Дисертації з теми "Application layer protocol"

The transmission of haptic information over the network has recently received significant attention. The wide spectrum of haptic applications makes it difficult to capture the widely varying requirements of these applications into one generic protocol. In this paper, we introduce ALPHAN (Application Layer Protocol for Haptic Networking), a novel application layer protocol for haptic communication. The protocol is strategically placed at the application layer so that it can easily be customized according to the application requirements and needs. An extension to the HAptic Meta-Language (HAUL) is proposed to define its networking parameters. The protocol introduces the concept of Multiple Buffering where priorities are attributed to different sending buffers in a collaborative haptic environment. The protocol also supports some concepts introduced in previous haptic communication protocols like local lag and key packets.

The Session Initiation Protocol (SIP) was first published in 1999, by the Internet Engineering Task Force (IETF), to be the standard for multimedia transfers. SIP is a peer-to-peer signaling protocol that is capable of initiating, modifying, and terminating media sessions. SIP utilizes existing Internet Protocols (IP) such as Domain Name Service (DNS) and the Session Description Protocol (SDP), allowing it to seamlessly integrate into existing IP networks. As SIP has matured and gained acceptance, its deficiencies when functioning as a multipoint communications protocol have become apparent. SIP currently supports two modes of operation referred to as conferencing and multicasting. Conferencing is the unicast transmission of session information between conference members. Multicasting uses IP multicast to distribute session information. This thesis proposes an extension for the Session Initiation Protocol that improves functionality for multipoint communications. When using conferencing, a SIP user-agent has limited information about the conference it is taking part in. This extension increases the awareness of a SIP node by providing it with complete conference membership information, the ability to detect neighboring node failures, and the ability to automatically repair conference partitions. Signaling for conferencing was defined and integrated into a standard SIP implementation where it was used to demonstrate the above capabilities. Using a prototype implementation, the additional functionality was shown to come at the cost of a modest increase in transaction message size and processing complexity. IP multicast has limited deployment in todayâ s networks reducing the usability of this useful feature. Since IP multicast support is not guaranteed, the use of application layer multicast protocols is proposed to replace the use of IP multicast. An efficient means of negotiating an application layer protocol is proposed as well as the ability to provide the protocol with session information to begin operation. A ring protocol was defined and implemented using the proposed extension. Performance testing revealed that the application layer protocol had slightly higher processing complexity than conferencing, but on average had a smaller transaction message size.
Master of Science

The emerging technology of active RFID tags has strong potential in the areas of real time health monitoring, sorting of cargo, and large scale inventory management because of their longer communication range and larger data storage capacity. The market of active RFID is growing very rapidly and therefore there has been an increase in the number of companies engaging in this field. But very often it is found that the products available in the market are not always suited to the application at hand. To overcome this problem, off the shelf active RFID products which were reconfigurable and followed a standard PHY and MAC layer protocol were used for this work. By reprogramming the application layer protocol of the RFID hardware, these devices were made suitable for the desired application. This also allowed the RFID tags to extend their functionality by interfacing extra modules with themselves. The work presented in this thesis describes the way in which the microcontroller on board the active RFID tags and readers can be programmed so that the functionality of the RFID hardware can be changed as per requirements. It also shows that extra modules can be added to the tag by successfully interfacing an accelerometer module with the tag.
Master of Science

IP multicast is typically used to support message transmission among entities in collaborative virtual simulations running on Intranets, especially military training simulations. But, IP Multicast is mostly not available on the Internet because it is not deployable by ISP's due to undefined billing at the source and unlimited amount of overlay topologies for data transmission. Alternatively, researches have in recent years proposed the use of Application Layer Multicasting techniques (ALM) to alleviate this problem and to allow a somewhat scalable message passing among peers in a group of users on the Internet. As the number of users grows in the session, efficient handling of resources and scalable communication between users becomes critical due to network traffic and computation required to track all objects in the session. In this thesis, peer-to-peer communication architecture for distributed simulation is proposed. The architecture uses both proxies and end-systems to provide a number of communication services: (1) Best effort LAN multicast; (2) Timely-reliable LAN multicast; (3) Best effort peer to peer delivery on the Internet; (4) Timely-reliable peer to peer delivery on the Internet, and (5) Any combination of the above, including LAN to Internet translation and vice versa. The main achievement of this research could be summarized as the design, justification, and implementation of an architecture that, in comparison to others, has higher efficiency and guaranteed reliability for performing tightly synchronous collaborative tasks in Collaborative Virtual Environments (CVEs).

High-performance networking (HPN) is of significance today in order to enable next-generation applications using wired and wireless networks. Some of the examples of HPN include low-latency industrial sensing, monitoring and automation using Wireless Sensor Networks (WSNs). HPN however requires protocol optimization at many layers of the open system interface (OSI) network model in order to meet the stringent performance constraints of the given applications. Furthermore, these protocols need to be impervious to denial of service (DoS) and distributed DoS (DDoS) attacks. Some of the key performance aspects of HPN are low point-to-point and end-to-end latency, high reliability of transmitted frames and performance predictability under various network load situations. This work focuses on two discrete issues in designing protocols for HPN applications. The first research issue looks at the Medium Access Control (MAC) layer of the OSI network model for designing of MAC protocols that provide low-latency and high reliability for point-to-point communication under a WSN. Existing standards in this area are governed by IEEE 802.15.4 specification which defines protocols for MAC and PHY layers for short-range, low bit-rate, and low-cost wireless networks. However, the IEEE 802.15.4 specification is inefficient in terms of latency and reliability performance and, as a result, is unable to meet the stringent operational requirements as defined by counterpart wired sensor networks. Work presented under current research issue describes new MAC protocols that are able to show low-latency transmission performance under strict timing constants for power limited WSNs. This enhancement of the MAC protocols is named extended GTS (XGTS) contained under extended CFP (ECFP) and is published under the IEEE's 802.15.4e standard. The second research issue focuses on the application layer of the OSI network model to design protocols that enhance the robustness of the text based protocols to various traffic inputs. The purpose of this is to increase the reliability of the given text based application layer protocol under a varied load. Session Initiation Protocol (SIP) is used as a case study and the work aims to build algorithms that ensure that SIP can continue to function under specific traffic conditions, which would otherwise deem the protocol useless due to DoS and DDoS attacks. Proposed algorithms investigate techniques that enhance the robustness of the SIP against parsing attacks without performing a deep parse of the protocol data unit (PDU). The desired effect of this is to reduce the time spent in parsing the SIP messages at a SIP router and as a result increase the number of SIP messages processed per unit time at a SIP router.

This thesis analyzes Application Layer security protocols for certificate enrollment and management. EDHOC, Ephemeral Diffie-HellmanOver COSE, is a recently developed key exchange protocol whichis designed to provide authentication and key-exchange functionality with compact message sizes and minimum round-trip-time. The workof this thesis extends the EDHOC protocol with a certificate enrollment functionality, targeting IoT constrained devices and it has been implemented for analysis and evaluation purposes. The main scope of this document is to study the security, performance and scalability (in descendingorder of importance) of enrollment over EDHOC compared to other certificate enrollment protocols.
Detta examensarbete analyserar säkerhetsprotokoll av typen ApplicationLayer för certifikatregistrering och hantering. EDHOC, Ephemeral Diffie-Hellman Over COSE, har implementerats, analyserats och utvärderats. EDHOC är ett nyligen utvecklat Application Layer-protokoll som är utformat för att tillhandahålla autentiserings- och nyckelfunktionsfunktioner med kompakta meddelandestorlekar och minimala rundturstider, inriktat på IoT-begränsade enheter. Huvudområdet för examensarbetet är att studera säkerhet, prestanda och skalbarhet (i fallande ordning av betydelse) hos EDHOC jämfört med andra föreslagna Application Layer-säkerhetsprotokoll som utför certifikatsskrivning.

