El aparato digestivo permite que los alimentos se conviertan en nutrientes y proporcionen al organismo las calorías y los elementos fundamentales para la vida, al mismo tiempo que se expulsan y eliminan los productos residuales de forma adecuada. La motilidad intestinal es muy importante para conseguir la segmentación del quimo y el tránsito intestinal y está determinada por la actividad mioeléctrica de las capas musculares intestinales. Dicha actividad también se le denomina electroenterograma (EEnG). La señal mioeléctrica es el resultado de una componente de baja frecuencia que en condiciones fisiológicas está siempre presente llamada onda lenta (OL) o ritmo eléctrico básico (BER) que constituye el marcapasos intestinal; y una componente de alta frecuencia llamada spike bursts o potenciales rápidos de acción que está asociada a las contracciones intestinales. El análisis del EEnG es un paso clave para monitorizar la actividad intestinal. El estudio del BER intestinal no sólo proporciona información acerca del ritmo básico de las contracciones del intestino, sino que puede ayudar a diagnosticar algunas patologías gastrointestinales. Para ofrecer esta herramienta como aplicación clínica, el registro de la señal del EEnG debe ser no invasivo. El objetivo de la presente Tesis Doctoral es detectar la actividad del marcapasos intestinal y caracterizar el ritmo eléctrico básico en el EEnG externo, comparándolo y estudiando su relación con el EEnG interno. Las señales analizadas fueron obtenidas simultáneamente en la superficie abdominal y en la serosa intestinal de perros Beagle en estado de ayuno. Los métodos de estimación autoregresivo (AR), autoregresivo de media móvil (ARMA), Prony y clasificación de señales múltiples (MUSIC), se emplearon para determinar la distribución espectral de potencia asociada a la actividad de la onda lenta, tanto en los registros internos como externos. Por otro lado, para estudiar la relación entre el espectro de la señal captada en superficie y las señales internas, se estimaron las funciones de coherencia utilizando los modelos autoregresivo multivariante (ARM) y MUSIC. / Moreno Vázquez, JDJ. (2011). Estudio espectral del ritmo eléctrico básico del intestino delgado para la monitorización no invasiva del marcapasos intestinal [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14276

The continuous evolution of the optical communication technology in the last few years has allowed the growing users demand for higher bandwidth to be satisfactorily attended. This new demand is mainly attributed to the growing popularity of bandwidth-intensive networking applications, such as Internet protocol television (IPTV), high-definition television (HDTV), e-learning, e-health, super high-definition (SHD) class digital movies, and e-culture based on 3-D full-HD video. These applications will eventually require differentiated service types and diversified data rates. As a result, capability of supporting differentiated-quality of service (QoS) and multirate transmission are becoming a challenge for future optical networks. Among many multiplexing techniques, optical code-division multiple-access (OCDMA) constitutes a potential candidate for next generation optical networks, particularly due to features like asynchronous operation, simplified network control, easy addition of new users, and possibility of differentiated-QoS at the physical layer. The performance of this access technique is mainly limited by multiple-access interference (MAI). Although in multirate, multiservice OCDMA systems MAI is considered to be binomially distributed, others probability distributions for the MAI analyzes and consequently the bit error rate (BER) have been used as an approximation. In this context, this dissertation proposes a new formalism to evaluate the BER performance of 1-D and 2-D multirate, multiservice OCDMA systems considering MAI as binomially distributed, resulting in a more accurate BER expression. Also, the proposed approach does not require knowledge a priori of the generated code sequences themselves, which means that the system performance analysis is achieved more easily using only the code parameters. Furthermore, a multirate OCDMA system employing 1-D optical orthogonal code (OOC) and 2-D