Dissertations / Theses on the topic 'Time Division Multiplexing Access'

The wavelength-division-multiplexed passive optical network (WDM-PON) offers many advantages such as large bandwidth per user, easy management, high network security and low insertion loss enabling long-reach and/or high split-ratio. However, with the rapid development and growing interest for deployment of WDM-PON, the PON systems are becoming increasingly vulnerable to various failures. Therefore, network supervision becomes extremely important to guarantee an appropriate level of network reliability performance. The aim of PON supervision is to provide automated test and diagnostic capability without compromising the available bandwidth for services. An essential function is to detect any kind of deterioration in the network that can cause suspended services and to remotely localize these faults in order to avoid the high cost arising from troubleshooting. In this thesis, we evaluate several existing WDM PON supervision methods, based on which two simple and cost-effective new solutions are proposed to localize fiber failures in WDM PON systems. In the first solution, a conventional optical time domain reflectometry (OTDR) and a switch unit are employed, while in the second method, a novel architecture based on N×N arrayed waveguide grating (AWG) is proposed. Both methods are able to localize failures in feeder fiber and drop fibers without e.g. using expensive tunable OTDRs. A patent has been filed based on the second solution. The first proposed method is validated by simulations using VPI Transmission Maker. According to the results, this supervision method is able to give accurate measurement of many different types of failures that may happen in a fiber link. Furthermore, VPI is examined in terms of its future applicability in modeling complete PON supervision methods based on OTDR.

The general objective of this proposed research is to design and develop signal acquisition and tracking algorithms for multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems for fixed wireless access applications. The algorithms are specifically targeted for systems that work in time division multiple access and frequency division multiple access frame modes. In our research, we first develop a comprehensive system model for a MIMO-OFDM system under the influence of the radio frequency (RF) oscillator frequency offset, sampling frequency (SF) offset, RF oscillator phase noise, frequency selective channel impairments and finally the additive white Gaussian noise. We then develop the acquisition and tracking algorithms to estimate and track all these parameters. The acquisition and tracking algorithms are assisted by a preamble consisting of one or more training sequences and pilot symbol matrices. Along with the signal acquisition and tracking algorithms, we also consider design of the MIMO-OFDM preamble and pilot signals that enable the suggested algorithms to work efficiently. Signal acquisition as defined in our research consists of time and RF synchronization, SF offset estimation and correction, phase noise estimation and correction and finally channel estimation. Signal tracking consists of RF, SF, phase noise and channel tracking. Time synchronization, RF oscillator frequency offset, SF oscillator frequency offset, phase noise and channel estimation and tracking are all research topics by themselves. A large number of studies have addressed these issues, but usually individually and for single-input single-output (SISO) OFDM systems. In the proposed research we present a complete suite of signal acquisition and tracking algorithms for MIMO-OFDM systems along with Cramr-Rao bounds for the SISO-OFDM case. In addition, we also derive the Maximum Likelihood (ML) estimates of the parameters for the SISO-OFDM case. Our proposed research is unique from the existing literature in that it presents a complete receiver implementation for MIMO-OFDM systems and accounts for the cumulative effects of all possible acquisition and tracking errors on the bit error rate (BER) performance. The suggested algorithms and the pilot/training schemes may be applied to any MIMO OFDM system and are independent of the space-time coding techniques that are employed.