Загальний обсяг роботи: 76 сторінок, 19 ілюстрацій, 17 таблиць, перелік посилань із X найменувань. Актуальність теми. Область використання платформи Thingspeak обмежена необхідністю використання протоколу HTTP для взаємодії з клієнтськими пристроями. В останні роки набувають все більшої популярності альтернативні протоколи, спроектовані для інтернету речей і пристрої на їх базі, чим обумовлена необхідність розширення платформи Thingspeak для додавання підтримки даних протоколів і пристроїв. Мета та задачі дослідження Аналіз підходів до розширення області використання платформи Thingspeak з подальшим забезпеченням можливості використання існуючих рішень, які взаємодіють, використовуючи протокол який не підтримуються розглянутою платформою. Головним завданням є дослідження, що полягає у проектуванні проміжного додатку для забезпечення взаємодії пристроїв, які використовують протокол MQTT з платформою Thingspeak. Вирішення поставлених завдань та досягнуті результати В результаті виконання роботи була реалізована система, що здійснює трансляцію протоколів MQTT та HTTP з проміжною конвертацією даних у формат, що відповідає моделі даних платформи Thingspeak. Дана реалізація також включає можливість встановлення правил, за якими відбувається конвертація. Для керування параметрами конвертації даних було розроблено веб-додаток з графічним інтерфейсом адміністратора. Система проста у розгортанні та може бути використана як доповнення до розгорнутої платформи Thingspeak. Об’єкт дослідження. Інтернет речей. Предмет дослідження. Мережева взаємодія між додатками Інтернету речей. Підходи до створення додатків, які виконують функцію трансляції протоколів прикладного рівня. Методи дослідження. Для вирішення проблеми в даній роботі використовуються методи аналізу, синтезу, системного аналізу, порівняння та логічного узагальнення результатів. Наукова новизна. Наукова новизна роботи полягає у аналізі та реалізації методів, що дозволяють конвертувати не підтримуваний системою Thingspeak протокол MQTT у HTTP. Практичне значення одержаних результатів. Розроблений додаток може бути розгорнутий на кафедральній інфраструктурі. Він включає в собі зручний користувацький інтерфейс для встановлення конфігурацій та може бути використаний для інтеграції існуючих додатків з підтримкую протоколу MQTT та кафедральної платформи Thingspeak.
The thesis contains 76 pages, 19 figures, 19 tables, 25 references. Relevance. The scope of the Thingspeak platform is limited by the need to use the HTTP protocol to interact with client devices. In recent years, alternative protocols have been developed for the Internet of things and devices on their base are becoming increasingly popular, due to the need to expand the Thingspeak platform to add support for these protocols and devices. Purpose. An analysis of approaches to extending the use of the Thingspeak platform, further enabling the use of existing solutions that implement the protocol but are not supported by the platform under consideration. The main task is to study the design of an intermediate application to interoperate devices that use the MQTT protocol with the Thingspeak platform. Results. As a result of the work, a system that transmits MQTT and HTTP protocols with an intermediate data conversion into a format that matches the Thingspeak data model was implemented. This implementation also includes the ability to set the rules for which the conversion is carried out. To manage the data conversion parameters, a web application with a graphical user interface was developed. The system is easy to deploy and can be used as a complement to existing technology with Thingspeak platform. Object of research. Internet of Things. Subject of research. Networking between Internet applications of things. Approaches to creating applications that perform the function of translating application level protocols. Research methods. In order to solve the problem in this work, methods of analysis, synthesis, system analysis, comparison and logical generalization of the results are used. Scientific novelty. The scientific novelty of the work consists in the analysis and implementation of methods that allow the conversion of the Thingspeak-compliant MQTT protocol to HTTP. Practical value. The developed application can be deployed on the existing university infrastructure. It includes a convenient interface for describing configurations and can be used to integrate existing applications supporting the MQTT protocol and the Thingspeak platform.
Общий объем работы 76 страниц, 19 иллюстраций, 19 таблицы, список литературы из 25 наименований. Актуальность темы. Область применения платформы Thingspeak ограничена необходимостью использования протокола HTTP для взаимодействия с клиентскими устройствами. В последние годы приобретают все большую популярность альтернативные протоколы, разработанные для интернета вещей и устройства на их базе, чем обусловлена необходимость расширения платформы Thingspeak для добавления поддержки данных протоколов и устройств. Цель и задачи исследования. Анализ подходов к расширению области использования платформы Thingspeak с последующим обеспечением возможности использования существующих решений, реализующих протокол, но не поддерживаются рассматриваемой платформой. Главной задачей является исследование, заключающееся в проектировании промежуточного приложения для обеспечения взаимодействия устройств, использующих протокол MQTT с платформой Thingspeak. Решение поставленных задач и достигнутые результатах В результате выполнения работы была реализована система, осуществляющая трансляцию протоколов MQTT и HTTP с промежуточной конвертацией данных в формат, соответствующий модели данных платформы Thingspeak. Данная реализация также включает возможность установки правил, по которым происходит конвертация. Для управления параметрами конвертации данных был разработан веб-приложение с графическим интерфейсом администратора. Система проста в развертывании и может быть использована как дополнение к развернутой платформе Thingspeak. Объект исследования. Интернет вещей. Предмет исследования. Сетевое взаимодействие между приложениями Интернета вещей. Подходы к созданию приложений, которые выполняют функцию трансляции протоколов прикладного уровня. Методи исследования. Для решения проблемы в данной работе используются методы анализа, синтеза, системного анализа, сравнения и логического обобщения результатов. Научная новизна. Научная новизна работы заключается в анализе и реализации методов, позволяющих конвертировать неподдерживаемый системой Thingspeak протокол MQTT в HTTP. Практическое значение полученных результатов Разработанное приложение может быть развернуто на кафедральной инфраструктуре. Оно включает в себя удобный интерфейс для описания конфигураций и может быть использован для интеграции существующих приложений с поддержкой протокола MQTT и кафедральной платформы Thingspeak.

This research investigates Denial of Service (DoS) attacks targeting the Internet’s Application Layer protocols, namely Session Initiation Protocol (SIP), and SPDY, the proposed second version of the Hyper Text Transfer Protocol (HTTP 2.0). The attack detection methodology was set using a Statistical Process Control (SPC) technique and Monitoring charts, as well as Cumulative Summation (CUSUM) and Exponential Weighted Moving Average (EWMA). The techniques tackle different possible flooding attacks, typically through monitoring the incoming messages. The system works by sensing sudden changes and detecting abnormal traffic increases alerting for an attack, and then triggering an alarm on the DoS attack. The scenarios are designed for SIP to simulate normal traffic behaviour and attack traffic behaviour; some scenarios were set to have a large ratio of the non-acknowledged requests, and another scenario was set to simulate a slight increase in the ratio. There was a scenario in which its traffic was imported from another SIP related research. In addition, the thesis discusses the results of DoS attacks targeting the SPDY protocol; one scenario is about a large increase in the total number of the sent requests by a user towards a SPDY proxy, and another scenario is set with a slight increase. SPC was tested on all previously mentioned scenarios; they have shown significant results in detecting the attacks, either it was large sudden flooding, or slight low rate DoS flood, as the low rate DoS attacks are very difficult and sometimes impossible to detect. SPC was tested to aim in false attack alarms reduction, as they are also difficult to deal with. These techniques were applied in two approaches: in the first approach, the Offline implementation, the statistical values of the whole observations, the mean and the standard deviation, are found and then applied to the equations. In the second approach, the Online implementation, the statistical values were updated on getting a new observation and immediately applying the SPC equations; there has not been any other research that discussed such an approach. The first approach represents a system with previous knowledge and experience of the ongoing traffic. This reduces the overhead spent in finding the mean and the standard deviation every time a new observation is added to the sequence. The second approach represents a system that is newly starting with no knowledge, or a system which was reset after detecting an attack. Finally, a framework was suggested to effectively employ the previous contributions in detecting the flood of the traffic.

L’évolution des applications vers le multimédia et des réseaux vers une hétérogénéité d’architectures protocolaires, a placé la notion de Qualité de Service au cœur des architectures de communication émergentes ; Ceci soulève la question de l’expression de la QdS et de l’adaptation aux besoins applicatifs de la diversité des services disponibles. Cette thèse propose un cadre sémantique et syntaxique pour décrire les contraintes applicatives et les services sous-jacents, et sélectionner et composer les services de communication, répondant aux besoins applicatifs. Les systèmes satellitaires intègrent une propriété naturelle de diffusion de l’information, ce qui en fait un composant de l’Internet de nouvelle génération. Nous montrons comment, grâce au cadre générique, les services orientés gestion de QdS spécifiques d’une architecture de communication satellitaire peuvent être composés, afin de délivrer une adaptation efficace entre les ressources satellitaires et les besoins applicatifs.