optical fast frequency hopping (OFFH) codes is also investigated. A performance comparison in terms of BER for the OOC-based system assuming both Poisson and binomial distribution for the MAI is investigated. A further comparison of an OFFH-based multirate system assuming both gaussian and binomial distribution for the MAI is also analyzed. It is shown that BER performance in multirate scenarios can be overestimated or underestimated by many orders of magnitude depending on the assumed distribution for the MAI and on the number of simultaneous users. Moreover, it is presented for the first time a hybrid OCDM/WDM optical packet switch capable of supporting multirate and differentiated-QoS transmission. The architecture of the proposed multirate switch and its performance in terms of packet loss probability are also presented. Finally, it is shown that using a gaussian or Poisson distribution for the MAI might not be appropriate for a reliable BER estimate, since they are not acceptable approximations to assess the performance of multirate, multiservice systems with good accuracy. / A contínua evolução da tecnologia de comunicações ópticas observada nos últimos anos vem possibilitando atender a crescente demanda dos usuários por maior largura de banda. Esta nova demanda é atribuída principalmente à popularidade crescente de aplicações de banda larga, tais como TV por protocolo de Internet (IPTV), televisão de alta definição (HDTV), ensino online, e-saúde, filmes digitais de super alta definição (SHD) e e-cultura baseado em vídeo 3-D full-HD. Esta vasta gama de aplicações acabará por necessitar de tipos de serviços diferenciados e taxas de transmissão de dados diversificadas. Como resultado, capacidades de suportar diferenciamento de qualidade de serviço (QoS) e transmissão de múltiplas taxas estão se tornando um desafio para as redes ópticas futuras. Dentre muitas técnicas de multiplexação existentes, OCDMA constitui-se em um candidato potencial para as redes ópticas de próxima geração, particularmente devido a características como operação assíncrona, controle de rede simplificada, fácil adição de novos usuários, e também possibilidade de QoS diferenciado na camada física. O desempenho desta técnica de acesso múltiplo é limitado principalmente por interferência múltipla de acesso (MAI). Embora em sistemas OCDMA de múltiplas taxas e multiserviços a MAI deva ser considerada binomialmente distribuída, outras distribuições de probabilidade para a análise da MAI e, consequentemente, da BER têm sido utilizadas como uma aproximação. Neste contexto, este trabalho propõe um novo formalismo para avaliar o desempenho da BER de sistemas OCDMA 1-D e 2-D de múltiplas taxas e multisserviços considerando a MAI como binomialmente distribuída, o que resulta em uma expressão mais precisa para a BER. Além disso, o método proposto neste trabalho não requer conhecimento, a priori, das sequências de códigos geradas, o que significa que a análise do desempenho do sistema é obtida mais facilmente utilizando apenas os parâmetros do código. Um sistema OCDMA de múltiplas taxas empregando códigos 1-D OOC e 2-D OFFH será também investigado. Uma comparação do desempenho em termos de BER para o sistema baseado em OOC supondo tanto a distribuição de Poisson quanto a binomial para a MAI é investigada. De forma análoga, uma comparação para o sistema de múltiplas taxas baseado em OFFH supondo desta vez tanto a distribuição gaussiana quanto a binomial para a MAI também é analisada. É mostrado que a BER em cenários de múltiplas taxas pode ser superestimada ou subestimada em várias ordens de grandeza, dependendo da distribuição suposta para a MAI e do número de usuários simultâneos no sistema. Além disso, é apresentado pela primeira vez um switch óptico híbrido de pacotes OCDM/WDM capaz de prover transmissões de múltiplas taxas e serviços diferenciados. A arquitetura do switch proposto e seu desempenho em termos de probabilidade de perda de pacotes também são apresentados. Finalmente, é mostrado que o uso da distribuição gaussiana ou poissoniana para a MAI pode não ser apropriado para uma estimativa confiável de BER, uma vez que não são aproximações aceitáveis para avaliar o desempenho de sistemas de múltiplas taxas e multiserviços com boa precisão.

