Η παρούσα διπλωματική εργασία έχει ως αντικείμενο τη μελέτη τεχνικών αντιμετώπισης θορύβων και παρεμβολών σε αστικό περιβάλλον κυτταρικής κινητής τηλεφωνίας τρίτης γενιάς. Ξεκινώντας γίνεται αναφορά στις κινητές επικοινωνίες, την ιστορική τους διαδρομή, από τα πρώτα τους βήματα τη δεκαετία του 1940 εως τη σημερινή 4η γενιά και τη ραγδαία άνθισή τους τις τελευταίες δεκαετίες. Περιγράφεται αναλυτικά η κυτταρική ιδέα ανάπτυξης των τηλεπικοινωνιακών συστημάτων, οι βασικές αρχές της και τα τεχνικά χαρακτηριστικά της καθώς και τα διεθνή πρότυπα από τα οποία ορίζεται. Ακολουθεί η αναλυτική περιγραφή του συστήματος UMTS, το οποίο δίνει το στίγμα της κυτταρικής κινητής τηλεφωνίας 3ης γενιάς, ενώ το τρίτο κεφάλαιο πραγματεύεται την ασύρματη μετάδοση σε ανοιχτό χώρο, τα μοντέλα διάδοσης και τους διάφορους παράγοντες που μπορεί να επηρεάσουν ένα ασύρματο κανάλι. Ο θόρυβος και οι παρεμβολές ορίζονται και περιγράφονται διεξοδικά στο τέταρτο κεφάλαιο.Στο πέμπτο κεφάλαιο αναπτύσσονται οι τεχνικές αντιμετώπισής τους και στη συνέχεια ακοιλουθεί η περιγραφή μιας συγκεκριμένης τοπολογίας. / The objective of this work is the study of the different reduction techniques for Noise and Interference in 3G cellular mobile telecommunication systems at an urban environment.First a reference is made in mobile communications, their historic journey and their rapid evolution in recent decades.An analytical specification of the cellular concept of development, the technical characteristics and the international standards is made.Follows the description of the umts,the wireless transmission in an environment, the diffusion model and factors that may affect a wireless channel.The noise and interference are defined and described.Chapter five describes the reduction methods,at chapter six a specific topology is described and at last there are some conclusions.

Masters of Science / This thesis offers some prototypes to provide browser-based and mobile video communication services for Deaf people and evaluates these prototypes. The aim of this research is to identify an acceptable video communication technology for Deaf people by designing and evaluating several prototypes. The goal is to find one that Deaf people would like to use in their day-to-day life. The thesis focuses on two technologies | browser-based systems and mobile applications. Several challenges emerged, for example, specific Deaf user requirements are difficult to obtain, the technical details must be hidden from end users, and evaluation of prototypes includes both technical and social aspects. This thesis describes work to provide South African Sign Language communication for Deaf users in a disadvantaged Deaf community in Cape Town. We posit an experimental design to evaluate browser-based and mobile technologies in order to learn what constitutes acceptable video communication for Deaf users. Two browser-based prototypes and two mobile prototypes were built to this effect. Both qualitative data and quantitative data are collected with user tests to evaluate the prototypes. The video quality of Android satisfies Deaf people, and the portable asynchronous communication is convenient for Deaf users. The server performance is low on bandwidth, and will therefore cost less than other alternatives, although Deaf people feel the handset is costly. / South Africa