Desde comienzos del siglo XXI, los sistemas de radiodifusión terrestre han sido culpados de un uso ineficiente del espectro asignado. Para aumentar la eficiencia espectral, los organismos de estandarización de TV digital comenzaron a desarrollar la evolución técnica de los sistemas de TDT de primera generación. Entre otros, uno de los objetivos principales de los sistemas de TDT de próxima generación (DVB-T2 y ATSC 3.0) es proporcionar simultáneamente servicios de TV a dispositivos móviles y fijos. El principal inconveniente de esta entrega simultánea son los diferentes requisitos de cada condición de recepción. Para abordar estas limitaciones, se han considerado diferentes técnicas de multiplexación. Mientras que DVB-T2 acomete la entrega simultánea de los dos servicios mediante TDM, ATSC 3.0 adoptó la Multiplexación por División en Capas (LDM). LDM puede superar a TDM y a FDM al aprovechar la relación de Protección de Error Desigual (UEP), ya que ambos servicios, llamados capas, utilizan todos los recursos de frecuencia y tiempo con diferentes niveles de potencia. En el lado del receptor, se distinguen dos implementaciones, de acuerdo con la capa a decodificar. Los receptores móviles solo están destinados a obtener la capa superior, conocida como Core Layer (CL). Para no aumentar su complejidad en comparación con los receptores de capa única, la capa inferior, conocida como Enhanced Layer (EL), es tratada como un ruido adicional en la decodificación. Los receptores fijos aumentan su complejidad, ya que deben realizar un proceso de Cancelación de Interferencia (SIC) sobre la CL para obtener la EL. Para limitar la complejidad adicional de los receptores fijos, las capas de LDM en ATSC 3.0 están configuradas con diferentes capacidades de corrección, pero comparten el resto de bloques de la capa física, incluido el TIL, el PP, el tamaño de FFT, y el GI. Esta disertación investiga tecnologías avanzadas para optimizar el rendimiento de LDM. Primero se propone una optimización del proceso de demapeo para las dos capas de LDM. El algoritmo propuesto logra un aumento de capacidad, al tener en cuenta la forma de la EL en el proceso de demapeo de la CL. Sin embargo, el número de distancias Euclidianas a computar puede aumentar significativamente, conduciendo no solo a receptores fijos más complejos, sino también a receptores móviles más complejos. A continuación, se determina la configuración de piloto ATSC 3.0 más adecuada para LDM. Teniendo en cuenta que las dos capas comparten el mismo PP, surge una contrapartida entre la densidad de pilotos (CL) y la redundancia sobre los datos (EL). A partir de los resultados de rendimiento, se recomienda el uso de un PP no muy denso, ya que ya han sido diseñados para hacer frente a ecos largos y altas velocidades. La amplitud piloto óptima depende del estimador de canal en los receptores (ej., se recomienda la amplitud mínima para una implementación Wiener, mientras que la máxima para una implementación FFT). También se investiga la potencial transmisión conjunta de LDM con tres tecnologías avanzadas adoptadas en ATSC 3.0: las tecnologías de agregación MultiRF, los esquemas de MISO distribuido y los de MIMO colocalizado. Se estudian los potenciales casos de uso, los aspectos de implementación del transmisor y el receptor, y las ganancias de rendimiento de las configuraciones conjuntas para las dos capas de LDM. Las restricciones adicionales de combinar LDM con las tecnologías avanzadas se consideran admisibles, ya que las mayores demandas ya están contempladas en ATSC 3.0 (ej., una segunda cadena de recepción). Se obtienen ganancias significativas en condiciones de recepción peatonal gracias a la diversidad en frecuencia proporcionada por las tecnologías MultiRF. La conjunción de LDM con esquemas de MISO proporciona ganancias de rendimiento significativas en redes SFN para la capa fija con el esquema de Alamouti.
Since the beginning of the 21st century, terrestrial broadcasting systems have been blamed of an inefficient use of the allocated spectrum. To increase the spectral efficiency, digital television Standards Developing Organizations settled to develop the technical evolution of the first-generation DTT systems. Among others, a primary goal of next-generation DTT systems (DVB-T2 and ATSC 3.0) is to simultaneously provide TV services to mobile and fixed devices. The major drawback of this simultaneous delivery is the different requirement of each reception condition. To address these constraints different multiplexing techniques have been considered. While DVB-T2 fulfilled the simultaneous delivery of the two services by TDM, ATSC 3.0 adopted the LDM technology. LDM can outperform TDM and FDM by taking advantage of the UEP ratio, as both services, namely layers, utilize all the frequency and time resources with different power levels. At receiver side, two implementations are distinguished, according to the intended layer. Mobile receivers are only intended to obtain the upper layer, known as CL. In order not to increase their complexity compared to single layer receivers, the lower layer, known as EL is treated as an additional noise on the CL decoding. Fixed receivers, increase their complexity, as they should performed a SIC process on the CL for getting the EL. To limit the additional complexity of fixed receivers, the LDM layers in ATSC 3.0 are configured with different error correction capabilities, but share the rest of physical layer parameters, including the TIL, the PP, the FFT size, and the GI. This dissertation investigates advanced technologies to optimize the LDM performance. A demapping optimization for the two LDM layers is first proposed. A capacity increase is achieved by the proposed algorithm, which takes into account the underlying layer shape in the demapping process. Nevertheless, the number of Euclidean distances to be computed can be significantly increased, contributing to not only more complex fixed receivers, but also more complex mobile receivers. Next, the most suitable ATSC 3.0 pilot configuration for LDM is determined. Considering the two layers share the same PP a trade-off between pilot density (CL) and data overhead (EL) arises. From the performance results, it is recommended the use of a not very dense PP, as they have been already designed to cope with long echoes and high speeds. The optimum pilot amplitude depends on the channel estimator at receivers (e.g. the minimum amplitude is recommended for a Wiener implementation, while the maximum for a FFT implementation). The potential combination of LDM with three advanced technologies that have been adopted in ATSC 3.0 is also investigated: MultiRF technologies, distributed MISO schemes, and co-located MIMO schemes. The potential use cases, the transmitter and receiver implementations, and the performance gains of the joint configurations are studied for the two LDM layers. The additional constraints of combining LDM with the advanced technologies is considered admissible, as the greatest demands (e.g. a second receiving chain) are already contemplated in ATSC 3.0. Significant gains are found for the mobile layer at pedestrian reception conditions thanks to the frequency diversity provided by MultiRF technologies. The conjunction of LDM with distributed MISO schemes provides significant performance gains on SFNs for the fixed layer with Alamouti scheme. Last, considering the complexity in the mobile receivers and the CL performance, the recommended joint configuration is MISO in the CL and MIMO in the EL.
Des de començaments del segle XXI, els sistemes de radiodifusió terrestre han sigut culpats d'un ús ineficient de l'espectre assignat. Per a augmentar l'eficiència espectral, els organismes d'estandardització de TV digital van començar a desenvolupar l'evolució tècnica dels sistemes de TDT de primera generació. Entre altres, un dels objectius principals dels sistemes de TDT de pròxima generació (DVB-T2 i el ATSC 3.0) és proporcionar simultàniament serveis de TV a dispositius mòbils i fixos. El principal inconvenient d'aquest lliurament simultani són els diferents requisits de cada condició de recepció. Per a abordar aquestes limitacions, s'han considerat diferents tècniques de multiplexació. Mentre que DVB-T2 escomet el lliurament simultani dels dos serveis mitjançant TDM, ATSC 3.0 va adoptar la Multiplexació per Divisió en Capes (LDM). LDM pot superar a TDM i a FDM en aprofitar la relació de Protecció d'Error Desigual (UEP), ja que tots dos serveis, cridats capes, utilitzen tots els recursos de freqüència i temps amb diferents nivells de potència. En el costat del receptor, es distingeixen dues implementacions, d'acord amb la capa a decodificar. Els receptors mòbils solament estan destinats a obtenir la capa superior, coneguda com Core Layer (CL). Per a no augmentar la seua complexitat en comparació amb els receptors de capa única, la capa inferior, coneguda com Enhanced Layer (EL), és tractada com un soroll addicional en la decodificació. Els receptors fixos augmenten la seua complexitat, ja que han de realitzar un procés de Cancel·lació d'Interferència (SIC) sobre la CL per a obtenir l'EL. Per a limitar la complexitat addicional dels receptors fixos, les capes de LDM en ATSC 3.0 estan configurades amb diferents capacitats de correcció, però comparteixen la resta de blocs de la capa física, inclòs el TIL, el PP, la grandària de FFT i el GI. Aquesta dissertació investiga tecnologies avançades per a optimitzar el rendiment de LDM. Primer es proposa una optimització del procés de demapeo per a les dues capes de LDM. L'algoritme proposat aconsegueix un augment de capacitat, en tenir en compte la forma de l'EL en el procés de demapeo de la CL. No obstant açò, el nombre de distàncies Euclidianes a computar pot augmentar significativament, conduint NO sols a receptors fixos més complexos, sinó també a receptors mòbils més complexos. A continuació, es determina la configuració de pilot ATSC 3.0 més adequada per a LDM. Tenint en compte que les dues capes comparteixen el mateix PP, es produeix una contrapartida entre la densitat de pilots (CL) i la redundància sobre les dades (EL). A partir dels resultats de rendiment, es recomana l'ús d'un PP no gaire dens, ja que ja han sigut dissenyats per a fer front a ecos llargs i altes velocitats. L'amplitud pilot òptima depèn de l'estimador de canal en els receptors (ex., es recomana l'amplitud mínima per a una implementació Wiener, mentre que la màxima per a una implementació FFT). També s'investiga la potencial transmissió conjunta de LDM amb tres tecnologies avançades adoptades en ATSC 3.0: les tecnologies d'agregació de MultiRF, els esquemes de MISO distribuït i els de MIMO colocalitzat. S'estudien els potencials casos d'ús, els principals aspectes d'implementació del transmissor i el receptor, i els guanys de rendiment de les configuracions conjuntes per a les dues capes de LDM. Les restriccions addicionals de combinar LDM amb les tecnologies avançades es consideren admissibles, ja que les majors demandes ja estan contemplades en ATSC 3.0 (ex., una segona cadena de recepció). S'obtenen guanys significatius per a la capa mòbil en condicions de recepció per als vianants gràcies a la diversitat en freqüència proporcionada per les tecnologies MultiRF. La conjunció de LDM amb esquemes MISO distribuïts proporciona guanys de rendiment significatius en xarxes SFN per a la capa fixa amb l'esquema d'Alamouti.
Garro Crevillén, E. (2018). Advanced Layered Divsion Multiplexing Technologies for Next-Gen Broadcast [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/105559
TESIS

