279 research outputs found

    Legibility of machine readable codes used for gas turbine part tracking

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    Gas turbines are comprised of many parts, which are often expensive and required to survive a harsh environment for significant periods (with or without reconditioning). To differentiate between parts, and facilitate keeping accurate historical records, they are often given a unique identification number. However, manually recording and tracking these is difficult. This has led to increased adoption of machine readable codes to help reduce or eliminate many of the issues currently faced (mostly human error). The harsh environment of a gas turbine means that typical methods of applying machine readable codes, such as printed adhesive labels, are simply not durable enough. Direct part marking (DPM) is necessary to ensure the desired longevity of the code over the part's useful life. The research presented in this thesis was approached in two main phases. Firstly, the author sought to investigate the technical solutions available for the elements required of a part tracking system (encoding, marking and scanning). This included identifying the characteristics of each and their compatibility with one other (across elements). In conjunction with Alstom, criteria were identified that were used as a basis for comparison so that the preferred technical solutions could be determined. The outcome of this process was enhanced by the author developing a number of industrial contacts experienced in implementing part tracking systems. The second phase related to the legibility of the codes. The harsh environment of a gas turbine results in surface degradation that may in turn reduce the legibility of any machine readable codes present. To better understand why read failures occur, the author _rst looked to the scanning process. Data Matrix symbols (marked via dot peen) require the scanner to capture an image for processing. Image capture is typically achieved using a charge-coupled device (CCD), each pixel of which induces a charge proportional to the incident illumination. This illumination is received via reflection from the surface of the part and hence the Data Matrix marked on it. Several surface features were identified that govern the way in which the part surface will reflect light back to the scanner: surface roughness, dot geometry and surface colour. These parameters are important because they link the degradation mechanisms occurring { broadly categorised as deposition, erosion or corrosion { with the scanning process. Whilst the degradation mechanisms are distinctly different in their behaviour, their effect on surface reflectivity is common in that they can all be characterised via the surface parameters identified. This was deduced theoretically and so the author completed tests (utilising shot blasting to change the surface roughness and oxidation to change its colour, independently) to show that these surface parameters do indeed change with the introduction of surface degradation and that there is a commensurate change in symbol legibility. Based on the learning derived with respect to Data Matrix legibility, the author has proposed a framework for developing a tool referred to as a Risk Matrix System. This tool is intended to enhance the application of part tracking to gas turbine engines by enabling symbol durability to be assessed based on the expected operating conditions. The research presented is the first step in fully understanding the issues that affect the legibility of symbols applied to gas turbine parts. The author's main contribution to learning has been the identification of knowledge from various other sources applicable to this situation and to present it in a coherent and complete manner. From this foundation, others will be able to pursue relevant issues further; the author has made a number of recommendations to this effect

