Le développement dans les micros systèmes électromécaniques (MEMS) combiné avec l'émergence des nouvelles technologies de l'information et de la communication a permis l'intégration des fonctionnalités de collecte, de traitement et de transmission des données dans un seul dispositif minuscule qui est le capteur sans fil. En voie de conséquence, les réseaux composés de ces capteurs offrent aujourd'hui une pléiade d'avantages par rapport aux réseaux traditionnels notamment en termes de simplicité et de coût de déploiement. Ceci a conduit au développement d'une gamme très variée d'applications des réseaux de capteurs sans fil dans les domaines de la santé, de l'environnement, de l'industrie, des infrastructures, des activités spatiales, ou encore des activités militaires et dans plusieurs autres domaines. Cependant, de nouveaux défis surgissent des caractéristiques particulières de ces réseaux. En réalité, de nombreuses applications de ces réseaux sont critiques et exigent qu'un fonctionnement correct du réseau soit maintenu le plus longtemps possible. Par contre, les environnements dans lesquels ces réseaux sont déployés rendent la mission de maintien en condition correcte de ces réseaux très compliquée et même parfois impossible ; d'où la nécessité d'intégrer des mécanismes d'auto-correction qui visent à surmonter les problèmes qui puissent surgir dans le réseau sans intervention humaine. Dans ce contexte, nous avons, dans cette thèse, concentré notre étude sur les techniques et les mécanismes mis en œuvre pour améliorer la propriété de tolérance aux pannes dans les réseaux de capteurs sans fil. Tout d'abord, nous avons proposé des approches centralisées et distribuées pour l'auto-rétablissement de la connectivité et la réallocation des canaux dans un contexte de réseaux de capteurs sans fil reposant sur des communications multi-canal après la panne d'un nœud critique. Après la formulation du problème sous la forme d'un problème d'optimisation multi-objectif, nous avons proposé des algorithmes basés sur des heuristiques de coloration de graphes et d'arbre de Steiner, très connus dans la théorie de graphes pour la résolution de ce type de problèmes. Dans une deuxième partie de cette thèse, nous avons étudié un cas d'application particulier, l'agriculture de précision, et avons proposé une solution distribuée pour le rétablissement du fonctionnement du réseau de capteurs sans fil / The development in Micro Electro-Mechanic Systems (MEMS) combined with the emergence of new information and communication technologies allowed the integration of the data sensing, processing and transmission in a single tiny device which is the wireless sensor. Consequently, the networks formed by these sensors offer a lot advantages compared with the traditional networks, in particular in terms of the deployment simplicity and cost. This led to the development of a wide range of Wireless Sensor Networks' applications in the domains of health, environment, industry, infrastructures, spatial activities, or even military activities and in many other domains. However, new challenges appear from the particular characteristics of these networks. In fact, many applications of this type of networks are critical and require that the correct functioning of the network is maintained as long as possible. However, the environments in which these networks are deployed return the mission of network maintenance very complicated or even impossible; hence, the necessity of integrating mechanisms of self-correction which aim to overcome the appeared problems without a human intervention. In this context, we focused our study on the techniques and mechanisms implemented to improve the property of fault tolerance in the wireless sensor networks. First, we proposed centralized and distributed approaches for the connectivity restoration and the channel reallocation in a multi-channel communication context after the failure of a critical node. After the formulation of the problem as a multi-objective optimization problem, we proposed some algorithms based on the heuristics of graphs coloring and Steiner tree, very known in the graph theory to solve this type of problems. In a second part in this thesis, we studied a particular application case, precision agriculture, and we proposed a distributed solution for the failure recovery in wireless sensor networks

