Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This thesis investigates orthogonal frequency division multiplexing (OFDM) as a viable modulation technique for an ultrasonic acoustic underwater modem. The underwater environment provides a challenging setting for acoustic communications. Long delay spreads due to multipath propagation, severe Doppler frequency shifts, frequency dependent absorption and very limited bandwidth are but some of the challenges to overcome. OFDM essentially provides the parallel transmission of symbols in the frequency domain by simultaneously modulating many closely spaced orthogonal subcarriers. The resulting long parallel symbol rate together with the cyclic extension of symbols render the signal robust against intersymbol interference (ISI) caused by multipath propagation. Intercarrier interference (ICI) between the overlapping frequency responses of subcarriers is mitigated by their property of orthogonality. Doppler spread contributes to the loss of orthogonality and can result in severe ICI. A method of measuring the Doppler shift by means of including a preamble and postamble symbol with each data frame is proposed. The detected frequency offset is corrected by resampling the frame at the desired sample rate. Not only do the ambles serve as a mechanism for timing and frequency synchronisation, but they are also applied in the channel estimation process. The equalisation of channel response is required for the coherent demodulation of the received symbols. An investigation into different phase shift keying (PSK) and quadrature amplitude modulation (QAM) constellations reveal optimal arrangements for minimal symbol errors. The optimised QAM constellations do not lend themselves to Gray-coding, so that an efficient interleaving scheme is needed to mitigate the non-uniform distribution of bit errors among symbol errors. Forward error correction is provided via a Bose Chaudhuri Hocquenghem (BCH) block code. Variable code rates, together with the ability to switch between different constellations, enable the modem to perform so-called variable modulation in an attempt to maximise the throughput under specific channel conditions. The modulation/demodulation scheme is wholly defined in software as to provide flexibility and facilitate experimentation with different signal processing methods. The accompanying hardware platform allows for the transmission of a pre-generated signal and the recording of a received signal for off-line processing. The prototype design serves as a proof of concept and thus provides only simplex communication. Field tests over limited distances demonstrate the successful operation of the prototype modem. We conclude that OFDM is indeed a suitable modulation technique for acoustic underwater communication. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die toepassing van ortogonale frekwensiedeling multipleksering (OFDM) as modulasie tegniek op ʼn onderwater kommunikasie modem. Die onderwater omgewing bied vele uitdagings vir akoestiese kommunikasie. Lang vertraging-verstrooiings as gevolg van multipad voortplanting, Doppler frekwensieskuif, frekwensieafhanklike absorpsie, en beperkte bandwydte is van die uitdagings wat oorkom moet word. In essensie bied OFDM die parallelle versending van ʼn aantal simbole deur die gelyktydige modulasie van verskeie nou-gespasieerde subdraers in die frekwensiegebied. Die gevolglike lang parallelle simboolperiodes, tesame met die sikliese uitbreiding van simbole, verleen immuniteit teen intersimbool steurnisse (ISI) wat ontstaan as gevolg van multipad voortplanting. Die ortogonaliteit van naburige draers in die frekwensiegebied beperk interdraer steuring (ICI) tussen hul oorvleuelende frekwensie weergawes. Doppler frekwensieskuif kan egter lei tot die verlies aan ortogonaliteit en bydra tot ernstige interdraer steurings. ʼn Metode wat gebruik maak van aanhef en slot simbole, ingesluit by elke raam, word voorgestel om die Dopplerskuif te meet. Die bepaalde frekwensieafset word gekorrigeer deur die monstertempo van die raam aan te pas na die verlangde tempo. Buiten die tyd- en frekwensie-sinkronisasie funksies van die aanhef en slot simbole, speel dit ook ʼn belangrike rol in die ontrekking van die frekwensie weergawe van die kanaal. Die effening van die kanaal se frekwensieweergawe is noodsaaklik vir die koherente demodulasie van die ontvangde simbole. ʼn Ondersoek na verskillende fase verskuif sleuteling (PSK) en kwadratuur amplitude modulasie (QAM) konstellasies het optimale rangskikkings opgelewer vir minimale simboolfoute. Hierdie optimale QAM konstellasies verleen hulself egter nie na Gray-kodering nie. ʼn Effektiewe invlegtegniek is nodig om die nie-uniforme verspreiding van bisfoute tussen simboolfoute te