    Eficiência energética avançada para sistema OFDMA CoMP coordenação multiponto

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    Doutoramento em Engenharia EletrotécnicaThe ever-growing energy consumption in mobile networks stimulated by the expected growth in data tra ffic has provided the impetus for mobile operators to refocus network design, planning and deployment towards reducing the cost per bit, whilst at the same time providing a signifi cant step towards reducing their operational expenditure. As a step towards incorporating cost-eff ective mobile system, 3GPP LTE-Advanced has adopted the coordinated multi-point (CoMP) transmission technique due to its ability to mitigate and manage inter-cell interference (ICI). Using CoMP the cell average and cell edge throughput are boosted. However, there is room for reducing energy consumption further by exploiting the inherent exibility of dynamic resource allocation protocols. To this end packet scheduler plays the central role in determining the overall performance of the 3GPP longterm evolution (LTE) based on packet-switching operation and provide a potential research playground for optimizing energy consumption in future networks. In this thesis we investigate the baseline performance for down link CoMP using traditional scheduling approaches, and subsequently go beyond and propose novel energy e fficient scheduling (EES) strategies that can achieve power-e fficient transmission to the UEs whilst enabling both system energy effi ciency gain and fairness improvement. However, ICI can still be prominent when multiple nodes use common resources with di fferent power levels inside the cell, as in the so called heterogeneous networks (Het- Net) environment. HetNets are comprised of two or more tiers of cells. The rst, or higher tier, is a traditional deployment of cell sites, often referred to in this context as macrocells. The lower tiers are termed small cells, and can appear as microcell, picocells or femtocells. The HetNet has attracted signiffi cant interest by key manufacturers as one of the enablers for high speed data at low cost. Research until now has revealed several key hurdles that must be overcome before HetNets can achieve their full potential: bottlenecks in the backhaul must be alleviated, as well as their seamless interworking with CoMP. In this thesis we explore exactly the latter hurdle, and present innovative ideas on advancing CoMP to work in synergy with HetNet deployment, complemented by a novel resource allocation policy for HetNet tighter interference management. As system level simulator has been used to analyze the proposed algorithm/protocols, and results have concluded that up to 20% energy gain can be observed.O aumento do consumo de energia nas TICs e em particular nas redes de comunicação móveis, estimulado por um crescimento esperado do tráfego de dados, tem servido de impulso aos operadores m oveis para reorientarem os seus projectos de rede, planeamento e implementa ção no sentido de reduzir o custo por bit, o que ao mesmo tempo possibilita um passo signicativo no sentido de reduzir as despesas operacionais. Como um passo no sentido de uma incorporação eficaz em termos destes custos, o sistema móvel 3GPP LTE-Advanced adoptou a técnica de transmissão Coordenação Multi-Ponto (identificada na literatura com a sigla CoMP) devido à sua capacidade de mitigar e gerir Interferência entre Células (sigla ICI na literatura). No entanto a ICI pode ainda ser mais proeminente quando v arios n os no interior da célula utilizam recursos comuns com diferentes níveis de energia, como acontece nos chamados ambientes de redes heterogéneas (sigla Het- Net na literatura). As HetNets são constituídas por duas ou mais camadas de células. A primeira, ou camada superiora, constitui uma implantação tradicional de sítios de célula, muitas vezes referidas neste contexto como macrocells. Os níveis mais baixos são designados por células pequenas, e podem aparecer como microcells, picocells ou femtocells. A HetNet tem atra do grande interesse por parte dos principais fabricantes como sendo facilitador para transmissões de dados de alta velocidade a baixo custo. A investigação tem revelado at e a data, vários dos principais obstáculos que devem ser superados para que as HetNets possam atingir todo o seu potencial: (i) os estrangulamentos no backhaul devem ser aliviados; (ii) bem como sua perfeita interoperabilidade com CoMP. Nesta tese exploramos este ultimo constrangimento e apresentamos ideias inovadoras em como a t ecnica CoMP poder a ser aperfeiçoada por forma a trabalhar em sinergia com a implementação da HetNet, complementado ainda com uma nova perspectiva na alocação de recursos rádio para um controlo e gestão mais apertado de interferência nas HetNets. Com recurso a simulação a níível de sistema para analisar o desempenho dos algoritmos e protocolos propostos, os resultados obtidos concluíram que ganhos at e a ordem dos 20% poderão ser atingidos em termos de eficiência energética

