Dissertations / Theses on the topic '004.25:004.62'

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.05 – комп’ютерні системи та компоненти. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019. Дисертаційна робота присвячена вирішенню науково-практичної задачі, яка полягає в розробленні та дослідженні моделей та структур даних на основі асоціативної пам’яті для комп’ютерних систем проектування структур технологічних процесів. Метою дисертаційної роботи є розроблення структури даних на основі асоціативної пам’яті для комп’ютерних систем проектування структур технологічних процесів. Об’єкт дослідження – процеси обробки інформації з використанням асоціативної пам’яті. Предмет дослідження – моделі структур даних на основі асоціативної пам’яті для комп’ютерних систем проектування структур технологічних процесів. У вступі обґрунтовано актуальність теми дисертаційної роботи; сформульовано мету та задачі дослідження; наведено зв’язок дисертації з науковими темами та програмами; визначено об’єкт та предмет дослідження; висвітлені положення, які визначають практичне значення отриманих результатів та їх наукову новизну; висвітлено особистий внесок здобувача в одержаних результатах, їх апробацію та публікації. У першому розділі проведено аналіз переваг та недоліків сучасних методів зберігання та обробки інформації при проектуванні структур технологічних процесів, який показав, що існуючі методи на основі стандартного зберігання не забезпечують необхідної швидкодії для реалізації інтелектуальних інтерфейсів. При створенні одиничних технологічних процесів з використанням баз даних, час економиться на те, що текст переходів в тій чи іншій мірі вже присутній в базі даних, але вибір стратегії обробки, обладнання та інструменту, залишається в руках технологів. Всі необхідні дані повинні зберігатися в базі і бути доступними при необхідності отримання інформації. Створити таку базу даних дозволяють структури даних на основі асоціативної пам’яті, які можуть зберігати великий обсяг інформації та дають можливість коригувати її в процесі експлуатації. Тому виникає необхідність розробки такої асоціативної пам’яті, що дозволить зберігати та обробляти велику кількість формалізованої інформації, яка на даний час зберігається у вигляді базових структур (списки, черги, дерева та ін.). Що, в свою чергу, дозволить будувати ТП для складних, високоточних виробів, з можливістю коригування даних в процесі побудови ТП та асоціювати з однією деталлю декілька технологічних процесів. В роботі пропонується для вирішення цієї задачі виконати розроблення та дослідження нейронних мереж асоціативної пам’яті, моделей та структур даних для комп’ютерної системи проектування технологічних процесів. Другий розділ присвячено розробці нових нейронних мереж на основі двонаправленої асоціативної пам’яті. Запропоновано нейронну мережу N-направленої асоціативної пам'яті, що складається з N шарів нейронів та дозволяє зберігати множинні асоціації. Запропоновано нейронні мережі асоціативної пам’яті, що здатні відновлювати по вхідній інформації безліч асоціативних вхідних зображень, по множині вхідних даних один вихідний елемент та по комбінації вхідних елементів множину вихідних. Тобто розроблена асоціативна пам’ять 1→ N , N →1 та 1 2 N → N . Запропоновано багатошарову асоціативну пам'ять з керуючими нейронами, що дозволяє будувати ланцюги асоціативних даних з можливістю коригування в процесі функціонування мережі. Розроблені нейронні мережі на основі асоціативної пам’яті, які можуть бути використані при проектуванні складних нейронних мереж деревовидної структури, що можуть використовуватися при побудові системи зберігання та обробки даних в інформаційних системах. У третьому розділі розглядається розроблення нових видів асоціативної пам’яті, які дозволяють зберігати інформацію на основі базових структур та комбінувати їх для ефективної обробки інформації. При побудові складної системи зберігання інформації в якості елементів пам'яті використовуються не окремі осередки, а їх об'єднання, що зберігають такі структури як списки, масиви, черги і т.п. Кожна з них являє собою структурований елемент, завдяки якому забезпечується пошук і обробка даних, що зберігаються в ньому. Багаторівневе комбінування цих елементів, кожен з яких можна представити як деяку множину елементів асоціативної пам'яті, є перспективним для реалізації інтелектуальних інтерфейсів, логічного висновку, обробки зображень, розпізнавання образів. У четвертому розділі розглядаються моделі структур даних на основі нейронних мереж асоціативної пам’яті для проектування структур технологічних процесів. Запропоновано структури даних на основі асоціативної пам’яті для зберігання інформації, що необхідна для проектування структури технологічного процесу. Запропоновано ієрархічну нейронну мережу на основі асоціативної пам’яті для вибору обладнання для однієї операції технологічного процесу. Результати роботи впроваджені: – в державному підприємстві "Південний державний проектно- конструкторський та науково-дослідний інститут авіаційної промисловості" (м. Харків) при виготовленні високоточних виробів; – в навчальному процесі НТУ "ХПІ" на кафедрі обчислювальної техніки та програмування при викладанні учбових дисциплін: "Основи нейрокомп’ютингу", "Системи штучного інтелекту", а також в курсових, дипломних та наукових роботах студентів спеціальності 123 "Комп’ютерна інженерія".
There is the dissertation of the obtaining the scientific degree of the technical sciences candidate in specialty 05.13.05 – computer systems and components – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. The dissertation solves the scientific and practical problem of development and researching models data structures based on associative memory for computer systems of technological processes structure design. The purpose of the dissertation is the development and researching of data structures based on associative memory for computer systems of technological processes structure design. The object of study is the processes of processing information using associative memory. The subject of study is the models of data structures based on associative memory for computer systems of technological processes structure design. The introduction substantiates the relevance of the dissertation work topic; the purpose and tasks of research are formulated; the connection of the dissertation with scientific themes and programs is given; the object and the subject of the research are determined; the provisions, that determine the practical value of the obtained results and their scientific novelty, are highlighted; the personal contribution of the applicant in the obtained results, their approbation and publication are highlighted. In the first section the analysis of the advantages and disadvantages of current methods of storing and processing information for the design of structures processes, which showed that existing methods based on standard storage do not provide the performance required for the implementation of intelligent interfaces. When creating single technological processes using databases, time is saved by the fact that the transition text is already present in the database to some extent, but the choice of processing strategy, equipment and tools remains in the hands of technologists. All necessary data should be stored in the database and be accessible when necessary to obtain information. Such a database is made possible by associative memory data structures, which can store a large amount of information and allow it to be corrected during operation. Therefore, there is a need to develop associative memory that will allow the storage and processing of a large amount of formalized information, which is currently stored as basic structures (lists, queues, trees, etc.). This, in turn, will allow the construction of TP for complex, high-precision products, with the ability to correct data in the process of TP construction and associate several technological processes with one detail. In order to solve this problem, the paper proposes to develop and research neural networks of associative memory, models and data structures for the computer system of technological process design. The second section is devoted to the development of new neural networks based on bidirectional associative memory. A neural network of N-directed associative memory, consisting of N layers of neurons and allowing multiple associations to be stored, is proposed. Associative memory neural networks have been proposed that are capable of restoring a plurality of associative input images by input, by multiple inputs, by one output element, and by a combination of input elements by multiple outputs. That is, the associative memory 1→ N , N →1 and 1 2 N → N were developed. Multilayer associative memory with control neurons is proposed, which allows the construction of associative data circuits with the possibility of correction during the operation of the network. Developed neural networks based on associative memory that can be used in the design of complex neural networks of tree structure that can be used in the construction of storage and data processing systems in information systems. The second section is devoted to the development of new types of associative memory that allow us to store information based on underlying structures and combine them for efficient information processing. When constructing a complex system of information storage, the memory elements are used not by individual cells, but by their associations, which store such structures as lists, arrays, queues, etc. Each of them is a structured element by which search and processing of the data stored in it is provided. The multilevel combination of these elements, each of which can be represented as some of the elements of associative memory, is promising for the implementation of intelligent interfaces, logical inference, image processing, pattern recognition. The fourth section discusses the model data structures based on neural networks, associative memory structures to design processes. Data structures based on associative memory are proposed for storing the information needed to design the process structure. A hierarchical neural network based on associative memory is proposed to select equipment for a single process operation. The results of the dissertation work are introduced: – in the state enterprise "State project and scientific aviation industry research institute" in the manufacture of high-precision products; – in the educational process of the NTU "KhPI" at the department of computer engineering and programming during the teaching of the academic disciplines: "Fundamentals of Neurocomputing", "Artificial intelligence systems", and also in courses, thesis and scientific works of students of the specialty 123 "Computer engineering".

The ever growing Internet Protocol (IP) traffic driven by both consumer and business applications pose a fundamental challenge for network operators. Optical networks offering terabyte capacity and advanced switching capability is at the forefront of transport technology. As optical networks and data traffic proliferate there is a growing need to scale cost effectively and allow for multiple switching technologies. Addressing this, the G.709 Optical Transport Network (OTN) combined with the intelligence of the Generalised Multi Protocol Label Switching (GMPLS) control plane is identified to reduce transport costs and deliver enhanced network and performance management functions. Connections are established using GMPLS suite of protocols namely routing, signaling and the Path Computation Element (PCE). The conventional wavelength resource reservation mechanism in the Optical Channel (OCh) layer is stud- ied and shortcomings identified. Two distributed wavelength resource reservation algorithms that improve end-to-end wavelength allocation are proposed and offer significant network blocking performance improvement. Further, the Resource Reservation Protocol with Traffic Engineering (RSVP- TE) / PCE wavelength reservation is extended to the newly defined Optical channel Data Unit (ODU) digital layer to provision at sub-wavelength granularity. Network blocking performance, rough estimates of unit cost and wavelength utilisation in comparison with OCh layer are analysed showing improved network blocking performance and wavelength utilisation at the expense of increased cost unit. Also at higher transmission bit rates of 40Gbps and beyond, it is inefficient to provision light paths without taking into consideration the optical performance requirements of the client signal. To demonstrate Impairment-Aware (lA) wavelength resource reservation, the conventional RSVP- TE and best performing proposed algorithm are adapted for 10/ 40 Gbps client signals and network blocking performance is observed. Further, hardware-accelerated control plane functions to overcome challenges posed by overhead processing for short-lived connections in dynamic high-speed networks is discussed.