Le probleme pose par ces systemes de telecommunications par satellite est d'acheminer un trafic donne avec un minimum d'equipements. Dans cette these, les problemes d'optimisation correspondants sont repertories et modelises

Orthogonal Frequency Division Multiplexing (OFDM) is a modulation scheme with numerous advantages that has for years been employed as the leading physical interface in many wired and wireless communication systems. Recently, with advancements made in digital signal processing, there has been a surge of interest in applying OFDM techniques for optical communications. This thesis presents extensive research on optical OFDM and how it is being applied in access networks. With the aid of theoretical analysis, simulations and experiments, it is shown that the system performance of direct-detection optical OFDM (DD-OOFDM) in the presence of MZM non-linear distortion can be improved by proper biasing and selection of appropriate drive to the MZM. Investigations are conducted to illustrate how a variation in the number of subcarriers and the modulation format influences the sensitivity of the DD-OOFDM system to the MZM non-linear distortion. The possibility of improving the spectral efficiency by reduction of the width of the guard band is also investigated. This thesis also looks into the radio-over-fibre (RoF) transmission of Multiband OFDM UWB as a transparent and low-cost solution for distributing multi-Gbit/s data to end-users in FTTH networks. Due to relaxed regulatory requirements and the wide bandwidth available, UWB operation in the 60-GHz band is also considered for this FTTH application scenario. Four techniques for enabling MB-OFDM UWB RoF operation in the 60-GHz band are experimentally demonstrated. The impacts of various parameters on the performance of the techniques as well as the limitations imposed by fibre distribution are illustrated. Finally, a digital pre-distorter is proposed for compensating for the MZM non-linearity. Experimental demonstration of this digital pre-distortion in an UWB over fibre transmission system shows an increased tolerance to the amplitude of the driving OFDM signal as well as an increase in the optimum modulation index of the OFDM signal.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Um sistema de interrogação de sensores a rede de Bragg utilizando multiplexação no tempo e multiplexação no comprimento de onda é proposto e demonstrado. O sistema apresenta uma solução para a medição de grandezas associadas ao espectro de reflexão de redes de Bragg, possibilitando o aumento do número de sensores a rede de Bragg monitorados através de grandes distâncias em uma mesma fibra óptica, sem um aumento significativo dos custos. O aspecto inovador deste sistema reside na particular associação das seguintes características: o uso de fonte pulsada de banda larga, a disposição, em série, de um grande número de sensores a rede de Bragg de baixa refletividade, a técnica de reutilização dos mesmos comprimentos de onda nominais em grupos contendo vários sensores com comprimentos de onda nominais distintos e um processo de filtragem espectral e análise de sinais pulsados utilizando o filtro DWDM comercial. Aspectos teóricos e experimentais considerando os princípios de trabalho desta técnica são discutidos. Comparações entre resultados simulados e experimentais do sistema implantado mostram boa concordância. Resultados experimentais apontam uma faixa dinâmica de 1,7 nm, podendo encontrar aplicações em medição de temperatura com uma faixa de 150°C. Incertezas com valores médios abaixo de 20 picometros foram obtidas. Simulações experimentais apontam a possibilidade de utilização de um número de aproximadamente 70 sensores com 0,4% de refletividade, por comprimento de onda. Considerando a largura de banda do dispositivo DWDM (1539- 1565 nm) utilizado neste sistema, e um espaçamento de 7 nm por comprimento de onda nominal de sensor, extrapolações mostram que este número pode chegar a 210 sensores em três diferentes comprimentos de onda nominais de sensor. Considerando as bandas C e L este número pode chegar a aproximadamente 1000 sensores em 14 diferentes comprimentos de onda nominais de sensor.
An interrogation system of fiber Bragg grating sensors using time division multiplexing and wavelength division multiplexing is proposed and demonstrated. The system presents a solution to measure the magnitudes associated to the reflection spectrum of the fiber Bragg gratings, making possible to increase the number of the Bragg gratings sensors monitored through large distances at the same fiber optic, without a great increase in the costs. The innovative aspect of this system is the particular association of the following characteristics: the use of a pulsed broad band source, the disposition, in series, of a large number of low reflectivity Bragg gratings sensors, the reusing technique of the same nominal wavelengths in groups containing several numbers of sensors with distinct nominal wavelengths, and a spectral analyzing and filtering process of pulsed signals using a commercial DWDM filter. Theoretical and experimental aspects regarding the working principles of this technique are discussed. Comparisons between experimental and simulated results show a good agreement. Experimental results indicate that a dynamic range of 1,7 nm was obtained. It can be used in temperature measurement systems, with a 150°C range. Uncertainties equivalent to approximately 20 picometers was obtained. Experimental simulations indicate that it would be possible to use a number of approximately 70 sensors with 0,4% reflectivity at each nominal sensor wavelength. Considering the DWDM filter bandwidth (1539-1565 nm) used in this system, and a spectral separation of 7 nm by nominal sensor wavelength, extrapolations indicate that a number of 210 sensors can be obtained, in three different nominal sensor wavelength. Using the C-band and the L-band, a number of 1000 sensors can be obtained, in fourteen different nominal sensor wavelength.

Reconfigurable computing architectures are well suited for the dynamic data flow processing requirements of software-defined radio. The software radio concept has quickly evolved to include spectrum sensing, awareness, and cognitive algorithms for machine learning resulting in the cognitive radio model. This work explores the application of reconfigurable hardware to the physical layer of cognitive radios using non-contiguous multi-carrier radio techniques. The practical tasks of spectrum sensing, frame detection, synchronization, channel estimation, and mutual interference mitigation are challenges in the communications and the computing fields that are addressed to optimally utilize the capacity of opportunistically allocated spectrum bands. FPGA implementations of parameterizable OFDM and filter bank multi-carrier (FBMC) radio prototypes with spectrum awareness and non-contiguous sub-carrier allocation were completed and tested over-the-air. Sub-carrier sparseness assumptions were validated under practical implementation and performance considerations. A novel algorithm for frame detection and synchronization with mutual interference rejection applicable to the FBMC case was proposed and tested.
Ph. D.