The continuous evolution of the optical communication technology in the last few years has allowed the growing users demand for higher bandwidth to be satisfactorily attended. This new demand is mainly attributed to the growing popularity of bandwidth-intensive networking applications, such as Internet protocol television (IPTV), high-definition television (HDTV), e-learning, e-health, super high-definition (SHD) class digital movies, and e-culture based on 3-D full-HD video. These applications will eventually require differentiated service types and diversified data rates. As a result, capability of supporting differentiated-quality of service (QoS) and multirate transmission are becoming a challenge for future optical networks. Among many multiplexing techniques, optical code-division multiple-access (OCDMA) constitutes a potential candidate for next generation optical networks, particularly due to features like asynchronous operation, simplified network control, easy addition of new users, and possibility of differentiated-QoS at the physical layer. The performance of this access technique is mainly limited by multiple-access interference (MAI). Although in multirate, multiservice OCDMA systems MAI is considered to be binomially distributed, others probability distributions for the MAI analyzes and consequently the bit error rate (BER) have been used as an approximation. In this context, this dissertation proposes a new formalism to evaluate the BER performance of 1-D and 2-D multirate, multiservice OCDMA systems considering MAI as binomially distributed, resulting in a more accurate BER expression. Also, the proposed approach does not require knowledge a priori of the generated code sequences themselves, which means that the system performance analysis is achieved more easily using only the code parameters. Furthermore, a multirate OCDMA system employing 1-D optical orthogonal code (OOC) and 2-D optical fast frequency hopping (OFFH) codes is also investigated. A performance comparison in terms of BER for the OOC-based system assuming both Poisson and binomial distribution for the MAI is investigated. A further comparison of an OFFH-based multirate system assuming both gaussian and binomial distribution for the MAI is also analyzed. It is shown that BER performance in multirate scenarios can be overestimated or underestimated by many orders of magnitude depending on the assumed distribution for the MAI and on the number of simultaneous users. Moreover, it is presented for the first time a hybrid OCDM/WDM optical packet switch capable of supporting multirate and differentiated-QoS transmission. The architecture of the proposed multirate switch and its performance in terms of packet loss probability are also presented. Finally, it is shown that using a gaussian or Poisson distribution for the MAI might not be appropriate for a reliable BER estimate, since they are not acceptable approximations to assess the performance of multirate, multiservice systems with good accuracy. / A contínua evolução da tecnologia de comunicações ópticas observada nos últimos anos vem possibilitando atender a crescente demanda dos usuários por maior largura de banda. Esta nova demanda é atribuída principalmente à popularidade crescente de aplicações de banda larga, tais como TV por protocolo de Internet (IPTV), televisão de alta definição (HDTV), ensino online, e-saúde, filmes digitais de super alta definição (SHD) e e-cultura baseado em vídeo 3-D full-HD. Esta vasta gama de aplicações acabará por necessitar de tipos de serviços diferenciados e taxas de transmissão de dados diversificadas. Como resultado, capacidades de suportar diferenciamento de qualidade de serviço (QoS) e transmissão de múltiplas taxas estão se tornando um desafio para as redes ópticas futuras. Dentre muitas técnicas de multiplexação existentes, OCDMA constitui-se em um candidato potencial para as redes ópticas de próxima geração, particularmente devido a características como operação assíncrona, controle de rede simplificada, fácil adição de novos usuários, e também possibilidade de QoS diferenciado na camada física. O desempenho desta técnica de acesso múltiplo é limitado principalmente por interferência múltipla de acesso (MAI). Embora em sistemas OCDMA de múltiplas taxas e multiserviços a MAI deva ser considerada binomialmente distribuída, outras distribuições de probabilidade para a análise da MAI e, consequentemente, da BER têm sido utilizadas como uma aproximação. Neste contexto, este trabalho propõe um novo formalismo para avaliar o desempenho da BER de sistemas OCDMA 1-D e 2-D de múltiplas taxas e multisserviços considerando a MAI como binomialmente distribuída, o que resulta em uma expressão mais precisa para a BER. Além disso, o método proposto neste trabalho não requer conhecimento, a priori, das sequências de códigos geradas, o que significa que a análise do desempenho do sistema é obtida mais facilmente utilizando apenas os parâmetros do código. Um sistema OCDMA de múltiplas taxas empregando códigos 1-D OOC e 2-D OFFH será também investigado. Uma comparação do desempenho em termos de BER para o sistema baseado em OOC supondo tanto a distribuição de Poisson quanto a binomial para a MAI é investigada. De forma análoga, uma comparação para o sistema de múltiplas taxas baseado em OFFH supondo desta vez tanto a distribuição gaussiana quanto a binomial para a MAI também é analisada. É mostrado que a BER em cenários de múltiplas taxas pode ser superestimada ou subestimada em várias ordens de grandeza, dependendo da distribuição suposta para a MAI e do número de usuários simultâneos no sistema. Além disso, é apresentado pela primeira vez um switch óptico híbrido de pacotes OCDM/WDM capaz de prover transmissões de múltiplas taxas e serviços diferenciados. A arquitetura do switch proposto e seu desempenho em termos de probabilidade de perda de pacotes também são apresentados. Finalmente, é mostrado que o uso da distribuição gaussiana ou poissoniana para a MAI pode não ser apropriado para uma estimativa confiável de BER, uma vez que não são aproximações aceitáveis para avaliar o desempenho de sistemas de múltiplas taxas e multiserviços com boa precisão.