Die Rolle und Wahrnehmung des World Wide Web in seinen unterschiedlichen Nutzungskontexten ändert sich zunehmend – von einem frühen Fokus auf reine Web-Interaktion mit Kunden, Informationssuchern und anderen Nutzern hin zum Web als eine Komponente in einer mehrkanaligen Informations- und Kommunikationsstrategie. Diese zentrale Entwicklung ermöglicht Firmen, eine wachsende Menge digitaler Konsumenteninformationen zu sammeln, zu analysieren und zu verwerten. Während Firmen von diesen Daten profitieren (z.B. für Marketingzwecke und zur Verbesserung der Bedienungsfreundlichkeit), hat die Analyse und Nutzung von Onlinedaten zu einem signifikanten Anstieg der Datenschutzbedenken bei Konsumenten geführt, was wiederum ein Haupthindernis für erfolgreichen E-Commerce ist. Die Implikationen für eine Firma sind, dass Datenschutzerfordernisse bei der Datenanalyse und -nutzung berücksichtigt und Datenschutzpraktiken effizient nach außen kommuniziert werden müssen. Diese Dissertation erforscht den Grenzbereich zwischen den scheinbar konkurrierenden Interessen von Onlinekonsumenten und Firmen. Datenschutz im Internet wird aus einer Konsumentenperspektive untersucht und Datenschutzanforderungen werden spezifiziert. Eine Gruppe von Geschäftsanalytiken für Webseiten wird präsentiert und es wird verdeutlicht, wie Datenschutzanforderungen in den Analyseprozess integriert werden können. Ein Design zur besseren Kommunikation von Datenschutz wird vorgestellt, um damit eine effizientere Kommunikation der Datenschutzpraktiken einer Firma gegenüber Konsumenten zu ermöglichen. Die vorgeschlagenen Lösungsansätze gestatten den beiden Gegenparteien, widerstreitende Interessen zwischen Datennutzung und Datenschutz auszugleichen. Ein besonderer Fokus dieser Forschungsarbeit liegt auf Mehrkanalhändlern, die den E-Commerce Markt derzeit dominieren. Die Beiträge dieser Arbeit sind im Einzelnen: * Messung von Vorbedingungen für Vertrauen im Mehrkanalhandel Der Erfolg des Mehrkanalhandels und die Bedeutung von Datenschutz werden aus einer Konsumentenperspektive dargestellt. Ein Strukturgleichungsmodell zur Erklärung von Konsumentenvertrauen in einen Mehrkanalhändler wird präsentiert. Vertrauen ist eine zentrale Vorbedingung für die Kaufbereitschaft. Ein signifikanter Einfluss der wahrgenommenen Reputation und Größe physischer Filialen auf das Vertrauen in einen Onlineshop wurde festgestellt. Dieses Resultat bestätigt unsere Hypothese, dass kanalübergreifende Effekte zwischen dem physischen Filialnetzwerk und einem Onlineshop existieren. Der wahrgenommene Datenschutz hat im Vergleich den stärksten Einfluss auf das Vertrauen. Die Resultate legen nahe, Distributionskanäle weiter zu integrieren und die Kommunikation des Datenschutzes zu verbessern. * Design und Test eines Web-Analyse-Systems Der Forschungsbeitrag zu Konsumentenwahrnehmungen im Mehrkanalhandel motiviert die weitere Untersuchung der Erfolgsfaktoren im Internet. Wir präsentieren ein Kennzahlensystem mit 82 Kennzahlen zur Messung des Onlineerfolges von Webseiten. Neue Konversionsmetriken und Kundensegmentierungsansätze werden vorgestellt. Ein Schwerpunkt liegt auf der Entwicklung von Kennzahlen für Mehrkanalhändler. Das Kennzahlensystem wird auf Daten eines Mehrkanalhändlers und einer Informationswebseite geprüft. * Prototypische Entwicklung eines datenschutzwahrenden Web Analyse