beperk. Fout korrigering funksionaliteit word gebied deur ʼn Bose Chaudhuri Hocquenghem (BCH) blokkode. Verstelbare koderingstempo’s en die vermoë om tussen verskillende konstellasies te skakel, stel die modem in staat om sogenaamde verstelbare modulasie te gebruik in ʼn poging om die data deurset te optimeer onder spesifieke kanaal kondisies. Die modulasie en demodulasie skema is volledig in sagteware gedefinieer. Dit verleen buigbaarheid en vergemaklik eksperimentering met verskeie seinverwerkingstegnieke. Die meegaande hardeware platvorm stel die modem in staat om vooraf opgewekte seine uit te saai en rou ontvangde siene op te neem vir na-tydse verwerking. Die prototipe ontwerp dien as ʼn konseptuele bewys en bied dus slegs simplekse kommunikasie. Die suksesvolle werking van die modem is gedemonstreer deur toetsing oor beperkte afstande. Hieruit word afgelei dat OFDM inderdaad geskik is vir akoestiese onderwater kommunikasie.

Cette thèse se concentre sur l’amélioration conjointe de l'efficacité spectrale et de l'efficacité en puissance de schémas de transmission par satellite. L’émergence de nouveaux services et l'augmentation du nombre d’acteurs dans le domaine nécessitent de disposer de débits de plus en plus importants avec des ressources de plus en plus limitées. Les progrès réalisés ces dernières années sur la technologie embarquée et dans le domaine des communications numériques permettent de considérer des schémas de transmission à plus haute efficacité spectrale et en puissance. Cependant, l’enjeu majeur des schémas de transmission proposes actuellement reste de rentabiliser les ressources disponibles. L’étude développée dans cette thèse explore les possibilités d’amélioration conjointe de l’efficacité spectrale et de l’efficacité en puissance en proposant la combinaison de la modulation Cyclic Code-Shift-Keying (CCSK), dont l’efficacité en puissance augmente avec l’élévation du degré de la modulation, avec une technique de multiplexage par codage de type Code-Division Multiplexing (CDM) pour pallier la dégradation de l’efficacité spectrale liée à l’étalement du spectre induit par la modulation CCSK. Deux approches basées sur l’utilisation de séquences de Gold de longueur N sont définies: Une approche multi-flux avec un décodeur sphérique optimal en réception. La complexité liée à l’optimalité du décodeur conduit à des valeurs d'efficacité spectrale limitées mais l’étude analytique des performances, vérifiée par des simulations, montre une augmentation de l'efficacité en puissance avec l'efficacité spectrale. Une approche mono-flux justifiée par l’apparition de redondance dans les motifs résultant du multiplexage des séquences. L’approche mono-flux propose des valeurs d’efficacité spectrale équivalente aux schémas retenus dans le standard DVB-S2 avec une amélioration de l’efficacité en puissance à partir d’un certain seuil de rapport signal à bruit par rapport à ces schémas. Par la suite, l'étude porte sur la transposition de plusieurs symboles de modulation sur les porteuses d’un système OFDM et sur les bénéfices et avantages d’une telle approche. Elle se conclut sur l’apport d’un codage canal basé sur des codes par bloc non binaires Reed-Solomon et LDPC. La forme d’onde proposée offre des points de fonctionnement à haute efficacité spectrale et haute efficacité en puissance avec des perspectives intéressantes. Dans le contexte actuel, son application reste limitée par ses fluctuations d’amplitude mais est envisageable dans un contexte de transmission multiporteuse, comme attendu dans les années à venir. / This thesis focuses on jointly improving the spectral efficiency and the power efficiency of satellite transmission schemes. The emergence of new services and the increasing number of actors in this field involve higher transmission rates with increasingly limited resources. Recent progress in the embedded technologies and in digital communications offered to consider transmission schemes with higher spectral and power efficiency. Nevertheless, the major current challenge consists in making efficient use of resources. The study developed in this thesis explores the possibilities of jointly improving the spectral and power efficiency by offering a combination of the Cyclic-Code-Shift Keying modulation (CCSK), which power efficiency increases with the degree of modulation, with a multiplexing technique such as Code-Division Multiplexing (CDM) to offset the deterioration on the spectral efficiency due to the spread spectrum induced by CCSK. Two approaches based on the use of Gold sequences of length N are defined : A multi-stream approach with an optimal receiver implemented through sphere decoding. The complexity due to the receiver optimality leads to limited spectral efficiencies but the study of