    Optimization of high-throughput real-time processes in physics reconstruction

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    La presente tesis se ha desarrollado en colaboración entre la Universidad de Sevilla y la Organización Europea para la Investigación Nuclear, CERN. El detector LHCb es uno de los cuatro grandes detectores situados en el Gran Colisionador de Hadrones, LHC. En LHCb, se colisionan partículas a altas energías para comprender la diferencia existente entre la materia y la antimateria. Debido a la cantidad ingente de datos generada por el detector, es necesario realizar un filtrado de datos en tiempo real, fundamentado en los conocimientos actuales recogidos en el Modelo Estándar de física de partículas. El filtrado, también conocido como High Level Trigger, deberá procesar un throughput de 40 Tb/s de datos, y realizar un filtrado de aproximadamente 1 000:1, reduciendo el throughput a unos 40 Gb/s de salida, que se almacenan para posterior análisis. El proceso del High Level Trigger se subdivide a su vez en dos etapas: High Level Trigger 1 (HLT1) y High Level Trigger 2 (HLT2). El HLT1 transcurre en tiempo real, y realiza una reducción de datos de aproximadamente 30:1. El HLT1 consiste en una serie de procesos software que reconstruyen lo que ha sucedido en la colisión de partículas. En la reconstrucción del HLT1 únicamente se analizan las trayectorias de las partículas producidas fruto de la colisión, en un problema conocido como reconstrucción de trazas, para dictaminar el interés de las colisiones. Por contra, el proceso HLT2 es más fino, requiriendo más tiempo en realizarse y reconstruyendo todos los subdetectores que componen LHCb. Hacia 2020, el detector LHCb, así como todos los componentes del sistema de adquisici´on de datos, serán actualizados acorde a los últimos desarrollos técnicos. Como parte del sistema de adquisición de datos, los servidores que procesan HLT1 y HLT2 también sufrirán una actualización. Al mismo tiempo, el acelerador LHC será también actualizado, de manera que la cantidad de datos generada en cada cruce de grupo de partículas aumentare en aproxidamente 5 veces la actual. Debido a las actualizaciones tanto del acelerador como del detector, se prevé que la cantidad de datos que deberá procesar el HLT en su totalidad sea unas 40 veces mayor a la actual. La previsión de la escalabilidad del software actual a 2020 subestim´ó los recursos necesarios para hacer frente al incremento en throughput. Esto produjo que se pusiera en marcha un estudio de todos los algoritmos tanto del HLT1 como del HLT2, así como una actualización del código a nuevos estándares, para mejorar su rendimiento y ser capaz de procesar la cantidad de datos esperada. En esta tesis, se exploran varios algoritmos de la reconstrucción de LHCb. El problema de reconstrucción de trazas se analiza en profundidad y se proponen nuevos algoritmos para su resolución. Ya que los problemas analizados exhiben un paralelismo masivo, estos algoritmos se implementan en lenguajes especializados para tarjetas gráficas modernas (GPUs), dada su arquitectura inherentemente paralela. En este trabajo se dise ˜nan dos algoritmos de reconstrucción de trazas. Además, se diseñan adicionalmente cuatro algoritmos de decodificación y un algoritmo de clustering, problemas también encontrados en el HLT1. Por otra parte, se diseña un algoritmo para el filtrado de Kalman, que puede ser utilizado en ambas etapas. Los algoritmos desarrollados cumplen con los requisitos esperados por la colaboración LHCb para el año 2020. Para poder ejecutar los algoritmos eficientemente en tarjetas gráficas, se desarrolla un framework especializado para GPUs, que permite la ejecución paralela de secuencias de reconstrucción en GPUs. Combinando los algoritmos desarrollados con el framework, se completa una secuencia de ejecución que asienta las bases para un HLT1 ejecutable en GPU. Durante la investigación llevada a cabo en esta tesis, y gracias a los desarrollos arriba mencionados y a la colaboración de un pequeño equipo de personas coordinado por el autor, se completa un HLT1 ejecutable en GPUs. El rendimiento obtenido en GPUs, producto de esta tesis, permite hacer