Three 40/60-GHz optical-wireless bidirectional architectures are designed with a centralized light source in the central office based on wavelength reuse. Three super-broadband access networks are proposed and experimentally demonstrated for simultaneously delivering wired and wireless services over an optical fiber and an air link in a single transport platform. The transport feasibility in metro and wide-area access networks with multiple reconfigurable optical add-drop multiplexers (ROADMs) nodes is explored for 40-GHz and 60-GHz optical millimeter-wave signals. Additionally, the optical-wireless systems using the orthogonal frequency division multiplexing (OFDM) modulation format are analytically and experimentally demonstrated to mitigate the chromatic dispersion in optical fiber. This thesis also successfully implements the testbed trial for the delivery of uncompressed 270-Mb/s standard-definition television (SDTV) and 1.485-Gb/s high-definition television (HDTV) video signals over optical fiber and air links. The demonstration represents the first ever reported real applications over hybrid wired and wireless access networks, showing that our developed up-conversion schemes and designed architectures are highly suitable for super-broadband applications in next-generation optical-wireless access networks.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-08-07T18:53:34Z No. of bitstreams: 1 TELES DE SALES BEZERRA - DISSERTAÇÃO PPGCC 2017..pdf: 20064982 bytes, checksum: 40cc1a5d9429d5090373078fb560639d (MD5) / Made available in DSpace on 2018-08-07T18:53:34Z (GMT). No. of bitstreams: 1 TELES DE SALES BEZERRA - DISSERTAÇÃO PPGCC 2017..pdf: 20064982 bytes, checksum: 40cc1a5d9429d5090373078fb560639d (MD5) Previous issue date: 2017-12-21 / Capes / Os Sistemas de Comunicações móveis sem fio estão em uma crescente em relação a demanda por infraestrutura de comunicação, explicado pelo aumento do fornecimento de serviços aos usuários nas últimas décadas. Um dos recursos que está em escassez é o uso da banda, em que diversas técnicas tentam reutilizá-la, na tratativa de aumentar a disponibilidade de uso do espectro. Uma das opções de expansão do espectro, e consequentemente dos atuais serviços de redes móveis é o uso de outras faixas do espectro eletromagnético, que ainda não eram utilizadas nas comunicações móveis, como as ondas milimétricas. As comunicações que operam nas faixas de ondas milimétricas enfrentam obstáculos técnicos, como a necessidade de evolução de equipamentos específicos, problemas de cobertura e o quanto esses aspectos afetam a Qualidade de Serviço (QoS), em resumo, a viabilidade da comunicação requer uma avaliação cuidadosa. Há receio de que comunicações por ondas milimétricas sejam muito menos favoráveis que o uso de espectros mais usuais, principalmente nos problemas relacionados a cobertura. Projetistas de redes contam com diversas ferramentas para prever as características do ambiente, com o intuito de prever dificuldades na cobertura de sinal, para isso, fazem uso de modelos de previsão de perdas. Neste trabalho foi realizado um estudo sobre os problemas de cobertura e propagação de ondas milimétricas em ambientes urbanos fechados, sendo um prédio de escritórios e um shopping center. Para tanto, foram utilizados diversos modelos de previsão de perdas, a partir dos quais foi possível identificar que mesmo com o uso de modelos de perdas recomendados para ondas milimétricas, a minimização dos erros na predição é pequena, e comparada com modelos genéricos. / Wireless Mobile Communications Systems are on the rise in demand for resources, explained by the increased provision of services to users over the past few decades. One of the resources that is in shortage is the use of the band, in which several techniques try to reuse it, in the attempt to increase the availability of use of the spectrum. One of the options for spectrum expansion, and consequently of current mobile network services, is the use of other bands in the electromagnetic spectrum that were not yet used in mobile Communications such as millimeter waves. Communications that operate in the millimeter wave bands face technical obstacles, such as the need to evolve specific equipment, coverage problems and how these aspects affect Quality of Service, in short, the viability of communication requires a careful evaluation. There are fears that millimeter-wave Communications are far less favorable than the use of more usual spectra, especially in coverage-related problems. Network designers rely on several tools to predict the characteristics of the environment, in order to predict difficulties in signal coverage. For this, they use loss prediction models. In this work was carried out a study on the problems of coverage and propagation of millimeter waves in closed urban environments, being an office building and a shopping center. For this, several loss prediction models were used, through which we can identify that even with the use of recommended loss models for millimeter waves, the minimization of prediction errors is small, and compared with generic models.