performance, confirmed by simulations, shows an increase in power efficiency with spectral efficiency. A single-stream approach justified by the appearance of redundancy in the patterns following the sequences multiplexing. The single-stream approach offers spectral efficiencies equivalent to the adopted schemes in the DVB-S2 standard, with improved power efficiency from a certain level of signal to noise ratio compared to those schemes. Subsequently, the study focuses on the implementation of several modulation symbols on the subcarriers of an OFDM modulator and the benefits and advantages of such an approach. It concludes with the contribution of channel coding based on nonbinary block codes such as Reed-Solomon and LDPC codes. The proposed waveform offers operating points with high spectral efficiency and high power efficiency with attractive perspectives. In the current context, its application is limited by its amplitude fluctuations but is possible in a multicarrier transmission context, as expected in the years to come.

As redes de telecomunicações se dividem em redes de longa distância, redes metropolitanas e redes de acesso. As redes de longa distância e metropolitana usufruem a alta capacidade de largura de banda da fibra óptica, enquanto nas redes de acesso há um gargalo de largura de banda por causa do uso de pares de fios e cabo coaxial. Para solucionar este problema e oferecer aos usuários acesso banda larga de baixo custo foram propostas as redes ópticas passivas (passive optical network - PON). A PON é formada por dois elementos básicos, a unidade de rede óptica (optical network unit - ONU), localizada perto dos assinantes, e o terminal de linha óptica (optical line terminal - OLT), localizado próximo ao provedor de serviços. Dentre os padrões disponíveis para redes PON, o Ethernet (EPON), padronizado pelo grupo IEEE 802.3ah, é opção atraente porque ele é bastante difundido nas redes locais. O protocolo de controle multiponto (multipoint control protocol - MPCP), já especificado, é responsável pelo controle de acesso ao meio, fornecendo infra-estrutura de sinalização para transmissão entre OLT e ONUs. Entretanto, o algoritmo de alocação de largura de banda, que realiza o controle de acesso ao meio com base no MPCP, foi considerado fora do escopo de trabalho do grupo de trabalho, permitindo que seja desenvolvido pelos fornecedores de equipamentos. Neste trabalho, arquiteturas de rede EPON e o protocolo MPCP são descritos e algoritmos de alocação de largura de banda são avaliados mediante simulação computacional. São abordados os algoritmos de alocação de largura de banda que integram multiplexação estatística e técnicas para o suporte a classes de serviços diferenciados, com base no esquema de multiplexação por divisão no tempo (time division multiplexing - TDM). Algoritmos que integram a multiplexação por divisão em comprimento de onda (wavelength division multiplexing - WDM) à arquitetura EPON TDM são também investigados. Os algoritmos WDM-TDM permitem a atualização progressiva da EPON que emprega o esquema TDM para WDM. / Telecommunication networks are divided into core, metropolitan and access networks. The core and metropolitan networks use high capacity bandwidth optical fibers, while the access networks have bandwidth bottlenecks because of the use of twisted-pair wires and coaxial cable. To solve this problem and to offers the users broadband access at low cost the use of passive optical networks (PON) is proposed. A PON is formed by two basic elements, the optical network unit (ONU), positioned close to the customers and the optical line terminal (OLT), located close to the service provider. Within the available standards for PON networks, the Ethernet (EPON), standardised by the IEEE group 802.3ah, is an attractive option because it is already widely used in local networks. The multipoint control protocol (MPCP), already specified, is responsible for the media access control, providing signaling infrastructure for transmission between OLT and ONUs. However, the bandwidth allocation algorithm, that controls access based on MPCP, was considered outside the scope of the work group, permitting that this be developed by equipment providers. In this work, EPON architectures and the MPCP protocol are described and bandwidth allocation algorithms are evaluated with computational simulation. Bandwidth allocation algorithms which integrate statistical multiplexing and techniques to support for differentiated classes of service, based on time division multiplexing (TDM) scheme are investigated. Algorithms that integrate wavelength division multiplexing (WDM) to the EPON TDM architecture are also investigated. The WDM-TDM algorithms permit the progressive upgrade of EPON based TDM to WDM schemes.