frente al reto de ejecutar una secuencia de reconstrucción en tiempo real, bajo las condiciones actualizadas de LHCb previstas para 2020. As´ı mismo, se completa por primera vez para cualquier experimento del LHC un High Level Trigger que se ejecuta únicamente en GPUs. Finalmente, se detallan varias posibles configuraciones para incluir tarjetas gr´aficas en el sistema de adquisición de datos de LHCb.The current thesis has been developed in collaboration between Universidad de Sevilla and the European Organization for Nuclear Research, CERN. The LHCb detector is one of four big detectors placed alongside the Large Hadron Collider, LHC. In LHCb, particles are collided at high energies in order to understand the difference between matter and antimatter. Due to the massive quantity of data generated by the detector, it is necessary to filter data in real-time. The filtering, also known as High Level Trigger, processes a throughput of 40 Tb/s of data and performs a selection of approximately 1 000:1. The throughput is thus reduced to roughly 40 Gb/s of data output, which is then stored for posterior analysis. The High Level Trigger process is subdivided into two stages: High Level Trigger 1 (HLT1) and High Level Trigger 2 (HLT2). HLT1 occurs in real-time, and yields a reduction of data of approximately 30:1. HLT1 consists in a series of software processes that reconstruct particle collisions. The HLT1 reconstruction only analyzes the trajectories of particles produced at the collision, solving a problem known as track reconstruction, that determines whether the collision data is kept or discarded. In contrast, HLT2 is a finer process, which requires more time to execute and reconstructs all subdetectors composing LHCb. Towards 2020, the LHCb detector and all the components composing the data acquisition system will be upgraded. As part of the data acquisition system, the servers that process HLT1 and HLT2 will also be upgraded. In addition, the LHC accelerator will also be updated, increasing the data generated in every bunch crossing by roughly 5 times. Due to the accelerator and detector upgrades, the amount of data that the HLT will require to process is expected to increase by 40 times. The foreseen scalability of the software through 2020 underestimated the required resources to face the increase in data throughput. As a consequence, studies of all algorithms composing HLT1 and HLT2 and code modernizations were carried out, in order to obtain a better performance and increase the processing capability of the foreseen hardware resources in the upgrade. In this thesis, several algorithms of the LHCb recontruction are explored. The track reconstruction problem is analyzed in depth, and new algorithms are proposed. Since the analyzed problems are massively parallel, these algorithms are implemented in specialized languages for modern graphics cards (GPUs), due to their inherently parallel architecture. From this work stem two algorithm designs. Furthermore, four additional decoding algorithms and a clustering algorithms have been designed and implemented, which are also part of HLT1. Apart from that, an parallel Kalman filter algorithm has been designed and implemented, which can be used in both HLT stages. The developed algorithms satisfy the requirements of the LHCb collaboration for the LHCb upgrade. In order to execute the algorithms efficiently on GPUs, a software framework specialized for GPUs is developed, which allows executing GPU reconstruction sequences in parallel. Combining the developed algorithms with the framework, an execution sequence is completed as the foundations of a GPU HLT1. During the research carried out in this thesis, the aforementioned developments and a small group of collaborators coordinated by the author lead to the completion of a full GPU HLT1 sequence. The performance obtained on GPUs allows executing a reconstruction sequence in real-time, under LHCb upgrade conditions. The developed GPU HLT1 constitutes the first GPU high level trigger ever developed for an LHC experiment. Finally, various possible realizations of the GPU HLT1 to integrate in a production GPU-equipped data acquisition system are detailed