Orientador: Helio Waldman / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-05T14:57:27Z (GMT). No. of bitstreams: 1 Savasini_MarcioSaenz_M.pdf: 1495771 bytes, checksum: 8580ad17c20a8326cbb9cee63471d096 (MD5) Previous issue date: 2005 / Resumo: Este trabalho tem como objetivo analisar a redução na probabilidade de bloqueio com o uso de conversores de comprimento de onda e esquemas de proteção em redes ópticas. É apresentada a proteção por roteamento em sub-grafos, um método de criar caminhos de proteção dependentes a falha para cada conexão. Alguns esquemas para eliminar realocações desnecessárias de conexões no caso de falha, sem penalizar fortemente a aceitação de novas conexões, foram sugeridos e comparados. Outro tema abordado no trabalho foi o ganho do uso de conversores de comprimento de onda em redes em malha em um ambiente dinâmico de tráfego. Foi utilizado nas simulações um número limitado de conversores plenos espalhados pela rede. Foi analisada a quantidade suficiente de conversores para se ter uma probabilidade de bloqueio satisfatória, pensando em minimizar os investimentos a serem feitos no momento de uma expansão da rede. Para um melhor entendimento dos problemas estudados há uma descrição do funcionamento da rede óptica e seus elementos principais e dos algoritmos de roteamento e alocação de comprimento de onda utilizados e descritos na literatura / Abstract: This work examines the blocking reduction with the use of wavelength converters and some protection schemes in optical networks. Sub-Graph Routing Protection, a protection method that creates different failure-dependent protection paths for each connection is presented. Some schemes were proposed and compared, aiming at eliminating unnecessary connection reallocations on a failure occurrence, without compromising the acceptance of new connections. Another topic studied for this work is the conversion gain, when wavelength converters are used in mesh topology networks under dynamic traffic. A limited number of total converters were used in the simulations. The sufficient amount of converters for a satisfactory blocking probability was analyzed, for minimizing investments in a network upgrade. For a better problem formulation understanding the optical network and its elements were explained. The routing and wavelength allocation algorithms proposed in the literature are also detailed. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Jacobus Willibrodus Swart / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T12:25:16Z (GMT). No. of bitstreams: 1 Ximenes_AugustoRonchini_M.pdf: 16128462 bytes, checksum: 20fb62b3a104e71ac8afffc21dd2a9c2 (MD5) Previous issue date: 2011 / Resumo: O aumento no número de usuários, assim como a demanda por maior taxa de transferência de dados, está impulsionando o desenvolvimento de novas tecnologias, uma vez que o padrão clássico de comunicação está atingindo sua saturação. Vídeos em alta definição, chamadas em vídeo-conferência e downloads em alta velocidade deixaram de ser uma particularidade para se tornarem básicos, oferecendo constantes desafios em todos os níveis de projeto de um dispositivo. Atualmente, a maneira adotada para se criar um canal de comunicação sem fio (wireless) baseia se na modulação da informação de interesse em torno de uma freqüência muito mais alta, chamada portadora. Para cada protocolo tem-se reservada uma banda do espectro, porém, dependendo da região e do número de usuários dividindo a banda, tende-se a ter esta banda saturada, reduzindo a capacidade de comunicação para cada usuário. Freqüentemente, observam-se cenários onde algumas bandas de freqüência estão extremamente ocupadas e regiões vizinhas no espectro completamente vazias. De modo a operar o espectro com maior inteligência, surgiram conceitos com o de Rádios Cognitivos (CR - Cognitive Radios), onde algoritmos monitoram o espectro de modo a utilizar um canal somente quando este estiver livre, mudando de banda se necessário. Isto requer circuitos susceptíveis à operação em banda larga. Sendo assim, este projeto propõe a realização de um amplificador de banda larga empregando um novo método de cancelamento de ruído, além do projeto de um misturador de baixo ruído utilizando técnicas recentes exploradas na literatura, de modo a obter uma cadeia de recepção para uso em banda larga. O LNA apresenta casamento de impedância e ganho de potência de 12dB na banda de 50 MHz até 5 GHz, com NF variando de 1,4 - 2,4 dB, enquanto consome 15 mW de potência sob tensão de alimentação de 1,5 V. O desempenho em NF, quando levado em consideração a potência consumida e o nó tecnológico, é o melhor comparado aos recentes projetos que o autor tem conhecimento. O cancelamento de ruído é obtido através de uma condição específica do circuito, requerendo uma corrente extra de polarização, já inclusa na potência total do circuito. Para compor a cadeia de recepção e, consecutivamente, a conversão do sinal em banda base de modo homodyne, projetou-se um par de Misturadores de modo a re-utilizar a corrente extra requerida pelo LNA no cancelamento do ruído. Desta maneira, obteve-se na cadeia de recepção o ganho de tensão de 26 dB na saída de cada Misturador, em Fase (I) e Quadratura (Q), para uma banda de 50 MHz até 6,5 GHz, com SSB NF variando de 6,1 - 9,2 (3,1 - 6,2 dB para DSB), consumindo os mesmos 15 mW e tendo a banda estendida pelos Misturadores. Os circuitos foram fabricados na tecnologia UMC 0,13'mu'm Mixed/RF CMOS e algumas medidas preliminares foram obtidas e serão mostradas nesta dissertação. O LNA apresentou ganho, casamento de impedância e potência próximos aos valores obtidos nas simulações, mostrando boa confiabilidade dos valores projetados / Abstract: The increase in the number of users as well as the demand for higher data transfer rate is driving development of new technologies, since the classical communication is reaching its saturation. Videos in high definition, video-conference calls and high-speed downloads are no longer a special feature to become basic, offering constant challenges at all levels in the design of a device. Currently, the way adopted to create a wireless communication channel is based on the modulation of interesting information about a much higher frequency, called carrier. For each protocol, a reserved bandwidth of the spectrum has been assigned, however, depending on the region and the number of users sharing the band, it tends to have saturated the band, reducing the communication ability of each user. Often, there are scenarios where some bands are extremely busy and neighboring regions in the spectrum are completely empty. In order to operate the spectrum with higher intelligence emerged with the concept of Cognitive Radio (CR), where algorithms monitor the channel in order to use them only when it is free, and changing band if necessary. This requires circuits to be susceptible for broadband operation. Therefore, this project proposes a broadband amplifier using a new method for noise cancellation, and the design of a low noise mixer using techniques explored in the recent literature, in order to get broadband receiver chain. The LNA provides impedance matching and power gain of 12dB from 50MHz to 5GHz band with NF ranging from 1.4 - 2.4 dB, while consuming 15mW of power under a supply voltage of 1.5 V. Its NF performance, when taken into consideration the power consumption and technology node, is the best compared to recent projects that the author is aware of. The noise cancellation is achieved by a specific condition of the circuit, requiring an extra biasing current, already included in the total circuit power. To compose the chain of reception and, consecutively, the conversion of the baseband signal in homodyne mode, a pair of Mixers were designed, re-using the extra current required by the LNA for noise cancellation. Thus, it was achieved at receiver chain a voltage gain of 26dB at the output of each Mixer, at Phase (I) and Quadrature (Q), for bandwidth of 50MHz to 6.5 GHz with SSB NF ranging from 6.1 - 9.2 (3.1 - 6.2dB for DSB), also consuming the same 15mW and having a band enhancement provided by the Mixers. The circuits were fabricated in UMC technology 0.13'mu'm Mixed/RF CMOS and some preliminary measurements were obtained and are shown in this dissertation. The LNA presented gain, impedance matching and power close to the values obtained in the simulations, showing good reliability on the projected values / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Meste em Engenharia Elétrica