Orientador: Alberto Luiz Serpa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T08:29:26Z (GMT). No. of bitstreams: 1 SarraciniJunior_Fernando_M.pdf: 6793847 bytes, checksum: effab2db853f18298e45c0a677c2ee50 (MD5) Previous issue date: 2006 / Resumo: A implementação de controladores de ordem reduzida (fixa) demanda um menor esforço de processamento e consequentemente recursos de hardware menos sofisticados em relação à implementação de controladores de ordem completa. Este trabalho mostra que a implementação prática de controladores H 00 de ordem fixa voltados para o controle de estruturas flexíveis é factível. A obtenção de tais controladores é um problema considerado difícil por ser nãoconvexo. Para contornar as dificuldades numéricas de obtenção dos controladores de ordem fixa, uma combinação do método Lagrangiano Aumentado com Desigualdades Matriciais Lineares (LMls) é utilizada. Uma estrutura de viga com engaste em uma de suas extremidades é modelada através do método de Elementos Finitos. Controladores Hoc de ordem fixa e de ordem completa são projetados com base em um modelo matemático truncado. Incertezas de modelagem e a presença de modos próximos na região de frequência de interesse dificultam a obtenção de controladores que garantam a estabilidade e um desempenho satisfatório. Para contornar estas dificuldades, usa-se a técnica de controle robusto Hoo e filtros de ponderação. Dessa forma, procura-se minimizar o efeito das incertezas e evitar que modos que não foram considerados durante a fase de projeto dos controladores não sejam excitados, garantido assim a não ocorrência do fenômeno denominado spillover. Controladores Hoo de ordem completa e ordem fixa são implementados na prática e os resultados experimentais são comparados com resultados simulados / Abstract: The implementation of reduced (fixed ) order controllers requires a smaller computational effort and. consequently, less advanced hardware resources in relation to the implementation of full order controllers. This work shows that the practical implementation of fixed order Hoo controllers directed toward the control of flexible structures is viable. Obtaining such controllers is considered a difficult task for being a non-convex problem. To overcome the numerical difficulties of attainment of fixed order controllers, a combination of the Lagrangian method increased with Linear Matrix Inequalities (LMIs) is used. A cantilever beam is modelled with the Finite Element Method. Fixed and full order controllers are designed based on a truncated mathematical model. Modelling uncertainties and the existence of near modes in the frequency range of interest make difficult the attainment of controllers that assure the stability and the performance of the system. To overcome this difficulty, the robust Hoo control and weighing filters are used. In this way, it is desired to minimize the effect of uncertainties and avoid the excitement of non-modelled modes, assuring that the spillover phenomenon does not occur. Full order and fixed order H x controllers are implemented in the practice and the experimental results are compared with the simulated results / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Os sistemas ópticos atuais, baseados em fibras monomodo, operam próximos ao limite teórico da capacidade. Sistemas ópticos baseados em multiplexação modal (Mode Division Multiplexing – MDM) possibilitam o aumento da capacidade do sistema por meio do uso de fibras de poucos modos. Nestes sistemas, a propriedade de ortogonalidade entre os modos propagantes permite que cada modo espacial carregue um sinal óptico específico. O amplificador à fibra dopada com érbio (Erbium-Doped Fiber Amplifier – EDFA) segue fundamental para assegurar a transmissão em longas distâncias. No entanto, devido às distintas distribuições de intensidade dos modos que compõem o sinal de entrada, cada modo experimenta diferentes valores de ganho. Desta