The Internet of Things market grows at an extreme rate each passing year. Devices will gather more data, which puts a lot of pressure on the communication between the devices and the cloud. The protocols used needs to be fast, secure, reliable and send any type of content. This thesis work conducts a research of the three most popular application level protocols ; MQTT, HTTP and AMQP, to examine which is best suited in an Internet of Things environment. The project is made with Axians AB to provide insight regarding the protocols, so that the company can decide which protocol will be best suited for their projects. A theoretical study of the performance was made, followed by case studies on different aspects of the protocol. The case studies were made using a Dell gateway and a 4G connection to mimic a real world project. Scripts were developed to measure different performance attributes of the protocols. The analysis and discussion of the results proved that MQTT or AMQP is the best protocols, depending on the project.

Monitoring and controlling smart grid assets in a timely and reliable manner is highly desired for emerging smart grid applications. Wireless Sensor Networks (WSNs) are anticipated to be widely utilized in a broad range of smart grid applications due to their numerous advantages along with their successful adoption in various critical areas including military and health care. Despite these advantages, the use of WSNs in such critical applications has brought forward a new challenge of ful lling the Quality of Service (QoS) requirements of these applications. Providing QoS support is a challenging issue due to highly resource constrained nature of sensor nodes, unreliable wireless links and harsh operation environments. In this thesis we critically investigate the problem of QoS provisioning in WSNs. We identify challenges, limitations and requirements for applying QoS provisioning for WSNs in smart grid applications. We nd that the topic of data prioritization techniques at the MAC layer to provide delay bounds in condition monitoring applications is not well developed. We develop six novel QoS schemes that provide data di erentiation and reduce the latency of high priority tra c in a smart grid context. These schemes are namely; Delay-Responsive Cross layer (DRX), Fair and Delay-aware Cross layer (FDRX), Delay-Responsive Cross layer with Linear backo (LDRX), Adaptive Realistic and Stable Model (ARSM), Adaptive Inter-cluster head Delay Control (AIDC) and QoS-aware GTS Allocation (QGA). Furthermore, we propose a new Markov-based model for IEEE 802.15.4 MAC namely, Realistic and Stable Markovbased (RSM). RSM considers actual network conditions and enhances the stability of the WSNs. We show through analytical and simulation results that all of the presented schemes reduce the end-to-end delay while maintaining good energy consumption and data delivery values.

To provide Internet applications with good performance, the transport protocol TCP is designed to optimize the throughput of data transfers. Today, however, more and more applications rely on low latency rather than throughput. Such applications can be referred to as data-limited and are not appropriately supported by TCP. Another emerging problem is associated with the use of novel networking techniques that provide infrastructure-less networking. To improve connectivity and performance in such environments, multi-path routing is often used. This form of routing can cause packets to be reordered, which in turn hurts TCP performance. To address timeliness issues for data-limited traffic, we propose and experimentally evaluate several transport protocol adaptations. For instance, we adapt the loss recovery mechanisms of both TCP and SCTP to perform faster loss detection for data-limited traffic, while preserving the standard behavior for regular traffic. Evaluations show that the proposed mechanisms are able to reduce loss recovery latency with 30-50%. We also suggest modifications to the TCP state caching mechanisms. The caching mechanisms are used to optimize new TCP connections based on the state of old ones, but do not work properly for data-limited flows. Additionally, we design a SCTP mechanism that reduces overhead by bundling several packets into one packet in a more timely fashion than the bundling normally used in SCTP. To address the problem of packet reordering we perform several experimental evaluations, using TCP and state of the art reordering mitigation techniques. Although the studied mitigation techniques are quite good in helping TCP to sustain its performance during pure packet reordering events, they do not help when other impairments like packet loss are present.

Paper V was in manuscript form at the time of the defense.

In medico-legal investigations involving unidentified skeletal remains, forensic anthropologists commonly assist law enforcement and medical examiners in their analysis and identification. The traditional documentation techniques employed by the forensic anthropologist during their analysis include notes, photographs, measurements and radiographic images. However, relevant visual information of the skeleton can be lacking in morphological details in 2D images. By creating a 3D representation of individual bones using a laser-scanner, it would be possible to overcome this limitation. Now that laser scanners have become increasingly affordable, this technology should be incorporated in the documentation methodologies of forensic anthropology laboratories. Unfortunately, this equipment is rarely used in forensic anthropology casework. The goal of this project is to investigate the possible visualization applications that can be created from digitized surface models of bone for use in medico-legal investigations. This research will be achieved in two phases. First, examples of human bone as well as replicas of bone will be scanned using a NextEngine™ laser scanner. In conjunction with this will be the exploration and documentation of protocols for scanning different bone types and processing the scan data for creating a 3D model. The second phase will investigate how the resulting 3D model can be used in lieu of the actual remains to achieve improved documentation methodologies through the use of several commercial computer graphics programs. The results demonstrate that an array of visual applications can be easily created from a 3D file of bone, including virtual curation, measurement, illustration and the virtual reconstruction of fragmented bone. Based on the findings of this project, the implementation of laser scanning technology is recommended for forensic anthropology labs to enhance documentation, analysis and presentation of human bone.
ID: 031908492; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Accepted in partial fulfillment of the requirements for honors in the major in DEPT HERE.; Thesis (B.A.)--University of Central Florida, 2012.; Includes bibliographical references.
B.A.
Bachelors
Sciences
Anthropology

Over the last 10 years, Wireless Sensor Networks (WSNs) have evolved as a hot interdisciplinary research area. What started as a concept of ubiquitous computing with the initial assumptions of low-cost and low power sensing, has now progressed to the development of new wireless sensing applications supported by the advancement of computing devices. Similarly, a vast number of said applications have also emerged with varying Quality of Service (QoS) requirements. It is our argument that the current approach whereby there is a need to customise protocols for individual applications contributes to the slow uptake WSN in the real world. Likewise, we believe that generalised solutions are not always appropriate and while tailor-made solutions are costly. Therefore, we advocate that protocols that understand the notion of a classification of WSN applications can be a potential solution to this problem; in that the tailoring pertains to the type of application or their behaviour classes. Hence, we present the design of a classification-based cross-layer WSN stack that considers Dual-Mode Periodic Data Collection and Event- Driven Monitoring (D-PEDM) applications. In this thesis, we first derive the D-PEDM protocol configuration parameters through thorough analysis of the QoS requirements, physical constraints, and resource constraints of D-PEDM applications. Once the DPEDM protocol configuration parameters are derived, we design an Emergent Broadcast Slot (EBS) scheme, as well as Medium Access Control (YA-MAC) and efficient Priority Based Routing (PBR) protocols. We evaluate each protocol individually as well as an integrated cross-layer stack using the WSN standard test-beds. Further, we show how an Adaptive Rate Control (ARC) protocol can be used with these types of applications. More specifically we introduce the EBS synchronisation scheme that efficiently handles control messages (broadcast messages) in Duty-Cycled Multi-hop (DCM) networks by integrating routing and application broadcast messages together. This approach minimises the overhead caused by control messages that results in improved application level throughput. Additionally, EBS enables efficient decentralised sleep-awake coordination among neighbourhood nodes that improves the power usage in battery-powered sensor devices up to 5-6 times. To meet the latency requirements of the D-PEDM applications, YA-MAC provides support to handle unicast messages in an asynchronous manner that not only reduces the event traffic latency but also reduces contention in the network. To further improve the latency and reliabilities of bursty event traffic; PBR uses a priority queuing mechanism and traffic differentiation schemes. In the traffic differentiation scheme, PBR gives priority to event traffic and diverts non-priority traffic away from the event traffic path to alternative random paths. This favours the QoS of event traffic in many ways: first, it reduces the contention in the event traffic path resulting in less collisions and fewer back-offs at MAC layer, which in turn significantly improves end-to-end event traffic latency (by 10 ms per hop). Additionally, the MAC layers reduced numbers of back-offs inherently reduces re-transmissions by 70% thereby reducing the energy consumption by 2/3. Furthermore, PBR increases the probability of event data reaching the Sink/Base-station as compared to that of when both event and non-event share same paths. The D-PEDM cross-layer stack, which includes EBS, YA-MAC, and PBR, achieves 80% application level throughput while operating in less than 10% duty-cycle in presence of relatively high unicast data traffic.