Electronic services are emerging as the de-facto enabler of interaction interoperability across organization boundaries. Cross-organizational interactions are often "choreographed", i.e. specified by a messaging protocol from a global point of view independent of the local view of each interacting organization. Local requirements motivating an interaction as well as the global contextual requirements governing the interaction inevitably evolve over time, requiring adaptation of the corresponding interaction protocol. Adaptation of an interaction protocol must ensure the satisfaction of both sets of interaction requirements while maintaining consistency between the global view and the local views of an interaction specification. Such adaptation is not possible with the current state-of-the-art representations of choreographed interactions, as they capture only operational messaging specifications detached from both local organizational requirements as well as global contextual requirements. This thesis presents three novel contributions that tackle adaptation of choreographed interaction protocols: an automated technique for deriving an interaction protocol from requirements, a formalization of consistency between local and global views, and a framework for guiding the adaptation of a choreographed interaction. A choreographed interaction is specified using models of organizational requirements motivating the interaction. We employ the formal semantics embedded in requirements models to automatically derive an interaction protocol. We propose a framework for relating the global and local views of interaction specification and maintaining consistency between them. We develop a metamodel for interaction specification, from which we enumerate adaptation operations. We build a catalogue that provides guidance on performing each operation and propagating changes between the global and local views. These contributions are evaluated using examples from the literature as well as a real-world case study.

The emergence of Bluetooth as a wireless network solution assists in bringing together multiple technologies in different sectors and provides rapid interconnections to form a network paradigm. Typically, up to 8 Bluetooth devices can form a centralized network, called a piconet, controlled by a master node, which allocates transmission slots to all other nodes (slaves) in the piconet. However, the structure of inter-piconet connection: called the scatternet is not defined in the Bluetooth Specification. To develop a new scatternet structure, many challenges such as topology formation, intra and inter-piconet scheduling and packet routing are considered. The thesis addresses these critical issues based on the scatternet formation using Bluetooth. The scatternet, presented in this thesis, employs a tree hierarchy structure formation with a Leader root of three hierarchies. Within the scatternet, the new concept exploits clock and frequency synchronization for all new piconets creation. This synchronization prevents interferences and the need for guard time while switching piconet. Thus enabling a device to switch from one piconet to another at every slot. Furthermore, an innovative intra-piconet design is proposed to improve QoS within Bluetooth piconet. By exploiting the device queue status, the scheme defines a predictable polled sequence, and an adaptive traffic allocation. This offers a better fairness, and a significant power reduction when compared to the conventional Round Robin scheme. Moreover, with the perfect scatternet synchronization, the devices switch to other piconets to transmit data and, within one slot time, return to the initial piconet before the next predicted poll time exchange occurs. This considerably improves the traffic data transfer, especially for a significant number of devices present within the area. In addition, a new routing process is developed in this thesis, which facilitates communication within the scatternet. From the scatternet tree hierarchy position, a new addressing node routing is proposed to keep the overhead network low, and guarantees that any packet forwarded reaches its destination. The performance of the new scatternet is evaluated for each scatternet phase, through a Matlab simulation program, and the significant improvement of Bluetooth QoS achieved through the proposed approach is fully demonstrated. This thesis also presents a primary implementation of the scatternet concept using a dedicated Bluetooth hardware system.

This thesis reports a series of five experiments which were designed to assess two research objectives; 1) to ascertain whether CMC improves episodic and semantic collaborative recall and 2) to challenge the existing assumptions regarding semantic recall by establishing if "the nominal group effect" prevails in semantic recall. In each experiment, nominal group recall was compared with different types of collaborative recall, which included face-to-face collaboration and two types of computer mediated communication (CMC), namely synchronous (parallel) and asynchronous (serial/cyclic). Parallel communication comprised the simultaneous communication of group members in an online environment who had complete freedom over when they made contributions and attended/responded to other group members. Serial/cyclic communication employed a taking procedure where group members were exposed to each others' answers, but only one group member could contribute at a time. Two types of turn-taking procedure were examined; serial was a once-through approach where each group member got one chance to contribute (Experiment 1) and cyclic was a round-robin protocol where group members continually took turns to contribute for the duration of the recall trial (Experiments 3- 5). In Experiment 1, participants generated items from semantic categories as nominal, face-to-face, parallel and serial triads, i.e. groups. Results failed to provide evidence of the nominal group effect and there was no evidence to suggest a benefit from collaborating using one medium over another. Experiment 2 examined episodic and semantic recall in nominal, face-to-face and parallel collaboration. For episodic retrieval, participants were required to memorise categorised word lists and for semantic retrieval, participants were required to generate words beginning with specified orthographic digraphs i.e. 'br', 'he', 'po'. Results demonstrated a nominal group effect throughout episodic and semantic retrieval. Experiment 3 examined the effects of CMC when task complexity was increased to encompass the generation of words from a fixed set of letters in a Scrabble task. Once again, nominal groups generated the highest number of items, followed by parallel, face-to-face and cyclic groups. Experiments 4 and 5 extended the recent work of Finlay, Hitch and Meudell (200 1) and Blumen arid Rajaram (2008), who found that when collaborative retrieval was followed by individual retrieval, individuals were able to benefit from prior exposure, despite their initial losses acquired collaboratively. Results demonstrated improved individual episodic recall following face-to-face, parallel and cyclic collaboration, but there was no benefit for semantic retrieval.

The initial rapid expansion of the Internet, in terms of complexity and number of hosts, was followed by an increased interest in its overall parameters and the quality the network offers. This growth has led, in the first instance, to extensive research in the area of network monitoring, in order to better understand the characteristics of the current Internet. In parallel, studies were made in the area of protocol performance modelling, aiming to estimate the performance of various Internet applications. A key goal of this research project was the analysis of current Internet traffic performance from a dual perspective: monitoring and prediction. In order to achieve this, the study has three main phases. It starts by describing the relationship between data transfer performance and network conditions, a relationship that proves to be critical when studying application performance. The next phase proposes a novel architecture of inferring network conditions and transfer parameters using captured traffic analysis. The final phase describes a novel alternative to current TCP (Transmission Control Protocol) models, which provides the relationship between network, data transfer, and client characteristics on one side, and the resulting TCP performance on the other, while accounting for the features of current Internet transfers. The proposed inference analysis method for network and transfer parameters uses online nonintrusive monitoring of captured traffic from a single point. This technique overcomes limitations of prior approaches that are typically geared towards intrusive and/or dual-point offline analysis. The method includes several novel aspects, such as TCP timestamp analysis, which allows bottleneck bandwidth inference and more accurate receiver-based parameter measurement, which are not possible using traditional acknowledgment-based inference. The the results of the traffic analysis determine the location of the eventual degradations in network conditions relative to the position of the monitoring point. The proposed monitoring framework infers the performance parameters of network paths conditions transited by the analysed traffic, subject to the position of the monitoring point, and it can be used as a starting point in pro-active network management. The TCP performance prediction model is based on the observation that current, potentially unknown, TCP implementations, as well as connection characteristics, are too complex for a mathematical model. The model proposed in this thesis uses an artificial intelligence-based analysis method to establish the relationship between the parameters that influence the evolution of the TCP transfers and the resulting performance of those transfers. Based on preliminary tests of classification and function approximation algorithms, a neural network analysis approach was preferred due to its prediction accuracy. Both the monitoring method and the prediction model are validated using a combination of traffic traces, ranging from synthetic transfers/environments, produced using a network simulator/emulator, to traces produced using a script-based, controlled client and uncontrolled traces, both using real Internet traffic. The validation tests indicate that the proposed approaches provide better accuracy in terms of inferring network conditions and predicting transfer performance in comparison with previous methods. The non-intrusive analysis of the real network traces provides comprehensive information on the current Internet characteristics, indicating low-loss, low-delay, and high-bottleneck bandwidth conditions for the majority of the studied paths. Overall, this study provides a method for inferring the characteristics of Internet paths based on traffic analysis, an efficient methodology for predicting TCP transfer performance, and a firm basis for future research in the areas of traffic analysis and performance modelling.

This thesis is concerned with the link layer design of indoor (IrDA) and outdoor infrared links, as well as the performance of the higher layers of two major Wireless Personal Area Network (WPAN) technologies: IrDA and Bluetooth. Recent advancesin wireless technology have made it possible to put networking technology into small portable devices. During the past few years, WPAN technologies have been the subject of a tremendous growth both in research and development. Although many studies have been conducted on wireless links to address different issues on physical and link layers, wireless communications are still characterised by high error rates becauseof the frequently changing medium. On the other hand, performance studies of the higher layers are also very important. In this thesis, for the first time, a comprehensivestudy of the interactions betweenthe higher and the lower protocol layers of IrDA and Bluetooth has been carried out to improve the overall system performance. Mathematical models for the link layers are introduced for the infrared systems: infrared data association (IrDA) and free space optics (FSO). A model for the IrDA (indoor infrared) link layer is developed by considering the presence of bit errors. Based on this model, the effect of propagation delay on the link through put is investigated. An optimization study is also carried out to maximize the link throughput. FSO (outdoor infrared) links are often characterized by high speed and long link distance. A mathematical model for the FSO link layer is also developed. Significant improvement of the link throughput is achieved by optimizing the link parameters. Based on the link layer model, the performance of the IrDA higher layers (transport, session and application layers) is investigated. First, a mathematical model of TinyTP (transport protocol) is elaborated and subsequently verified by simulations. The effects of multiple connections and available buffer size are investigated. The throughput at the TinyTP level is optimized for different buffer sizes. Subsequently, the session layer, including Object Exchange (OBEX) and IrDA Burst (IrBurst) protocols, is studied and modelled. The derived mathematical model is verified by simulation results. A set of protocol parameters and hardware selection guidelines is proposed to optimize the overall system performance while also keeping the hardware requirementto a minimum. Finally, two rapidly developing IrDA applications, IrDA financial messaging(IrFM) and IrDA simple connection (IrSC), are studied. IrFM is investigated by comparison to other digital payment technologies, while the performance of IrSC is compared in two different technical approaches. In order to improve the throughput and minimize the transmission delay for the Bluetooth data applications, a systematic analysis is carried out for the Bluetooth Logical Link Control and Adaptation Layer Protocol (L2CAP). L2CAP is layered above the Bluetooth link layer (Baseband) and is essential to Bluetooth data applications. A simple and intuitive mathematical model is developed to derive simple equations for the L2CAP throughput and the average packet delay. The derived throughput equation, which is validated by simulations, takes into account bit errors as well as packet retry limits. Finally, a number of easy-to-implement performance enhancement schemes are proposed, including the optimum use of the protocol parameters.