forma, o objetivo principal no projeto de EDFAs de poucos modos (Few-Mode Erbium-Doped Fiber Amplifier – FM-EDFA) é determinar os melhores parâmetros opto-geométricos da fibra para produzir uma amplificação eficiente. A metodologia normalmente empregada é baseada na resolução das equações de taxa e de propagação. Nesta tese, é proposta uma metodologia alternativa de projeto de FM-EDFA, baseada em uma nova figura de mérito. Este parâmetro quantifica o nível de inversão da população dos íons na fibra a partir da integral de superposição (overlap integral), considerando tanto o perfil de dopagem da fibra dopada com érbio para poucos modos (Few-Mode Erbium-Doped Fiber – FM-EDF) quanto as distribuições de intensidade dos sinais de entrada e de bombeio. A aplicação desta metodologia permite reduzir, em cerca de 25-40 vezes, o número de resoluções das equações de taxa e de propagação e, consequentemente, diminuir o tempo de processamento e reduzir o esforço computacional. Como consequência da maior velocidade de processamento, torna-se possível a aplicação de métodos de otimização mais rigorosos, permitindo uma busca em um espaço irrestrito de soluções. Especificamente, a partir de uma metodologia baseada em algoritmos genéticos, obteve-se um perfil de dopagem otimizado. É também demonstrado que os perfis com geometria circular exibem melhores características, como excelente desempenho do FM-EDFA e maior facilidade de fabricação. Por meio da análise da figura de mérito, é mostrado que o desempenho do FM-EDFA é afetado pelas características do modo de bombeio. Finalmente, o desempenho de um sistema óptico MDM é avaliado, simulado por meio da integração entre as ferramentas MatLab® e VPItransmissionMakerTM, comprovando a necessidade do projeto de um amplificador específico para sistemas MDM. / Modern optical systems based on single-mode fiber, operate close to the theoretical capacity limit. By using few-mode fibers, optical systems based on modal division multiplexing (MDM) allows increased system capacity. In these systems, orthogonality between the propagating modes allows each spatial mode to carry a specific optical signal. The erbium doped fiber amplifier (EDFA) remains essential to ensure long distance transmission. However, due to the distinct intensity profile distributions of the modes which comprise the input signal, each mode experiences a different value of optical gain. Thus, the main objective in the few-mode EDFA design (FM-EDFA) is to determine the best opto-geometrical fiber parameters in order to produce an efficient amplification. The methodology normally used is based on the simultaneous resolution of the rate and propagation equations. In this thesis, we propose an alternative methodology for the FM-EDFA design, based on a new figure of merit which quantifies the level of population inversion for the Er ions in the fiber, by means of a overlap integral considering both the doping profile of the few-mode erbium doped fiber (FM-EDF) as well as the intensity distributions of the optical signals and pump beams. This methodology reduces, by a factor of 25-40, the number of resolutions of the rate and propagation equations, thereby decreasing processing time and computational effort. As a consequence of the improved processing speed, it becomes possible to apply more rigorous optimization methods in an unrestricted solution space. Specifically, by using a genetic algorithm technique, we obtained an optimized doping profile. It is also shown that profiles with circular geometry exhibit improved features, such as excellent FM-EDFA performance and ease of manufacturing. By analyzing the figure of merit, it is shown that the FM-EDFA performance is affected by the characteristics of the pump mode. Finally, the performance of an MDM optical system is evaluated, by integrating Matlab and VPI simulation tools, to demonstrate the need for specific amplifier designs in MDM systems.