In last years phenomena of wireless communication technologies became a primary interest of big development laboratories whole world. Domain of point to point links which are realized by laser technology with narrow beam divergence and very sensitive photo-detectors is ordinarily used these days. This trend of using light waves as carrier medium turned interests of scientist to the sphere of wide area networks which is domain of wi-fi radio technologies. One of new trends in this sphere is also in-door free space optics. With expansion which leads to using LED's in everyday applications and with technological progress of last years, also grows tendency of most effective utilization of LED systems. The result of this effort is thought which considerate LED as source of artificial lighting and source of carrier medium for modulated signal. This kind of device must fulfill hygienic standards for illumination and also must be able to work with high frequency by which is signal modulated. These systems can provide links with sufficient capacity in order of hundred megabits.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / Bit errors often occur in a wireless communications link when impairments alter the transmitted signal. It is advantageous to be able to predict how well a system will tolerate transmission problems. This paper details laboratory performance measurements and comparisons in terms of evaluating configurations of a digital receiver for Feher patented Quadrature Phase Shift Keying (FQPSK-B) demodulation. The transmitted signal is subjected to calibrated levels of impairments while the receiver performance is monitored in real-time.

Multiuser and cooperative orthogonal frequency division multiplexing(OFDM) systems are being actively researched and adopted in wireless standards, owing to their advantages of robustness to multipath fading, modularity, and ability to achieve high data rates. In OFDM based systems, perfect frequency and timing synchronization is essential to maintain orthogonality among the subcarriers at the receiver. In multiuser OFDM on the uplink, timing offsets (TOs) and/or carrier frequency offsets (CFOs) of different users, caused due to path delay differences between different users, Doppler and/or poor oscillator alignment, can destroy orthogonality among subcarriers at the receiver. This results in multiuser interference (MUI)and consequent performance degradation. In this thesis, we are concerned with the analysis and mitigation of the effect of large CFOs and TOs in multiuser OFDM systems, including uplink orthogonal frequency division multiple access (OFDMA),uplink single-carrier frequency division multiple access(SC-FDMA), and cooperative OFDM. Uplink OFDMA: In the first part of this thesis, we analytically quantify the effect of large CFOs and TOs on the signal-to-interference plus noise ratio(SINR) and uncoded bit error rate(BER) performance of uplink OFDMA on Rayleigh and Rician fading channels, and show analytical results to closely match with simulation results. Such an SINR/BER analysis for uplink OFDMA in the presence of both large CFOs as well as TOs has not been reported before. We also propose interference cancelling(IC) receivers to mitigate the performance degradation caused due to large CFOs and TOs of different users. SC-FDMA versus OFDMA: An issue with uplink OFDMA is its high peak-to-average power ratio(PAPR).Uplink SC-FDMA is proposed in the standards as a good low-PAPR alternative to uplink OFDMA; e.g., SC-FDMA has been adopted in the uplink of 3GPP LTE. A comparative investigation of uplink SC-FDMA and OFDMA from a sensitivity to large CFOs and TOs view point has not been reported in the literature. Consequently, in the second part of the thesis, we carry out a comparative study of the sensitivity of SC-FDMA and OFDMA schemes to large CFOs and TOs of different users on the uplink. Our results show that while SC-FDMA achieves better performance due to its inherent frequency diversity advantage compared to OFDMA in the case of perfect synchronization, its performance can get worse than that of OFDMA in the presence of large CFOs and TOs. We further show that use of low-complexity multistage IC techniques, with the knowledge of CFOs and TOs of different users at the receiver, can restore the performance advantage of SC-FDMA over OFDMA. Cooperative OFDM: Cooperative OFDM is becoming popular because of its ability to provide spatial diversity in systems where each node has only one antenna. In most studies on cooperative communications, perfect time synchronization among cooperating nodes is assumed. This implies that the transmissions from different cooperating nodes reach the destination receiver in orthogonal time slots. In practice, however, due to imperfect time synchronization, orthogonality among different nodes’ signals at the destination receiver can be lost, causing inter-symbol interference(ISI).In the third part of the thesis, we investigate cooperative OFDM communications using amplify-and-forward(AF) protocol at the relay, in the presence of imperfect timing synchronization. We derive analytical expressions for the ISI as function of timing offset for cooperative OFDM with AF protocol, and propose an IC receiver to mitigate the effects of timing offset induced ISI.

