment of the promise given in Acts 1:8. Moreover, it allows us to distinguish between protagonists and their influence. Using different distance measurements, we were not only able to describe the high level of solidarity in this network but could also find strong evidences for Peter, Philip and Barnabas being key figures. Acts 1-12 describes mission as led by God and performed by different people with Jerusalem as the centre of activity. This mission is both peripheral and open to people with diverse social, religious and geographic backgrounds. In the novel network of people belonging to the body of Christ human leadership is not important. It was not possible to apply this method to all exegetical questions due to the fact that there are only limited historic sources available.
In der neutestamentlichen Wissenschaft wurden verschiedene Methoden wie die Prosopographie zur Erforschung bestimmter Personenkreise verwendet. Diese Arbeit beschäftigt sich mit der Rekonstruktion des frühchristlichen sozialen Netzwerks nach der Darstellung in Apg 1-12. Dazu wird die Methode der sozialen Netzwerkanalyse (SNA), der critical spatiality sowie die Proximal Point Analyse (PPA) verwendet. Dabei werden die methodischen Ansätze von verschiedenen historischen Netzwerkanalysen zusammengetragen und durch eine Verknüpfung von SNA und critical spatiality eine einheitliche Herangehensweise hergeleitet, die auch geographische wie soziale Distanzen darstellen kann. Dabei finden sich in Apg 1-12 sowohl exegetische Fragestellungen, auf die diese Methode aufgrund der schlechten Quellenlage nicht angewendet werden kann, als auch Fragestellungen, die mit dieser Methode unter neuen Gesichtspunkten interpretiert werden kann. So lässt sich im rekonstruierten Netzwerk von Apg 1-12 der erste Abschnitt der Erfüllung der Verheißung aus Apg 1,8 erkennen. Außerdem hilft die SNA, die einzelnen Akteure und ihr Handeln in der Apg besser zu würdigen. So ist ein eigenes Kapitel nicht nur Petrus, sondern auch Philippus und Barnabas gewidmet. Apg 1-12 stellt eine Mission dar, deren alleiniger Urheber Gott ist und die von verschiedensten Menschen mit der Stadt Jerusalem als Zentrum überwiegend dezentral und offen für verschiedene soziale, religiöse und geographische Hintergründe ausgeführt wird. Sie zeichnet ein besonderes Bild vom urchristlichen sozialen Netzwerk, das wenig menschliche Leitung beinhaltet und sich qualitativ unterscheidet. Die Analyse mit verschiedenen Zentralitätsmaßen zeigt ebenfalls die starke Verbundenheit der urchristlichen Gemeinschaft und den signifikanten Beitrag mehrerer Personen
New Testament
M. Th. (New Testament)

Data visualization techniques comprise crucial resources in many research and professional areas. Effective representations often contribute to the understanding of the overall picture behind a large volume of data, sometimes leading to novel discoveries or to an ef cient synthesis. Due to the large amount of data that computers handle nowadays, many modern data visualizations techniques were designed to deal with such large data sets, exhibiting unique characteristics. In the information era, computers (and their operators) and networks are also amongst the biggest sources of raw data, though they are also used in its processing and storage. Many network monitoring systems and security appliances make usage of traditional data visualization techniques in reporting functionalities or to provide practitioners with status information. The scope of this work falls within the intersection of the elds of network security and data visualization techniques. Its objectives are to study modern approaches to represent data, which may be currently being used in other areas, and apply one of those approaches in the visualization of network traf c and attacks. Assessing the usefulness of the visualizations was also an objective, along with the constitution of a large data set of representations for several traf c classes and classical network attacks. A technique known as Circos, widely used for genomic representations, was the one applied for achieving the objectives of this masters program. Many representations for at least 18 different traf c traces were produced along this work, with many analyzed with detail in this dissertation. These traces, containing traf c generated by contemporary applications and classical network attacks or probing activities, were selected from two datasets. In order to produce the Circos, a minimal set of traf c characteristics was identi ed,and several scripts for automating the processing were implemented. Towards the nal part of this work, an experiment based on the (human) comparison between nine labeled and nine unlabeled Circos was set up to demonstrate that the obtained representations were useful up to the point of being used to identify traf c classes or attacks. During the experiment, it was possible to correctly identify eight, out of the nine, traces (one of the attacks was incorrectly classi ed as HTTP traf c), proving the usefulness of this technique in this eld.
As técnicas de visualização de dados contêm recursos vitais em várias áreas, desde a pesquisa até há área pro ssional. Representações e cazes estão frequentemente a contribuir para a compreensão do quadro geral, a partir de um grande volume de dados, às vezes permite novas descobertas ou para uma síntese e ciente. Devido há grande quantidade de dados que os computadores lidam nos dias de hoje, muitas técnicas modernas de visualização de dados foram desenvolvidas para lidar com os grandes conjuntos de dados, permitindo perceber características únicas. Na era da informação, os computadores (e os seus utilizadores) e as redes estão entre as maiores fontes de dados, embora eles também sejam utilizados no seu processamento e armazenamento. Muitos sistemas de monitorização de rede e dispositivos de segurança fazem uso de técnicas de visualização de dados tradicionais para reportar funcionalidades ou para fornecer informações pro ssionais sobre o estado dos dados. O âmbito deste trabalho insere-se no cruzamento dos campos, das técnicas de segurança de rede e de visualização dos dados. Os objectivos são estudar abordagens modernas para representar os dados, que podem actualmente ser utilizados em outras áreas, e aplicar uma dessas abordagens na visualização de tráfego de rede e ataques. Avaliar a sua utilidade das visualiza ções também era um objectivo, juntamente com a constituição de um grande conjunto de representações para várias classes de tráfego e ataques de rede clássicos. A técnica conhecida como Circos, amplamente utilizada para representações genéticas, foi aplicada para alcançar os objectivos deste programa de mestrado. Muitas representações para pelo menos 18 conjuntos de tráfego diferentes foram produzidas ao longo deste trabalho, com muitas analisadas detalhadamente nesta dissertação. Esses conjuntos, contendo tráfego gerados pelas aplicações contemporâneas e ataques clássicos de rede ou actividades de sondagem, foram seleccionados a partir de dois conjuntos de dados. De forma a produzir o Circos, um conjunto mínimo de características de tráfego foram identi cadas, e foram implementados vários scripts para automatizar o processo. Para a parte nal deste trabalho, uma experiência baseada na comparação (humana) entre nove conjuntos conhecidos e nove desconhecidos foram criados. Para demonstrar que as representações foram úteis para identi car as classes de tráfegos ou ataques. Durante a experiência, foi possível identi car correctamente oito, dos nove conjuntos (um dos ataques foi incorrectamente classi cado como tráfego Hypertext Transfer Protocol (HTTP)), comprovando a utilidade desta técnica nesta área.