Le réseau de capteurs sans fil (WSN) est un des protagonistes contribuant à l’évolution et au développement de l’Internet des objets (IoT). Plusieurs cas d’usage peuvent être trouvés dans les différents domaines comme l’industrie du transport maritime où le fret conteneurisé compte environ pour 60% du commerce mondial. Dans ce contexte, la société TRAXENS a développé un dispositif radio alimenté par batterie appelé TRAX-BOX et conçu pour être fixé aux containeurs dans l’objectif de les traquer et les surveiller tout au long de la chaine logistique. Dans cette thèse, je vais présenter une nouvelle pile protocolaire WSN appelée TRAX-NET et conçue pour permettre aux TRAX-BOX de s’auto-organiser dans un réseau sans fil et coopérer pour délivrer les données acquises au serveur TRAXENS d’une façon énergiquement efficiente. Les résultats des simulations et des tests sur le terrain montrent que TRAX-NET est bien optimisé pour les différents scenarios pour lesquels il a été développé et satisfait les exigences de l’application concernée mieux que les autres solutions étudiées dans la littérature. TRAX-NET est une solution complète et adaptée au suivi des conteneurs de fret de par le monde
Wireless Sensor Networks (WSN) is one of the protagonists contributing to the evolution and the development of the Internet of Things (IoT). Several use cases can be found today in the different fields of the modern technology including the container shipping industry where containerized cargo accounts for about 60 percent of all world seaborne trade. In this context, TRAXENS developed a battery-powered device named TRAX-BOX designed to be attached to the freight containers in order to track and monitor the shipping goods along the whole supply chain. In this thesis, we present a new energy-efficient self-organizing WSN protocol stack named TRAX-NET designed to allow the TRAX-BOX devices to cooperate to deliver the sensed data to the TRAXENS platform.The results of simulations and field tests show that TRAX-NET well perform in the different scenarios in which it is supposed to operate and better fulfil the requirements of the assumed application in comparison with the existing schemes

Wireless Sensor Networks (WSNs) have been an exciting topic in recent years. The services offered by a WSN can be classified into three major categories: monitoring, alerting, and information on demand. WSNs have been used for a variety of applications related to the environment (agriculture, water and forest fire detection), the military, buildings, health (elderly people and home monitoring), disaster relief, and area or industrial monitoring. In most WSNs tasks like processing the sensed data, making decisions and generating emergency messages are carried out by a remote server, hence the need for efficient means of transferring data across the network. Because of the range of applications and types of WSN there is a need for different kinds of MAC and routing protocols in order to guarantee delivery of data from the source nodes to the server (or sink). In order to minimize energy consumption and increase performance in areas such as reliability of data delivery, extensive research has been conducted and documented in the literature on designing energy efficient protocols for each individual layer. The most common way to conserve energy in WSNs involves using the MAC layer to put the transceiver and the processor of the sensor node into a low power, sleep state when they are not being used. Hence the energy wasted due to collisions, overhearing and idle listening is reduced. As a result of this strategy for saving energy, the routing protocols need new solutions that take into account the sleep state of some nodes, and which also enable the lifetime of the entire network to be increased by distributing energy usage between nodes over time. This could mean that a combined MAC and routing protocol could significantly improve WSNs because the interaction between the MAC and network layers lets nodes be active at the same time in order to deal with data transmission. In the research presented in this thesis, a cross-layer protocol based on MAC and routing protocols was designed in order to improve the capability of WSNs for a range of different applications. Simulation results, based on a range of realistic scenarios, show that these new protocols improve WSNs by reducing their energy consumption as well as enabling them to support mobile nodes, where necessary. A number of conference and journal papers have been published to disseminate these results for a range of applications.

Cette thèse étudie les optimisations d’allocation de ressources dans le lien retour de systèmes satellites à faisceaux multipleslimités par les interférences et pouvant être vus comme des systèmes MIMO virtuels. Cette thèse se focalise sur lesinterférences générées par les utilisateurs positionnés dans différents faisceaux et transmettant en même temps et avec lamême fréquence. Le nombre de fréquences (couleurs) présent dans le système satellite modifie la bande passante et de cefait la capacité du système. Quand ce nombre est réduit, par ex. une seule couleur, le niveau d’interférences augmente maisla bande passante dans chaque faisceau est plus grande. Il y a donc un compromis entre nombre de couleurs et niveaud’interférences. L’influence du canal satellite est tout d’abord évaluée en analysant le taux d’erreur obtenu avec diversestechniques de suppression d’interférences. La thèse s’oriente ensuite vers la théorie de l’information et étudie l’impact dunombre de couleurs sur les débits totaux. La détection multi-utilisateurs est prise en compte pour dériver les débitsutilisateurs et en particulier le critère max-min est appliqué, montrant une amélioration du niveau d’équité. Les différentsrésultats sont utilisés pour optimiser l’allocation des ressources mais l’ordonnancement pour des systèmes MIMO à grandeéchelle représente une tâche difficile, le domaine de recherche étant de taille prohibitive. De ce fait cette thèse étudie aussides algorithmes heuristiques à complexité réduite, basés sur la théorie des graphes, visant à trouver des ordonnancementssous-optimaux. Enfin le nombre de faisceaux et d’utilisateurs pris en compte pour l’ordonnancement sont étudiés pourproposer de nouveaux algorithmes satisfaisant des contraintes de qualité de service
This Ph.D. investigates resource management optimisations in the return-link of interference-limited multi-beam satellitesystems which can be seen as virtual MIMO systems. It focuses on the interference that users located in different beamsgenerate towards each other, when transmitting data at the same time and on the same frequency. The number offrequencies (colours) present in the satellite system rules the overall bandwidth and therefore the system capacity. Whenthe number of colours becomes low, e.g. considering one colour, the level of interference increases dramatically but thebandwidth available in each beam gets higher. Hence there is a tradeoff between number of colours and level ofinterference. The influence of the satellite channel is first studied by analysing the BER obtained through interferencecancellation techniques. The Ph.D. then moves towards information theory and investigates the impact of the colours onthe achievable sum rates. MUD schemes are then used to derive the per-user rates, and the max-min criterion is applied tothe user rates showing an improvement of the level of fairness between users. The different outcomes are used to optimisethe resource management. However, scheduling for large scale MIMO systems, as in the return-links of satellitecommunications, represents a challenging task, since the search space is prohibitive large. For this reason this Ph.D. alsoinvestigates low complexity heuristic algorithms based on graph theory with the aim of finding sub-optimal schedules.Finally, the number of spot beams and the number of users considered for scheduling are studied so as to propose newalgorithms aiming to satisfy quality of service constraints

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Aplicações multimídia são muito populares na internet. Grande parte delas necessita de multicast para escalar. É sabido que multicast em nível de redes não foi implementado como desejado. Protocolos em nível de aplicação são a solução atual. Apesar do sucesso dos protocolos ALM (Application Layer Multicast), a maioria dos protocolos existentes são custosos e acarretam grande sobrecarga de controle à rede. Neste trabalho, apresentamos um novo protocolo de fluxo contínuo baseado em árvore, utilizando a desigualdade triangular entre cada três peers para gerenciamento dinâmico da topologia (o PALMS+). O novo protocolo é simples e com baixa sobrecarga. Mesmo assim, seu desempenho é tão bom quanto o estado da arte. Experimentos realizados na plataforma Oversim (OMNet++) demonstraram que o PALMS+ manteve desempenho tão bom quanto o estado da arte (e.g. protocolo NICE), mesmo quando submetido a alto churn em uma rede heterogênea. De fato, a sobrecarga nos peers do novo protocolo é menor que 10% da sobrecarga gerada pelo NICE. O protocolo PALMS+ entrega os dados em menos de 1,5s. O novo protocolo mostra-se adequado a vídeo ao vivo, escalando mesmo em cenários realistas e com alto churn.
Multimedia applications are very popular on the internet. Many of these applications need multicast to scale. However, network layer multicast has not been implemented in the internet. Application layer multicast (ALM) protocols are a practical alternative. However, despite their popularity, many existing ALM protocols and mechanisms are expensive and bring a large overhead control on the network. In the present work, a new protocol is proposed for content distribution based on tree, using the triangular inequality between every three peers to dynamic topology control (the PALMS+). The new protocol is simple and with low overhead. Nevertheless, its performance as good as the state of the art. Experimental results conducted with the OverSim platform (OMNet++) suggest that PALMS+ improves the performance of a state-of-art implementation of ALM protocol when compared against the NICE protocol. Furthermore, the control message overhead at peers using the PALMS+ protocol is reduced by 10%, when compared with NICE. In the PALMS+ protocol, chunks are delivered up to 1,5s. Results confirm that proposed implementation of PALMS+ is very suitable to real-time video streaming, even when churn is high.