This thesis is related to the Bit Error Rate (BER) estimation for any digital communication system. In many designs of communication systems, the BER is a Key Performance Indicator (KPI). The popular Monte-Carlo (MC) simulation technique is well suited to any system but at the expense of long time simulations when dealing with very low error rates. In this thesis, we propose to estimate the BER by using the Probability Density Function (PDF) estimation of the soft observations of the received bits. First, we have studied a non-parametric PDF estimation technique named the Kernel method. Simulation results in the context of several digital communication systems are proposed. Compared with the conventional MC method, the proposed Kernel-based estimator provides good precision even for high SNR with very limited number of data samples. Second, the Gaussian Mixture Model (GMM), which is a semi-parametric PDF estimation technique, is used to estimate the BER. Compared with the Kernel-based estimator, the GMM method provides better performance in the sense of minimum variance of the estimator. Finally, we have investigated the blind estimation of the BER, which is the estimation when the sent data are unknown. We denote this case as unsupervised BER estimation. The Stochastic Expectation-Maximization (SEM) algorithm combined with the Kernel or GMM PDF estimation methods has been used to solve this issue. By analyzing the simulation results, we show that the obtained BER estimate can be very close to the real values. This is quite promising since it could enable real-time BER estimation on the receiver side without decreasing the user bit rate with pilot symbols for example.

La vitesse des liens séries haut débit (USB, SATA, PCI-express, etc.) a atteint les multi-gigabits par seconde, et continue à augmenter. Deux des principaux paramètres électriques utilisés pour caractériser les performances des SerDes sont la gigue transmis à un niveau de taux d’erreur donné et la capacité du récepteur à suivre la gigue à un taux d’erreur donné.Modéliser le bruit de phase des différents components du SerDes, et extraire la gigue temporelle pour la décomposer, aideraient les ingénieurs en conception de circuits à atteindre les meilleurs résultats pour les futures versions des SerDes. Générer des patterns de gigue synthétiques de bruits blancs ou colorés permettrait de mieux analyser les effets de la gigue dans le système pendant la phase de vérification.La boucle d’asservissement de phase est un des contributeurs de la gigue d’horloge aléatoire et déterministe à l’intérieur du système. Cette thèse présente une méthode pour modéliser la boucle d’asservissement de phase avec injection du bruit de phase et estimation de la gigue temporelle. Un modèle dans le domaine temporel en incluant les effets de non-linéarité de la boucle a été créé pour estimer cette gigue. Une nouvelle méthode pour générer des patterns synthétiques de gigue avec une distribution Gaussienne à partir de profils de bruit de phase coloré a été proposée.Les standards spécifient des budgets séparés de gigue aléatoire et déterministe. Pour décomposer la gigue de la sortie de la boucle d’asservissement de phase (ou la gigue généré par la méthode présentée), une nouvelle technique pour analyser et décomposer la gigue a été proposée. Les résultats de modélisation corrèlent bien avec les mesures et cette technique aidera les ingénieurs de conception à identifier et quantifier proprement les sources de la gigue ainsi que leurs impacts dans les systèmes SerDes.Nous avons développé une méthode, pour spécifier la boucle d’asservissement de phase en termes de bruit de phase. Cette méthode est applicable à tout standard (USB, SATA, PCIe, …) et définit les profils de bruits de4phases pour les différentes parties de la boucle d’asservissement de phase, pour s’assurer que les requis des standards sont satisfaits en termes de gigue. Ces modèles nous ont également permis de générer les spécifications de la PLL, pour des standards différents. / Bit rates of high speed serial links (USB, SATA, PCI-express, etc.) have reached the multi-gigabits per second, and continue to increase. Two of the major electrical parameters used to characterize SerDes Integrated Circuit performance are the transmitted jitter at a given bit error rate (BER) and the receiver capacity to