International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper presents initial results of an investigation on bandwidth efficient waveforms for telemetry, tracking and commands (TT&C). Included in the investigation are waveforms that are currently being considered by the International Consultative Committee for Space Data Systems (CCSDS) and American Institute of Aeronautics and Astronautics (AIAA) for standards, advanced waveforms and others that have the potential to become future standards. The goal of this investigation is to recommend a suite of bandwidth efficient modulation schemes for further investigation. This suite of modulation scheme should be suitable for various TT&C applications with data rates ranging from a few hundreds Bit Per Second (bps) to a few hundreds Mega bps (Mbps). First, the philosophy of waveform evaluation is described. The description includes a list of waveform attributes leading to quantitative and qualitative figures of merit for bandwidth efficient waveforms. Then quantitative results for the two most important waveform attributes (bandwidth efficiency and bit error rate performance) are presented. These results will be used by a follow-on study to significantly reduce the number of candidate waveforms, so that all attributes can be more thoroughly evaluated.

Modern communication systems require higher data rates which have increased thedemand for high speed transceivers. For a system to work efficiently, all blocks ofthat system should be fast. It can be seen that analog interfaces are the main bottleneckin whole system in terms of speed and power. This fact has led researchersto develop high speed analog to digital converters (ADCs) with low power consumption.Among all the ADCs, flash ADC is the best choice for faster data conversion becauseof its parallel structure. This thesis work describes the design of such a highspeed and low power flash ADC for analog front end (AFE) of a transceiver. Ahigh speed highly linear track and hold (TnH) circuit is needed in front of ADCwhich gives a stable signal at the input of ADC for accurate conversion. Twodifferent track and hold architectures are implemented, one is bootstrap TnH andother is switched source follower TnH. Simulations show that high speed with highlinearity can be achieved from bootstrap TnH circuit which is selected for the ADCdesign.Averaging technique is employed in the preamplifier array of ADC to reduce thestatic offsets of preamplifiers. The averaging technique can be made more efficientby using the smaller number of amplifiers. This can be done by using the interpolationtechnique which reduces the number of amplifiers at the input of ADC. Thereduced number of amplifiers is also advantageous for getting higher bandwidthsince the input capacitance at the first stage of preamplifier array is reduced.The flash ADC is designed and implemented in 150 nm CMOS technology for thesampling rate of 1.6 GSamples/sec. The bootstrap TnH consumes power of 27.95mW from a 1.8 V supply and achieves the signal to noise and distortion ratio(SNDR) of 37.38 dB for an input signal frequency of 195.3 MHz. The ADC withideal TnH and comparator consumes power of 78.2 mW and achieves 4.8 effectivenumber of bits (ENOB).