In recent years there has been a marked growth in the use of wireless cellular telephones, PCs and the Internet. This proliferation of information technology has hastened the advent of wireless networks which aim to increase the accessibility and reach of communications devices. Ambient Intelligence (Ami) is a vision of the future of computing in which all kinds of everyday objects will contain intelligence. To be effective, Ami requires Ubiquitous Computing and Communication, the latter being enabled by wireless networking. The IEEE's 802.11 task group has developed a series of radio based replacements for the familiar wired ethernet LAN. At the same time another IEEE standards task group, 802.15, together with a number of industry consortia, has introduced a new level of wireless networking based upon short range, ad-hoc connections. Currently, the most significant of these new Wireless Personal Area Network (WPAN) standards is Bluetooth, one of the first of the enabling technologies of Ami to be commercially available. Bluetooth operates in the internationally unlicensed Industrial, Scientific and Medical (ISM) band at 2.4 GHz. unfortunately, this spectrum is particularly crowded. It is also used by: WiFi (IEEE 802.11); a new WPAN standard called Zig- Bee; many types of simple devices such as garage door openers; and is polluted by unintentional radiators. The success of a radio specification for ubiquitous wireless communications is, therefore, dependant upon a robust tolerance to high levels of electromagnetic noise. This thesis addresses the optimisation of low power WPANs in this context, with particular reference to the physical layer radio specification of the Bluetooth system.

The current Internet consists of a large collection of Autonomous Systems (ASes) or domains, each being a network or group of networks managed by a single authority such as an Internet Service Provider (ISP) or a commercial enterprise. These ASes employ their own network policies and routing protocols. In order to support all the Internet traffic caused by everyday applications such as peer-to-peer content downloading, multimedia streaming, voice over IP, online gaming, video conferencing, etc., network providers seek to optimise their network resource usage in an efficient manner utilising Traffic Engineering (TE) techniques. These techniques control traffic routing so as to optimise operational IP network performance and can be classified into intra-AS and inter-AS. Network providers use intra-AS TE techniques to control traffic routing within their network to achieve objectives such as load balancing and/or minimising resource consumption. On the other hand, they use inter-AS TE techniques to control inbound and outbound traffic to achieve load balancing over inter-AS resources and/or minimise peering costs. Unfortunately, due to a variety of events such as malicious attacks, misconfiguration, router CPU overload, interface failure and accidental damage, various failures, and in particular link failures, occur as part of daily network operations. Research has revealed that both single intra- and inter- AS link failure are common events and transient in nature. The potential impact of a link failure can be delay, packet discard, service disruption and severe congestion due to the shifting of an excessive amount of traffic to alternative paths that are already highly utilised. Given the shortlived nature of transient failures, network operators may not have sufficient time to re-configure their networks before the failure is restored, resulting to the detrimental failure impact. In order to manage this situation, in this thesis we propose proactive network provisioning approaches that predict the impact of transient link failures and implement remedial solutions to alleviate the detrimental failure impact. The contributions of our thesis are as follows: o Improving intra-AS primary path robustness. Routing traffic flows though high availability network segments results in minimising their path failure probability and also in reducing the amount of backup resources required to protect these primary paths. We therefore propose a heuristic algorithm with four link cost functions that take link availability into account to improve primary path availability in MPLS networks while optimising network resources. o Making inter-AS outbound TE robust to inter-AS link failure for long-term and short-term network provisioning. Transient inter-AS link failures are as common as intra-AS link failures and can have similar detrimental consequences. We therefore propose an IP tunnelling approach that can provide fast rerouting and also an algorithm that provides primary and secondary egress points to achieve load balancing under both no failure and also single inter-AS link failure states for long-term network provisioning. We solve this algorithm using a tabu search heuristic. Additionally, network conditions such as traffic variations and destination prefix reachability change, these events may make the long-term outbound TE solutions inaccurate. We therefore propose a short-term network provisioning framework that provides inter-AS outbound robust TE solutions considering the network dynamics. Making both intra-AS and inter-AS outbound TE robust to intra- or inter-AS link failure. Due to the common and transient nature of both intra- and inter-AS link failures, there are significant interactions between them. As a result, the overall network performance may not be truly robust to intra- and inter-AS link failures if they are considered separately. We therefore propose a joint robust TE approach that balances the intra- and inter-AS load balancing under intra- or inter-AS link failure taking into account their interactions. In summary, in this thesis we aim to propose robust approaches for both intra-AS and inter-AS outbound TE so as to optimise IP operational network performance under both normal and also failure conditions.

Arising from the fact that the terrestrial network is becoming more IP-centric, it is crucial to be able to support IP services over the satellite component of UMTS as well to achieve close synergy with the terrestrial counterpart for seamless communication. Nevertheless, the direct utilization of the IP protocol suite in a mobile environment is not straightforward, and when coupled with the additional constraints and shortcomings that satellite-based systems pose, it imposes additional challenges to the integration of satellite systems into the IP-based T-UMTS and the global Internet. In this thesis, we study the feasibility of establishing multimedia sessions over S-UMTS based on the SIP protocol, and investigate efficient solutions to transport SIP signalling, taking into account not only the larger satellite propagation delay but also the impact of the S-UMTS radio interface arid channel impairment. The preservation of maximum commonality between T- & S-UMTS is the aim of our work to facilitate an effective integration of both segments. Given that a dedicated channel needs to be used for the transport of SIP signalling, the Random Access Channel (RACH) is first investigated. The impact of the different RACH transmission control parameters on the access performance over S-UMTS is studied with their trade-offs identified. It is further demonstrated how QoS differentiation could be provided on the RACH through Access Service Classes (ASCs). Two schemes have also been proposed to decrease the risk of code/signature collision, where it has been shown that when network-wide synchronization is already in place, these schemes perform better than the ETSI S-UMTS scheme as the access rate increases. By incorporating a link layer retransmission based on the RLC-AM mechanisms, it has been shown that SIP session establishment can work acceptably well over S-UMTS with performance comparable to the circuit-switched call setup. It is further demonstrated that with proper configuration of RLC parameters and retransmission options, the session setup performance under various channel conditions can be substantially improved. Two schemes that mitigate the inefficiencies of the existing UMTS RLC-AM procedure for session setup over S-UMTS have also been proposed. The main advantage of the first scheme lies in its ability to recover the missing last radio segments in a single round-tip whilst minimizing the feedback and avoiding redundant retransmissions. The second approach minimises redundant retransmissions when more than one feedback report trigger is configured, where improved system performances are obtained. Finally, in the joint study of SIP's own reliability mechanisms and RLC retransmission scheme, it has been shown that precious radio and network resources can be saved by making SIP and RLC 'more co-operative' through different degree of awareness of each other. Key words: S-UMTS, IP, Session Initiation Protocol, Random Access Charmel, Radio Link Control.

Grid computing is diverse and heterogeneous in nature, spanning across multiple domains where resources are not owned or managed by a single administration. This brings about many challenges to Grid resource management and exposes the user to the Grid middleware complexities. Thus this research develops a user-centric resource broker that insulates the users from the Grid complexities, alleviating them from the burden of having to know the various mechanisms of the Grid middleware. The broker is based on the SNAP (Service Negotiation and Acquisition Protocol) framework and focuses on applications that require resources on demand. It is important for applications that require resources on demand to reserve the necessary resources within the minimum time possible. Thus the work in this thesis has developed a three-phase commit protocol which enhances the traditional twophase commit protocol. Performance evaluation has been carried out to evaluate the SNAP-based resource broker using the traditional two-phase commit protocol and the newly developed three-phase commit protocol. The evaluation has been conducted on a local Grid test-bed, a distributed Grid infrastructure (the White Rose Grid) and through mathematical modelling and simulation. Throughout the evaluation, the SNAP-based resource broker using the three-phase commit protocol provides a significant performance enhancement, over the use of the traditional twophase commit protocol, in terms of the time taken between submission (to the broker) of user requirements and the job beginning execution.

For years the Internet networking community has been struggling to develop ways to manage networks. Initial attempts brought mechanisms and protocols that focused on managing and configuring individual networking devices i.e. the Simple Network Management Protocol (SNMP). This model worked well in early deployments of IP management systems for local and metropolitan area networks but now, with the evolution of Quality of Service (QoS) models such as the Differentiated Services (DiffServ) framework, the complexity and overhead of operating and administrating networks increases enormously. There is also a need to be able to program management systems and network components to adapt to emerging requirements and subsequently be able to dynamically change the behaviour of the whole system to support modified or additional functionality. The emerging Policy-based Network Management paradigm claims to be a solution to these requirements. Policy-based Management can guide the behaviour of a network or distributed system through high-level declarative directives that are dynamically introduced, checked for consistency, refined and evaluated, resulting typically in a series of low-level actions. The objective of this thesis is to investigate the application of Policy-based Management in the context of QoS Management of IP DiffServ Networks. By using policies as a means for building extensible hierarchical management systems, we propose a novel Policy-based QoS management architecture and specify the relevant policies that can drive its behaviour dynamically, providing a holistic approach to the area of policies for QoS Management. We first present our view on policies as a means of extending the functionality of management systems dynamically, in conjunction with pre-existing "hard-wired" management logic and provide a generic framework for their application to hierarchical distributed management systems. The programmability aspect of policies is an issue which has not been properly addressed in the literature and constitutes an important contribution of this thesis. We then propose a single architecture for managing an IP DiffServ network, identifying the required functional components and their interactions addressing both service management and resource provisioning (traffic engineering) aspects of QoS Management. The design of the architecture caters for both offline and dynamic operation. Furthermore, we identify the parameters of the functional components of the architecture that are influenced by policies and present an object oriented representation of those policies based on the Policy Core Information Model (PCIM). This work differentiates from relevant work on QoS policies since it addresses the area of QoS Management in its totality defining policies related to service management and traffic engineering both at a network and element management level. Finally, we validate the proposed policy-based framework by presenting a detailed description of the design and implementation of the components of the policy management sub-system needed to be deployed in order to make our system policy-driven and present examples of QoS policies describing their transformation from their definition by the operator until their enforcement.

Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.05 – комп’ютерні системи та компоненти. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019. Дисертаційна робота присвячена вирішенню науково-практичної задачі, яка полягає в розробленні та дослідженні моделей та структур даних на основі асоціативної пам’яті для комп’ютерних систем проектування структур технологічних процесів. В дисертаційній роботі запропоновано архітектури, алгоритми навчання та функціонування і програмні компоненти, що реалізують розроблені нейронні мережі N-направленої асоціативної пам’яті, багатошарової асоціативної пам’яті та асоціативної пам’яті з керуючими нейронами, що використовується в базі даних для проектування структури технологічного процесу; розроблено структуру даних на основі нейронних мереж асоціативної пам’яті, яка дозволяє більш ефективно моделювати технологічні процеси. Проведені експериментальні дослідження вдосконаленої комп'ютерної системи проектування структур технологічних процесів як на рівні математичного моделювання, так і на реальному об'єкті, підтвердили достовірність запропонованих рішень.
There is the dissertation of the obtaining the scientific degree of the technical sciences candidate in specialty 05.13.05 – computer systems and components – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2019. The research is devoted to solving a scientific and practical problem, which is to develop and study the models and structures of data based on associative memory for computer systems of technological processes structure design. In the research work, architecture, algorithms of training and functioning and software components are proposed that implement the developed neural networks of N-directional associative memory, multilayered associative memory and associative memory with control neurons used in the database for the design of the structure of the technological process; the structure of data on the basis of neural networks of associative memory is developed, which allows you more effectively to model technological processes. Experimental studies of the improved computer system design of structures of technological processes were carried out at the level of mathematical modeling and on the real object, the reliability of the proposed decisions are confirmed.

In recent years the growth in demand for multimedia applications delivered over a network has been extensive illustrated by the phenomenal expansion of the World Wide Web in today's Internet. Increasing amounts of electronic information are presented in a multimedia format and delivered over networks, which generates increased traffic demands. In short, future networks will not only comprise multiple, interconnected data transport platforms but will also need to handle an increasing range of distributed multimedia services, delivered to a diverse user community that is increasingly becoming mobile.

Mobile ad hoc networks (MANETs) have become increasingly important in view of their promise of ubiquitous connectivity beyond traditional fixed infrastructure networks. Such networks, consisting of potentially highly mobile nodes, have provided new challenges by introducing special consideration stemming from the unique characteristics of the wireless medium and the dynamic nature of the network topology. The TCP protocol, which has been widely deployed on a multitude of internetworks including the Internet, is naturally viewed as the de facto reliable transport protocol for use in MANETs. However, assumptions made at TCP’s inception reflected characteristics of the prevalent wired infrastructure of networks at the time and could subsequently lead to sub-optimal performance when used in wireless ad hoc environments. The basic presupposition underlying TCP congestion control is that packet losses are predominantly an indication of congestion in the network. The detrimental effect of such an assumption on TCP’s performance in MANET environments has been a long-standing research problem. Hence, previous work has focused on addressing the ambiguity behind the cause of packet loss as perceived by TCP by proposing changes at various levels across the network protocol stack, such as at the MAC mechanism of the transceiver or via coupling with the routing protocol at the network layer. The main challenge addressed by the current work is to propose new methods to ameliorate the illness-effects of TCP’s misinterpretation of the causes of packet loss in MANETs. An assumed restriction on any proposed modifications is that resulting performance increases should be achievable by introducing limited changes confined to the transport layer. Such a restriction aids incremental adoption and ease of deployment by requiring minimal implementation effort. Further, the issue of packet loss ambiguity, from a transport layer perspective, has, by definition, to be dealt with in an end-to-end fashion. As such, a proposed solution may involve implementation at the sender, the receiver or both to address TCP shortcomings. Some attempts at describing TCP behaviour in MANETs have been previously reported in the literature. However, a thorough enquiry into the performance of those TCP agents popular in terms of research and adoption has been lacking. Specifically, very little work has been performed on an exhaustive analysis of TCP variants across different MANET routing protocols and under various mobility conditions. The first part of the dissertation addresses this shortcoming through extensive simulation evaluation in order to ascertain the relative performance merits of each TCP variant in terms of achieved goodput over dynamic topologies. Careful examination reveals sub-par performance of TCP Reno, the largely equivalent performance of NewReno and SACK, whilst the effectiveness of a proactive TCP variant (Vegas) is explicitly stated and justified for the first time in a dynamic MANET environment. Examination of the literature reveals that in addition to losses caused by route breakages, the hidden terminal effect contributes significantly to non-congestion induced packet losses in MANETs, which in turn has noticeably negative impact on TCP goodput. By adapting the conservative slow start mechanism of TCP Vegas into a form suitable for reactive TCP agents, like Reno, NewReno and SACK, the second part of the dissertation proposes a new Reno-based congestion avoidance mechanism which increases TCP goodput considerably across long paths by mitigating the negative effects of hidden terminals and alleviating some of the ambiguity of non-congestion related packet loss in MANETs. The proposed changes maintain intact the end-to-end semantics of TCP and are solely applicable to the sender. The new mechanism is further contrasted with an existing transport layer-focused solution and is shown to perform significantly better in a range of dynamic scenarios. As solution from an end-to-end perspective may be applicable to either or both communicating ends, the idea of implementing receiver-side alterations is also explored. Previous work has been primarily concerned with reducing receiver-generated cumulative ACK responses by “bundling” them into as few packets as possible thereby reducing misinterpretations of packet loss due to hidden terminals. However, a thorough evaluation of such receiver-side solutions reveals limitations in common evaluation practices and the solutions themselves. In an effort to address this shortcoming, the third part of this research work first specifies a tighter problem domain, identifying the circumstances under which the problem may be tackled by an end-to-end solution. Subsequent original analysis reveals that by taking into account optimisations possible in wireless communications, namely the partial or complete omission of the RTS/CTS handshake, noticeable improvements in TCP goodput are achievable especially over long paths. This novel modification is activated in a variety of topologies and is assessed using new metrics to more accurately gauge its effectiveness in a wireless multihop environment.

This thesis is concerned with the study of secure wireless routing protocols, which have been deployed for the purpose of exchanging information in an adhoc networking enviromnent. A discrete event simulator is developed, utilising an adaptive systems modelling approach and emergence that aims to assess networking protocols in the presence of adversarial behaviour. The model is used in conjunction with the characteristics that routing protocols have and also a number of cryptographic primitives that can be deployed in order to safeguard the information being exchanged. It is shown that both adversarial behaviour, as well as protocol descriptions can be described in a way that allows for them to be treated as input on the machine level. Within the system, the output generated selects the fittest protocol design capable of withstanding one or more particular type of attacks. As a result, a number of new and improved protocol specifications are presented and benchmarked against conventional metrics, such as throughput, latency and delivery criteria. From this process, an architecture for designing wireless routing protocols based on a number of security criteria is presented, whereupon the decision of using particular characteristics in a specification has been passed onto the machine level.

Cette thèse se positionne dans le contexte des réseaux sans fil multi-sauts (réseaux de capteurs/actionneurs/robots mobiles). Ces réseaux sont composés d’entités indépendantes à la puissance limitée et fonctionnant sur batteries qui communiquent exclusivement par voie radio. Pour pouvoir relayer les messages d’un robot à une station de base, on utilise des protocoles dits « de routage» qui ont en charge de déterminer quel robot doit relayer le message. Nous nous sommes basés sur le protocole CoMNet, qui adapte la topologie du réseau à son trafic lors du routage afin d’économiser de l’énergie en déplaçant les robots. Mais modifier la topologie c'est aussi modifier les possibilités de routage. Nous proposons donc MobileR (Mobile Recursivity) qui choisit le prochain noeud en ayant anticipé par le calcul les conséquences de tous les changements de topologie possibles. Un autre problème vient du fait qu’il y a souvent plusieurs nœuds qui détectent un même événement et vont émettre des messages à router vers la station de base. Ces messages vont finir par se croiser, et le nœud de croisement va sans cesse être relocalisé sur chacun des chemins. Le protocole PAMAL (PAth Merging ALgorithm) détecte ces intersections : il va provoquer une fusion des chemins de routage en amont du nœud de croisement et une agrégation de paquets en aval. Enfin, le protocole GRR (Greedy Routing Recovery) propose un mécanisme de récupération pour augmenter le taux de délivrance des messages dans les réseaux de capteurs/actionneurs avec obstacle(s). En effet, les protocoles de routage actuels échouent face à un obstacle. GRR va permettre de contourner l’obstacle en relocalisant des nœuds tout autour
This thesis is about wireless multi-hop networks such as sensor/actuator networks and actuator networks. Those networks are composed of independent entities which have limited computing and memory capabilities and are battery powered. They communicate through the radio medium and do not require any static infrastructure. In order to relay messages between actuators up to the base station, we use what is called "routing protocols". My works rely on CoMNet, the first geographic routing protocol which aims to adapt the network topology to the routed traffic in order to save energy. Nevertheless, CoMNet does not consider the consequences of those relocations more than in a one-hop way. We proposed MobileR (Mobile Recursivity), which anticipates the routing in a multi-hop manner through computations over its one-hop neighbors. Hence it can select the “best” next forwarding node according to its knowledge. Another important topic is that events are likely to be detected by multiple sensors and all of them transmit message toward the destination. But those messages are likely to cross over an intersection node. This crossing provokes useless oscillation for it and premature node death. The PAMAL (PAth Merging ALgorithm) routing algorithm detects those routing path crossing and provokes a path merging upstream and uses a packet aggregation downstream. Finally, the Greedy Routing Recovery (GRR) protocol takes controlled mobility into account in order to increase delivery rate on topology with holes or obstacles. GRR includes a dedicated relocation pattern which will make it circumvent routing holes and create a routing path