Optical orthogonal frequency division multiplexing (O-OFDM) is a potential candidate for 100 Gigabit Ethernet (GbE) and beyond due to its high spectral efficiency and strong resilience towards chromatic and polarization mode dispersion. In this thesis, investigations have been performed into the feasibility of O-OFDM in high speed optical fibre communications. First, an overview of OFDM fundamentals and optical fibre communications is given. Numerical simulations which were performed to characterise and optimise real-time OFDM transceivers are then presented. The effects of a variety of design parameters on the performance of the system are studied. Amongst the key parameters included in the study are the quantisation and clipping noise in data converters, and the quantisation errors in the fast Fourier transform and its inverse (FFT/IFFT). Optimum parameters that give the best trade-off between performance and cost in terms of bit precision are determined. It was found that these parameters depend on the modulation format as well as the size of the FFT used in the system. The thesis then presents the design of a multi-gigabit real-time O-OFDM transmitter based on field programmable gate array (FPGA) implementation. The 21.4 GS/s real-time transmitter was built and used to transmit 8.36 Gb/s directly-detected single sideband QPSK-OFDM signals over 1600 km of uncompensated standard single mode fibre. This was one of the first demonstrations of real-time OFDM transmitters operating at such high line rates. It remains the longest transmission distance achieved with a real-time OFDM transmitter. The next step in confirming the feasibility of O-OFDM involves the design and assessment of application-specific integrated circuit (ASIC) implementations. In the final part of the thesis, digital signal processing (DSP) circuits for 21.8 Gb/s and 43.7 Gb/s QPSK- and 16-QAM-encoded O-OFDM transceivers with 50 data subcarriers were designed at the register-transfer-level, and synthesis and simulations were carried out to assess their performance, power consumption, and chip area. The aim of the study is to determine the suitability of OFDM technology for low-cost optical interconnects. Power calculations based on synthesis for a 65nm standard-cell library show that the DSP components of the transceiver consume 18.2 mW/Gb/s and 12.8 mW/Gb/s in the case of QPSK and 16-QAM respectively. The effects of modulation format and FFT size on the area and power consumption of the transceivers are also quantified. Finally, characterisation results showing the trade-offs between energy consumption and chip footprint are presented and analysed to help designers optimise the transceivers according the requirements and specifications.

Growing demands for capacity have stimulated the development of high-speed optical shared media networks. At present, most research on optical networking has concentrated on wavelength-division multiplexing (WDM). Optical time-division multiplexing (OTDM), which offers advantages over WDM networks, is considered as an alternative to WDM for future networks proving a single stream data rates of 100 Gb/s using a single wavelength. In such systems all optical routers, which overcome the bottleneck of optoelectronic conversion, play an important role. This thesis concentrates on the modelling and simulation of a novel optical router, which uses two terahertz optical asymmetric demultiplexers (TOAD) as the routing element for OTDM systems. In this work, the author has developed a mathematical model of an all optical router based on TOADs. The model architecture is based on a system, which has as its input an OTDM packet containing header and payload information. The model simulates extraction of header information, using one TOAD, from the data stream, which is subsequently used to make a routing decision. The payload information is routed through a second TOAD according to the information contained in the header. A comprehensive theoretical analysis supported by computer simulations has been carried out to study characteristics of crosstalk, noises, signal to noise ratio (SNR), Bit error rate (BER), and power penalty of the router. The results obtained, whenever possible, have been compared with the experimented data. The performance analysis of the all optical router is shown by the simulation results. The proposed router is capable of routing packet containing data in excess of 250 Gb/s all in optical domain. New models of all optical router with multi-input and outputs have been developed i.e. 1x4 router, 2x2 router, which are based on 1x2 TOAD routers. Results show that threshold switching energy is present at 0.2 pJ. Higher values result in a decrease in crosstalk and lower values result in negligible switching. Also shown is crosstalk induced penalty depends on the crosstalk level of individual 1x2 switches as well as on the size and architecture of the switching fabric. Finally, it has been shown that the proposed all-optical router has potentially useful characteristics as a component for high-speed optical TDM networks due to its ultrafast switching capability compared with existing devices. At this stage a simple 8 by 8 Banyan network is presented, however further work will enhance the model to a network with more inputs and outputs.

This thesis describes the investigation of time-division multiplexing for use in mUlticomponent laser Doppler anemometry (LDA). To make two- or three- dimensional velocity measurements of a flow, two or three separate velocity measurements in different, non-collinear or non-coplanar directions respectively must be taken from which the flow vector can be calculated. It is necessary to separate each velocity channel. Conventionally, the separation is carried out by optical techniques, such as separating the signal from each channel by wavelength or polarisation, with one detector per channel. In time division multiplexing, each channel is switched On and off in turn. A single detector records a stream of interleaved pulses, and each channel is extracted by taking every other or every third pulse. The envelope of the amplitudes of the pulses varies at the Doppler frequency. A novel system has been demonstrated which uses a single laser diode source and a single detector. The distribution of the pulses to each channel and the delay between each channel is carried out using a optical fibre network with fibre delay lines, with a consequent reduction in 'electronic complexity. The characteristics of the optoelectronic components used in the system are tested, and two signal processing schemes are investigated. A two-dimensional Doppler difference fibre-linked probe was constructed to demonstrate the technique. Hybrid instruments using two Doppler difference channels and a reference beam channel to measure orthogonal velocity components offer the possibility of avoiding the errors introduced by non-orthogonal systems. A pulsed-diode reference beam anemometer based on optical fibres and suitable for inclusion in a time-division multiplexed hybrid instrument was tested.

Dense wavelength division multiplexing (DWDM) is becoming the technology of choice for meeting the increasing bandwidth demands in optical networks. DWDM has been used to increase the capacity of long-haul optical transport systems. Efforts are being made to move DWDM into the broadband access network serving residential and business subscribers. First, a new centralized DWDM PON scheme is demonstrated for bi-directional upstream and downstream transmissions. The proposed DWDM PON scheme is implemented using optical carrier suppression and separation (OCSS) technology to generate a wavelength pair from a single laser source at the central office. This method enables the co-location of both upstream and downstream DWDM transmitters in the central office. In addition, the complexity, cost, and maintenance of the optical network unit are reduced by enabling wavelength independent operation. Second, a new multistage architecture is proposed for the delivery of information to groups of subscribers located at different distances from the central office. A 25 GHz DWDM comb is generated using OCSS technology, and error-free transmission of four 10 Gbps channels is demonstrated. Finally, a new wide area access network with bi-directional DWDM amplification using semiconductor optical amplifiers (SOAs) is demonstrated. The detrimental effect of SOA crosstalk resulting from cross gain modulation can be suppressed using a constant intensity modulation format such as differential phase shift keying (DPSK). The feasibiity of bi-directional DPSK transmission of 16 interleaved DWDM channels using an in-line SOA has been studied experimentally. In addition, the reduction of bi-directional SOA reflections has been realized by optimizing the SOA bias current and facet reflectivities.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV
High speed real-time data transportation is most important for telemetry systems, especially for large-scale distributed systems. This paper introduces a STDM (Sync Time Division Multiplexing) network structure for data transportation between devices in telemetry systems. The data in these systems is transported through virtual channels between devices. In addition, a proper frame format is designed based on PCM format to meet the needs of synchronization and real-time transportation in large-scale distributed telemetry systems.