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No. of bitstreams: 1 guilhermeribeirocolen.pdf: 4525385 bytes, checksum: e90d041d33c901d139d8476b96e02078 (MD5) Previous issue date: 2016-03-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta tese concentra-se na redução da complexidade computacional e na necessidade de largura de banda associada com a utilização de técnicas de alocação de recursos em sistemas de comuniação via rede elétrica (power line communication – PLC) com base no esquema de multiplexação por divisão ortogonal na frequência (orthogonal frequency division multiplexing – OFDM). Neste contexto, é introduzida a técnica sub-ótima chamada de temporal compressive resource allocation (TCRA). Esta técnica é capaz de explorar a relação existente entre microslots (exploração no domínio do tempo) para reduzir o número de vezes por segundo que alocação de recursos é executada. Além disso, é proposto um novo parâmetro, denominado de banda de coerência da relação sinal ruído normalizada (normalized signal to noise ratio – nSNR) para informar precisamente a planicidade da nSNR. A eficácia deste parâmetro é comparada com a banda de coerência. Diante disto, sua modelagem estatística para ambientes in-home, outdoor de baixa tensão e PLC-wireless é apresentada considerando distribuições de componentes individuais e misturas de Gaussianas. Com base na definição da banda de coerência da nSNR, é descrita a técnica sub-ótima denominada spectral compressive resource allocation (SCRA). Ela explora a relação existente entre os sub-canais adjacentes (exploração no domínio da frequência) para reduzir a dimensão do vector de nSNR, que é a principal informação de entrada para a técnicas de alocação de recursos. Com base no fato de que a geometria de tiles associadas com a transformada de Fourier discreta limita os ganhos associados com o uso da técnica SCRA em conjunto com o esquema OFDM, é introduzido pela primeira vez o esquema chamado multiplexação por divisão ortogonal no tempo-frequência (orthogonal time-frequency division multiplexing – OTFDM). Este esquema se baseia na transformada ortogonal de Stockwell discreta para oferecer diferentes geometrias de tiles e funciona tanto para comunicação de dados em banda de base quanto em banda passante. Os resultados numéricos baseados em canais PLC medidos e no uso de protótipo de transceptores PLC mostram que as técnicas TCRA e SCRA podem trocar redução de complexidade computacional por perda de taxa de transmissão e que economia de complexidade computacional relevante pode ser realizada com baixas perdas na taxa de transmissão. Ademais, os resultados numéricos mostram que o esquema OTFDM pode ser superado pelo esquema de OFDM se a informação de estado de canal não está disponível no lado do transmissor. No entanto, a disponibilidade de tais informações no lado do transmissor permite a utilização do esquema OTFDM em conjunto com a técnica SCRA atingir uma melhoria notável em comparação com o esquema OFDM trabalhando com a técnica SCRA. / This dissertation focuses on the computational complexity reduction and on the need for network bandwidth associated with the use of resource allocation techniques in power line communication (PLC) system based on orthogonal frequency division multiplexing (OFDM) scheme. In this context, the so-called temporal compressive resource allocation (TCRA) technique, which is a sub-optimal technique, is introduced. The TCRA is capable of exploiting the existing relationship among microslots (time domain exploitation) to reduce the number of times per second the resource allocation technique is executed. Also, a noval parameter, called nSNR coherence bandwidth, that precisely informs the flatness of the normalized signal to noise ratio (nSNR) is proposed. The effectiveness of this parameter is compared to the coherence bandwidth. Also, its statistical modeling for in-home, outdoor and low-voltage, and hybrid PLC-wireless channels with single-component and Gaussian mixture distributions is presented. Based on the nSNR coherence bandwidth definition, the spectral compressive resource allocation (SCRA) technique, which is a suboptimal technique, is outlined. The SCRA technique exploits the existing relationship among adjacent subchannels (frequency domain exploitation) to reduce the dimensionality of the nSNR vector, which is the main feeding information for the resource allocation technique. Based on the fact that the geometry of the tiles associated with the discrete Fourier transform limits the gains associated with the use of the SCRA together with the OFDM scheme, the so-called orthogonal time-frequency division multiplexing (OTFDM) scheme is, for the first time, introduced. The OTDFM scheme, which is based on the discrete orthogonal Stockwell transform, offers different tile geometries and works in both baseband and passband data communications. Numerical results based on measured PLC channels and the use of prototype of PLC transceivers show that TCRA and SCRA techniques can trade computational complexity reduction with data rate loss and relevant computational complexity savings may be accomplished with low data rate losses. Moreover, the numerical results show that the OTFDM scheme may be outperformed by the OFDM scheme if channel state information is not available at the transmitter side; however, the availability of such information at the transmitter side allow the use of the OTFDM scheme together with the SCRAs achieve remarkable improvement in comparison with OFDM scheme working with the SCRA technique.