The Transmission Control Protocol (TCP) has been designed for reliable data transport over the Internet. The performance of TCP is strongly influenced by its congestion control algorithms that limit the amount of traffic a sender can transmit based on end-to-end available capacity estimations. These algorithms proved successful in environments where applications rate requirements can be easily anticipated, as is the case for traditional bulk data transfer or interactive applications. However, an important new class of Internet applications has emerged that exhibit significant variations of transmission rate over time. Variable-rate traffic poses a new challenge for congestion control, especially for applications that need to share the limited capacity of a bottleneck over a long delay Internet path (e.g., paths that include satellite links). This thesis first analyses TCP performance of bursty applications that do not send data continuously, but generate data in bursts separated by periods in which little or no data is sent. Simulation analysis shows that standard TCP methods do not provide efficient support for bursty applications that produce variable-rate traffic, especially over long delay paths. Although alternative forms of congestion control like TCP-Friendly Rate Control and the Datagram Congestion Control Protocol have been proposed, they did not achieve widespread deployment. Therefore many current applications that rely upon User Datagram Protocol are not congestion controlled. The use of non-standard or proprietary methods decreases the effectiveness of Internet congestion control and poses a threat to the Internet stability. Solutions are therefore needed to allow bursty applications to use TCP. Chapter three evaluates Congestion Window Validation (CWV), an IETF experimental specification that was proposed to improve support for bursty applications over TCP. It concluded that CWV is too conservative to support many bursty applications and does not provide an incentive to encourage use by application designers. Instead, application designers often avoid generating variable-rate traffic by padding idle periods, which has been shown to waste network resources. CWV is therefore shown to not provide an acceptable solution for variable-rate traffic. In response to this shortfall, a new modification to TCP, TCP-JAGO, is proposed. This allows variable-rate traffic to restart quickly after an inactive (i.e., idle) period and to effectively utilise available network resources while sending at a lower rate than the available rate (i.e., during an application-limited period). The analysis in Chapter five shows that JAGO provides faster convergence to a steady-state rate and improves throughput by more efficiently utilising the network. TCP-JAGO is also shown to provide an appropriate response when congestion is experienced after restart. Variable-rate TCP traffic can also be impacted by the Initial Window algorithm at the start or during the restart of a session. Chapter six considers this problem, where TCP has no prior indication of the network state. A recent proposal for a larger initial window is analysed. Issues and advantages of using a large IW over a range of scenarios are discussed. The thesis concludes by presenting recommendations to improve TCP support for bursty applications. This also provides an incentive for application designers to choose TCP for variable-rate traffic.

Modern computer systems are advancing from multi-core to many-core designs and System-on-chips (SoC) are becoming increasingly complex while integrating a great variety of components, thus constituting complex distributed systems. Such architectures rely on extremely complex communication protocols to exchange data with required performance. Arguing formally about the correctness of communication is an acknowledged verification challenge. This thesis presents a generic framework that formalises the idea of incremental modelling and step-wise verification to tackle this challenge: to control the overall complexity, features are added incrementally to a simple initial model and the complexity of each feature is encapsulated into an independent modelling step. Two main strategies reduce the verification effort. First, models are constructed with verification support in mind and the verification process is spread over the modelling process. Second, generic correctness results for framework components allow the verification to be reduced to discharging local assumptions when a component is instantiated. Models in the framework are based on abstract state machines formalised in higher order logic using the Isabelle theorem prover. Two case studies show the utility and breadth of the approach: the ARM AMBA Advanced High-performance Bus protocol, an arbiter-based master-slave bus protocol, represents the family of SoC protocols; the PCI Express protocol, an off-chip point-to-point protocol, illustrates the application of the framework to sophisticated, performance-related features of current and future on-chip protocols. The presented methodology provides an alternative to the traditional monolithic and post-hoc verification approach.

L'un des défis majeurs de l'évolution de l'architecture Internet est la définition d'une architecture protocolaire permettant d'améliorer le routage, et en particulier (i) conserver un système de routage gérable avec les technologies actuelles et futures c'est-à-dire, avec quelques millions d'états, (ii) offrir une architecture apte à faciliter la programmabilité du plan de transfert, (iii) proposer un système de routage évolutif pouvant être régulièrement optimisé avec uniquement les informations sur les flux actifs, (iv) fournir une séparation entre localisateurs et identificateurs pour la mobilité IP avancée, (v) faciliter un déploiement incrémental, (vi) mieux servir les services applicatifs "over-the-top". Le protocole LISP (\textit{Locator/Identifier Separation Protocol}) a été identifié comme l'un des protocoles émergents à cet égard. Dans son état actuel, il répond très bien aux besoins susmentionnés. Cependant, il subit des limitations lorsqu'il s'agit de prendre en compte la résilience et la capacité à réagir rapidement aux mises à jour de l'état du réseau. Ces inconvénients peuvent être compensés en améliorant l'architecture du plan de contrôle et ses algorithmes de routage. Dans cette thèse, nous proposons une nouvelle architecture réseau-système et expérimentons de nouvelles primitives de plan de contrôle, ainsi que d'algorithmes de diffusion des états, en testant son passage à l'échelle avec différentes conditions de réseau. Nous concevons et construisons d'abord un nœud de plan de données et de plan de contrôle LISP open source. Nous le comparons avec d'autres implémentations en montrant que notre implémentation atteint des performances adaptées aux vrais déploiements. Nous montrons comment notre implémentation a permis la mise en oeuvre d'une plateforme d'expérimentation à grande échelle, la plate-forme LISP-Lab, en opération aussi bien les fonctions de plan de transfert que les fonctions de plan de contrôle. En suite, nous proposons une nouvelle solution pour les migrations à chaud de machines virtuelles à travers des centres de données géographiquement répartis sur des réseaux IP étendus. Des tests dans un testbed réel connecté nativement à Internet montrent qu'avec notre approche, nous pouvons facilement atteindre des temps d'arrêt inférieurs à la seconde lors de la migration sur une grande échelle, même pour des clients très distants. En outre, nous avons étudié des protocoles d'optimisation de réseau multicouche, en particulier en relation avec le protocole MPTCP (Multipath Transport Control Protocol), auquel LISP peut offrir une diversité de chemins pour l’agrégation de bande passante, ainsi qu’une plus grande confidentialité et fiabilité des connexions. Bien que nous ne puissions bénéficier que de quelques nœuds de réseau superposés, nous avons pu évaluer expérimentalement nos propositions en montrant l'impact positif de notre solution, l'impact négatif des longs temps d'aller-rétour sur certains sous-flux MPTCP, et la forte corrélation entre le temps d'aller-retour différentiel et le débit. Enfin, nous avons travaillé sur une refonte du plan de contrôle de LISP afin d’améliorer son fonctionnement du à l'échelle d’Internet, en facilitant la coopération entre les systèmes de mapping LISP et en introduisant plus d'automatisation dans la procédure de fourniture de services de connectivité LISP. Nous croyons qu'une telle optimisation pourrait sensibiliser la communauté des fournisseurs de services, générant de nouvelles opportunités commerciales liées aux services de cartographie LISP et l'application de politiques d'ingénierie de trafic interdomaines avancées dans le but d'obtenir de meilleures garanties de qualité de service
One of the major challenges in the evolution of the Internet architecture is the definition of a protocol architecture that allows to solve the following major issues in Internet routing and traffic forwarding capabilities, (i) keeping a routing state that is manageable with current and forthcoming computing infrastructure – i.e., with few millions of states, (ii) offering a scalable pull architecture in support of data-plane programmability, (iii) offering a scalable forwarding plane able to be regularly optimized with only active flows information, (iv) offering locator/identifier separation for advanced IP mobility, (v) is incrementally deployable, (vi) can enhance the support of over-the-top services. The Locator/Identifier Separation Protocol (LISP) has been identified as one of the rising protocols in this respect. In its current status, it supports the above mentioned requirements at a level that is acceptable for basic networking environments. However, it shows too limited capacities when it comes to take into consideration fault resiliency and capability to react fast to network state updates. These shortcomings can be compensated by enhancing the control-plane architecture, and the routing algorithms therein. In this dissertation, we propose new protocol features and experiment novel control-plane primitives, as well as hybrid distributed-centralized routing state dissemination algorithms, to scale with different network conditions. We first design and build own open source LISP data-plane and control plane node, comparing it with other implementations, showing how our implementation can scale for large networks and reach performances suitable for real deployments. We present how our implementation served to operate all network nodes (data-plane and control-plane nodes) of a large scale experimentation testbed, the LISP-Lab testbed. Then we propose a novel LISP-based solution for VM live migrations across geographically separated datacenters over wide area IP networks. Experimenting it at large scale, we show that with our approach we can easily reach sub-second downtimes upon Internet-wide migration, even for very distant clients. Moreover, we investigate cross-layer network optimization protocols, in particular in relation with the Multipath Transport Control Protocol (MPTCP) to which LISP can deliver path diversity in support of bandwidth increase, confidentiality support and connection reliability, also using LISP traffic engineering network overlays. Despite we could benefit from only few overlay network nodes, we could experimentally evaluate our proposals showing the positive impact by using our solution, the negative impact of long round-trip times on some MPTCP subflows, and the strong correlation between the differential round-trip time among subflows and the throughput performance. Finally, we worked on a framework to improve LISP operation at the Internet scale, by facilitating cooperation between LISP Mapping Systems and introducing more automation in the LISP connectivity service delivery procedure. We believe such optimization could raise awareness among the service providers’ community, yielding new business opportunities related to LISP mapping services and the enforcement of advanced inter-domain traffic engineering policies for the sake of better quality of service guarantees