Services Die Analyse von Webdaten erfordert die Wahrung von Datenschutzrestriktionen. Der Einfluss von Datenschutzbestimmungen auf das Kennzahlensystem wird diskutiert. Wir präsentieren einen datenschutzwahrenden Web Analyse Service, der die Kennzahlen unseres Web-Analyse-Systems berechnet und zudem anzeigt, wenn eine Kennzahl im Konflikt mit Datenschutzbestimmungen steht. Eine syntaktische Erweiterung eines etablierten Datenschutzstandards wird vorgeschlagen. * Erweiterung der Analyse von Datenschutzbedürfnissen aus Kundensicht Eine wichtige Anwendung, die Resultate des beschriebenen Web Analyse Services nutzt, sind Personalisierungssysteme. Diese Systeme verbessern ihre Effizienz mit zunehmenden Informationen über die Nutzer. Daher sind die Datenschutzbedenken von Webnutzern besonders hoch bei Personalisierungssystemen. Konsumentendatenschutzbedenken werden in einer Meta-Studie von 30 Datenschutzumfragen kategorisiert und der Einfluss auf Personalisierungssysteme wird beschrieben. Forschungsansätze zur datensschutzwahrenden Personalisierung werden diskutiert. * Entwicklung eines Datenschutz-Kommunikationsdesigns Eine Firma muss nicht nur Datenschutzanforderungen bei Web-Analyse- und Datennutzungspraktiken berücksichtigen. Sie muss diese Datenschutzvorkehrungen auch effektiv gegenüber den Seitenbesuchern kommunizieren. Wir präsentieren ein neuartiges Nutzer-Interface-Design, bei dem Datenschutzpraktiken kontextualisiert erklärt werden, und der Kundennutzen der Datenübermittlung klar erläutert wird. Ein Nutzerexperiment wurde durchgeführt, das zwei Versionen eines personalisierten Web-Shops vergleicht. Teilnehmer, die mit unserem Interface-Design interagierten, waren signifikant häufiger bereit, persönliche Daten mitzuteilen, bewerteten die Datenschutzpraktiken und den Nutzen der Datenpreisgabe höher und kauften wesentlich häufiger. / The aim of this thesis is to explore the border between the competing interests of online consumers and companies. Privacy on the Internet is investigated from a consumer perspective and recommendations for better privacy management for companies are suggested. The proposed solutions allow the resolution of conflicting goals between companies’ data usage practices and consumers’ privacy concerns. The research is carried out with special emphasis on retailers operating multiple distribution channels. These retailers have become the dominant player in e-commerce. The thesis presents a set of business analyses for measuring online success of Web sites. New conversion metrics and customer segmentation approaches have been introduced. The analysis framework has been tested on Web data from a large multi-channel retailer and an information site. The analysis of Web data requires that privacy restrictions must be adhered to. Thus the impact of legislative and self-imposed privacy requirements on our analysis framework is also discussed. We propose a privacy-preserving Web analysis service that calculates our set of business analyses and indicates when an analysis is not compliant with privacy requirements. A syntactical extension of a privacy standard is proposed. Moreover, an overview of consumer privacy concerns and their particular impact on personalization systems is provided, that is summarized in a meta-study of 30 privacy surveys. A company must not only respect privacy requirements in its Web analysis and usage purposes but it must also effectively communicate these privacy practices to its site visitors. A privacy communication design is presented, which allows more efficient communication of a Web site’s privacy practices directed towards the users. Subjects who interacted with our new interface design were significantly more willing to share personal data with the Web site. They rated its privacy practices and the perceived benefit higher and made considerably more purchases.