Les systèmes de communication sans fil caractérisés par des services à haute vitesse sont en évolution permanentes malgré les restrictions en termes de la capacité du système et les conflits de couverture intérieure. Récemment, les réseaux “SmallCells” basés sur le standard LTE présentent une solution prometteuse en offrant les services demandés avec une meilleure couverture à l’intérieur et augmentant la capacité du système. Cependant, de nombreux défis rencontrent les constructeurs et les opérateurs pour un déploiement efficace de ces systèmes. Dans cette thèse, afin de développer ce type de réseaux et d’apporter des améliorations considérables de Qualité de Service (QoS) et de débits, nous adoptons une stratégie se basant complémentairement sur deux différents niveaux : couche de liaison (MAC) et couche physique. En première partie, au niveau de la couche de liaison, nous proposons deux algorithmes d’ordonnancement et d’allocation conjointes de ressources se basant sur la technique d’Adaptation de Modulation et de Codage (AMC) et sur le contrôle de puissance pour les deux liaisons descendante et montante respectivement. Deux catégories distinctes d’utilisateurs qui diffèrent par la Qualité de Service demandée sont considérées. Ces algorithmes sont nommés respectivement : “Downlink AMC-QRAP” et “Uplink AMC-QRAP”. L’adaptation conjointe de puissance de transmission et de type de Modulation&Codage répond forcement aux variations de la qualité de la liaison sur chaque canal radio destiné à être alloué. Cependant, les deux liaisons, descendante et montante diffèrent par leurs spécificités. En particulier, comme mode de transmission du signal, le système 3GPP LTE utilise la technique OFDMA pour la liaison descendante et la technique SC-FDMA, plus efficace en termes d’énergie, pour la liaison montante. Une modélisation sous forme de problèmes d’optimisation linéaire est ainsi conçue. Comme compromis entre les architectures de réseaux: centralisée et distribuée, nous utilisons l’architecture de groupes ou “clusters” ainsi proposée dans la littérature. Dans la deuxième partie de notre recherche, nous avons abord´e les techniques de la “couche physique” en termes de traitement de signal comme une approche d’amélioration du système LTE. Ainsi, deux contributions basées sur la “transformée en ondelettes” (Wavelet Transform) sont proposées. Premièrement, vu que la technique de modulation multi-porteuse OFDM souffre de plusieurs limitations en termes d’efficacité spectrale et énergétique, de synchronisation et d’interférence entre porteuses, nous proposons une méthode alternative basée sur les ondelettes. Nous avons démontré que la substitution de la transformée de Fourier par la transformée en ondelettes dans la technique OFDM permet de dépasser les différentes limitations de l’OFDM. Enfin, nous avons propos´e une approche pour délimiter et détecter les différents canaux de ressources alloués. Elle est utilisée dans l’algorithme d’ordonnancement de la transmission montante pour améliorer la fiabilité de la transmission et réduire le temps de convergence du problème d’optimisation. Des simulations étendues selon différentes densités de réseau ont été réalisées, en utilisant plusieurs paramètres tels que l’efficacité spectrale, la puissance de transmission, le taux de satisfaction en termes de débits demandés et la capacité du réseau. Nous avons comparé nos méthodes à plusieurs travaux existants dans la littérature et prouvé la surperformance pour les différents paramètres pris en compte. / Responding to the huge demand for high data rates and satisfying Quality of Service (QoS) requirements are the main objectives of the wireless mobile operators. LTE-based small cell system is a promising technology offering the required services, enhanced indoor coverage and increased system capacity. However, many challenges face the constructors and the operators for an effective deployment of these systems. In this thesis, in order to evolve such systems and adduce significant enhancement in terms of QoS and throughput, we adopt a complementary strategy based on both data link layer and physical layer.First, we propose, on the link layer level, two scheduling and joint resource allocation algorithm based on the Adaptive Modulation and Coding (AMC) and the power control mechanism for OFDMA-Downlink and SC-FDMA-Uplink connections respectively. Namely, they refer to: “Downlink AMC-QRAP” and “Uplink AMC-QRAP”. The joint adaptation of the transmission power and the Modulation and Coding Scheme reliably interacts with the link quality on each allocated sub-channel. Two distinct user categories are considered to differentiate between different QoS levels required. Accordingly, a linear optimization model is performed for the problem resolution. A clustering approach proposed in the literature has been used as a tradeoff between centralized and distributed schemes. Particularly, we used the spectrum sensing technique as proposed on the physical layer to detect surrounding transmissions.After that, we tackle the physical layer “signal processing” techniques as an LTE enhancement approach. Thus, two contributions based on the “wavelet transform” (WT) are proposed.The “wavelet-based OFDM” technique is firstly proposed as an alternative transmission mode for both downlink and uplink of the LTE and beyond wireless systems. In fact, theOFDM suffers from several limitations in terms of PAPR, spectral efficiency, synchronization cost and the inter-carrier interference. We proved that with substituting the Fourier transform by the wavelet transform in the OFDM technique, the different OFDM limitations can be significantly overcame. Second, we proposed an enhanced spectrum sensing approach based on WT tool that accurately delimits the occupied resource blocks in the whole spectrum. These physical layer enhancements help improving the scheduling algorithm for the uplink proposed in our second contribution.Extensive network simulations with different network densities have been conducted, using several metrics such as spectral efficiency, throughput satisfaction rate, user outage and transmission power. We have compared our methods to several existing works in the literature and proved the outperformance for the different considered metrics.