Кваліфікаційну роботу магістра присвячено дослідженню та реалізації методів автоматизованого перекладу природної мови на основі нейромережевої моделі “послідовність-послідовність”. Розглянуто основні принципи та підходи до підготовки тренувальної вибірки даних, у тому числі з використанням глибоких нейронних мереж у якості енкодерів. Досліджено та проаналізовано наявні методи вирішення задачі перекладу природної мови, зокрема, було розглянуто декілька нейромережевих архітектур глибокого машинного навчання. Наведено приклади створення та обробки корпусів природної мови для вирішення задачі формування тренувальної та тестувальної вибірок даних. Було проведено повну оцінку вартості створення комп’ютерної системи, необхідної для вирішення поставленого завдання, а також описано повний процес розгортання програмного забезпечення на даному середовищі за допомогою сторонніх платформ.
The master's thesis is devoted to the research and implementation of methods of automated translation of natural language on the basis of the neural network model "sequence-sequence". The basic principles and approaches to the preparation of training data sampling, including the use of deep neural networks as encoders, are considered. The existing methods of solving the problem of natural language translation have been studied and analyzed, in particular, several neural network architectures of deep machine origin have been considered. Examples of creation and processing of natural language corpora to solve the problem of forming training and test data samples are given. A full assessment of the cost of creating a computer system required to solve the problem was performed, as well as a complete process of deploying software in this environment using third-party platforms. The results of the research were a complete review of existing solutions to solve the problem, choosing the best technology, improving the latter, implementation and training of a deep neural network model such as sequence-sequence" for the problem of natural language translation.
1. ВСТУП 2. АНАЛІЗ ПРЕДМЕТНОЇ ОБЛАСТІ 3. ОБҐРУНТУВАННЯ ОБРАНИХ ЗАСОБІВ 4. РЕАЛІЗАЦІЯ СИСТЕМИ ПЕРЕКЛАДУ ПРИРОДНОЇ МОВИ НА ОСНОВІ МОДЕЛІ "ПОСЛІДОВНІСТЬ-ПОСЛІДОВНІСТЬ" ТА НЕЙРОМЕРЕЖЕВОЇ АРХІТЕКТУРИ ТРАСНФОРМЕРС 5. ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ

Робота виконана на кафедрі автоматизації технологічних процесів і виробництв факультету прикладних інформаційних технологій та електроінженерії Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України. Захист відбудеться «22» грудня 2020р. о 14.00год. на засіданні екзаменаційної комісії №22 у Тернопільському національному технічному університеті імені Івана Пулюя
Метою магістерської роботи є розробка автоматизованої системи перевірки інформації для онлайн-майданчику з продажу автомобілів, яка дозволить перевіряти інформацію із користувацького оголошення в реєстрах відомостей про транспортні засоби та їх власників, а також перевірки авто на факт розшуку. Для досягнення цієї мети потрібно: дослідити предметну область, провести аналіз використання відкритих даних при розробці онлайн сервісів та здійснити постановку проблеми; побудувати модель автоматизованої системи перевірки інформації; визначити технології розробки; реалізувати систему і розробити методику перевірки інформації з реєстру; провести тестування і оцінку якості розробленої системи.
The purpose of the master's thesis is to develop an automated information verification system for the online platform for the sale of cars, which will verify the information from the user's ad in the registers of vehicles and their owners, as well as checking cars for search. To achieve this goal you need: explore the subject area, analyze the use of open data in the development of online services and pose a problem; build a model of an automated information verification system; identify development technologies; implement the system and develop a methodology for verifying information from the register; to test and evaluate the quality of the developed system.
Вступ 5 1 Аналітична частина 6 1.1 Загальні поняття відкритих даних 6 1.2 Загальний стан та статус відкритих даних в Україні 10 2 Науково-дослідна частина 14 2.1 Формати та набори відкритих даних 14 3 Технологічна частина 21 3.1 Опис та обґрунтування використовуваних технологій 21 3.2 Вибір мови програмування 22 3.3 Вибір системи керування базами даних 24 3.4 Огляд засобів для відображення системи 25 4 Конструкторська частина 28 4.1 Розробка онлайн-майданчику з продажу автомобілів 28 4.2 Розробка модуля автоматизованої системи перевірки інформації 34 5 Спеціальна частина 41 5.1 Розробка онлайн-сервісів в Україні на основі відкритих даних 41 6 Охорона праці та безпека в надзвичайних ситуаціях 49 6.1 Гігієнічні вимоги до параметрів виробничих приміщень в яких експлуатується інформаційна система 49 6.2 Напрацювання заходів щодо протипожежної стійкості автоматизованих систем перевірки інформації під час надзвичайних ситуацій техногенного характеру 54 Висновки 60 Перелік посилань 61

Les protocoles historiques d’Internet (TCP/IP) qui servaient à interconnecter les tous premiers ordinateurs ne sont plus adaptés à la diffusion massive de contenus qui en est fait aujourd’hui. De nouveaux protocoles réseau centrés sur les contenus (Information-Centric Networking) sont actuellement conçus pour optimiser ces échanges en pariant sur un changement de paradigme où les contenus, plutôt que les machines sont adressables à l’échelle d’Internet. Cependant, un tel changement ne peut se faire que progressivement et si tous les impératifs opérationnels sont assurés. Ainsi, cette thèse a pour objectif d’étudier et de lever les principaux verrous technologiques empêchant l’adoption du protocole NDN (Name Data Networking) par les opérateur en garantissant la sécurité, les performances, l’interopérabilité, la bonne gestion et le déploiement automatisé d’un réseau NDN. Dans un premier temps, nous évaluons les performances actuelles d’un réseau NDN à l’aide d’un outil de notre conception, ndnperf, et constatons le coût élevé pour un serveur utilisant ce protocole. Puis nous proposons un ensemble de solutions pour améliorer l’efficacité d’un serveur NDN pouvant être jusqu’à 6,4 fois plus efficient que les paramètres de base. Ensuite nous nous intéressons à la sécurité de NDN à travers l’évaluation de l’attaque par empoisonnement de contenus, connue pour être critique mais jamais caractérisée. Cette étude se base sur deux scénarios, en utilisant un serveur et un client pour effectuer la pollution, ou en exploitant une faille dans le traitement des paquets au niveau du routeur. Nous montrons ainsi la dangerosité de l’attaque et proposons une correction de la faille la permettant. Dans un troisième temps, nous cherchons à adapter le protocole HTTP pour qu’il puisse être transporté sur un réseau NDN à des fins d’interopérabilité. Pour ce faire, nous avons développé deux passerelles qui effectuent les conversions nécessaires pour qu’un contenu web puisse rentrer ou sortir d’un réseau NDN. Après avoir décrit notre solution, nous l’évaluons et l’améliorons afin de pouvoir bénéficier d’une fonctionnalité majeure de NDN, à savoir la mise en cache des contenus dans le réseau à hauteur de 61,3% lors de tests synthétiques et 25,1% lors de simulations de navigation avec plusieurs utilisateurs utilisant une loi Zipf de paramètre 1,5. Pour finir, nous proposons une architecture à base de microservices virtualisés et orchestrés pour le déploiement du protocole NDN en suivant le paradigme NFV (Network Function Virtualization). Les sept microservices présentés reprennent soit une fonction atomique du routeur, soit proposent un nouveau service spécifique. Ces fonctions peuvent ensuite être chaînées pour constituer un réseau optimisé. Cette architecture est orchestrée à l’aide d’un manager qui nous permet de pleinement tirer parti des avantages des microservices comme la mise à l’échelle des composants les plus lents ou encore le changement dynamique de topologie en cas d’attaque.Une telle architecture, associée aux contributions précédentes, permettrait un déploiement rapide du protocole NDN, notamment grâce à un développement facilité des fonctions, à l’exécution sur du matériel conventionnel, ou encore grâce à la flexibilité qu’offre ce type d’architecture
Internet historical protocols (TCP/IP) that were used to interconnect the very first comput-ers are no longer suitable for the massive distribution of content that is now being made. New content-based network protocols (Information-Centric Networking) are currently being designed to optimize these exchanges by betting on a paradigm shift where content, rather than machines, are addressable across the Internet. However, such a change can only be made gradually and if all operational imperatives are met. Thus, this thesis aims to study and remove the main tech-nological obstacles preventing the adoption of the NDN (Name Data Networking) protocol by operators by guaranteeing the security, performance, interoperability, proper management and automated deployment of an NDN network. First, we evaluate the current performance of an NDN network thanks to a tool we made, named ndnperf, and observe the high cost for a provider delivering fresh content using this protocol. Then, we propose some optimizations to improve the efficiency of packet generation up to 6.4 times better than the default parameters. Afterwards, we focus on the security of the NDN protocol with the evaluation of the content poisoning attack, known as the second more critical attack on NDN, but never truly characterized. Our study is based on two scenarios, with the usage of a malicious user and content provider, or by exploiting a flaw we found in the packet processing flow of the NDN router. Thus, we show the danger of this kind of attacks and propose a software fix to prevent the most critical scenario. Thirdly, we are trying to adapt the HTTP protocol in a way so that it can be transported on an NDN network for interoperability purposes. To do this, we designed an adaptation protocol and developed two gateways that perform the necessary conversions so that web content can seamlessly enter or exit an NDN network. After describing our solution, we evaluate and improve it in order to make web content benefit from a major NDN feature, the in-network caching, and show up to 61.3% cache-hit ratio in synthetic tests and 25.1% in average for browsing simulations with multiple users using a Zipf law of parameter 1.5. Finally, we propose a virtualized and orchestrated microservice architecture for the deploy-ment of an NDN network following the Network Fonction Virtualization (NFV) paradigm. We developed seven microservices that represent either an atomic function of the NDN router or a new one for specific purposes. These functions can then be chained to constitute a full-fledged network. Our architecture is orchestrated with the help of a manager that allows it to take the full advantages of the microservices like scaling the bottleneck functions or dynamically change the topology for the current needs (an attack for example). Our architecture, associated with our other contributions on performance, security and in-teroperability, allows a better and more realistic deployment of NDN, especially with an easier development of new features, a network running on standard hardware, and the flexibility allowed by this kind of architecture