Internet når idag över 8 miljoner människor i Sverige och är en naturlig del av vardagen för många. För företag betyder detta en viktig marknadsföringskanal som inte bör underskattas. Genom att kommunicera med målgruppen via plattformer såsom sociala nätverk, bloggar och mikrobloggar kan företag erbjuda mervärde och bygga relationer online. Genom att utnyttja rätt marknadsföringskanal kan onlinemarknadsföring undvika att uppfattas som påträngande för konsumenten och istället inspirera på ett hjälpfullt sätt.Syftet med studien är att med en kartläggning av fast-fashionkonsumenters nätbeteende och attityder fastställa hur modeföretaget Gina Tricot som har flera försäljningskanaler kan öka besöksfrekvensen till den virtuella butiken genom marknadsföring online. Uppsatsen har en kvalitativ ansats med en fallstudiedesign. De insamlade empiriska data är av både kvalitativ och kvantitativ natur då både en bredd och ett djup har eftersträvats. Datamaterialet består av en webbenkät med 181 respondenter, strukturerade intervjuer på stan med 120 respondenter, två gruppintervjuer samt en personlig intervju med en marknadskoordinator.Det empiriska materialet har analyserats utifrån den teoretiska referensramen bestående av teorier om onlinemarknadsföring, konsumentbeteende samt multi-channel-återförsäljning. Studien har visat att bloggar är en stark marknadsföringskanal för modeföretag då konsumenterna känner en stor tillit till bloggare samt då det hjälper dem att förkorta köpprocessen. Analysen visar även att det genom sociala nätverk är viktigt för modeföretag att bygga relationer samt aktivt kommunicera med målgruppen för att skapa lojalitet. Andra starka kanaler har visat sig vara nyhetsbrev samt banners. För att stärka Gina Tricots webbutik har ett behov observerats av att uppmärksamma det breda sortiment som finns representerat på Internet då större utbud visat sig vara det starkaste motivet till onlineshopping i studien. Resultatet visade även att webbutiken behöver erbjuda en högre visuell upplevelse då exponeringen av produkterna på ginatricot.com idag inte överkommer den stora riskuppfattning som köp av kläder online innebär för konsumenten. Sett utifrån ett marknadsföringsperspektiv kan denna förändring ha en positiv word of mouth effekt samt kan till fördel användas vid exponering av produkter på sociala nätverk.Internet reaches today over 8 million people in Sweden and has become a natural part of the everyday life. For companies this means a marketing channel too important to ignore. By communicating with the target group via social networks, blogs and micro blogs the company is able to offer an added value and to build relationships online. By choosing the right marketing channel and strategy the online marketing is able to avoid being seen as intrusive and the consumer could instead perceive the marketing as inspiring and helpful. When using a multichannel perspective offering e-commerce, marketing online becomes important to manage increased awareness and generate more traffic to the web site.The purpose of the study is by the identification of fast fashion consumer’s behavior and attitudes determine how the fashion company Gina Tricot is able to increase the traffic to their virtual store through marketing online. The paper has a case study design with a qualitative approach. The empirical data are both qualitative and quantitative to ensure a depth and a width to the thesis. The gathering of the data has been made through a web survey which consists of 181 respondents, 120 structured interviews, two group interviews and one interview with a market coordinator. The gathered empirics have been analyzed according to the theoretical framework which consists of theories regarding online marketing, consumer behavior and multi-channel retailing.The findings made in the thesis show that blogs are a strong marketing channel because of the great trust consumers feel towards bloggers and since blogs also help consumers to abbreviate the buying process. The analysis also shows that it is important to build relationships on social networks and to actively keep a two-way communication in order to create loyalty. Other effective marketing channels are companies’ newsletters and banner ads. To strengthen the image of the online store of Gina Tricot we have observed a need to inform the consumer of the wide and more unique assortment they offer online since a larger assortment and uniqueness has shown being the strongest reason for online shopping in this thesis. The result also showed that the web shop needs to provide a higher visual experience since the exposure of today’s products on ginatricot.com do not overcome the consumer’s risk perception of buying clothes online. From a marketing perspective this change can have a positive word of mouth effect among consumers and can be used positively when displaying products on social networks. / Program: Textilekonomutbildningen