Orientador: Lee Luan Ling / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T02:24:35Z (GMT). No. of bitstreams: 1 YakovNae_M.pdf: 7990917 bytes, checksum: 122c511d9ba839a2f1464fbe7fca09b4 (MD5) Previous issue date: 2011 / Resumo: Gerência de armazenamento em Redes de Sensores Sem Fio (RSSF) é uma questão muito crítica. Além da RSSFs conter uma vasta quantidade de armazenamento agregada, ela não pode ser usada inteiramente. Portanto, o sistema inteiro falha quando o primeiro sensor tem sua capacidade de armazenamento esgotada, deixando uma grande capacidade de armazenamento inutilizada. Sugere-se que os sensores devem-se ser capazes de detectar as capacidades de armazenamentos inutilizadas, para prolongar as suas funcionalidades. Entretanto, em RSSF de larga escala isso pode ser muito difícil uma vez que os sensores podem não ter conhecimento da existência dos outros. Neste trabalho apresenta-se duas principais contribuições: otimização da capacidade total de armazenamento para RSSF em grande escala e uma nova abordagem de roteamento - Deterministic "Random" Walk (Passeio "Aleatório" Determinístico). Apresenta-se um novo modelo de armazenamento via construção "sob demanda" de Cadeias de Armazenamento Distribuídas ( Distributed Storage Chains (DSC). Estas cadeias representam parcerias entrem os sensores que podem compartilhar suas capacidades de armazenamento. Resultando, os sensores não estão sujeitos às suas limitações de armazenamento, mas para à capacidade total de armazenamento disponível no sistema. Constrói-se estas cadeia via passeio determinístico sobre a topologia sugerida. Todavia, mostra-se que estes passeios apresentam um comportamento aleatório que é muito eficiente em termos de localização de capacidade de armazenamento disponível / Abstract: Storage management of Wireless Sensor Networks (WSN) is a very critical issue in terms of system's lifetime. While WSNs host a vast storage capacity on the aggregate, that capacity cannot be used entirely. Eventually, the entire network may fail when the first sensor has its own storage capacity depleted, leaving behind a large amount of unutilized storage capacity. We suggest that sensors should be able to detect unutilized storage capacity in order to prolong their functionality. However, for large scale WSNs this can be a difficult task, since sensors may not be aware of the existence of others. This work has two main contributions: an optimization of the overall storage capacity for large scale WSNs and a novel routing approach of deterministic "random" walk. We present a new storage model by building "on - demand" Distributed Storage Chains (DSC). These chains represent partnership between sensors that share their storage capacity. As a result, sensors are no longer subjected to their own storage limitations but to the total amount of available storage in the WSN. We construct these chains via deterministic walks over our suggested topology. However, we show that these walks resemble the behavior of random walks and are therefore highly efficient in terms of locating available storage / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

M.Com. ( Business Management) / This study wants to express an opinion on the implementation of an activity-based costing system in a service company with specific reference to Telkom SA Ltd. (hereafter Telkom), which has implemented a costing system as a first step towards an activity-based costing system. This studyis seenas a follow-up study on the work doneby Van Dyk(1993), which was also seconded to the Cost Management team within the Financial Management section of Telkom. His research paper was entitled: "Activity-based costing as a managerial control measure in a service organisation". His work in chapter one on the historical overview of accounting, the evolution of cost management systems and the description of the cost accounting system of Telkom must be seen as stepping stones on which this study will build. In chapter two Van Dyk(1993) concentrated on the influence oft he five competitive forces in the formulation of a generic strategy and the role of the value chain concept in order to understand the behaviour of costs. All of this work must be seen as the foundation and complementary to this study.