Dans cette thèse, nous proposons une nouvelle approche pour modéliser et estimer les délais de bout-en-bout dans les réseaux de capteurs sans-fil (WSN). Notre approche combine les approches analytiques et expérimentales pour inférer un modèle Markovien modélisant le comportement d'un protocole de contrôle d'accès au médium (MAC) exécuté sur les nœuds d'un réseau de capteurs. À partir de ce modèle Markovien, le délai de bout en bout est ensuite obtenu par une approche analytique basée sur une analyse dans le domaine fréquentiel pour calculer la probabilité de distribution de délais pour un taux d'arrivée spécifique. Afin d’obtenir une estimation du délai de bout en bout, indépendamment du trafic en entrée, la technique de régression non-linéaire est utilisée sur un ensemble d’échantillons limités. Cette approche nous a permis de contourner deux problèmes: 1) la difficulté d'obtenir un modèle Markovien du comportement d’un protocole MAC en tenant compte de son implémentation réelle, 2) l'estimation du délai de bout-en-bout d’un WSN multi-sauts. L'approche a été validée sur un testbed réel (IOT-LAB) et pour plusieurs protocoles (X-MAC, ContikiMAC, IEEE 802.15.4) ainsi que pour un protocole de routage (RPL)
In this thesis, we propose an approach that combines both measurements and analytical approaches for infering a Markov chain model from the MAC protocol execution traces in order to be able to estimate the end to end delay in multi-hop transmission scenarios. This approach allows capturing the main features of WSN. Hence, a suitable Markov chain for modelling the WSN is infered. By means of an approach based on frequency domain analysis, end to end delay distribution for multi-hop scenarios is found. This is an important contribution of our approach with regard to existing analytical approaches where the extension of these models for considering multi-hop scenarios is not possible due to the fact that the arrival distribution to intermediate nodes is not known. Since local delay distribution for each node is obtained by analysing the MAC protocol execution traces for a given traffic scenario, the obtained model (and therefore, the whole end to end delay distribution) is traffic-dependant. In order to overcome this problem, we have proposed an approach based on non-linear regression techniques for generalising our approach in terms of the traffic rate. Results were validated for different MAC protocols (X-MAC, ContikiMAC, IEEE 802.15.4) as well as a well-known routing protocol (RPL) over real test-beds (IOT-LAB)

Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη εφαρμογής για την προσομοίωση, με χρήση του προγράμματος προσομοίωσης OPNET της λειτουργίας του πρωτοκόλλου IPFIX που χρησιμοποιείται για τη συλλογή και την προώθηση δικτυακών δεδομένων στους σταθμούς διαχείρισης του δικτύου. Το πρωτόκολλο αυτό βοηθάει τους διαχειριστές του δικτύου να παρακολουθήσουν «monitoring» την ροή των δεδομένων εντός του δικτύου. Το πρώτο μέρος της εργασίας περιέχει την μελέτη και την ανάλυση της λειτουργίας του πρωτοκόλλου αυτού σε θεωρητικό επίπεδο με σκοπό την κατανόηση της ανάγκης ύπαρξης ενός ομοιόμορφου προτύπου για την εξαγωγή πληροφοριών από δικτυακές συσκευές. Ταυτόχρονα γίνεται εκτενής αναφορά στο διαδεδομένο Netflow της εταιρείας Cisco πάνω στο οποίο είναι βασισμένο το Πρωτόκολλο Εξαγωγής Πληροφοριών Ροής Ipfix. Στο δεύτερο μέρος της διπλωματικής παρατίθεται η ανάπτυξη ενός δικτύου με σκοπό να επεξηγήσουμε τον τρόπο με τον οποίο παρατηρούνται τα δεδομένα μέσα σε αυτό. Η εκτέλεση της εφαρμογής για διαφορετικά είδη κίνησης και διαφορετική ένταση κίνησης ή και για διαφορετικό τρόπο συλλογής των δεδομένων στο OPNET επιτρέπει την εξαγωγή χρήσιμων συμπερασμάτων για το κόστος και την επίδοση του πρωτοκόλλου.
The goal of this diploma thesis is the development of an application in order to simulate the function of the IPFIX Protocol, which is used to collect and transmit network data to the network management stations. For this purpose OPNET (Optimized Network Engineering Tools) was used. Briefly, IPFIX helps network managers to monitor the flow of data within the network. Throughout the first part of this dissertation emphasis is given to the study and analysis of the protocol in theory, and this way the need for a protocol that is in charge of extracting information out of network devices is underlined. In addition, extensive coverage of the widespread Cisco Netflow protocol has been made since IPFIX is based on it. Throughout the second part of this dissertation a network is presented in order to explain the way data is observed within it. The execution of the application for different, kinds of traffic, traffic intensity and ways of collecting data, using OPNET, enables us to export useful conclusions considering cost and performance of the protocol.

Στο παρόν κείμενο μελετώνται οι τεχνικές υλοποίησης L2 MPLS VPNs Cicruit Cross Connect (CCC) και Any Trasfer over MPLS (AToM) που παρέχουν οι δύο κύριοι κατασκευαστές δικτυακού υλικού Juniper και Cisco αντίστοιχα. Πρόθεση της μελέτης είναι να διερευνηθούν τα ιδιαίτερα τεχνικά χαρακτηριστικά της κάθε τεχνικής και στην συνέχεια να μελετηθούν τρόποι επίτευξης της διαλειτουργικότητας μεταξύ των δύο. Το τελευταίο είναι χρήσιμο στην περίπτωση που μια υπηρεσία παροχής L2 MPLS VPNs επεκτείνεται σε ένα δίκτυο που αποτελείται από εξοπλισμό και των δύο κατασκευαστών. Στην ιδιαίτερη περίπτωση του ΕΔΕΤ το οποίο είναι ένα αμιγώς «Cisco» δίκτυο το παραπάνω έχει εφαρμογή στο όριο διασύνδεσης με το GEANT το οποίο αντίστοιχα είναι ένα αμιγώς «Juniper» δίκτυο. Συνεπώς η παροχή L2 MPLS VPN μεταξύ οποιουδήποτε φορέα που συνδέεται στο ΕΔΕΤ( πχ ενός ακαδημαϊκού ιδρύματος) και ενός άλλου φορέα που είναι πίσω από το Geant ( φυσικά εκτός ΕΔΕΤ) προϋποθέτει την επίλυση των προβλημάτων διαλειτουργικότητας μεταξύ των δύο τεχνικών.
The subject of this paper is the implementation techniques of L2 MPLS VPNs Cicruit Cross Connect (CCC) and Any Trasfer over MPLS (AtoM) that are provided by the two main manufactures of network connection (Juniper and Cisco). Furthermore this paper searches the special technical features of each technique and tries to find ways of interoperability between those two. This is useful when a providing L2 MPLS VPNs service expands in a network that consists of equipment of these two main manufactures . In the special occasion of EDET, which is a completely «Cisco» network the upper has implementation in the connection limits with GEANT, which is a completely «Juniper» network. Therefore the providing of L2 MPLS VPN between any carrier that is connected with EDET (eg. Academic Institute) and another carrier that is behind GEANT (of course out of EDET) presupposes the solution of the interoperability problems between these techniques.

Στην παρούσα διατριβή παρουσιάζονται μεθοδολογίες σχεδιασμού που επιτρέπουν την μείωση την κατανάλωση ενέργειας σε υλοποιήσεις ασύρματων εφαρμογών πολυμέσων. Οι προτεινόμενες μεθοδολογίες βελτιστοποιούν την διαχείριση της μνήμης, η κατανάλωσης της οποίας είναι η κυρίαρχη συνιστώσα της συνολικής κατανάλωσης ισχύος στις εφαρμογές πολυμέσων. Επιπλέον, η διατριβή πραγματεύεται τεχνικές για χαμηλής κατανάλωσης διαμερισμό, ο οποίος είναι απαραίτητος για την εκτέλεση σε πραγματικό χρόνο των υψηλής υπολογιστικής πολυπλοκότητας εφαρμογών πολυμέσων. Στόχο της παρούσας διατριβής αποτελεί και η βελτιστοποίηση, όσον αφορά την κατανάλωση ισχύος, των κυκλωμάτων ασύρματης μετάδοσης των πολυμέσων. Στο πλαίσιο αυτό η διατριβή ασχολείται με τεχνικές διαχείρισης ισχύος, και προτείνει υλοποιήσεις που χρησιμοποιούν τις τεχνικές αυτές. Οι μεθοδολογίες και τεχνικές λαμβάνουν υπόψη και την επιφάνεια ολοκλήρωσης και ταχύτητα εκτέλεσης. Τα ισοζύγια (trade-offs) αναγνωρίζονται, και όπου αυτά υπάρχουν προτείνονται μέθοδοι για την αποδοτική τους επίλυση.
In this Ph.D. dissertation, design methodologies that enable energy minimization of wireless multimedia application realizations are presented. The proposed methodologies mainly optimize the management of the memory subsystem, which role is dominant as far as energy dissipation of multimedia application is concerned. Furthermore, techniques for the low-power partitioning, which is required for the real-time implementation of the highly computational complex multimedia applications, are proposed. Apart from the multimedia processing itself the dissertation, also focuses on the transmition of the multimedia content. To this end, power management techniques applicable for the design of wireless receivers are proposed. The proposed techniques are employed for the design of real-life implementation of low and medium rate receivers. Apart from energy minimization The proposed methodologies and techniques take into account constraints regarding the integration area as well as the processing time. The involved trade-offs are identified, and methods for their efficient exploration are proposed

Ανάλυση λειτουργιών πρωτοκόλλου ΜΙΜΕ για τη διαχείριση ομάδων συζητήσεων (forums) και ηλεκτρονικού ταχυδρομείου (e-mail) σε ιστοσελίδες δικτυακού τόπου
Analysis of features of MIME presentation protocol

Мета роботи полягає у розробці архітектури IoT-інфраструктури з використанням технології Blockchain. У дипломній роботі проаналізовано сучасний стан технологій Blockchain та IoT, та визначено основну проблематику їх застосування; оцінено та проведено тестування ефективності, продуктивності та можливості масштабування. Розроблено функціональну структуру та архітектуру IoT- інфраструктури з використанням ключових елементів LBM та OBM. За допомогою цих елементів розроблено мережу накладення, яка потенційно може складатися з великої кількості вузлів.