track jitter at a given BER.Modeling the phase noise of the different SerDes components, extracting the time jitter and decomposing it, would help designers to achieve desired Figure of Merit (FoM) for future SerDes versions. Generating white and colored noise synthetic jitter patterns would allow to better analyze the effect of jitter in a system for design verification.The phase locked loop (PLL) is one of the contributors of clock random and periodic jitter inside the system. This thesis presents a method for modeling the PLL with phase noise injection and estimating the time domain jitter. A time domain model including PLL loop nonlinearities is created in order to estimate jitter. A novel method for generating Gaussian distribution synthetic jitter patterns from colored noise profiles is also proposed.The Standard Organizations specify random and deterministic jitter budgets. In order to decompose the PLL output jitter (or the generated jitter from the proposed method), a new technique for jitter analysis and decomposition is proposed. Modeling simulation results correlate well with measurements and this technique will help designers to properly identify and quantify the sources of deterministic jitter and their impact on the SerDes system.We have developed a method, for specifying PLLs in terms of Phase Noise. This method works for any standard (USB, SATA, PCIe, …), and defines Phase noise profiles of the different parts of the PLL, in order to be sure that the standard requirements are satisfied in terms of Jitter.

In this dissertation an in-depth study was conducted into the design, implementation and evaluation of a QPSK-based receiver structure for application in a UMTS WCDMA environment. The novelty of this work lies with the specific receiver architecture aimed to optimise the BER performance when possibly sparse data streams are transmitted. This scenario is a real possibility according to Verd´u et al [1] and Hagenauer et al [2–6]. A novel receiver structure was conceptualised, developed and evaluated in both narrowband and wideband scenarios, where it was found to outperform conventional receivers when a sparse data stream is transmitted. In order to reach the main conclusions of this study, it was necessary to develop a realistic simulation platform. The developed platform is capable of simulating a communication system meeting the physical layer requirements of the UMTS WCDMA standard. The platform can also perform narrowband simulations. A flexible channel emulator was developed that may be configured to simulate AWGN channel conditions, frequency non-selective fading (either Rayleigh or Rician with a configurable LOS component and Doppler spread), or a full multipath scenario where each path has a configurable LOS component, Doppler spread, path gain and path delay. It is therefore possible to even simulate a complex, yet realistic, COST207-TU channel model. The platform is also capable of simulating MUI. Each interfering user has a unique and independent multipath fading channel, while sharing the same bandwidth. Finally, the entire platform executes all simulations in baseband for improved simulation times. The research outputs of this work are summarised below: <ul> <li>A parameter, the sparseness measure, was defined in order to quantify the level by which a data stream differs from an equiprobable data stream.</li> <li>A novel source model was proposed and developed to simulate data streams with a specified amount of sparseness.</li> <li>An introductory investigation was undertaken to determine the effect of simple FEC techniques on the sparseness of an encoded data stream.</li> <li>Novel receiver structures for both narrowband and wideband systems were proposed, developed and evaluated for systems where possibly sparse data streams may be transmitted.</li> <li>Analytic expressions were derived to take the effect of sparseness into account in communication systems, including expressions for the joint PDF of a BPSK branch, the optimal decision region of a detector in AWGN conditions as well as the BER performance of a communication system employing the proposed optimal receiver in both AWGN channel conditions as well as in flat fading channel conditions.