Bandwidth limitation of conventional electrical demultiplexer restricts the data capacity of long-haul optical time division multiplexing (OTDM) systems. It is desirable to demultiplex the OTDM signal in optical domain, thereby lifting the bandwidth limitation of the electrical demultiplexer. The general principle of all-optical time division demultiplexing is to effect asymmetric changes to the optical properties of the target and non-target channels. The different optical properties of the target and non-target channels facilitate the separation of the target channel(s) from the aggregate OTDM signal. The change of optical properties of the OTDM signal can be achieved by exploiting various types of nonlinear optics effects, such as cross-phase modulation and four-wave mixing. Although the technical viability of all-optical demultiplexing has been successfully demonstrated in laboratories, there is still a lack of understanding regarding the noise and crosstalk characteristics of all-optical demultiplexers. This PhD study attempts to investigate noise and crosstalk performance of two types of all-optical time division demultiplexers, namely nonlinear optical loop mirror (NOLM) and terahertz optical asymmetric demultiplexer (TOAD). In order to evaluate the noise and crosstalk performance of NOLM and TOAD demultiplexers, mathematical models are developed to simulate the transmission window for demultiplexing the target channel. The shape of the transmission window is dependent on the device parameters of the demultiplexers. Varying input parameters of the mathematical models can simulate the effects of changing device parameters on the transmission window. Nevertheless, it is onerous to calculate transmission windows for infinite combinations of device parameters. To simplify the noise and crosstalk analysis, device parameters of NOLM and TOAD demultiplexers are optimised for maximising the peak of the transmission windows. Noise and crosstalk models are also developed forNOLM and TOAD demultiplexers. The optimised device parameters of NOLM and TOAD demultiplexers are fed into the noise and crosstalk models for analysis. Simulation results show that a tradeoff between noise and crosstalk exists for the two types of demultiplexers. Device parameters can be optimised to minimise either noise or crosstalk, but not both. Finally, the noise and crosstalk models are connected to a receiver model, where the bit-error-rate (BER) performance of OTDM systems is evaluated. The BER performances of the NOLM and TOAD demultiplexing are compared using the optimised device parameters. It is found that TOAD has a slightly better BER performance compared with NOLM for lower baseband bit rate (i.e. a larger number of OTDM channels for an aggregate bit rate).

With high date rates using Enhanced Uplink (EUL), a conventional signal to interference ratio (SIR) based power control algorithm may lead to a power rush due to self interference or incompatible SIR target [2]. Time division (TD) scheduling in Wideband Code Division Multiplex Access (WCDMA) is considered to be a key feature in achieving high user data rates. Unfortunately, power oscillation/peak is observed in time division multiplexing (TDM) at the transition between active and inactive transmission time intervals [1]. Therefore there is a need to revisit power control algorithms for different time division scheduling scenarios. The objective of power control in the context of this study is to minimize the required rise over thermal noise (RoT) for a given data rate, subject to the constraint that the physical layer control channel quality is sufficient (assuming that the dedicated physical control channel (DPCCH) SIR should not go below 3dB with a probability of at most 5%). Another goal is to minimize the local oscillation in power (power peaks) that may occur, for example due to transitions between active and inactive transmission time intervals. The considered hybrid power control schemes are: (1) non-parametric Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) during active transmission time intervals + Received Signal Code Power (RSCP) ILPC during inactive transmission time intervals and (2) RSCP ILPC during active transmission time intervals + GSIR ILPC during inactive transmission time intervals. Both schemes are compared with pure GSIR and pure RSCP ILPC. Link level simulations with multiple users connected to a single cell show that: The power peak problem is obviously observed in GSIR + GSIR transmit power control (TPC), but in general it performs well in all time division scenarios studied. GSIR outperforms other TPC methods in terms of RoT, especially in the TU channel model. This is because it is good in combating instantaneously changed fading and accurately estimates SIR. Among all TPC methods presented, GSIR + GSIR TPC is best in maintaining the quality of the DPCCH channel. No power rush is observed when using GSIR + GSIR TPC. RSCP + RSCP eliminates the power peak problem and outperforms other TPC methods presented under the 3GPP Pedestrial A (pedA) 3km/h channel in terms of RoT. However, in general it is worse in maintaining the control channel’s quality than GSIR + GSIR TPC. GSIR + RSCP ILPC eliminates the power peak problem and out-performs GSIR power control in the scenario of 2 and 4 TDM high data rate (HDR) UE and 2 TDM HDR UE coexistence with 4 Code DivisionMultiplex (CDM) LDR UE, in the pedA 3km/h channel, in terms of RoT. However, the control channel quality is not maintained as well during inactive transmission time intervals. It is not recommended to use RSCP + GSIR TPC since it performs worst among these TPC methods for most of the cases in terms of RoT, even though it is the second best in maintaining the control channel quality. The power peak is visible when using RSCP + GSIR TPC. To maintain the control channel’s quality, a minimum SIR condition is always used on top of all proposed TPC methods. However, when there are several connected TDM HDR UEs in the cell, results indicates that it is challenging to meet the quality requirement on the control channels. So it may become necessary to limit the number of connected terminals in a cell in a time division scenario.
Med den höga datahastighet som Enhanced Uplink (EUL) medger kan en konventionell algoritm för effektkontroll baserad på signal to interference ratio (SIR) leda till effekthöjning beroende på självinterferens eller felaktigt SIR mål. Time division (TD) schedulering vid Wideband Code Division Multiple Access (WCDMA) anses vara en nyckelfunktion för att uppnå höga datahastigheter. I övergången mellan aktiv och inaktiv transmissionstidsintervall vid time division multiplexing (TDM) har effektoscillering/effektpeak observerats. Detta gör det nödvändigt att se över algoritmerna för effektkontroll vid olika scenarion av TD schedulering. Målet med effektkontrollen i denna studie är att minimera rise over thermal noise (RoT) för en given datahastighet givet begränsningen att kvaliteten på physical layer control channel är tillräcklig (beaktande att dedicated physical control channel (DPCCH) SIR inte understiger 3dB med en sannolikhet på som mest 5%). Ett annat mål är att minimera den lokala effektoscillationen (effektpeakar) som kan inträffa till exempel vid övergång mellan aktiv och inaktiv transmissionstidsintervall. De undersökta hybrida metoderna för effektkontroll är: (1) icke-parametrisk Generalized rake receiver SIR (GSIR) Inner Loop Power Control (ILPC) vid aktiv transmissionstidsintervall + Received Signal Code Power (RSCP) ILPC vid inaktiv transmissionstidsintervall och (2) RSCP ILPC under aktiv transmissionstidsintervall + GSIR ILPC under inaktiv transmissiontidsintervall. Båda metoderna jämförs med ren GSIR och ren RSCP ILPC. Länk nivå simulering med flera användare anslutna till en enda cell visar att: Problemet med effektpeakar observeras tydligt vid GSIR + GSIR transmit power control (TPC) men generellt sett presterar den bra i alla studerade TD scenarion. GSIR presterar bättre än andra TPC metoder beträffande RoT, speciellt i TU kanal modellen. Detta beror på att metoden är bra på att motverka momentant förändrad fading och med god precision estimerar SIR. Bland alla presenterade TPC metoder är GSIR + GSIR TPC den bästa på att behålla en god kvalitet på DPCCH kanalen. Ingen effekthöjning har observerats vid GSIR + GSIR TPC. RSCP + RSCP eliminerar problemet med effektpeakar och presterar bättre än andra TPC metoder presenterade under 3GPPs Pedestrial A (pedA) 3km/h kanal beträffande RoT. Dock är metoden generellt sett sämre på att behålla kontrollkanalens kvalitet än GSIR + GSIR TPC. GSIR + GSIR ILPC eliminerar problemet med effektpeakar och presterar bättre än GSIR power control i ett scenario med 2 och 4 TDM high data rate (HDR) UE och 2 TDM HDR UE tillsammans med 4 Code Division Multiplex (CDM) LDR UE i pedA 3km/h kanalen beträffande RoT. Dock kan inte kvaliteten på kontrollkanalen behållas i detta fall heller under inaktiv transmissionstidsintervall. Det är inte rekommenderat att använda RSCP + GSIR TPC eftersom den presterar sämst av alla TPC metoder beträffande RoT i de allra flesta fall. Till dess fördel är att den är den näst bästa på att behålla kvaliteten på kontrollkanalen. Effektpeakar har observerats när RSCP + GSIR TPC använts. För att behålla kontrollkanalens kvalitet används alltid en minimum SIR nivå ovanpå alla föreslagna TPC metoder. När det finns flera anslutna TDM HDR UEs i cellen indikerar resultaten att det är en utmaning att behålla kvalitetskraven på kontrollkanalen. På grund av detta kan det bli nödvändigt att begränsa antalet anslutna terminaler i en cell i ett TD scenario.