The research work reported in this thesis is focused on the chiral analysis, quantification of enantiomeric composition, assignment of absolute configuration of molecules with chosen functional groups. The weak intra-molecular hydrogen bonding interactions are detected by exploiting several multinuclear and multi-dimensional techniques. Pulse sequences have been designed to manipulate the spin dynamics to derive specific information from the complex NMR spectra encountered in diverse situations. Broadly, the thesis can be classified in to three sections. The section I containing two chapters reports the introduction of new chiral auxiliaries and protocols developed for enantiomeric discrimination, measurement of enantiomeric contents, assignment of absolute configuration for molecules possessing specific functional groups using chiral solvating and derivatizing agents. The section II, reports NMR experimental evidence for the observation of the rare type of intramolecular hydrogen bonds involving organic fluorine in biologically important organic molecules, that are corroborated by extensive DFT based theoretical calculations. The section II also discusses the H/D exchange mechanism as a tool for quantification of HB strengths in organic building blocks. The section III reports the two different novel NMR methodologies designed for deriving information on the scalar interaction strengths in an orchestrated manner. The designed sequences are able to completely eradicate the axial peaks, prevents the evolution of unwanted couplings and also yields ultrahigh resolution in the direct dimension, permitting the accurate measurement of scalar couplings for a particular spin. The brief summary about each chapter is given below. Chapter 1 provides a general introduction to one and two dimensional NMR spectroscopy. The pedagogical approach has been followed to discuss the conceptual understanding of spin physics and the NMR spectral parameters. The basic introduction to chirality, existing approaches in the literature for discrimination of enantiomers and the assignment of absolute configuration of molecules with chosen functional groups and their limitations are briefly discussed. The brief introduction to hydrogen bond, experimental methods to obtain the qualitative information about the strengths of hydrogen bonds, and the theoretical approaches employed in the thesis to corroborate the NMR experimental findings have been provided. The mechanism of H/D exchange, the utilization of exchange rates to derive strengths of intra-molecular hydrogen bond in small molecules have also been discussed. This chapter builds the bridge for the rest of the chapters. Each of these topics are discussed at length in the corresponding chapters. Part I: NMR Chiral Analysis: Novel Protocols Chapter 2 discusses a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, amino alcohols. The protocol involves the in-situ formation of chiral ammonium borate salt from a mixture of C2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept has been convincingly demonstrated for the visualization of enantiomers of a large number of chiral and pro-chiral amines and amino alcohols. The protocol also permits the precise measurement of enantiomeric composition. The significant advantage of the protocol is that it can be performed directly in the NMR tube, without any physical purification. The structure of the borate complex responsible for the enantiodifferentiation of amines has also been established by employing multinuclear NMR techniques and DFT calculations. From DOSY and 11B NMR experiments it has been ascertained that there are only two possible complexes or entities which are responsible for differentiating enantiomers. From the combined utility of DFT calculations and the 11B NMR chemical shifts, the structure of the borate complex has been determined to be an amine-coordinated complex with the N atom of the amine. Chapter 3 discusses a simple chiral derivatizing protocol involving the coupling of 2-formylphenylboronic acid and an optically pure [1,1-binaphthalene]-2,2-diamine for the rapid and accurate determination of the enantiopurity of hydroxy acids and their derivatives, possessing one or two optically active centres. It is established that this protocol is not only rapid method for discrimination of enantiomers but also highly effective for assigning the absolute configuration of various chiral hydroxy acids and their derivatives. The developed protocol involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and 2-formylphenylboronic acid with (S)-[1,1-binaphthalene]-2,2-diamine as chiral derivatizing agents. The absence of aliphatic peaks from the derivatizing agent, large chemical shift separation between the discriminated peaks of diastereomers, and the systematic change in the direction of displacement of peaks for an enantiomer in a particular diastereomeric complex, permitted the unambiguous assignment of absolute configuration. Part II : Rare Type of Intramolecular Hydrogen Bonding In chapter 4 The rare occurrence of intramolecular hydrogen bonds of the type N–H˖˖˖F–C, in the derivatives of imides and hydrazides in a low polarity solvent, is convincingly established by employing multi-dimensional and multinuclear solution state NMR experiments. The observation of 1hJFH, 2hJFN, and 2hJFF of significant strengths, where the spin polarization is transmitted through space among the interacting NMR active nuclei, provided strong and conclusive evidence for the existence of intra-molecular hydrogen bonds. Solvent induced perturbations