    Mobility Analysis and Management for Heterogeneous Networks

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    The global mobile data traffic has increased tremendously in the last decade due to the technological advancement in smartphones. Their endless usage and bandwidth-intensive applications will saturate current 4G technologies and has motivated the need for concrete research in order to sustain the mounting data traffic demand. In this regard, the network densification has shown to be a promising direction to cope with the capacity demands in future 5G wireless networks. The basic idea is to deploy several low power radio access nodes called small cells closer to the users on the existing large radio foot print of macrocells, and this constitutes a heterogeneous network (HetNet). However, there are many challenges that operators face with the dense HetNet deployment. The mobility management becomes a challenging task due to triggering of frequent handovers when a user moves across the network coverage areas. When there are fewer users associated in certain small cells, this can lead to significant increase in the energy consumption. Intelligently switching them to low energy consumption modes or turning them off without seriously degrading user performance is desirable in order to improve the energy savings in HetNets. This dynamic power level switching in the small cells, however, may cause unnecessary handovers, and it becomes important to ensure energy savings without compromising handover performance. Finally, it is important to evaluate mobility management schemes in real network deployments, in order to find any problems affecting the quality of service (QoS) of the users. The research presented in this dissertation aims to address these challenges. First, to tackle the mobility management issue, we develop a closed form, analytical model to study the handover and ping-pong performance as a function of network parameters in the small cells, and verify its performance using simulations. Secondly, we incorporate fuzzy logic based game-theoretic framework to address and examine the energy efficiency improvements in HetNets. In addition, we design fuzzy inference rules for handover decisions and target base station selection is performed through a fuzzy ranking technique in order to enhance the mobility robustness, while also considering energy/spectral efficiency. Finally, we evaluate the mobility performance by carrying out drive test in an existing 4G long term evolution (LTE) network deployment using software defined radios (SDR). This helps to obtain network quality information in order to find any problems affecting the QoS of the users

    Spectral-energy efficiency trade-off for next-generation wireless communication systems

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    The data traffic in cellular networks has had and will experience a rapid exponential rise. Therefore, it is essential to innovate a new cellular architecture with advanced wireless technologies that can offer more capacity and enhanced spectral efficiency to manage the exponential data traffic growth. Managing such mass data traffic, however, brings up another challenge of increasing energy consumption. This is because it contributes into a growing fraction of the carbon dioxide (CO2) emission which is a global concern today due to its negative impact on the environment. This has resulted in creating a new paradigm shift towards both spectral and energy efficient orientated design for the next-generation wireless access networks. Acquiring both improved energy efficiency and spectral efficiency has, nonetheless, shown to be a difficult goal to achieve as it seems improving one is at the detriment to the other. Therefore, the trade-off between the spectral and energy efficiency is of paramount importance to assess the energy consumption in a wireless communication system required to attain a specific spectral efficiency. This thesis looks into this problem. It studies the spectral-energy efficiency tradeoff for some of the emerging wireless communication technologies which are seen as potential candidates for the fifth generation (5G) mobile cellular system. The focus is on the orthogonal frequency division multiple access (OFDMA), mobile femtocell (MFemtocell), cognitive radio (CR), and the spatial modulation (SM). Firstly, the energy-efficient resource allocation scheme for multi-user OFDMA (MU-OFDMA) system is studied. The spectral-energy efficiency trade-off is analysed under the constraint of maintaining the fairness among users. The energy-efficient optimisation problem has been formulated as integer fractional programming. We then apply an iterative method to simplify the problem to an integer linear programming (ILP) problem. Secondly, the spectral and energy efficiency for a cellular system with MFemtocell deployment is investigated using different resource partitioning schemes. Femtocells are low range, low power base stations (BSs) that improve the coverage inside a home or office building. MFemtocell adopts the femtocell solution to be deployed in public transport and emergency vehicles. Closed-form expressions for the relationships between the spectral and energy efficiency are derived for a single-user (SU) MFemtocell network. We also study the spectral efficiency for MU-MFemtocells with two opportunistic scheduling schemes. Thirdly, the spectral-energy efficiency trade-off for CR networks is analysed at both SU and MU CR systems against varying signal-to-noise ratio (SNR) values. CR is an innovative radio device that aims to utilise the spectrum more efficiently by opportunistically exploiting underutilised licensed spectrum. For the SU system, we study the required energy to achieve a specific spectral efficiency for a CR channel under two different types of power constraints in different fading environments. In this scenario, interference constraint at the primary receiver (PR) is also considered to protect the PR from harmful interference. At the system level, we study the spectral and energy efficiency for a CR network that shares the spectrum with an indoor network. Adopting the extreme-value theory, we are able to derive the average spectral efficiency of the CR network. Finally, we propose two innovative schemes to enhance the capability of (SM). SM is a recently developed technique that is employed for a low complexity multipleinput multiple-output (MIMO) transmission. The first scheme can be applied for SU MIMO (SU-MIMO) to offer more degrees of freedom than SM. Whereas the second scheme introduces a transmission structure by which the SM is adopted into a downlink MU-MIMO system. Unlike SM, both proposed schemes do not involve any restriction into the number of transmit antennas when transmitting signals. The spectral-energy efficiency trade-off for the MU-SM in the massive MIMO system is studied. In this context, we develop an iterative energy-efficient water-filling algorithm to optimises the transmit power and achieve the maximum energy efficiency for a given spectral efficiency. In summary, the research presented in this thesis reveals mathematical tools to analysis the spectral and energy efficiency for wireless communications technologies. It also offers insight to solve optimisation problems that belong to a class of problems with objectives of enhancing the energy efficiency