Ce travail de thèse traite du développement d’une antenne microphonique compacte et d’une chaîne de traitement du signal dédiée, pour la reconnaissance et la localisation angulaire de cibles aériennes. L’approche globale proposée consiste en une détection initiale de cible potentielle, la localisation et le suivi de la cible, et une détection affinée par un filtrage spatial adaptatif informé par la localisation de la cible. Un algorithme original de localisation goniométrique est proposé. Il utilise l’algorithme RANSAC sur des données pression-vitesse large bande [100 Hz - 10 kHz], estimées en temps réel, dans le domaine temporel, par des différences et sommes finies avec des doublets de microphones à espacements inter-microphoniques adaptés à la fréquence. L’extension de la bande passante de l’antenne en hautes fréquences est rendue possible par l’utilisation de différences finies d’ordre élevé, ou de variantes de la méthode PAGE (Phase and Amplitude Gradient Estimation) adaptées à l’antenne développée. L’antenne acoustique compacte ainsi développée utilise 32 microphones MEMS numériques répartis dans le plan horizontal sur une zone de 7.5 centimètres, selon une géométrie d’antenne adaptée aux l’algorithmes de localisation et de filtrage spatial employés. Des essais expérimentaux de localisation et de suivi de trajectoire contrôlée par une sphère de spatialisation dans le domaine ambisonique ont montré une erreur de localisation moyenne de 4 degrés. Une base de données de signatures acoustiques de drones en vol a été créée, avec connaissance de la position du drone par rapport à l’antenne microphonique apportée par des mesures GPS. L’augmentation des données par bruitage artificiel, et la sélection dedescripteurs acoustiques par des algorithmes évolutionnistes, ont permis de détecter un drone inconnu dans un environnement sonore inconnu jusqu’à 200 mètres avec le classifieur JRip. Afin de faciliter la détection et d’en augmenter la portée, l’étape de détection initiale est précédée d’une formation de voies différentielle dans 4 directions principales (nord, sud, est, ouest), et l’étape de détection affinée est précédée d’une formation de voies de Capon informée par la localisation et le suivi de la cible à identifier. / This thesis deals with the development of a compact microphone array and a dedicated signal processing chain for aerialtarget recognition and direction of arrival (DOA) estimation. The suggested global approach consists in an initial detection ofa potential target, followed by a DOA estimation and tracking process, along with a refined detection, facilitated by adaptivespatial filtering. An original DOA estimation algorithm is proposed. It uses the RANSAC algorithm on real-time time-domainbroadband [100 Hz - 10 kHz] pressure and particle velocity data which are estimated using finite differences and sums ofsignals of microphone pairs with frequency-dependent inter-microphone spacings. The use of higher order finite differences, or variants of the Phase and Amplitude Gradient Estimation (PAGE) method adapted to the designed antenna, can extend its bandwidth at high frequencies. The designed compact microphone array uses 32 digital MEMS microphones, horizontally disposed over an area of 7.5 centimeters. This array geometry is suitable to the implemented algorithms for DOA estimation and spatial filtering. DOA estimation and tracking of a trajectory controlled by a spatialization sphere in the Ambisonic domain have shown an average DOA estimation error of 4 degrees. A database of flying drones acoustic signatures has been set up, with the knowledge of the drone’s position in relation to the microphone array set out by GPS measurements. Adding artificial noise to the data, and selecting acoustic features with evolutionary programming have enabled the detection of an unknown drone in an unknown soundscape within 200 meters with the JRip classifier. In order to facilitate the detection and extend its range, the initial detection stage is preceded by differential beamforming in four main directions (north, south, east, west), and the refined detection stage is preceded by MVDR beamforming informed by the target’s DOA.