This project focuses on wavelength division multiplexing passive optical network (WDM-PON) supervision using optical time domain reflectometer (OTDR) for detection and localization of any fault occurred in optical distribution network. The objective is to investigate the impact of OTDR monitoring signal on the data transmission in the WDM-PON based on wavelength re-use system, where the same wavelength is assigned for both upstream and downstream to each end user. Experimental validation has been carried out to measure three different schemes, i.e. back-to-back, WDM-PON with and without OTDR connection by using 1xN and NxN arrayed waveguide gratings. Furthermore, a comprehensive comparison has been made to trace out the effect of the monitoring signal which is transmitted together with the data through the implemented setup. Finally, the result has confirmed that the OTDR supervision signal does not affect the data transmission. The experiment has been carried out at Ericsson AB, Kista.

Wavelength division multiplexing passive optical network (WDM-PON) can meet growing bandwidth demand in access network by providing high bandwidth to the end users. Failure in the access network is becoming critical as a large volume of traffic might be affected. Therefore, an effective supervision mechanism to detect and localize the fault is required to shorten the service interruption time. Meanwhile, open access provides a certain freedom for end users to choose the service and hence boosts competition among service/network providers. On the other hand, to offer open access in WDM-PON could result in a substantial change on architectural design, e.g., multiple feeder fibers (FFs) instead of a single one may be required to connect different service/network providers. Consequently, the traditional supervision mechanisms don’t work properly in open WDM-PON. To fill in this gap, several fault supervision mechanisms to support open access in WDMPON are proposed in this thesis. They can be applied to both disjoint and co-located FF layout where the choice of providers is done through wavelength selection. The feasibility of such solutions has been validated by evaluating transmission performance. We have carried out simulations in VPItransmissionMaker for different deployment scenarios. The results have confirmed that no significant degradation of the transmission performance is introduced by the proposed monitoring schemes compared to the benchmark, where no any fault supervision method is implemented.

We propose a linear mean square error channel estimator that exploits the joint space-time-frequency (STF) correlations of the wireless fading channel for applications in multiple-antenna orthogonal frequency division multiplexing systems. Our work generalizes existing channel estimators to the full dimensions including transmit spatial, receive spatial, time, and frequency. This allows versatile applications of our STF channel estimator to any fading environment, ranging from spatially-uncorrelated slow-varying frequency-flat channels to spatially-correlated fast-varying frequency-selective channels.
The proposed STF channel estimator reduces to a time-frequency (TF) channel estimator when no spatial correlations exist. In another perspective, the lower-dimension TF channel estimator can be viewed as an STF channel estimator with spatial correlation mismatch for space-time-frequency selective channels.
Computer simulations were performed to study the mean-square-error (MSE) behavior with different pilot parameters. We then evaluate the suitability of our STF channel estimator on a space-frequency block coded OFDM system. Bit error rate (BER) performance degradation, with respect to perfect coherent detection, is limited to less than 2 dB at a BER of 10-5 in the modified 3GPP fast-fading suburban macro environment. Modifications to the 3GPP channel involves reducing the base station angle spread to imitate a high transmit spatial correlation scenario to emphasize the benefit of exploiting spatial correlation in our STF channel estimator.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.
Dr. Alfred Andrew, Committee Member ; Dr. Ye (Geofferey) Li, Committee Member ; Dr. Nikil S. Jayant, Committee Member ; Dr. Gordon L. Stuber, Committee Chair ; Dr. Douglas B. Williams, Committee Member Vita. Includes bibliographical references.

La thèse propose une technique de multiplexage à complexité extrêmement réduite dans le cadre de communications filaires. L’étude bibliographique porte sur les systèmes d’accès multiple, l’environnement électromagnétique automobile, et la propagation dans un réseau de câbles. Un modèle de bruit est proposé pour modéliser les interférences électromagnétiques. Le modèle de propagation multi-trajet dans un réseau de câble est validé à l’aide de mesures. Les réflexions multiples sont donc parfaitement déterministes et maîtrisables. Cette conclusion nous mène à l’idée de les exploiter à des fins de multiplexage. La solution originale baptisée ScDMA est basée sur des mesures de réflectométrie : les émetteurs codent l’information à envoyer en faisant simplement varier leurs impédances de terminaison (par exemple une information binaire 0/1 peut être codée par une commutation impédance adaptée / circuit ouvert). Le récepteur envoie des signaux judicieusement choisis, mesure les signaux réfléchis et décode l’information à l’aide d’algorithmes de classification. Les performances de ce nouveau type de communication sont étudiées : capacités théoriques au sens de la théorie de l’information, limitations physiques de débit, limitations théoriques de taux d’erreur et nombre maximal d’émetteurs. Les compromis lors de la conception du système complet sont présentés. Le dernier chapitre décrit le prototype réalisé pour prouver la véracité du concept. Le nouveau système d’accès multiple proposé (ScDMA) est original par plusieurs de ses aspects. Les perspectives restent nombreuses
The thesis proposes an extremely low-complexity multiplexing system over cable networks. The bibliographic goes through classical multiple access systems, the automotive electromagnetic environment, and the propagation into cable networks. A noise model is proposed to model electromagnetic interferences. The multi-path propagation model is validated with measurements. The multiple reflections are therefore perfectly deterministic and controllable. The latter conclusion leads us to the idea of exploiting them in order to achieve multiplexing. The innovative solution baptized ScDMA is based on reflectometry measurements: the transmitters encode data information by simply varying their termination impedances (for instance binary information 0/1 might be encoded with a switch between matched impedance and open circuit). The receiver sends some signals carefully selected, measure the reflected signals and decode the information by using classification algorithms. The performance of this new communication method is investigated: theoretical capacity from the information theory perspective, data rate physical limitations, error rate theoretical limits, and maximum number of transmitters. System-level trade-off when desiging the whole system are presented. The last chapter describes the prototype realized as a proof of concept. The novel multiple access system (ScDMA) and its features are innovative. Numerous perspectives still remain