</li> <li>Numerous BER performance curves were obtained comparing the proposed receiver structure with conventional receivers in a variety of channel conditions, including AWGN, frequency non-selective fading and a multipath COST207-TU channel environment, as well as the effect of MUI</li></ul>. AFRIKAANS : In hierdie verhandeling word ’n in-diepte studie gedoen rakende die ontwerp, implementasie en evaluasie van ’n KPSK-gebaseerde ontvanger struktuur wat in ’n UMTS WKVVT omgewing gebruik kan word. Die bydrae van hierdie werk lˆe in die spesifieke ontvanger argitektuur wat daarop mik om die BFT werksverrigting te optimeer wanneer yl data strome versend word. Hierdie is ’n realistiese moontlikheid volgens Verd´u et al [1] en Hagenauer et al [2–6]. ’n Nuwe ontvanger struktuur is gekonsepsualiseer, ontwikkel en evalueer vir beide noueband en wyeband stelsels, waar dit gevind is dat dit beter werksverrigting lewer as tradisionele ontvangers wanneer yl data strome versend word. Dit was nodig om ’n realistiese simulasie platform te ontwikkel om die belangrikste gevolgtrekkings van hierdie studie te kan maak. Die ontwikkelde platform is in staat om ’n kommunikasie stelsel te simuleer wat aan die fisiese laag vereistes van die UMTS WKVVT standaard voldoen. Die platform kan ook noueband stelsels simuleer. ’n Aanpasbare kanaal simulator is ontwikkel wat opgestel kan word om SWGR kanaal toestande, plat duining (beide Rayleigh of Ricies met ’n verstelbare siglyn komponent en Doppler verspreiding), sowel as ’n veelvuldige pad omgewing (waar elke unieke pad ’n verstelbare siglyn komponent, Doppler verspreiding, pad wins en pad vertraging het) te emuleer. Dit is selfs moontlik om ’n komplekse, maar steeds realistiese COST207-TU kanaal model te simuleer. Die platform het ook die vermo¨e om VGS te simuleer. Elke steurende gebruiker het ’n unieke en onafhanklike veelvuldige pad deinende kanaal, terwyl dieselfde bandwydte gedeel word. Laastens, alle simulasies van die platvorm word in basisband uitgevoer wat verkorte simulasie periodes verseker. Die navorsingsuitsette van hierdie werk kan as volg opgesom word: <ul> <li>’n Parameter, die ylheidsmaatstaf, is gedefin¨ýeer om dit moontlik te maak om die vlak waarmee die ylheid van ’n datastroom verskil van ’n ewekansige stroom te versyfer.</li> <li>’n Nuwe bronmodel is voorgestel en ontwikkel om datastrome met ’n spesifieke ylheid te emuleer.</li> <li>’n Inleidende ondersoek is onderneem om vas te stel wat die effek van VFK tegnieke op die ylheid van ’n enkodeerde datastroom is.</li> <li>Nuwe ontvanger strukture is voorgestel, ontwikkel en evalueer vir beide noueband en wyeband stelsels waar yl datastrome moontlik versend kan word.</li> <li>Analitiese uitdrukkings is afgelei om die effek van ylheid in ag te neem in kommunikasie stelsels. Uitdrukkings vir onder andere die gedeelte WDF van ’n BFVK tak, die optimale beslissingspunt van ’n detektor in SWGR toestande, sowel as die BFT werksverrigting van ’n kommunikasie stelsel wat van die voorgestelde optimale ontvangers gebruik maak, hetsy in SWGR of in plat duinende kanaal toestande.</li> <li>Talryke BFT werksverrigting krommes is verkry wat die voorgestelde ontvanger struktuur vergelyk met die konvensionele ontvangers in ’n verskeidenheid kanaal toestande, insluitend SWGR, plat duinende kanale en ’n veelvuldige pad COST207-TU kanaal omgewing, sowel as in die teenwoordigheid van VGS.</li></ul></p Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

During the race towards the4th generation (4G) cellular-based digital communication systems, a growth in the demand for high capacity, multi-media capable, improved Quality-of-Service (QoS) mobile communication systems have caused the developing mobile communications world to turn towards betterMultiple Access (MA) techniques, like Code Division Multiple Access (CDMA) [5]. The demand for higher throughput and better QoS in future 4G systems have also given rise to a scheme that is becoming ever more popular for use in these so-called ‘bandwidth-on-demand’ systems. This scheme is known as adaptive channel coding, and gives a system the ability to firstly sense changes in conditions, and secondly, to adapt to these changes, exploiting the fact that under good channel conditions, a very simple or even no channel coding scheme can be used for Forward Error Correction(FEC). This will ultimately result in better system throughput utilization. One such scheme, known as incremental redundancy, is