and the variable temperature NMR experiments unambiguously supported the presence of intramolecular hydrogen bond. The two dimensional HOESY and 15N–1H HSQC experiments reveals the existence of multiple conformers in some of the investigated molecules. The 1H DOSY experimental results discarded any possibility of self or cross-dimerization of the molecules. The results of DFT based calculations, viz., Quantum Theory of Atoms In Molecules (QTAIM) and Non Covalent Interaction (NCI), are in close agreement with the NMR experimental findings. In chapter 5 the rates of hydrogen/deuterium (H/D) exchange determined by 1H NMR spectra have been utilized to derive the strength of hydrogen bonds and to monitor the electronic effects in the site-specific halogen substituted Benz amides and anilines. The theoretical fitting of the time dependent variation in the integral areas of 1H NMR resonances to the first order decay function permitted the determination of H/D exchange rate constants (k) and their precise half-lives (t1/2) with high degree of reproducibility. The comparative study also permitted the determination of relative strengths of hydrogen bonds and the contribution from electronic effects on the H/D exchange rates. Part III: Novel NMR Methodologies for the Precise Measurement of 1H-1H Couplings Chapter 6 describes two novel NMR methodologies developed for the precise measurement of 1H-1H couplings. Poor chemical shift dispersion and the pairwise interaction among the entire coupled network of protons results in the severely complex and overcrowded one dimensional 1H NMR spectra, hampering both the resonance assignments and the accurate determination of nJHH. The available two-dimensional selective refocusing (SERF) based experiments suffer from the evolution of magnetization from uncoupled protons as intense uninformative axial peaks. This creates ambiguity in the identification of peaks belonging to the coupled partners of a selectively excited proton, hindering the extraction of their interaction strengths. This challenge has been circumvented by designing two novel experimental technique, cited as “Clean-G-SERF” and “PS-Clean-G-SERF”. The Clean-G-SERF technique completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton. The method permits the accurate determination of spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. The PS-Clean-G-SERF technique has been designed for the complete elimination of axial peaks and undesired couplings, with a blend of ultra-high resolution achieved by real time broad band mononuclear decoupling has been discussed in this chapter. The spin dynamics involved in both these pulse sequences have been discussed. The diverse applications of both these novel experiments have been demonstrated.

No description available.

The radio frequency (RF) spectrum as a natural resource is severely under-utilized over time and space due to an inefficient licensing framework. As a result, in-creasing cellular and wireless network usage is placing significant demands on the licensed spectrum. This has led to the development of cognitive radios, software defined radios and mm-wave radios. Cognitive radios (CRs) enable more efficient spectrum usage over a wide range of frequencies and hence have emerged as an effective solution to handle huge network demands. They promise versatility, flex-ability and cognition which can revolutionize communications systems. However, they present greater challenges to the design of radio frequency (RF) front-ends. Instead of a narrow-band front-end optimized and tuned to the carrier frequency of interest, cognitive radios demand front-ends which are versatile, configurable, tun-able and capable of transmitting and receiving signals with different bandwidths and modulation schemes. The primary purpose of this thesis is to design a re-configurable, wide-band and low phase-noise fast settling frequency synthesizer for cognitive radio applications. Along with frequency generation, an area efficient multi-band low noise amplifier (LNA) with integrated built-in-self-test (BIST) and a strong immunity to interferers has also been proposed and implemented for these radios. This designed LNA relaxes the specification of harmonic content in the synthesizer output. Finally some preliminary work has also been done for mm-wave (V-band) frequency synthesis. The Key Contributions of this thesis are: A frequency synthesizer, based on a type-2, third-order Phase Locked Loop (PLL), covering a frequency range of 0.1-5.4 GHz, is implemented using a 0.13 µm CMOS technology. The PLL uses three voltage controlled oscillators (VCOs) to cover the whole range. It is capable of switching between any two frequencies in less than 3 µs and has phase noise values, compatible with most communication standards. The settling of the PLL in the desired state is achieved in dynamic multiple steps rather than traditional single step settling. This along with other circuit techniques like a DAC-based discriminator aided charge pump, fast acquisition pulse-clocked based PFD and timing synchro-negation is used to obtain a significantly reduced settling time A single voltage controlled LC-oscillator (LC-VCO) has been designed to cover a wide range of frequencies (2.0-4.1 GHz) using an area efficient and switch-able multi-tap inductor and a capacitor bank. The switching of the multi-tap inductor is done in the most optimal manner so as to get good phase-noise at the output. The multi-tap inductor provides a significant area advantage, and in spite of a degraded Q, provides an acceptable phase noise of -123 dBc/Hz and -113 dBc/Hz at an offset of 1 MHz at carrier frequencies of 2 and 4 GHz, respectively. Implemented in a 0.13 µm CMOS technology, the oscillator with ≈ 69 % tuning range, occupies an active area of only 0.095 mm2. An active inductor based noise-filter has been proposed to improve the phase-noise performance of the oscillator without much increase in the area. A variable gain multi-band low noise amplifier (LNA) is designed to operate over a wide range of frequencies (0.8 GHz to 2.4 GHz) using an area efficient switchable-π network. The LNA can be tuned to different gain and linearity combinations for different band settings. Depending upon the location of the interferers, a specific band can be selected to provide optimum gain and the best signal-to-intermodulation ratio. This is accomplished by the use of an on-chip Built-in-Self-Test (BIST) circuit. The maximum power gain of the amplifier is 19 dB with a return loss better than 10 dB for 7 mW of power consumption. The noise figure is 3.2 dB at 1 GHz and its third-order intercept point (I I P3) ranges from -15 dBm to 0 dBm. Implemented in a 0.13 µm CMOS technology, the LNA occupies an active area of about 0.29 mm2. Three different types of VCOs (stand-alone LC VCO, push-push VCO and a ring oscillator based VCO) for generating mm-wave frequencies have been implemented using 65-nm CMOS technology and their measured results have been analyzed

Compressed sensing has been proposed as a computationally efficient method to estimate the finite-dimensional signals. The idea is to develop an undersampling operator that can sample the large but finite-dimensional sparse signals with a rate much below the required Nyquist rate. In other words, considering the sparsity level of the signal, the compressed sensing samples the signal with a rate proportional to the amount of information hidden in the signal. In this dissertation, first, we employ compressed sensing for physical layer signal processing of directional millimeter-wave communication. Second, we go through the theoretical aspect of compressed sensing by running a comprehensive theoretical analysis of compressed sensing to address two main unsolved problems, (1) continuous-extension compressed sensing in locally convex space and (2) computing the optimum subspace and its dimension using the idea of equivalent topologies using Köthe sequence. In the first part of this thesis, we employ compressed sensing to address various problems in directional millimeter-wave communication. In particular, we are focusing on stochastic characteristics of the underlying channel to characterize, detect, estimate, and track angular parameters of doubly directional millimeter-wave communication. For this purpose, we employ compressed sensing in combination with other stochastic methods such as Correlation Matrix Distance (CMD), spectral overlap, autoregressive process, and Fuzzy entropy to (1) study the (non) stationary behavior of the channel and (2) estimate and track channel parameters. This class of applications is finite-dimensional signals. Compressed sensing demonstrates great capability in sampling finite-dimensional signals. Nevertheless, it does not show the same performance sampling the semi-infinite and infinite-dimensional signals. The second part of the thesis is more theoretical works on compressed sensing toward application. In chapter 4, we leverage the group Fourier theory and the stochastical nature of the directional communication to introduce families of the linear and quadratic family of displacement operators that track the join-distribution signals by mapping the old coordinates to the predicted new coordinates. We have shown that the continuous linear time-variant millimeter-wave channel can be represented as the product of channel Wigner distribution and doubly directional channel. We notice that the localization operators in the given model are non-associative structures. The structure of the linear and quadratic localization operator considering group and quasi-group are studied thoroughly. In the last two chapters, we propose continuous compressed sensing to address infinite-dimensional signals and apply the developed methods to a variety of applications. In chapter 5, we extend Hilbert-Schmidt integral operator to the Compressed Sensing Hilbert-Schmidt integral operator through the Kolmogorov conditional extension theorem. Two solutions for the Compressed Sensing Hilbert Schmidt integral operator have been proposed, (1) through Mercer's theorem and (2) through Green's theorem. We call the solution space the Compressed Sensing Karhunen-Loéve Expansion (CS-KLE) because of its deep relation to the conventional Karhunen-Loéve Expansion (KLE). The closed relation between CS-KLE and KLE is studied in the Hilbert space, with some additional structures inherited from the Banach space. We examine CS-KLE through a variety of finite-dimensional and infinite-dimensional compressible vector spaces. Chapter 6 proposes a theoretical framework to study the uniform convergence of a compressible vector space by formulating the compressed sensing in locally convex Hausdorff space, also known as Fréchet space. We examine the existence of an optimum subspace comprehensively and propose a method to compute the optimum subspace of both finite-dimensional and infinite-dimensional compressible topological vector spaces. To the author's best knowledge, we are the first group that proposes continuous compressed sensing that does not require any information about the local infinite-dimensional fluctuations of the signal.