User modeling enables in the computation of the traffic density in a cellular network, which can be used to optimize the placement of base stations and radio network controllers as well as to analyze the performance of resource management algorithms towards meeting the final goal: the calculation and maximization of network capacity and throughput for different data rate services. An analytical model is presented for approximating the user distributions in multi-cell third generation wideband code division multiple access (WCDMA) networks using 2-dimensional Gaussian distributions by determining the means and the standard deviations of the distributions for every cell. This model allows for the calculation of the inter-cell interference and the reverse-link capacity of the network. An analytical model for optimizing capacity in multi-cell WCDMA networks is presented. Capacity is optimized for different spreading factors and for perfect and imperfect power control. Numerical results show that the SIR threshold for the received signals is decreased by 0.5 to 1.5 dB due to the imperfect power control. The results also show that the determined parameters of the 2-dimensional Gaussian model match well with traditional methods for modeling user distribution. A call admission control algorithm is designed that maximizes the throughput in multi-cell WCDMA networks. Numerical results are presented for different spreading factors and for several mobility scenarios. Our methods of optimizing capacity and throughput are computationally efficient, accurate, and can be implemented in large WCDMA networks.

Reliable communication over the noisy channel has become one of the major concerns in the field of digital wireless communications. The low density parity check codes (LDPC) has gained lot of attention recently because of their excellent error-correcting capacity. It was first proposed by Robert G. Gallager in 1960. LDPC codes belong to the class of linear block codes. Near capacity performance is achievable on a large collection of data transmission and storage.In my thesis I have focused on hardware implementation of (3, 6) - regular LDPC codes. A fully parallel decoder will require too high complexity of hardware realization. Partly parallel decoder has the advantage of effective compromise between decoding throughput and high hardware complexity. The decoding of the codeword follows the belief propagation alias probability propagation algorithm in log domain. A 9216 bit, (3, 6) regular LDPC code with code rate ½ was implemented on FPGA targeting Xilinx Virtex 4 XC4VLX80 device with package FF1148. This decoder achieves a maximum throughput of 82 Mbps. The entire model was designed in VHDL in the Xilinx ISE 9.2 environment.

Includes bibliography. / South Africa needs a modern, sophisticated telecommunications network to ensure economic development and political stability. The same network must also provide affordable and reliable service to a great percentage of the population. The telecommunications industry is currently monopolised by Telkom, a state-owned business enterprise (SBE), and does not appear capable of meeting these basic requirements. The purpose of this paper is to present a case for restructuring Telkom and liberalising the telecommunications industry to best serve the needs of the South African economy. The objective for restructuring the telecommunications industry must be to maximise long-term consumer welfare for all South Africans. This paper argues that consumer welfare will be maximised only by dismantling the statutory monopoly structure and moving toward a highly competitive, privately owned telecommunications industry. The economic issues, of course, cannot be discussed realistically without reference to political, social and historical variables, all of which are also considered. By focusing primarily on economic issues, however, this paper strives to avoid the ideological disputes which usually surround discussions of state ownership. This paper focuses on the telecommunications industry because it represents the single most important infrastructural component in a modern economy. It also presents a unique opportunity if managed well, and a grave danger if allowed to continue in its current structure.

Bibliography: pages 233-235. / The CCITT X.400 Message Handling System resides in the Application Layer of the seven-layer Reference Model for Open Systems Interconnection. It bypasses the services of the Presentation Layer completely to interact directly with the Session Layer. The objectives of this thesis are to show how the general Session Layer may be tailored to be minimally conformant to the requirements of X. 400; to produce a formal specification of this session layer; and to show how this session layer may be implemented on a real system. The session services required by X. 400 are those of the Halfduplex, Minor Synchronization, Exceptions and Activity Management functional units of the CCITT X.215 Session Service Definition. These services, and particularly their use by X.400, are described in detail. State tables describing these services are derived from the general session service state tables. Those elements of the CCITT X. 225 Session Protocol Specification which are required to provide only those services required by X. 400 are described in detail. State tables describing this session protocol are derived from the general session protocol state tables. A formal specification of the session layer for X.400 is presented using the Formal Description Technique Estelle. This specification includes a complete session entity, which characterizes the entire session layer for X.400. A session entity for supporting X.400 is partially implemented and interfaced to an existing X.400 product on a real system. Only the Session Connection Establishment Phase of the session protocol is implemented to illustrate the technique whereby the entire session protocol may be implemented. This implementation uses the C programming language in the UNIX operating system environment.