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Avec la croissance actuelle du marché des applications de transfert de données multimédia à très haut débit, les bandes de fréquences autour de 60 GHz sont une nouvelle alternative promettant des performances intéressantes en terme de débits mais soulèvent des défis techniques et technologiques au niveau des architectures et circuits. C'est dans ce cadre que s'inscrit cette thèse, qui propose une approche multi bande impulsionnelle MBOOK avec un récepteur à détection d'énergie, et qui analyse plus spécifiquement les verrous au niveau de l'émetteur. L'étude du canal de propagation à 60 GHz, basée sur les modèles de canaux du standard IEEE 802.15.3c, a permis de démontrer la potentialité de cette architecture et permet d'atteindre des débits de 2 Gbps à 2metres dans un environnement de type résidentiel. Le dimensionnement de l'architecture ainsi que des performances des principaux blocs ont conduit à plusieurs possibilités pour l'architecture de l'émetteur MBOOK à 60 GHz. Les critères ont été d'assurer un compromis performances, consommation. Une étude approfondie sur l'étude des imperfections de certains blocs critiques et l'impact sur l'impulsion transmise, et donc sur les performances du système ont été établies. Le banc de filtres, nécessaire à l'émission et à la réception, représente l'un des verrous, et nous proposons une solution de filtrage à base de lignes couplées. L'étude des solutions de génération d'impulsions, des étages de commutation, et des étages d'amplification de l'émetteur sont détaillées et discutées dans les deux derniers chapitres / With the current increasing market request concerning high speed data rates applications, the 60 GHz frequency bands seems to be one of the new promising alternatives for high data rate wireless communications. In this context, the development of new systems operating at these frequencies becomes a very attractive research subject. This study focuses on nomadic systems offering high data and reconfigurable rates, low complexity, low power consumption for short communications. One of the important tasks in the millimetre wave architecture design is to consider the channel propagation characteristics simultaneously with the technological performance of integrated circuits and antennas. This requires a co-design of the entire system. Therefore, we begun by studying the characteristics of the channel propagation channel at 60GHz according to the IEEE 802.15.3c and IEEE 802.11.ad models. This PHD thesis proposes a new transceiver architecture based on multi-band impulse mode, with On Off Keying modulation schema and non coherent receiver. This architecture is dedicated to nomadic systems offering high data and reconfigurable rates, low complexity, low power consumption for short communications. Analysis and performances for the proposed architecture are presented. More than 2 Gbps at 2 m are obtained. The imperfections of some critical blocks and their impact on the transmitted pulses were analysed and thus the performance of the system has been established. The potentiality of microstrip band pass filter bank presenting a constant relative bandwidth and reasonable insertion losses is presented in this study. The study of pulse generation solutions, switchers, amplification stages and antennas are detailed and discussed in the last two chaptersconstant relative bandwidth and reasonable insertion losses is presented in this study.The study of pulse generation solutions, switchers, amplification stages and antennas are detailed and discussed in the last two chapters.

Este trabalho propõe a análise da comunicação sem fio para um sistema de controle distribuído de semáforos, a partir da revisão das literaturas, realização de simulações e experimentos, os quais consideram as especificações estabelecidas para o sistema de semáforos. As simulações e os experimentos se baseiam na avaliação do comportamento da comunicação perante a alteração de alguns parâmetros de configuração da rede. O estudo apresentado envolve análises relacionadas ao padrão IEEE 802.11g e às definições da camada física apresentadas nas especificações do padrão. Os métodos utilizados envolvem o estudo e experimentação de parâmetros relacionados à potência de transmissão e recepção, além de análise dos esquemas de modulação utilizados pelo padrão IEEE 802.11g. A metodologia aplicada a este trabalho envolve o conhecimento das características e capacidade dos esquemas de modulação responsáveis pela definição das taxas de transmissão. As análises mostram que a possibilidade de adequação dos parâmetros de configuração de rede, levando em consideração o cenário de aplicação, pode ser um fator essencial para o bom desempenho de todo o sistema. / This work proposes the analysis of wireless communication for a distributed control system of traffic lights, from the review of the literature and conducting simulations and experiments, which consider the specifications established for traffic light system. The simulations and experiments are based on the evaluation of the communication behavior towards changing some network configuration parameters. The study presented involves analysis related to the IEEE 802.11g standard and definitions of the physical layer shown in standard specifications. The methods used involve the study and testing of parameters related to power transmission and reception, and analysis of modulation schemes used by the IEEE 802.11g standard. The methodology applied to this work involves the knowledge of the characteristics and capacity of modulation schemes responsible for setting transmission rates. The analyses show that the possibility of adaptation network configuration parameters considering the application scenario may be an essential factor to the performance of the entire system.