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Internet applications such as media streaming, collaborative computing and massive multiplayer are on the rise,. This leads to the need for multicast communication, but unfortunately group communications support based on IP multicast has not been widely adopted due to a combination of technical and non-technical problems. Therefore, a number of different application-layer multicast schemes have been proposed in recent literature to overcome the drawbacks. In addition, these applications often behave as both providers and clients of services, being called peer-topeer applications, and where participants come and go very dynamically. Thus, servercentric architectures for membership management have well-known problems related to scalability and fault-tolerance, and even peer-to-peer traditional solutions need to have some mechanism that takes into account member's volatility. The idea of location awareness distributes the participants in the overlay network according to their proximity in the underlying network allowing a better performance. Given this context, this thesis proposes an application layer multicast protocol, called LAALM, which takes into account the actual network topology in the assembly process of the overlay network. The membership algorithm uses a new metric, IPXY, to provide location awareness through the processing of local information, and it was implemented using a distributed shared and bi-directional tree. The algorithm also has a sub-optimal heuristic to minimize the cost of membership process. The protocol has been evaluated in two ways. First, through an own simulator developed in this work, where we evaluated the quality of distribution tree by metrics such as outdegree and path length. Second, reallife scenarios were built in the ns-3 network simulator where we evaluated the network protocol performance by metrics such as stress, stretch, time to first packet and reconfiguration group time
Atualmente aplica??es em grupo na Internet est?o em ascens?o, como por exemplo transmiss?o de ?udio e v?deo, computa??o colaborativa e jogos com m?ltiplos participantes. Isso leva ? necessidade de comunica??o multicast, mas infelizmente o suporte a este tipo de servi?o n?o est? amplamente dispon?vel pela camada de rede. Por isso, no atual est?gio tecnol?gico surgiram solu??es de protocolos multicast implementados na camada de aplica??o para suprir tal defici?ncia. Al?m disso, estas aplica??es muitas vezes se apresentam simultaneamente como provedores e clientes dos servi?os utilizados, caracterizando-as como aplica??es denominadas peer-to-peer, possuindo caracter?sticas din?micas, onde os participantes podem entrar e sair de um grupo com uma freq??ncia muito alta. Assim, algoritmos centralizados de ger?ncia de grupo n?o apresentam bom desempenho para essa classe de aplica??es, e mesmo as solu??es peer-to-peer tradicionais necessitam ter algum mecanismo que leve em considera??o essa volatilidade. A id?ia de consci?ncia de localiza??o permite distribuir os participantes na rede virtual de acordo com a sua proximidade na rede f?sica, permitindo um bom desempenho nas opera??es de gerenciamento do grupo. Diante deste contexto, nesta tese ? proposto um protocolo de comunica??o multicast na camada de aplica??o, chamado LAALM, que leva em considera??o a topologia da rede real no processo de montagem da rede virtual, utilizando uma nova m?trica denominada IPXY para prover a consci?ncia de localiza??o, atrav?s do processamento de informa??es locais. O LAALM foi implementado utilizando uma ?rvore distribu?da compartilhada e bi-direcional, possuindo uma heur?stica sub-?tima para o processo de inclus?o de novos participantes que visa minimizar o custo de constru??o da ?rvore de distribui??o de dados. A avalia??o do protocolo foi realizada de duas formas distintas: i) atrav?s de um simulador pr?prio onde se procurou avaliar a qualidade de constru??o da ?rvore de distribui??o gerada, avaliando-se m?tricas como o n?mero de filhos por cada n? e a dist?ncia final entre os n?s; ii) atrav?s de cen?rios real?sticos constru?dos no simulador de redes ns-3, onde foi avaliado o desempenho do protocolo atrav?s de m?tricas como stress, stretch e tempos de associa??o e reconfigura??o dos grupos

Les accords multilatéraux sur l’environnement sont généralement caractérisés par leur autorité normative atténuée en raison des difficultés pour les États de garantir leur application effective et efficace. La procédure de non-conformité, expérimentée pour la première fois par le Protocole de Montréal sur les substances qui appauvrissent la couche d’ozone et étendue depuis, tente d’apporter des solutions appropriées aux particularismes de cette branche du droit international public. L’étude de son développement, de son évolution et de sa sophistication à travers sa nature, sa place et sa fonction permet ainsi de déterminer si cette technique exécutive contribue au renforcement de l’autorité des accords multilatéraux sur l’environnement
Multilateral agreements on the environment are generally characterized by their normative authority diminished because of the difficulties for states to ensure their effective implementation and efficiency. The non-compliance procedure, for the first time experienced by the Montreal Protocol on Substances that Deplete the Ozone Layer and extended since then, attempts to provide appropriate solutions to the peculiarities of this branch of public international law.The study of its development, its evolution and sophistication through its nature, its place and function and to determine whether this technique helps to strengthen executive authority of multilateral environmental agreements

碩士
國立高雄第一科技大學
電腦與通訊工程所
94
ABSTRACT Internet brings a lot of facilities to people. Our every day lift almost can’t normal without network. Today, network has already become our part of the daily life, this makes a lot of people want to understand the network science and technology. In the network, the application layer is the one directly contact with users. People use the services applied from application layer to shopping, chat, learning etc. In the network, these has a set of mechanisms that are running behind one''s back, this set of mechanisms is the communication protocol. Essentially on the network, it is packets transmit between server and client. But, when and what message the packet should transmit is the essence of the communication protocol. How to understand the protocol is the key point of this thesis. The open source software snort is a cross-platform, lightweight intrusion detection system. The lightweight means it can easily be deployed on most any node of a network, with minimal disruption to operations. That is to say it can be easily configured by system administrators to suit there requirement. This thesis will utilize this some characteristics. We will use snort as the core to design a system to capture the packages, and design a friendly webpage interface to show these packages systematically. We hope the system could help them want to understand communication protocols.

Wireless and mobile systems play an increasingly important role in our lives. Fueled by an array of innovative services and applications, mobile data traffic is surging rapidly. Traditionally, wireless traffic growth is met by acquiring new spectrum. However, wireless spectrum demand is soon going to surpass it's availability. Thus, there is an urgent need for major innovations in wireless network architecture, so that our spectrum utilization can achieve its full potential. Motivated by this problem, we explore an alternative design of physical layer aware wireless systems.

Typical approaches towards improving wireless performance is confined within the physical (PHY) or link layers of the networking stack, providing only partial so- lutions. In this thesis, we advocate to consider the entire network architecture holis- tically. We show how rich PHY layer information can be utilized to address existing challenges in wireless networking - contention resolution, rate control, interference management, etc. We design, implement, and experimentally evaluate protocols to understand network-wide implications of PHY-aware systems. We also pursue the observation that PHY layer not only encode bits but also contain rich information about the ambience, and hence can be viewed as a sensor. This sensing informa- tion can be further coupled with other phone sensors, thereby benefitting pervasive mobile services and applications. We demonstrate how this synergy can contribute towards designing precise indoor localization systems, an important building block for next generation mobile applications.

Dissertation

碩士
國立成功大學
資訊工程學系碩博士班
100
The progress of Internet technology brings the rapid growth of multimedia application, especially the application of Voice over Internet Protocol such as Skype and MSN which are popular in the world. One of the well-known signaling protocols of VoIP, Session Initiation Protocol (SIP), widely spreads and commonly applies. The software and devices in use of SIP gradually increase. Each VoIP device needs to assign an IPv4 address for communication. Nowadays the IPv4 addresses have been exhausted because it still widely uses IPv4 addresses for network. IPv6 which can provide large address space is proposed to replace IPv4. However the IPv6 deployment is not widespread. The duration of transition from both IPv4 and IPv6 networks can make users or devices in IPv4 and IPv6 networks communicate with each other. One of transition mechanism, the IVI translation mechanism, allows users to access IPv4 and IPv6 networks. But the IVI translation does not translate the payload of packet. We implement a translation for SIP in VoIP with IVI translation mechanism such that it can translate SIP messages form IPv4 or IPv6 networks.

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes.

博士
國立成功大學
資訊工程學系碩博士班
95
As the progress of computing and wireless techniques, mobile communication has changed the modern life style. When users become mobile, they must suffer some kind of the handoff process from one domain to another. Thus, mobility management must be the key issue of mobile communication. From the past research, the handoff process may occur in (1) data link layer, (2) network layer, or (3) application layer. Nevertheless, the handoff problem can usually be resolved using the application-layer approach no matter which layer it occurs. The goal of this dissertation is to design and analyze application-layer mobility management protocols. First, we survey and investigate two application-layer protocols, which are (1) application-layer anycast and (2) Session Initiation Protocol (SIP). Then, we utilize and extend these two application-layer protocols to solve two handoff problems occurred in different layers, which are (1) Proxy Handoff and (2) network mobility, respectively. Next, we evaluate the proposed application-layer mobility management protocols using different methods, i.e., real implementation and simulation. Finally, we discuss and conclude the characteristics of application-layer mobility management protocols.