Η παρούσα εργασία αφορά την παρουσίαση μιας νέας ιδέας στην δρομολόγηση των ασυρμάτων ad hoc δικτύων, την δομημένη δρομολόγηση. Η ιδέα αυτή εξελίχθηκε σταδιακά στην διάνοιά μου τον τελευταίο ένα χρόνο, η ιδέα για την δόμηση μιας υπερκείμενης δομής πάνω από ένα ασύρματο ad hoc δίκτυο που θα καθοδηγούσε την αναζήτηση του κόμβου προορισμού. Η έρευνά μου είχε αρχίσει από τα p2p δίκτυα και τις δομές. Κάποια στιγμή συνειδητοποίησα ότι όλα αυτά είχαν άμεση σχέση με τα ad hoc δίκτυα. Όταν τελικά διαπίστωσα την ευρεία υιοθέτηση της πλημμύρας στους αλγορίθμους δρομολόγησης στα ad hoc, ήμουν βέβαιος πως σίγουρα θα μπορούσαμε να κάνουμε κάτι καλύτερο. Να αντικαταστήσουμε την αδόμητη, τυφλή, τεχνική της πλημμύρας με μια δομημένη, κατευθυνόμενη, αναζήτηση που θα ελαχιστοποιούσε την επιβάρυνση στο δίκτυο. Έτσι άρχισε η αναζήτησή μου, που κατέληξε στην ανάπτυξη του πρωτοκόλλου CONOS. Ενός πρωτοκόλλου που φιλοδοξεί να μετατρέψει τα ad hoc δίκτυα από μια εξειδικευμένη τεχνική σε μια καθημερινή πραγματικότητα. Το πρωτόκολλο CONOS περιγράφεται αναλυτικά στο δεύτερο μέρος αυτής της αναφοράς, και όπως φαίνεται από τις μετρήσεις που έχω κάνει, όντως ελαχιστοποιεί την επιβάρυνση στην αναζήτηση του κόμβου προορισμού. Ωστόσο απομένει να γίνει και άλλη έρευνα, το κεφάλαιο 6 συνοψίζει διάφορα ανοιχτά θέματα και προτάσεις για την αντιμετώπισή τους.
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Метою дипломної роботи є дослідження, проектування та розробка роботизованої системи мобільного розгортування мережі. Методи та програмні засоби, використані при виконанні розробки системи: Arduino sketch, Simple TCP Socket Tester, TCP/IP Builder. Опрацьовані відомі системи розгортування мереж, описана структура і схеми побудови та налаштування робота, програмні та апаратні засоби для розробки та, вивчено питання безпеки охорони праці.

Метою дипломної роботи є розробка методів та алгоритмів вибору каналів передачі голосу в мережі для забезпечення якості голосових послуг. Методи та програмні засоби, використані при виконанні розробки системи: Matlab Simulink, Simple TCP Socket Tester, TCP/IP Builder. Опрацьовані відомі системи розгортування мереж, описана структура і схеми побудови та налаштування маршрутизатора, програмні та апаратні засоби для розробки та вивчено питання безпеки охорони праці.

Στόχος της παρούσας διπλωματικής εργασίας είναι η μελέτη της μετάδοσης δεδομένων πάνω από Κινητά Δίκτυα 3ης Γενιάς και συγκεκριμένα του δικτύου UMTS (Universal Mobile Telecommunications Systems). Την τελευταία δεκαετία τόσο η Κυψελωτή Κινητή Τηλεφωνία όσο και το Διαδίκτυο έχουν γνωρίσει τρομακτική εξάπλωση παγκοσμίως. Η ανάγκη του ανθρώπου για κινητικότητα από τη μια, και η ανάγκη για πρόσβαση σε πληροφορία και υπηρεσίες από την άλλη, οδήγησε στη σύγκλιση των δυο παραπάνω «κόσμων» μέσα από τα Κινητά Δίκτυα 3ης Γενιάς. Το δίκτυο UMTS, οδηγείται προς τη φιλοσοφία ενός all-IP δικτύου, που επιτρέπει πρόσβαση υψηλών ταχυτήτων στο Διαδίκτυο. Στην παρούσα διπλωματική εργασία παρουσιάζεται αναλυτικά η αρχιτεκτονική και λειτουργική δομή του UMTS δίκτυο, ξεκινώντας από τα γενικά χαρακτηριστικά του, σε ότι αφορά το χρησιμοποιούμενο φάσμα, την αξιοποίηση του διατιθέμενου εύρους ζώνης και τη δομή των κυψελών του UMTS. Στη συνέχεια παρουσιάζεται η αρχιτεκτονική του δικτύου, με αναφορά στον εξοπλισμό του χρήστη, το Δίκτυο Επίγειας Ασύρματης Πρόσβασης (UTRAN) και το Δίκτυο Κορμού (Core Network), ενώ παρουσιάζονται και τα πρωτόκολλα σηματοδοσίας και επιπέδου χρήστη εντός του UMTS. Στη συνέχεια η εργασία ασχολείται με το θέμα της παροχής Ποιότητας Υπηρεσίας (Quality of Service – QoS) στο δίκτυο UMTS. Παρουσιάζονται οι τάξεις QoS και τα χαρακτηριστικά τους στο UMTS, και οι παράμετροι που αυτές παίρνουν για συγκεκριμένες υπηρεσίες (φωνή, video, εφαρμογές ροής πολυμέσων κτλ.). Παράλληλα με την Ποιότητα Υπηρεσίας, παρουσιάζεται και η υπηρεσία MBMS (Multimedia Broadcast / Multicast Service) που έχει σχεδιαστεί για το UMTS δίκτυο και αναλύεται η δομή και ο τρόπος υλοποίησης των λειτουργιών της, οι διαδικασίες υπηρεσιών MBMS, οι παράμετροι που αυτή παίρνει και γίνεται και ανάλυση των επιμέρους λειτουργιών της. Το δεύτερο μέρος της εργασίας αφορά την πειραματική αξιολόγηση του δικτύου UMTS στον εξομοιωτή ns-2, σε ότι αφορά τη μετάδοση διαφορετικών ειδών κίνησης και την αποτελεσματικότητα των διαφορετικών πρωτοκόλλων. Αρχικά περιγράφεται ο τρόπος παραγωγής κίνησης για τον εξομοιωτή και των μεθόδων που χρησιμοποιήθηκαν προς την κατεύθυνση αυτή. Στη συνέχεια παρουσιάζονται τα αποτελέσματα των πειραμάτων για την απόδοση του πρωτοκόλλου TCP πάνω από το δίκτυο UMTS, και παρουσιάζονται τα προβλήματα που προκύπτουν στη χρήση του πρωτοκόλλου αυτού, κυρίως λόγο του υψηλού bit error rate που παρουσιάζεται στο ασύρματο κανάλι. Μελετώνται σενάρια χρήσης που χρησιμοποιούν τόσο UMTS DCH (Dedicated Channels), όσο και HSDPA (High Speed Downlink Packet Access) μεταδόσεις. Με σκοπό τη μελέτη της μετάδοσης και πολυμεσικού περιεχομένου πάνω από το UMTS, έγιναν αντίστοιχα πειράματα στον εξομοιωτή και διαπιστώθηκε η δυνατότητα του UMTS να εγγυηθεί τις διαφορετικές απαιτήσεις αυτού του είδους κίνησης (κυρίως σε ότι αφορά την καθυστέρηση των πακέτων) και τη «φιλική» προς το TCP πρωτόκολλο συνύπαρξη στο δίκτυο. Τέλος, στη διπλωματική αυτή εργασία προτείνεται ένα σχήμα, για την ανάπτυξη ενός συστήματος μετάδοσης πολυμεσικού περιεχομένου πάνω από UMTS, το οποίο λαμβάνει υπόψη του την τρέχουσα κατάσταση του δικτύου και προσαρμόζει τη ροή των πολυμεσικών δεδομένων σε αυτή.
The purpose of this dissertation is to study data transmission using Third Generation (3G) Mobile Networks and in particular using the Universal Mobile Telecommunications Systems (UMTS) network. Over the last decade, Cellular Mobile Telephony and Internet have spread rapidly worldwide. The need for mobility on the one side and on the other side the need for access to information and services, led to the convergence of the two worlds using Third Generation Mobile Networks. The UMTS network is slowly becoming an all-IP network that allows high speed data Internet connection. This dissertation discusses the UMTS network’s architectural and functional framework starting from the general characteristics of the available bandwidth and the UMTS cells’ structure. The architectural design of the network is presented next with respect to the user’s equipment, the Universal Terrestrial Radio Access Network (UTRAN) and the Core Network, followed by the signaling protocol and the user level within UMTS. After that, the dissertation covers Quality of Service (QoS) issues while using the UMTS network. The two QoS groups are presented along with their UMTS characteristics, and certain parameters for specific services (such as voice, video, multimedia streaming applications, etc.). In addition, the Multimedia Broadcast/Multicast Service (MBMS) is discussed. MBMS is a service designed for the UMTS network and the procedure and services of its functionality are being analysed. The second part of this dissertation deals with the experimental evaluation of the UMTS network in the ns-2 simulator, regarding the transmission of different types of traffic and the efficiency of the different protocols. The method of the traffic generation is being discussed at first, along with the implemented modules. Following that, the results from the experiments on TCP protocol performance over the UMTS air interface are being presented and some issues that raise up due to the high bit error rate that occur in the wireless channel are being discussed. In this case, we study the performance of both UMTS Dedicated Channels (DCH) and the High Speed Downlink Packet Access) transmissions. In order to study the transmission of multimedia content over the UMTS, some experiments took place, and showed that UMTS is able of guaranteeing the different requirements of this type of traffic, especially regarding the packets’ time delays and the friendly behavior against the TCP protocol, when coexisting in the network traffic load. Finally, this dissertation proposes a scheme for developing a multimedia content transmission system over UMTS, which takes into consideration the current state of the network and adapts the multimedia data stream to these conditions.