Orientador: Celso de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T09:28:35Z (GMT). No. of bitstreams: 1 MinangoNegrete_JuanCarlos_M.pdf: 1358924 bytes, checksum: 0b87bf307832cb8c65d04765674c0306 (MD5) Previous issue date: 2014 / Resumo: O uso da técnica de multiplex espacial, transmissão de feixes de símbolos independentes usando múltiplas antenas de transmissão, tem sido proposta para atingir a exigência de taxas de dados maiores dos futuros sistemas de comunicações sem fio de banda larga. No entanto, quando a técnica de multiplex espacial é aplicada a uma rede celular, seu desempenho é afetado pela interferência de co-canal. Este trabalho avalia e compara os efeitos da interferência de co-canal na taxa de erro de bit média, BER, entre sistemas de transmissão digital com multiplex espacial e sistemas de transmissão digital com uma única antena de transmissão, onde os parâmetros da potência de transmissão e eficiência espectral são levados em consideração, a fim de se fazer comparações justas entre os dois sistemas. O enlace direto em um ambiente com desvanecimento plano e lento do tipo Rayleigh na presença de um interferente de co-canal dominante foi considerado. Além disso, o uso do detector ótimo, MV, no receptor e os esquemas de modulação BPSK, QPSK e M-QAM foram também considerados. Simulações de Monte Carlo foram feitas para a obtenção dos desempenhos em termos da BER como uma função da relação sinal-ruído por bit, Eb/N0, e da relação sinal-interferência, SIR. Os resultados da avaliação e comparação de desempenho entre os sistemas com multiplex espacial e com uma única antena de transmissão apresentados neste trabalho, constituem uma ferramenta importante a fim de se conhecer os benefícios reais da técnica de multiplex espacial aplicada a uma rede celular, como por exemplo nos padrões WiMAX ou LTE / Abstract: Spatial multiplexing technique, consisting of independent symbol transmission on multiple transmission antennas, has been proposed to meet the requirement for higher data rates of future wireless broadband communication systems. However, when spatial multiplexing technique is applied to a cellular network, the performance is affected by co-channel interference. This work evaluates and compares the effects of co-channel interference on the mean bit error rate, BER, of spatial multiplexing systems and single transmission antenna systems, where transmit power and spectral efficiency parameters are taken into consideration, in order to make a fair comparison between both systems. The downlink of a cellular network in slowly-varying flat Rayleigh fading environment and in the presence of a dominant co-channel interferer is considered. Furthermore, the use of Optimum Detector on the receiver and BPSK, QPSK and M-QAM modulations is also considered. Monte Carlo simulations are realized for obtaining the performance in terms of the BER as a function of per-bit signal-to-noise ratio, Eb/N0, and signal-to-interference ratio, SIR. The evaluation and comparison performance results between spatial multiplexing and a single transmission antenna systems presented in this work, are important tools in order to know the real benefits of spatial multiplexing technique applied to a cellular network, as the standards WiMAX or LTE / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Over the past two decades the mobile wireless communication systems has been growing fast and continuously. Therefore, the standardization bodies together with wireless researchers and mobile operators around the globe have been constantly working on new technical specifications in order to meet the demand for this rapid growth. The 3rd Generation Partnership Project (3GPP) one of the largest of such standardization bodies, works on developing the current third generation (3G) mobile telecommunication systems towards the future 4th generation. Research towards meeting the higher demands for higher data rates was the main reason for the birth of an evolution technology towards the 4th generation mobile systems. This evolution to the current 3rd generation UMTS systems was given the name E-UTRA/UTRAN Long Term Evolution (LTE) by the 3GPP. This thesis research has been carried out at the Telecommunications Research Center (ftw.) in Vienna. It was conducted in the framework of the C10 project “Wireless Evolution Beyond 3G”. One of the fields of research within this project is to have a special focus on the OFDM modulation schemes that are discussed under the new evolution technology (LTE) of the UMTS mobile networks. Therefore, this thesis focuses mainly in analyzing the new requirements, and evaluating them by designing a low-complexity UMTS-LTE OFDM based transceiver. This thesis aims mainly in studying the feasibility of this technology by means of simulation. / Tel: +46-704469795 Email: osman@ftw.at,amos04@student.bth.se, ammarmao@gmail.com