The growth of broadband Internet access has paved the way for the development of many new technologies. As the cost of implementing broadband access soars, the best alternative will be to use fixed wireless for these services. This thesis addresses the possibility of 3rd Generation (3G) mobile cellular wireless systems as the basis for fixed broadband wireless service. Two of the 3G technologies aimed at providing fixed broadband wireless access are Time Division Synchronous Code Division Multiple Access (TD-SCDMA) and Orthogonal Frequency Division Multiplexing (OFDM).

This thesis aims to provide a preliminary study on using TD-SCDMA and OFDM for broadband wireless systems. Currently, there is not enough theory and information to establish the feasibility of using either of these technologies for broadband wireless access. First, the basic features and background on synchronous CDMA and OFDM are presented for the reader to better understand these technologies. Then, an example TD-SCDMA system is described, and some analytical and experimental results are presented. Finally, TD-SCDMAâ s technologies, along with this systemâ s attributes, are compared analytically to that of Vector OFDM (VOFDM).
Master of Science

After establishing itself in the radio domain, Spread spectrum code-division multiplexing/multiple-access (CDMA) has seen a recent upsurge in optical domain as well. Due to its fairness, flexibility, service differentiation and increased inherent security, CDMA is proved to be more suitable for the bursty nature of local area networks than synchronous multiplexing techniques like Frequency/Wavelength Division Multiplexing (F/WDM) and Time Division Multiplexing (TDM). In optical domain, CDMA techniques are commonly known as Optical-CDMA (O-CDMA). All optical CDMA systems are plagued with the problem of multiple-access interference (MAI). Spectral amplitude coding (SAC) is one of the techniques used in the literature to deal with the problem of MAI. The choice of spreading code in any CDMA system is another way to ensure the successful recovery of data at the receiving end by minimizing the effect of MAI and it also dictates the hardware design of the encoder and decoder. This thesis focuses on the efficient design of encoding and decoding hardware. Perfect difference codes (PDC) are chosen as spreading sequences due to their good correlation properties. In most of the literature, evaluation of error probability is based on the assumptions of ideal conditions. Such assumptions ignore major physical impairments such as power splitting losses at the multiplexers of transmitters and receivers, and gain losses at the receivers, which may in practice be an overestimate or underestimate of the actual probability of error. This thesis aims to investigate thoroughly with the consideration of practical impairments the applications of PDCs and other spreading sequences in optical communications systems based on spectral-amplitude coding and utilizing codedivision as multiplexing/multiple-access technique. This work begins with a xix general review of optical CDMA systems. An open-ended practical approach has been used to evaluate the actual error probabilities of OCDM/A systems under study. It has been concluded from results that mismatches in the gains of photodetectors, namely avalanche photodiode (APDs), used at the receiver side and uniformity loss in the optical splitters results in the inaccurate calculation of threshold level used to detect the data and can seriously degrade the system bit error rate (BER) performance. This variation in the threshold level can be compensated by employing techniques which maintain a constant interference level so that the decoding architecture does not have to estimate MAI every time to make a data bit decision or by the use of balanced sequences. In this thesis, as a solution to the above problem, a novel encoding and decoding architecture is presented for perfect difference codes based on common zero code technique which maintains a constant interference level at all instants in CDM system and thus relieves the need of estimating interference. The proposed architecture only uses single multiplexer at the transmitters for all users in the system and a simple correlation based receiver for each user. The proposed configuration not only preserves the ability of MAI in Spectral-Amplitude Coding SAC-OCDM system, but also results in a low cost system with reduced complexity. The results show that by using PDCs in such system, the influence of MAI caused by other users can be reduced, and the number of active users can be increased significantly. Also a family of novel spreading sequences are constructed called Manchestercoded Modified Legendre codes (MCMLCs) suitable for SAC based OCDM systems. MCMLCs are designed to be used for both single-rate and Multirate systems. First the construction of MCMLCs is presented and then the bit error rate performance is analyzed. Finally the proposed encoding/decoding architecture utilizing perfect difference codes is applied in wireless infrared environment and the performance is found to be superior to other codes.

När olika datatyper överförs mellan två platser har, historiskt sett, detta skett på skildinfrastruktur; analoga signaler för sig, och digitala data för sig. Inom flygindustrin hanteras båda dessa datatyper än idag, då övergång från analoga röstsamtal till digitala röstsamtal tar tid. För att förenkla infrastrukturen är det önskvärt att skicka all data på samma medium. Time Division Multiplexing (TDM) möjliggör detta och har studerats med fokus på robusthet och prestanda. Studien har fokuserat på hur TDM-enheter ska konfigureras med avseende på Ethernet-frame-storlek för att till fullo utnyttja länkkapaciteten. Teoretiska resonemang har validerats av experimentella data som utförts på TDM-enheter sammankopplade med en fiberlänk. Antalet förlorade frames för systemet har mätts med varierande datatillförselshastighet. Detta upprepades för ett flertal Ethernet-frame-storlekar. Mindre frame-storlekar gav en högre möjlig överföringshastighet innan data förloras, och uppvisade koherens mellan teori och experiment. Stora frame-storlekar fyllde i snitt TDM-tidsluckorna sämre, och gjorde att databuffert på enheten fylldes snabbare än för mindre framstorlekar. Detta ledde till dataförluster i systemet. Andra faktorer, som overhead och payload, gjorde att framestorleken borde väljas efter applikation. Mindre datamängder som skickas ofta kan med fördel använda mindre frame-storlekar, medan stora datamängder som behöveröverföras snabbt effektivare överförs med större frame-storlekar.
When transferring different data types between two sites, they have historically been transferred on separate infrastructures; analog signals separately, and digital data separately. Within the aviation industry, both these data types are still handled today, as transition from analog voice data to digital voice data takes time. To simplify the infrastructure, it is desirable to send all data on the same medium. Time Division Multiplexing (TDM) makes this possible and has been studied with focus on robustness and performance. The study has focused on how TDM devices should be configured with respect to Ethernet frame size to fully utilize link capacity. Theoretical reasoning has been validated by experimental data performed on TDM devices coupled with a fiber link. The number of lost frames for the system has been measured while varying data rates. This was repeated for several Ethernet frame sizes. Smaller frame sizes showed a higher possible transfer rate before data loss was recorded. This shows coherence between theory and experiments. Larger frame sizes were less good at filling the TDM time slots, causing data buffer on the device to overflow faster than for smaller frame sizes. This created data loss in the system. Other factors, such as overhead and payload, implies that the frame size should be chosen by application. Smaller data volumes that are sent frequently have an advantage when using smaller frame sizes, while when handling largeramounts of data that need to be transmitted quickly, it is more efficient to use larger frame sizes