許多學者紛紛提出專屬資產對品牌忠誠度的影響，本研究主要想探討不同的專屬資產種對品牌忠誠度的影響。其中將專屬資產種類分為：特有使用知識專屬資產；特有實體設備、軟體或服務專屬資產；忠誠客戶優惠專屬資產；無形專屬資產；心理層面認同專屬資產；特有無形社會壓力專屬資產。 隨著網路普及，網路也漸漸改變我們的購物模式。近年來許多廠商紛紛採用多重通路的模式以增加其效益，而消費者也依本身偏好利用不同通路進行產品資訊蒐集及交易等行為。因此本研究的另一主軸為專屬資產種類將如何影響消費者對品牌之官方網站的購物態度及購物意願，又此對官方網站的購物態度將如何影響消費者之多重通路購物意願。本研究以百貨公司專櫃化妝品為例，探討專櫃品牌和消費者所建立的專屬資產種類會如何影響消費者之品牌忠誠度及對官方網站的購物態度、購物意願，以及對官方網站的購物態度又會如何影響其在百貨專櫃及在官方網站的購物意願。 研究結果發現，特有使用知識專屬資產、特有實體設備、軟體或服務專屬資產、忠誠客戶優惠專屬資產、無形專屬資產、心理層面認同專屬資產都和品牌忠誠度呈正相關，唯特有的無形社會壓力專屬資產對品牌忠誠度無顯著相關。而其中僅忠誠客戶優惠專屬資產對官方網站的購買意願呈負相關。對官方網站的購物態度則和在官網蒐集資訊在專櫃購買、在專櫃試用在官網購買、在官網蒐集資訊在官網購買皆呈現正相關，表示對官網的購物態度愈正面，愈可能透過官網進行資訊蒐集或購買之行為。

<p>Purpose/Aim: The aim of this thesis was to examine how multi channel publishing in different stages effect the work for journalists.</p><p>Material/Method: The thesis is based on ten case studies selected from the literature and one conducted especially for this thesis. The case studies have been categorized according to a model that describes three strategies for multi channel publishing. The first strategy is to have a primary publishing channel, the second is to have separate editorial staffs for all publishing channels and the third is to treat all publishing channels equally.</p><p>Main results: Journalists working for companies using the first strategy have not experienced any major differences in working conditions or work practices. For journalists employed by companies using the second strategy for multi channel publishing the effects on the journalists was noticeable but not major. The effects on journalists in companies using the third strategy are mainly stress and an uncertainty regarding how to use special media techniques.</p>

Purpose/Aim: The aim of this thesis was to examine how multi channel publishing in different stages effect the work for journalists. Material/Method: The thesis is based on ten case studies selected from the literature and one conducted especially for this thesis. The case studies have been categorized according to a model that describes three strategies for multi channel publishing. The first strategy is to have a primary publishing channel, the second is to have separate editorial staffs for all publishing channels and the third is to treat all publishing channels equally. Main results: Journalists working for companies using the first strategy have not experienced any major differences in working conditions or work practices. For journalists employed by companies using the second strategy for multi channel publishing the effects on the journalists was noticeable but not major. The effects on journalists in companies using the third strategy are mainly stress and an uncertainty regarding how to use special media techniques.

The popularity of ubiquitous Internet services has spurred the fast growth of wireless communications by launching data hungry multimedia applications to mobile devices. Powered by spectrum agile cognitive radios, the newly emerged cognitive radio networks (CRN) are proposed to provision the efficient spectrum reuse to improve spectrum utilization. Unlicensed users in CRN, or secondary users (SUs), access the temporarily idle channels in a secondary and opportunistic fashion while preventing harmful interference to licensed primary users (PUs). To effectively detect and exploit the spectrum access opportunities released from a wide spectrum, the heterogeneous wireless channel characteristics and the underlying prioritized spectrum reuse features need to be considered in the protocol design and resource management schemes in CRN, which plays a critical role in unlicensed spectrum sharing among multiple users. The purpose of this dissertation is to address the challenges of utilizing heterogeneous wireless channels in CRN by its intrinsic dynamic and diverse natures, and build the efficient, scalable and, more importantly, practical dynamic spectrum access mechanisms to enable the cost-effective transmissions for unlicensed users. Note that the spectrum access opportunities exhibit the diversity in the time/frequency/space domain, secondary transmission schemes typically follow three design principles including 1) utilizing local free channels within short transmission range, 2) cooperative and opportunistic transmissions, and 3) effectively coordinating transmissions in varying bandwidth. The entire research work in this dissertation casts a systematic view to address these principles in the design of the routing protocols, medium access control (MAC) protocols and radio resource management schemes in CRN. Specifically, as spectrum access opportunities usually have small spatial footprints, SUs only communicate with the nearby nodes in a small area. Thus, multi-hop transmissions in CRN are considered in this dissertation