already implemented in the Enhanced Data Rates for GSM Evolution (EDGE) standard. This study presents an extensive simulation study of a Multi-User (MU), adaptive channel coded Direct Sequence Spread Spectrum Multiple Access (DS/SSMA) communication system. This study firstly presents and utilizes a complex Base Band(BB) DS/SSMA transmitter model, aimed at user data diversity [6] in order to realize the MU input data to the system. This transmitter employs sophisticated double-sideband (DSB)Constant-Envelope Linearly Interpolated Root-of-Unity (CE-LI-RU) filtered General Chirp-Like (GCL) sequences [34, 37, 38] to band limit and spread user data. It then utilizes a fully user-definable, complex Multipath Fading Channel Simulator(MFCS), first presented by Staphorst [3], which is capable of reproducing all of the physical attributes of realistic mobile fading channels. Next, this study presents a matching DS/SSMA receiver structure that aims to optimally recover user data from the channel, ensuring the achievement of data diversity. In order to provide the basic channel coding functionality needed by the system of this study, three simple, but well-known channel coding schemes are investigated and employed. These are: binary Hamming (7,4,3) block code, (15,7,5) binary Bose-Chadhuri-Hocquenghem (BCH) block code and a rate 1/3 <i.Non-Systematic (NS) binary convolutional code [6]. The first step towards the realization of any adaptive channel coded system is the ability to measure channel conditions as fast as possible, without the loss of accuracy or inclusion of known data. In 1965, Gooding presented a paper in which he described a technique that measures communication conditions at the receiving end of a system through a device called a Performance Monitoring Unit (PMU) [12, 13]. This device accelerates the system’sBit Error Rate (BER) to a so-called Pseudo Error Rate(PER) through a process known as threshold modification. It then uses a simple PER extrapolation algorithm to estimate the system’s true BER with moderate accuracy and without the need for known data. This study extends the work of Gooding by applying his technique to the DS/SSMA system that utilizes a generic Soft-Output Viterbi Algorithm(SOVA) decoder [39] structure for the trellis decoding of the binary linear block codes [3, 41-50], as well as binary convolutional codes mentioned, over realistic MU frequency selective channel conditions. This application will grant the system the ability to sense changes in communication conditions through real-time BER measurement and, ultimately, to adapt to these changes by switching to different channel codes. Because no previous literature exists on this application, this work is considered novel. Extensive simulation results also investigate the linearity of the PER vs. modified threshold relationship for uncoded, as well as all coded cases. These simulations are all done for single, as well as multiple user systems. This study also provides extensive simulation results that investigate the calculation accuracy and speed advantages that Gooding’s technique possesses over that of the classic Monte-Carlo technique for BER estimation. These simulations also consider uncoded and coded cases, as well as single and multiple users. Finally, this study investigates the experimental real-time performance of the fully functional MU, adaptive coded, DS/SSMA communication system over varying channel conditions. During this part of the study, the channel conditions are varied over time, and the system’s adaptation (channel code switching) performance is observed through a real-time observation of the system’s estimated BER. This study also extends into cases with multiple system users. Since the adaptive coded system of this study does not require known data sequences (training sequences), inclusion of Gooding’s technique for real-time BER estimation through threshold modification and PER extrapolation in future 4G adaptive systems will enable better Quality-of-Service (QoS) management without sacrificing throughput. Furthermore, this study proves that when Gooding’s technique is applied to a coded system with a soft-output, it can be an effective technique for QoS monitoring, and should be considered in 4G systems of the future. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / MEng / unrestricted