Many medium access control protocols have been proposed for optical wavelength division multiplexing local area networks with a star topology. These protocols range from those based on the concept of fixed-assignment of communication subchannels, such as TDMA (Time Division Multiple Access); reservation of communication subchannels, such as DAS (Dynamic Allocation Scheme); or random-access to communication subchannels, such as DT-WDMA (Dynamic Time-Wavelength Division Multiple Access). In addition various hybrid protocols have been considered, for example, protocols incorporating both fixed-assignment and reservation rules, such as HTDM (Hybrid TDM). This thesis is on a novel hybrid protocol of fixed-assignment and random-access called "WTDMA with lightpath trespassing". This protocol combines the most desirable aspects of fixed-assignment and random-access protocols, while limiting their drawbacks. The performance of different versions of the protocol are analysed both mathematically and by stochastic simulation. The obtained results justify the introduction of the WTDMA with trespassing protocol, and indicate the situations where its use is advantageous.

It is often required in communication and navigation systems to be able to receive signals from multiple stations simultaneously. A common practice to do this is to use multiple hardware resources; a different set of resources for each station. In this thesis, a Coherent Amplitude Modulated (AM) receiver system was developed based on Software Defined Radio (SDR) technology enabling reception of multiple signals using hardware resources needed only for one station. The receiver system architecture employs Time Division Multiplexing (TDM) to share the single hardware resource among multiple streams of data. The architecture is designed so that it can be minimally modified to support any number of stations. The Verilog Hardware Description Language (HDL) was used to capture the receiver system architecture and design. The design and architecture are initially validated using HDL post-synthesis and post-implementation simulation. In addition, the receiver system architecture and design were implemented to a Xilinx Field Programmable Gate Array (FPGA) technology prototyping board for experimental testing and final validation.

This thesis describes the work done in evaluating the capacity of a multi-service third generation (3G) wireless communication system based on the Universal Mobile Telecommunication System (UNITS). More specifically, the study presented in these pages examines the Time Division Duplex (TDD) paradigm supported by the 3G Partnership Project (3GPP).
The goal is to establish the probability that a new connection attempt be successful as a function of the instantaneous load on the network. The sought capacity is evaluated with the help of an analytical model and a simulation tool. Both tools used a so-called system-level approach. The model and the simulator were developed based on 3GPP's standard and available data from link-level simulations.
Some of the significant results presented are: (1) A maximum of around 7 to 9 orthogonal codes can be used per timeslot. (2) A UMTS TDD CDMA system should be used in pico- and micro-cellular environments in order to support efficient data transmissions. (3) The multicode interference is often wrongfully neglected in capacity studies. (4) Capacity is downlink interference-limited, even with a modest MUD efficiency.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.
Includes bibliographical references (p. 153-159).
The increasing demand for high speed wireless connectivity at low cost proposes new challenges for communication systems designers to implement solutions that increase the data rate by utilizing the limited radio resources more efficiently at a low additional complexity. Sub-carrier Adaptive Modulation and Coding (AMC) exploits the high frequency diversity in wideband Orthogonal Frequency Division Multiplexing (OFDM) channels to obtain higher data rates. While prior work has discussed the value of sub-carrier AMC from a theoretical perspective, this work presents the design and performance of a real-time sub-carrier AMC system. We describe our OFDM transceiver prototype, which implements real-time subcarrier AMC for a wideband wireless channel. We discuss how our design achieves accurate and consistent Signal-to-Noise Ratio (SNR) estimates, which are critical for the success of AMC. We compare the performance of sub-carrier AMC with a non-adaptive scheme that assigns the same modulation and channel coding to all sub-carriers that can support that modulation and coding for the target Bit Error Rate (BER). For a conservative comparison, we compare against the uniform modulation/coding assignment that achieves the highest data rate. Our experiments over the wireless channel show that for a target coded BER of 10-5, our system achieves average data rates of 308.3 and 237.1 Mbps across a variety of Line-of-Sight (LOS) and Non Line-of-Sight (NLOS) locations respectively, which result in 34% and 40% gain over the best non-adaptive scheme. Equivalently, such data rate gain from AMC translates to an SNR improvement of 3 dB. Finally, our implementation of AMC incurs a low overhead of 1.1% of the data rate, and a reasonable complexity, occupying 9.95% of the total transceiver gates on the Field Programmable Gate Array (FPGA).
by Farinaz Edalat.
Ph.D.

Thesis (M.S.)--West Virginia University, 2001.
Title from document title page. Document formatted into pages; contains iv, 74 p. : ill. Includes abstract. Includes bibliographical references (p. 73-74).

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California
An advanced electro-optic hybrid rotary joint (EOHRJ) has been developed in Phase II of an AF SBIR effort with Physical Optics Corporation (POC) to replace cable wrap structure for multi-channel rotation-to-fixed (RTF) signal transmission. The EOHRJ meets AFFTC and other range special needs with a generic, high performance, rotary joint solution. At the moment, we have successfully installed and tested the EOHRJ on our KTM tracker system with the following capabilities: 1) able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low-speed signals; 2) able to accommodate multiple channel, high data rate (over gigabits per second), and bi-directional signal transmission; 3) able to be reliable for harsh environmental operation, adaptive to stringent sized requirement, and accommodating existing electrical and mechanical interfaces. The completed EOHRJ contains three uniquely integrated functional rings. The first and the outmost one is power ring, which provides RTF transmission channels for over 50 high voltage and high current channels. The second and the middle one is low speed electrical signal ring, which provides RTF transmission for over hundred control, feedback, and low speed data signals. The third and the inmost one is optical fiber slip ring, which, incorporating with current advanced signal multiplexing technologies (either time division or wavelength division multiplexing ) is able to provide multiple channel, high data rate, and bi-directional signal transmission. At the moment, the prototype module of the tree-layer EOHRJ has been successfully assembled in Air Force’s tracker system, and is providing a satisfactory performance. This paper presents our joint work on this project.

Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, Dec. 2004.
Thesis Advisor(s): Roberto Cristi, Murali Tummala. Includes bibliographical references (p. 45-46). Also available online.