博士
國立臺北科技大學
資訊工程系研究所
101
Application Layer Multicast (ALM) routing is an indispensable mechanism for efficient distribution of data from a source or many sources to many receivers. With the growing of Internet real-time and file sharing applications that demand large network resources and call for multicasting mechanism, the necessity of analyzing and deriving the minimum cost of ALM routing protocols and developing an efficient ALM routing protocol is explicit. According to the number of sources, ALM routing protocols can be categorized into single-source and multisource. The main goal of this research is to design a multisource ALM routing protocol with fast route recovery and low cost. With the goal, a multisource ALM routing with fast route recovery mechanism, distributed data forwarding trees (DMFTs), was firstly developed, and the theoretical minimum cost of multisource ALM routing protocols was found by deriving and proving a multiplicative property on the costs of multisource ALM routings relative to single-source ones. With the multiplicative property, the minimum cost of multisource ALM routings can be simply obtained by multiplying the minimum cost of single-source ALM routings by the number of sources. By analyzing the minimum costs of single-source and multisource ALM routings, the research discovered and proved the cost impact that the performance penalty of ALM continuously increases with multicast group size until a certain group size is reached. That is, as the multicast group size is over the certain value, the performance penalty starts to decrease. From theoretical analyses, the research proposed principles to design an ALM routing protocol. The objective of the principles is to reduce the delay and jitter of ALM routing by reducing the total cost of ALM routing tree. Applying the design principles on DMFTs, the research proposed a new multisource ALM routing protocol, cluster based distributed forwarding trees (CDMFTs). Through intensive computer simulations, it can be shown that the control overhead, dealy, jitter, link stress, and total tree length of CDMFTs were reduced by 2% to 80%, comparing to that of DMFTs. The results demonstrated the efficiency of CDMFTs as well as the effectiveness of the proposed design principles. The analytical analysis and design work provided useful insights for the researchers and developers of ALM routing protocols.

This thesis proposes and analyzes data fusion algorithms that operate on the physical layer of a wireless sensor network, in the context of three applications of cognitive radios: 1. Cooperative spectrum sensing via binary consensus; 2. Multiple transmitter localization and communication footprint identification; 3.Target self-localization using beacon nodes. For the first application, a co-phasing based data combining scheme is studied under imperfect channel knowledge. The evolution of network consensus state is modeled as a Markov chain, and the average transition probability matrix is derived. Using this, the average hitting time and average consensus duration are obtained, which are used to determine and optimize the performance of the consensus procedure. Second, using the fact that a typical communication footprint map admits a sparse representation, two novel compressed sensing based schemes are proposed to construct the map using 1-bit decisions from sensors deployed in a geographical area. The number of transmitters is determined using the K-means algorithm and a circular fitting technique, and a design procedure is proposed to determine the power thresholds for signal detection at sensors. Third, an algorithm is proposed for self-localization of a target node using power measurements from beacon nodes transmitting from known locations. The geographical area is overlaid with a virtual grid, and the problem is treated as one of testing overlapping subsets of grid cells for the presence of the target node. The column matching algorithm from group testing literature is considered for devising the target localization algorithm. The average probability of localizing the target within a grid cell is derived using the tools from Poisson point processes and order statistics. This quantity is used to determine the minimum required node density to localize the target within a grid cell with high probability. The performance of all the proposed algorithms is illustrated through Monte Carlo simulations.

碩士
國立中正大學
通訊工程研究所
95
Recently, researches on Application Layer Multicast (ALM) become more and more popular due to the prevailed broadband network and high performance personal computers. One of the key issues on designing ALM is the robustness to member failures. A noticeable solution is to build node-disjoint multicast trees such that failure of a member only affects one of the multicast trees and other members could still receive data from the rest multicast trees. In the literature, most of the researches focused on the homogeneous environment. However, the real network is the environment fulfilled with the heterogeneous computers and network devices. Therefore, in this thesis, we simulated several ALM protocols in heterogeneous environment to identify the key factor that affects the robustness of ALM protocols. From our simulation results, we have observed that the balanced structure of clusters affects the performance significantly. If the members are more aggregated such that each cluster is composed with large number of members, the system will be more robust to member failures.

The unique performance offerings of NiTi based shape memory alloys (SMAs), which includes the shape memory effect (SME), pseudoelasticity (PE) and biocompatibility have led to widespread acceptance of these alloys as valuable engineering materials. Over the past several decades the complex metallurgy behind the SME and PE properties has for the most part been uncovered and the design and engineering knowhow has been demonstrated; facilitating successful application of NiTi devices in numerous industries. Specifically, more mature applications in the medical industry including medical devices such as, catheters, guide wires, orthodontic arch wires, maxillofacial reconstruction implants, minimally invasive surgical tools, and arterial and gastrointestinal stents, have become common practice in modern medicine. Recently however, there has been a drive for more demanding functionality of SMAs for example to locally modify properties creating tuneable or gradient SME and PE performance. Unique processing protocols are therefore necessary to meet these demands and allow SMAs to reach their full potential in a wider range of applications. The current thesis successfully details the application of pulsed Nd:YAG laser processing along with post-processing techniques to locally tune both the SME and PE functional properties of monolithic binary NiTi wires and strip, while maintaining confidence in the retained corrosion performance and limited release of biologically harmful Ni ions. This extensive study contains three distinct parts which include: i) application of a laser induced vaporization protocol to locally embed multiple memories in a monolithic wire actuator; ii) uncovering the process, structure, and performance relationship of combined laser, cold working, and heat treatment processes; and iii) comprehensive characterization of surface characteristics and their relationship with corrosion performance and Ni ion release from laser processed material.

of energy-efficiency as well as the number of available applications. As a consequence there are challenges that need to be tackled for the future generation of WSNs. The research work from this Ph.D. thesis has involved the actual development of innovative WSN applications contributing to different research projects. In the Smart-Clothing project contributions have been given in the development of a Wireless Body Area Network (WBAN) to monitor the foetal movements of a pregnant woman in the last four weeks of pregnancy. The creation of an automatic wireless measurement system for remotely monitoring concrete structures was an contribution for the INSYSM project. This was accomplished by using an IEEE 802.15.4 network enabling for remotely monitoring the temperature and humidity within civil engineering structures. In the framework of the PROENEGY-WSN project contributions have been given in the identification the spectrum opportunities for Radio Frequency (RF) energy harvesting through power density measurements from 350 MHz to 3 GHz. The design of the circuits to harvest RF energy and the requirements needed for creating a WBAN with electromagnetic energy harvesting and Cognitive Radio (CR) capabilities have also been addressed. A performance evaluation of the state-of-the art of the hardware WSN platforms has also been addressed. This is explained by the fact that, even by using optimized Medium Access Control (MAC) protocols, if the WSNs platforms do not allow for minimizing the energy consumption in the idle and sleeping states, energy efficiency and long network lifetime will not be achieved. The research also involved the development of new innovative mechanisms that tries and solves overhead, one of the fundamental reasons for the IEEE 802.15.4 standard MAC inefficiency. In particular, this Ph.D. thesis proposes an IEEE 802.15.4 MAC layer performance enhancement by employing RTS/CTS combined with packet concatenation. The results have shown that the use of the RTS/CTS mechanism improves channel efficiency by decreasing the deferral time before transmitting a data packet. In addition, the Sensor Block Acknowledgment MAC (SBACK-MAC) protocol has been proposed that allows the aggregation of several acknowledgment responses in one special Block Acknowledgment (BACK) Response packet. Two different solutions are considered. The first one considers the SBACK-MAC protocol in the presence of BACK Request (concatenation) while the second one considers the SBACK-MAC in the absence of BACK Request (piggyback). The proposed solutions address a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under both ideal conditions (a channel environment with no transmission errors) and non ideal conditions (a channel environment with transmission errors). An analytical model is proposed, capable of taking into account the retransmission delays and the maximum number of backoff stages. The simulation results successfully validate our analytical model. For more than 7 TX (aggregated packets) all the MAC sub-layer protocols employing RTS/CTS with packet concatenation allows for the optimization of channel use in WSNs, v8-48 % improvement in the maximum average throughput and minimum average delay, and decrease energy consumption.