Este trabalho propõe a análise da comunicação sem fio para um sistema de controle distribuído de semáforos, a partir da revisão das literaturas, realização de simulações e experimentos, os quais consideram as especificações estabelecidas para o sistema de semáforos. As simulações e os experimentos se baseiam na avaliação do comportamento da comunicação perante a alteração de alguns parâmetros de configuração da rede. O estudo apresentado envolve análises relacionadas ao padrão IEEE 802.11g e às definições da camada física apresentadas nas especificações do padrão. Os métodos utilizados envolvem o estudo e experimentação de parâmetros relacionados à potência de transmissão e recepção, além de análise dos esquemas de modulação utilizados pelo padrão IEEE 802.11g. A metodologia aplicada a este trabalho envolve o conhecimento das características e capacidade dos esquemas de modulação responsáveis pela definição das taxas de transmissão. As análises mostram que a possibilidade de adequação dos parâmetros de configuração de rede, levando em consideração o cenário de aplicação, pode ser um fator essencial para o bom desempenho de todo o sistema. / This work proposes the analysis of wireless communication for a distributed control system of traffic lights, from the review of the literature and conducting simulations and experiments, which consider the specifications established for traffic light system. The simulations and experiments are based on the evaluation of the communication behavior towards changing some network configuration parameters. The study presented involves analysis related to the IEEE 802.11g standard and definitions of the physical layer shown in standard specifications. The methods used involve the study and testing of parameters related to power transmission and reception, and analysis of modulation schemes used by the IEEE 802.11g standard. The methodology applied to this work involves the knowledge of the characteristics and capacity of modulation schemes responsible for setting transmission rates. The analyses show that the possibility of adaptation network configuration parameters considering the application scenario may be an essential factor to the performance of the entire system.

Enhanced Data Rates for Global Evolution (EDGE) is one of the 3G wireless communication standards, which provides higher data rates by adopting 8-PSK modulation in TDMA system infrastructure of GSM. In this thesis, a turbo detection receiver for Enhanced General Packet Radio Services (EGPRS) system, which is the packet switching mode of EDGE, is studied. In turbo detection, equalization and channel decoding are performed iteratively. Due to 8-ary alphabet of EGPRS modulation, full state trellis based equalization, as usually performed in GSM, is too complex not only for turbo detection but even for conventional equalization / so suboptimum schemes have to be considered. The Delayed Decision Feedback Sequence Estimation (DDFSE) is chosen as suboptimal and less complex trellis based scheme and it is examined as a conventional equalization technique firstly. It is shown that the DDFSE has a fine tradeoff between performance and complexity and can be a promising candidate for EGPRS. Then it is employed to reduce the number of the trellis state in turbo detection. Max-log-MAP algorithm is used for soft output calculations of both SISO equalizer and SISO decoder. Simulation results illustrate that proposed turbo detection structure improves bit error rate and block error rate performance of the receiver with respect to the conventional equalization and decoding scheme. The iteration gain varies depending on modulation type and coding rate of Modulation Coding Scheme (MCS) employed in EGPRS.

One of the most important technologies used in modern communication systems is channel coding. Channel coding dates back to a paper published by Shannon in 1948 [1] entitled “A Mathematical Theory of Communication”. The basic idea behind channel coding is to send redundant information (parity) together with a message to make the transmission more error resistant. There are different types of codes that can be used to generate the parity required, including block, convolutional and concatenated codes. A special subclass of codes consisting of the codes mentioned in the previous paragraph, is sparse graph codes. The structure of sparse graph codes can be depicted via a graphical representation: the factor graph which has sparse connections between its elements. Codes belonging to this subclass include Low-Density-Parity-Check (LDPC) codes, Repeat Accumulate (RA), Turbo and fountain codes. These codes can be decoded by using the belief propagation algorithm, an iterative algorithm where probabilistic information is passed to the nodes of the graph. This dissertation focuses on noisy decoding of fountain codes using belief propagation decoding. Fountain codes were originally developed for erasure channels, but since any factor graph can be decoded using belief propagation, noisy decoding of fountain codes can easily be accomplished. Three fountain codes namely Tornado, Luby Transform (LT) and Raptor codes were investigated during this dissertation. The following results were obtained: <ol> <li>The Tornado graph structure is unsuitable for noisy decoding since the code structure protects the first layer of parity instead of the original message bits (a Tornado graph consists of more than one layer).</li> <li> The successful decoding of systematic LT codes were verified.</li> <li>A systematic Raptor code was introduced and successfully decoded. The simulation results show that the Raptor graph structure can improve on its constituent codes (a Raptor code consists of more than one code).</li></ol> Lastly an LT code was used to replace the convolutional incremental redundancy scheme used by the 2G mobile standard Enhanced Data Rates for GSM Evolution (EDGE). The results show that a fountain incremental redundancy scheme outperforms a convolutional approach if the frame lengths are long enough. For the EDGE platform the results also showed that the fountain incremental redundancy scheme outperforms the convolutional approach after the second transmission is received. Although EDGE is an older technology, it still remains a good platform for testing different incremental redundancy schemes, since it was one of the first platforms to use incremental redundancy. / Dissertation (MEng)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / MEng / unrestricted