    Low-Complexity Voronoi Shaping for the Gaussian Channel

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    Voronoi constellations (VCs) are finite sets of vectors of a coding lattice enclosed by the translated Voronoi region of a shaping lattice, which is a sublattice of the coding lattice. In conventional VCs, the shaping lattice is a scaled-up version of the coding lattice. In this paper, we design low-complexity VCs with a cubic coding lattice of up to 32 dimensions, in which pseudo-Gray labeling is applied to minimize the bit error rate. The designed VCs have considerable shaping gains of up to 1.03 dB and finer choices of spectral efficiencies in practice compared with conventional VCs. A mutual information estimation method and a log-likelihood approximation method based on importance sampling for very large constellations are proposed and applied to the designed VCs. With error-control coding, the proposed VCs can have higher information rates than the conventional scaled VCs because of their inherently good pseudo-Gray labeling feature, with a lower decoding complexity

    The Deep Space Network: A Radio Communications Instrument for Deep Space Exploration

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    The primary purpose of the Deep Space Network (DSN) is to serve as a communications instrument for deep space exploration, providing communications between the spacecraft and the ground facilities. The uplink communications channel provides instructions or commands to the spacecraft. The downlink communications channel provides command verification and spacecraft engineering and science instrument payload data

    Low-Density Graph Codes for slow fading Relay Channels

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    We study Low-Density Parity-Check (LDPC) codes with iterative decoding on block-fading (BF) Relay Channels. We consider two users that employ coded cooperation, a variant of decode-and-forward with a smaller outage probability than the latter. An outage probability analysis for discrete constellations shows that full diversity can be achieved only when the coding rate does not exceed a maximum value that depends on the level of cooperation. We derive a new code structure by extending the previously published full-diversity root-LDPC code, designed for the BF point-to-point channel, to exhibit a rate-compatibility property which is necessary for coded cooperation. We estimate the asymptotic performance through a new density evolution analysis and the word error rate performance is determined for finite length codes. We show that our code construction exhibits near-outage limit performance for all block lengths and for a range of coding rates up to 0.5, which is the highest possible coding rate for two cooperating users.Comment: Accepted for publication in IEEE Transactions on Information Theor

    A digital signal processing system developed for the optimal use of high density magnetic storage media

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    High density data recording has traditionally been an essential factor in the development of communication and transmission systems. However, recently more sophisticated applications, including video recording, have necessitated refinements of this technology. This study concentrates on the signal processing techniques used to inhance the packing density of stored data. A comparison of the spectral mapping characteristics of different codes illustrates that the need for equalization can be eliminated and that significant bandwidth reduction can be achieved. Secondly, consideration is given to the deleterious effects of flutter, its associated effects on high density data recording, and the constraints imposed on the development of a time base corrector. An analysis is made of the bandlimiting effect which results when the incoming data is convolved with the head impulse response. The bandwidth of the channel, the size of the head gap, and the velocity of the media are seen from this analysis to be intrinsically related. These signal processing techniques are implemented, the channel capacity computed, and a significant channel efficiency achieved
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