Οι εφαρμογές πολυμέσων έχουν αποκτήσει τα τελευταία χρόνια μία αυξανόμενη ζήτηση από τους χρήστες γενικά του Διαδικτύου καθώς προσφέρουν νέες και ποικιλόμορφες δυνατότητες ανταλλαγής πληροφοριών εικόνας και ήχου. Όμως οι εφαρμογές αυτές υπόκεινται σε περιορισμούς που έχουν να κάνουν κυρίως με τη φύση τους και χαρακτηρίζονται από τις υψηλές απαιτήσεις σε ρυθμό μετάδοσης δεδομένων (bandwidth-consuming applications) και την ευαισθησία τους στις καθυστερήσεις που παρουσιάζονται κατά τη μετάδοση των πακέτων από τον αποστολέα στο παραλήπτη (delay-sensitive applications). Από την άλλη μεριά οι εφαρμογές αυτές φέρεται ότι είναι λιγότερο ευαίσθητες στις απώλειες των πακέτων (packet-loss tolerant applications). Το ζητούμενο όμως με τις εφαρμογές πολυμέσων, πέρα από το εύρος των υπηρεσιών τις οποίες προσφέρουν, είναι και η παρεχόμενη ποιότητα των υπηρεσιών (Quality of Service, QOS) στο τελικό χρήστη. Η ποιότητα αυτή των υπηρεσιών συνδέεται άμεσα με τα προαναφερόμενα χαρακτηριστικά των εφαρμογών πολυμέσων. Η μέχρι τώρα προσέγγιση από την ερευνητική κοινότητα αλλά και τις εταιρείες παροχής υπηρεσιών Διαδικτύου (Internet Service Providers), σε ότι αφορά την εξασφάλιση της ποιότητας υπηρεσιών, έχει εστιασθεί είτε στην επιμέρους βελτιστοποίηση της απόδοσης των πρωτοκόλλων μετάδοσης, είτε στην εγκατάσταση επιπλέον εξοπλισμού για τη δημιουργία δικτύων διανομής πολυμέσων (Content Distribution Networks, CDNs) που τοποθετούνται συνήθως κοντά στον τελικό χρήστη. Επιπρόσθετα η αυξανόμενη προσπάθεια της ερευνητικής κοινότητας με σκοπό την αύξηση της ποιότητας υπηρεσιών προσέφερε νέες καινοτόμες λύσεις με την μορφή των υπηρεσιών-αρχιτεκτονικών όπως οι Ολοκληρωμένες Υπηρεσίες (Integrated services, Intserv) και οι Διαφοροποιημένες Υπηρεσίες (Differentiated Services, Diffserv) οι οποίες φιλοδοξούν να προσφέρουν εγγυήσεις ποιότητας υπηρεσιών σε συγκεκριμένες ομάδες χρηστών. Όμως και οι δύο αυτές αρχιτεκτονικές δεν κατάφεραν μέχρι τώρα να αποτελέσουν μια ολοκληρωμένη λύση για τη παροχή εγγυήσεων ποιότητας υπηρεσιών στο χρήστη λόγω των μεγάλων δυσκολιών στην εφαρμογή τους που έχουν να κάνουν τόσο με χρηματοοικονομικά κριτήρια όσο και με τη ίδια τη δομή του Διαδικτύου. Έτσι βλέπουμε ότι παρόλη τη πρόοδο που έχει γίνει μέχρι σήμερα στη τεχνολογία των δικτύων η παροχή ποιότητας υπηρεσίας στο Διαδίκτυο από άκρο σε άκρο δεν είναι ακόμη στις μέρες μας εφικτή με αποτέλεσμα οι υπηρεσίες μετάδοσης πολυμέσων στο Διαδίκτυο – π.χ “youtube” – να επηρεάζονται σημαντικά από τις όποιες μεταβολές στη κατάσταση του δικτύου. Προς το σκοπό αυτό η ερευνητική κοινότητα έχει στραφεί στη μελέτη μηχανισμών οι οποίοι θα είναι να θέση να προσαρμόζουν το ρυθμό μετάδοσης της πολυμεσικής πληροφορίας, ανάλογα με τις εκάστοτε συνθήκες του δικτύου, έτσι ώστε να προσφέρουν τη μέγιστη δυνατή ποιότητα υπηρεσίας στο τελικό χρήστη. Η προσπάθεια αυτή μπορεί να κατηγοριοποιηθεί σε δύο μεγάλες κατηγορίες ανάλογα με το τρόπο δρομολόγησης της πολυμεσικής πληροφορίας, όπως παρακάτω: • Μηχανισμοί προσαρμογής για unicast μετάδοση: Σε αυτή τη περίπτωση οι μηχανισμοί προσαρμογής προσαρμόζουν το ρυθμό μετάδοσης της πληροφορίας από ένα σημείο (αποστολέας) προς ένα σημείο (παραλήπτης). • Μηχανισμοί προσαρμογής εκπομπής πολλαπλής διανομής (multicast): Στη περίπτωση αυτή οι μηχανισμοί προσαρμογής προσαρμόζουν το ρυθμό μετάδοσης της πληροφορίας που λαμβάνει χώρα από ένα σημείο (αποστολέας) προς πολλά σημεία (παραλήπτες). Σε ότι αφορά τη unicast μετάδοση την επικρατέστερη πρόταση αποτελεί ο μηχανισμός ελέγχου συμφόρησης με την ονομασία TCP Friendly Rate Control (TFRC) που έχει γίνει αποδεκτός ως διεθνές πρότυπο από τη Internet Engineering Task Force (IETF). Στη περιοχή της multicast εκπομπής ο μηχανισμός TCP-friendly Multicast Congestion Control (TFMCC) έχει γίνει επίσης αποδεκτός ως πειραματικό πρότυπο από την IETF. Παρόλα αυτά όμως εργαστηριακές μελέτες και πειράματα έχουν δείξει ότι τόσο ο μηχανισμός TFRC όσο και ο TFMCC δεν είναι και οι πλέον κατάλληλοι μηχανισμοί προσαρμογής για τη μετάδοση πολυμέσων. Τα κυριότερα προβλήματα αφορούν στη “φιλικότητα” των μηχανισμών αυτών προς το πρωτόκολλο Transmission Control Protocol (TCP) καθώς και στις απότομες διακυμάνσεις του ρυθμού μετάδοσης. Ιδιαίτερα οι απότομες διακυμάνσεις του ρυθμού μετάδοσης είναι ένα στοιχείο μη επιθυμητό από τις εφαρμογές πολυμέσων και ιδιαίτερα από τις εφαρμογές πολυμέσων πραγματικού χρόνου. Στη περιοχή των ασυρμάτων δικτύων τα προβλήματα τα οποία αντιμετωπίζονται κατά τη μετάδοση των πολυμέσων δεν έχουν τόσο άμεση σχέση με τη συμφόρηση του δικτύου (αυτή παρατηρείται κυρίως στα ενσύρματα δίκτυα), όσο με τις απώλειες των πακέτων που είναι ένα άμεσο αποτέλεσμα του μέσου διάδοσης. Η μέχρι τώρα προσέγγιση αφορά στην επιμέρους βελτιστοποίηση των διαφόρων πρωτοκόλλων των στρωμάτων του OSI έτσι ώστε να μειωθούν τα προβλήματα διάδοσης και να ελαχιστοποιηθούν οι απώλειες πακέτων και οι καθυστερήσεις από τον αποστολέα στο παραλήπτη. Κατά τα τελευταία χρόνια όμως κερδίζει όλο και περισσότερο έδαφος μια διαφορετική προσέγγιση η οποία έχει επικρατήσει να ονομάζεται διεθνώς ως “cross-layer optimization-adaptation”. Κατά τη προσέγγιση αυτή διαφαίνεται ότι θα μπορούσαμε να πετύχουμε τη βελτιστοποίηση της παρεχόμενης ποιότητας στις εφαρμογές πολυμέσων μέσω κάποιων μηχανισμών προσαρμογής, που θα εμπλέκουν περισσότερα του ενός εκ των στρωμάτων του OSI στις τρέχουσες συνθήκες του δικτύου. Η μεθοδολογία, οι προκλήσεις, οι περιορισμοί καθώς και οι εφαρμογές της διαστρωματικής (cross layer) προσαρμογής αποτελούν ένα ανοικτό ερευνητικό πεδίο το οποίο βρίσκεται αυτή τη στιγμή σε εξέλιξη. Σκοπός της παρούσας Διδακτορικής Διατριβής είναι καταρχήν η μελέτη των υπαρχόντων μηχανισμών ελέγχου συμφόρησης που αφορούν τα ενσύρματα δίκτυα μη εγγυημένης ποιότητας, όπως το Διαδίκτυο. Προς τη κατεύθυνση αυτή αξιολογούνται αρχικά οι υπάρχοντες μηχανισμοί ελέγχου συμφόρησης και διαπιστώνονται τα κυριότερα προβλήματα τα οποία σχετίζονται με τη ποιότητα υπηρεσιών. Η αξιολόγηση γίνεται με βάση τα κριτήρια που αφορούν τόσο στη φιλικότητα των μηχανισμών αυτών προς το TCP όσο και στα κριτήρια που αφορούν τη ποιότητα υπηρεσιών των εφαρμογών πολυμέσων. Η αξιολόγηση αυτή μας οδηγεί στο σχεδιασμό νέων πρωτοκόλλων τα οποία υπόσχονται υψηλότερη φιλικότητα προς το TCP και καλύτερη ποιότητα υπηρεσιών. Ένα σημαντικό στοιχείο που διαφοροποιεί τα πρωτόκολλα αυτά από τις άλλες προσεγγίσεις είναι η ομαλή (smooth) συμπεριφορά κατά την οποία ελαχιστοποιούνται οι απότομες μεταβολές του ρυθμού μετάδοσης, που είναι μη επιθυμητές από τις εφαρμογές πολυμέσων, διατηρώντας παράλληλα ένα υψηλό ρυθμό απόκρισης στις απότομες μεταβολές των συνθηκών του δικτύου. Ένα δεύτερο σημαντικό στοιχείο της εργασίας αυτής είναι οι προσθήκες στις βιβλιοθήκες του προσομοιωτή ns-2 οι οποίες είναι ήδη αντικείμενο εκμετάλλευσης από άλλους ερευνητές. Για το σκοπό αυτό τα νέα πρωτόκολλα καθορίζονται πλήρως και ενσωματώνονται στις βιβλιοθήκες του προσομοιωτή ns-2 έτσι ώστε να είναι διαθέσιμα στην ερευνητική κοινότητα ως μέρος του προσομοιωτή, για περαιτέρω μελέτη και αξιολόγηση. Επεκτείνονται παράλληλα υπάρχοντα ερευνητικά εργαλεία προσομοιώσεων τα οποία επιτρέπουν την ανάλυση και την αξιολόγηση υπαρχόντων και μελλοντικών μηχανισμών προσαρμογής με βάση κριτήρια ποιότητας που αφορούν ειδικά τις εφαρμογές πολυμέσων, πλέον των “κλασσικών” κριτηρίων που σχετίζονται με μετρικά δικτύων. Σε ότι αφορά στα ασύρματα δίκτυα μελετάται η διαστρωματική προσαρμογή και εάν και κατά πόσο είναι δυνατό να επιτευχθεί η αύξηση της ποιότητας της παρεχόμενης υπηρεσίας μέσα από την εφαρμογή μια τέτοιας σχεδίασης. Μελετώνται οι διάφοροι τρόποι και μεθοδολογίες σχεδίασης μιας διαστρωματικής προσαρμογής και προτείνεται ένα νέο πλαίσιο με το οποίο είναι δυνατό να αυξήσουμε τη ποιότητα υπηρεσίας σε υβριδικά δίκτυα, που αποτελούνται τόσο από ενσύρματους όσο και από ασύρματους χρήστες.