Internet traffic is increasing exponentially, driven by new technologies such as Internet of Things (IoT) and rich streaming media. The traditional IP router becomes a bottleneck for further Internet expansion due to its high power consumption and inefficiency in processing the growing traffic. Router bypass has been introduced to overcome capacity limitations and the processing costs of IP routers. With router bypass, a portion of traffic is provisioned to bypass the router and is switched by the transport layer. Router bypass has shown to provide significant savings in network costs. These advantages are limited by a reduction in the statistical multiplexing associated with the subdivision of the available bandwidth typically into bypass and traditional portions thus limiting the interest in bypass techniques. This thesis will explore multiple techniques to enhance the efficiency of router bypass. The main goals are to address the issue of the reduction in statistical multiplexing and to add a dynamic approach to the router bypass mechanism. The recent advancements in the Optical Transport Network (OTN) play a major role in the transport network. This proposal takes full advantage of OTN in the router-bypassing context by applying recent developments such as Hitless Adjustments ODUflex (HAO), which allow the provisioned channels to be adjusted without re-establishing the connections. In addition, it will allow the bypassing mechanism to be flexible enough to meet the traffic behaviour needs of the future. This thesis will study multiple approaches to enhance the router bypass mechanism including: an adaptive provisioning style using various degrees of provisioning granularities and controlling the provisioning based on traffic behaviour. In addition, this thesis will explore the impact of automation in Software-Defined Networking (SDN) on router bypass. The application-driven infrastructure in SDN is moving the network to be more adaptive, which paves the way for an enhanced implementation of router bypass. Many challenges still face the industry to fully integrate the three layers (3, 2, and 1) to transform the current infrastructure into an adaptive application driven network. The IP router (layer 3) provisions and restores the connection regardless of the underlying layers (layer 2 and 1) and the transport layer does the same regardless of the IP layer. Although allowing every layer to develop without being constrained by other layers offers a huge advantage, it renders the transport layer static and not fully aware of the traffic behaviour. It is my hope that this thesis is a step forward in transforming the current network into a dynamic, efficient and responsive network. A simulation has been built to imitate the router bypassing concept and then many measurements have been recorded. / Graduate

Digital filters play a key role in many DSP applications and FIR filters are usually selected because of their simplicity and stability against IIR filters.In this thesis eight architectures for multi-stream FIR filtering are studied. Primarily, three kinds of architectures are implemented and evaluated: one-toone mapping, time-multiplexed and pipeline interleaving. During implementation, practical considerations are taken into account such as implementation approach and number representation. Of interest is to see the performance comparison of different architectures, including area and power. The trade-off between area and power is an attractive topic for this work. Furthermore, the impact of the filter order and pipeline interleaving are studied.The result shows that the performance of different architectures differ a lot even with the same sample rate for each stream. It also shows that the performance of different architectures are affected by the filter order differently. Pipeline interleaving improves area utilization at the cost of rapid increment of power. Moreover, it has negative impact on the maximum working frequency.All the FIR filter architectures are synthesized in a 65nm technology.