to enable the connections between any unlicensed users in the network. CRN typically consist of intermittent links of varying bandwidth so that the decision of routing is closely related with the spectrum sensing and sharing operations in the lower layers. An efficient opportunistic cognitive routing (OCR) scheme is proposed in which the forwarding decision at each hop is made by jointly considering physical characteristics of spectrum bands and diverse activities of PUs in each single band. Such discussion on spectrum aware routing continues coupled with the sensing selection and contention among multiple relay candidates in a multi-channel multi-hop scenario. An SU selects the next hop relay and the working channel based upon location information and channel usage statistics with instant link quality feedbacks. By evaluating the performance of the routing protocol and the joint channel and route selection algorithm with extensive simulations, we determine the optimal channel and relay combination with reduced searching complexity and improved spectrum utilization. Besides, we investigate the medium access control (MAC) protocol design in support of multimedia applications in CRN. To satisfy the quality of service (QoS) requirements of heterogeneous applications for SUs, such as voice, video, and data, channels are selected to probe for appropriate spectrum opportunities based on the characteristics and QoS demands of the traffic along with the statistics of channel usage patterns. We propose a QoS-aware MAC protocol for multi-channel single hop scenario where each single SU distributedly determines a set of channels for sensing and data transmission to satisfy QoS requirements. By analytical model and simulations, we determine the service differentiation parameters to provision multiple levels of QoS. We further extend our discussion of dynamic resource management to a more practical deployment case. We apply the experiences and skills learnt from cognitive radio study to cellular communications. In heterogeneous cellular networks, small cells are deployed in macrocells to enhance link quality, extend network coverage and offload traffic. As different cells focus on their own operation utilities, the optimization of the total system performance can be analogue to the game between PUs and SUs in CRN. However, there are unique challenges and operation features in such case. We first present challenging issues including interference management, network coordination, and interworking between cells in a tiered cellular infrastructure. We then propose an adaptive resource management framework to improve spectrum utilization and mitigate the co-channel interference between macrocells and small cells. A game-theory-based approach is introduced to handle power control issues under constrained control bandwidth and limited end user capability. The inter-cell interference is mitigated based upon orthogonal transmissions and strict protection for macrocell users. The research results in the dissertation can provide insightful lights on flexible network deployment and dynamic spectrum access for prioritized spectrum reuse in modern wireless systems. The protocols and algorithms developed in each topic, respectively, have shown practical and efficient solutions to build and optimize CRN.

Είναι γεγονός ότι το ηλεκτροκαρδιογράφημα είναι ένα πολύ καλά μελετημένο σήμα. Ειδικά τα τελευταία χρόνια, έχει προταθεί ένας μεγάλος αριθμός αλγορίθμων επεξεργασίας, συμπίεσης, αυτόματης διάγνωσης, φιλτραρίσματος, αποθορυβοποίησης και κωδικοποίησης. Σ’ αυτή τη διπλωματική εργασία, προτείνουμε ένα αποδοτικό αλγόριθμο κωδικοποίησης χωρίς απώλειες για δεδομένα από δωδεκακάναλλο ηλεκτροκαρδιογράφημα. Ο κωδικοποιητής υλοποιεί ένα πολυγραμμικό μοντέλο υψηλής απόδοσης, το οποίο είναι «ειδικευμένο στους ασθενείς», ενδοκαναλικής πρόβλεψη και εφαρμόζει το πρότυπο κωδικοποίησης MPEG-4 ALS για διακαναλική πρόβλεψη και κωδικοποίηση. Τα αποτελέσματα του αλγορίθμου συγκρίθηκαν με τεχνικές κωδικοποίησης εντροπίας χωρίς απώλειες και δείχνουν αύξηση της απόδοσης κωδικοποίησης. / The Electrocardiogram (ECG) is one of the most well studied medical signals. A large number of ECG processing algorithms have being proposed over the years covering the areas of ECG noise filtering, automated diagnostic interpretation and coding. In this master thesis, we propose a robust multi-channel ECG encoder architecture, which operates on 12-channel ECG data. The encoder utilizes highly efficient multi-linear patient specific models for inter-channel prediction and the MPEG-4 Audio Lossless Coding (ALS) architecture for intra-channel prediction and coding. The results of the algorithm show improved performance over standard encoding techniques.