Multimedia applications have gained in recent years an increasing demand from Internet users as they offer new opportunities and diverse multimedia services. These applications, however, are subject to restrictions which mainly have to do with its nature and are characterized by high requirements of the transmission rates (bandwidth-consuming applications) and their sensitivity to delays in the transmission of packets by the consignor to consignee (delay-sensitive applications). On the other hand, allegedly these applications are less sensitive to packet losses (packet-loss tolerant applications). The issue, however, with multimedia applications, except for the scope of the services which offer, is the Quality of Services (QoS) that is offered to the end user. This quality of services is directly linked to the above characteristics of multimedia applications. The approach so far by the research community and also the Internet Service Providers (ISPs), as regards ensuring the quality of service, has focused either to individually optimizing the efficiency of transmission protocols, or in the installation of additional equipment (servers) for the establishment of distribution networks (Content Distribution Networks, CDNS) which are normally positioned close to the final user. In addition, the growing effort of the research community with a view to increasing the quality of service offered new innovative solutions in the form of services-architectures like the Integrated Services (Intserv) and Differentiated Services (Diffserv ) which aspire to offer guarantees of quality of services in specific user groups. But these two architectures failed until now to become the solution for the provision of guarantees of quality of services to the end user due to difficulties in applying them which have to do with financial criteria and the structure of the Internet itself. Therefore, we can see that despite the progress made so far in networks technology the provision of QoS across the Internet is not still feasible with the result that multimedia services via the Internet (for example “YouTube”) are significantly affected by the changes of the network conditions. To this course, the research community has directed to the study of mechanisms which will be able to adjust the transmission rate of multimedia data, according to the conditions of the network, so as to offer the best possible quality of service to the end user. This effort could be classified into two broad categories, according to the way the multimedia information is routed, as follows: • Adaptation mechanisms for unicast transmission: In this case the adaptation mechanisms regulate the transmission rate between the sender and the receiver in a unicast connection. • Adaptation mechanisms for multicast transmission: In this case the adaptation mechanisms regulate the transmission rate between the sender and a group of receivers. Regarding the unicast transmission the predominant proposal is the congestion control mechanism that is termed as the “TCP-friendly Rate Control (TFRC) and has been accepted as an international standard by the Internet Engineering Task Force (IETF). In the area of multicast transmission the TCP-friendly Multicast Congestion Control (TFMCC) has also become acceptable as an experimental standard from IETF. Nevertheless, laboratory studies and experiments have shown that both TFRC and TFMCC are not the most suitable adaptation mechanisms for multimedia transmission. The main problems have to do with its friendliness towards the Transmission Connection Protocol (TCP) and the sudden fluctuations in the transmission. rate. These sharp variations of the transmission rates are an attribute non desirable by multimedia applications and particularly by real-time applications. In the area of wireless networks the problems with the transmission of multimedia data are not directly linked to the congestion of the network (this mainly occurs in wired networks) as the packet losses are a direct result of the free space propagation. The approach so far has aimed at the individual optimization of the various protocols of the OSI model so as to reduce the transmission problems and minimize packet losses and the delays from the sender to the end user. In recent years, however, a different approach which has prevailed to be termed internationally as “cross-layer optimization-adaptation” has earned more and more space. Under this approach we could be able to succeed the optimization of the service, regarding the quality of multimedia applications, by means of some adaptation mechanisms which will involve more than one of the OSI layers to current network conditions. The methodology, the challenges, the restrictions and the applications of cross layer adaptation constitute an open research area which is currently in progress. The aim of this dissertation is firs the study of the existing congestion control mechanisms which mainly concern best-effort wired networks, such as the Internet. In this direction we evaluate the existing congestion/flow control mechanisms and record the main problems related to the quality of service. The performance evaluation is based on criteria relating both to TCP-friendliness and the quality of service of multimedia applications. This performance evaluation leads us to the design of new protocols which promise greater TCP-friendliness and better quality of service. An important element that distinguishes these protocols of the other approaches is the “smooth” behavior by which we minimize the high oscillations of the transmission rate, which are not desirable by multimedia applications, while maintaining a high response to sudden changes of network conditions. A second important element of this dissertation is the additions we have made to the libraries of the ns-2 simulator which are already exploited by other researchers. For this purpose the new protocols are fully defined and incorporated into the ns-2 libraries so as to be available to the research community as part of the simulator, for further studies and evaluation. At the same time we expand existing research tools in order to enable the analysis and evaluation of existing and future mechanisms based on quality criteria specific to multimedia applications, along with network-centric criteria. Regarding the wireless networks we study the cross layer adaptation and how it is possible to achieve the increase in the quality of service by implementing such a design. We study the various ways and design methodologies of a cross layer adaptation and propose a new framework with which it is possible to increase the quality of service in hybrid networks consisting of both by wired and wireless users.