The popularity of ubiquitous Internet services has spurred the fast growth of wireless communications by launching data hungry multimedia applications to mobile devices. Powered by spectrum agile cognitive radios, the newly emerged cognitive radio networks (CRN) are proposed to provision the efficient spectrum reuse to improve spectrum utilization. Unlicensed users in CRN, or secondary users (SUs), access the temporarily idle channels in a secondary and opportunistic fashion while preventing harmful interference to licensed primary users (PUs). To effectively detect and exploit the spectrum access opportunities released from a wide spectrum, the heterogeneous wireless channel characteristics and the underlying prioritized spectrum reuse features need to be considered in the protocol design and resource management schemes in CRN, which plays a critical role in unlicensed spectrum sharing among multiple users. The purpose of this dissertation is to address the challenges of utilizing heterogeneous wireless channels in CRN by its intrinsic dynamic and diverse natures, and build the efficient, scalable and, more importantly, practical dynamic spectrum access mechanisms to enable the cost-effective transmissions for unlicensed users. Note that the spectrum access opportunities exhibit the diversity in the time/frequency/space domain, secondary transmission schemes typically follow three design principles including 1) utilizing local free channels within short transmission range, 2) cooperative and opportunistic transmissions, and 3) effectively coordinating transmissions in varying bandwidth. The entire research work in this dissertation casts a systematic view to address these principles in the design of the routing protocols, medium access control (MAC) protocols and radio resource management schemes in CRN. Specifically, as spectrum access opportunities usually have small spatial footprints, SUs only communicate with the nearby nodes in a small area. Thus, multi-hop transmissions in CRN are considered in this dissertation to enable the connections between any unlicensed users in the network. CRN typically consist of intermittent links of varying bandwidth so that the decision of routing is closely related with the spectrum sensing and sharing operations in the lower layers. An efficient opportunistic cognitive routing (OCR) scheme is proposed in which the forwarding decision at each hop is made by jointly considering physical characteristics of spectrum bands and diverse activities of PUs in each single band. Such discussion on spectrum aware routing continues coupled with the sensing selection and contention among multiple relay candidates in a multi-channel multi-hop scenario. An SU selects the next hop relay and the working channel based upon location information and channel usage statistics with instant link quality feedbacks. By evaluating the performance of the routing protocol and the joint channel and route selection algorithm with extensive simulations, we determine the optimal channel and relay combination with reduced searching complexity and improved spectrum utilization. Besides, we investigate the medium access control (MAC) protocol design in support of multimedia applications in CRN. To satisfy the quality of service (QoS) requirements of heterogeneous applications for SUs, such as voice, video, and data, channels are selected to probe for appropriate spectrum opportunities based on the characteristics and QoS demands of the traffic along with the statistics of channel usage patterns. We propose a QoS-aware MAC protocol for multi-channel single hop scenario where each single SU distributedly determines a set of channels for sensing and data transmission to satisfy QoS requirements. By analytical model and simulations, we determine the service differentiation parameters to provision multiple levels of QoS. We further extend our discussion of dynamic resource management to a more practical deployment case. We apply the experiences and skills learnt from cognitive radio study to cellular communications. In heterogeneous cellular networks, small cells are deployed in macrocells to enhance link quality, extend network coverage and offload traffic. As different cells focus on their own operation utilities, the optimization of the total system performance can be analogue to the game between PUs and SUs in CRN. However, there are unique challenges and operation features in such case. We first present challenging issues including interference management, network coordination, and interworking between cells in a tiered cellular infrastructure. We then propose an adaptive resource management framework to improve spectrum utilization and mitigate the co-channel interference between macrocells and small cells. A game-theory-based approach is introduced to handle power control issues under constrained control bandwidth and limited end user capability. The inter-cell interference is mitigated based upon orthogonal transmissions and strict protection for macrocell users. The research results in the dissertation can provide insightful lights on flexible network deployment and dynamic spectrum access for prioritized spectrum reuse in modern wireless systems. The protocols and algorithms developed in each topic, respectively, have shown practical and efficient solutions to build and optimize CRN.