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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Low Correlation Sequences Over AM-PSK And QAM Constellations

Anand, M 04 1900 (has links)
Direct-Sequence Code Division Multiple Access (DS-CDMA), over the last few years, has become a popular technique and finds a place in many modern communication systems. The performance of this technique is closely linked to the signature (or spreading) sequences employed in the system. In the past, there have been many successful attempts by research groups to construct families of signature sequences that offer the potential gains promised by theoretical bounds. In this thesis, we present constructions of families of signature sequences over the AM-PSK and QAM alphabet with low correlation. In this thesis, we construct a family of sequences over the 8-ary AM-PSK constella- tion, Family AOpt(16) that is asymptotically optimal with respect to the Welch bound on maximum magnitude of correlation for complex sequences. The maximum magnitude of correlation for this family, θmax, is upper bounded by √N , where N is the period of the sequences. The 8-ary AM-PSK constellation is a subset of the 16-QAM constellation. We also construct two families of sequences over 16-QAM, Family A16A, and Family A16,B , with the maximum magnitude of correlation upper bounded by √2√N . We construct a family, A(M 2), of sequences over the 2m+1-ary AM-PSK constellation of period N = 2r- 1 and family size (N + 1)/2m-1 . The 2m+1-ary AM-PSK constellation is a subset of the M 2-QAM constellation with M =2m . The maximum nontrivial normalized correlation parameter is bounded above by θmax < a √N where a ranges from 1.34 in the case of M 2 = 16 to √5 for large m. Apart from low correlation values, the family possesses several interesting and useful features. In Family A(M 2), users have the ability to transmit 2m bits of data per period of the spreading sequence. The sequences in Family A(M 2) are balanced; all points from the 2m+1-ary AM-PSK constellation occur approximately equally often in sequences of long period. The Euclidean distance between the signals assigned to a particular user in A(M 2), corresponding to different data symbols, is larger than the corresponding value for the case when 2m+1-PSK modulation and spreading is used. Perhaps most interestingly, Family A(M 2) permits users on the reverse link of a CDMA system to communicate asynchronously at varying data rates by switching between different QAM constellations. Family A(M 2) is compatible with QPSK sequence families S(p) in the sense that the maximum correlation magnitude is increased only slightly if one adds sequences from (p) S(p)\ S(0) to Family A(M 2). We also construct families of sequences over AM-PSK that tradeoff data rate per sequence period and θmax for a given family size. We have extended the construction of sequences over AM-PSK constellation to construct sequences over the M 2-QAM constellation for M =2m . The QAM sequence families, Families (AM 2), have size, data rate and minimum squared Euclidean distance same as the corresponding AM-PSK construction but have higher values of θmax. Also included in the thesis are constructions for large families of sequences over the M 2-QAM alphabet.
42

Étude et réalisation de sources photoniques intégrées sur InP pour les applications télécoms à hauts débits et à 1,55 µm / Study and fabrication of InP integrated photonic sources for high bit rate telecom applications at 1.55µm

Carrara, David 23 May 2012 (has links)
Les formats de modulation avancés, codant l’information sur la phase, la polarisation ou plusieurs niveaux d’amplitude de la lumière reçoivent aujourd’hui un intérêt croissant. En effet, ceux-ci permettent d’atteindre une meilleure efficacité spectrale et par conséquent des débits plus élevés. Ces caractéristiques sont actuellement très recherchées dans les télécommunications pour répondre à la demande constante d’augmentation de capacité des transmissions optiques fibrées. L’essentiel du travail effectué porte sur la génération de tels signaux dans des sources photoniques monolithiques sur InP faisant appel à un concept nouveau de commutation de phases optiques préfixées avec des modulateurs électro-absorbants. Une comparaison de notre technologie intégrée avec la technologie actuelle de génération de formats de modulation avancés démontre des possibilités nouvelles de réduction de taille, de diminution de consommation énergétique et d’évolution en vitesse de modulation jusqu’à 56 GBauds. Suite à la validation, par simulations, d’architectures de transmetteurs spécifiques pour la génération de formats de modulation avancés, nous réalisons en salle blanche les circuits photoniques intégrés d’étude. Les caractérisations statiques confirment le fonctionnement de toutes les fonctions intégrées des circuits et soulignent l’efficacité de la filière technologique. Pour une première démonstration de fonctionnalité nous choisissons un transmetteur BPSK capable de générer une modulation de phase à 12,4 GB. Ce résultat démontre la plus petite source intégrée BPSK à l’heure actuelle. Un autre circuit capable de générer des formats de modulation plus complexes est aussi caractérisé / Advanced modulation formats, encoding data on the phase, polarization or multi-level intensity of the light are currently a hot topic in the telecommunication domain. By using them, high spectral efficiency and therefore higher bit rate signals could be generated. Those characteristics are really attractive for the telecommunication systems manufacturers in order to answer to the constant need of increased bandwidth in fiber optic communications. The study of advanced modulation formats generation in Photonic Integrated Circuits (PICs) based on a new concept of preset phases switching by Electro-Absorption Modulators is the main task of the current work. Compared to the actual technology used for generate advanced modulations, our choice could allow a strong reduction of the dimensions and of the energy consumption of the transmitter as well as bit rate up to 56 GB. After validating specific transmitters’ architectures by simulations, we fabricated the studied photonic integrated circuits in clean room. Through static characterizations, we verify that all integrated functions of the transmitters are working and we show the efficiency of our technological choices. Using the available equipments at the lab, we prove the validity of our concept of EAM based phase switching by using a BPSK transmitter. A 12.4 GB BPSK modulation is obtained as well as a wide open eye diagram. This result demonstrates the smallest BPSK integrated photonic source at this time. Another photonic circuit able to generate more complex modulation formats is also measured
43

Simulation and evaluation of a DVB System using Simulink (Vol. II)

Prieto, Alberto Pastor January 2005 (has links)
<p>DVB (Digital Video Broadcasting) is the television digital system. It's however much more than a simple replacement for existing analogue television transmission, this system has many advantages such as picture quality and allows you a range of new features and services including subtitling, multiple audio tracks, interactive content, multimedia content. </p><p>The system is based in the OFDM technology, which allows DVB system to exploit the spectrum frequencies in a better way, saving spectrum, but OFDM has an important drawback that is the peak to average power ratio problem. OFDM is based on the FFT algorithms generating orthogonal subcarriers. </p><p>This thesis talks about the improvement of the PAPR problem using the soft compression method. </p><p>The simulation has been developed in Simulink® and Matlab®. With all the information presented in this thesis, any user can simulate the system. Thus, this thesis can be improved using other techniques to solve the PAPR problem.</p>
44

Transparent Satellite Switching using Flexible Frequency-band Reallocation

Yagüe, Edgar Cámara, Carretero, José Manuel Menéndez January 2006 (has links)
<p>The society expects a global interconected digital communication system offering multimedia services, information on demand and interchange of information with a high data rates and low cost. </p><p>All this can not be realized with the terrestrial nets used nowadays cause it is necessary a high economic inversion to get a competitive capacity to interchange information between server and user. The next generation of satellite must have characteristics which improve the current generation, one important requirement is that the same satellite could make a treatment of the different input signals. With this we can avoid a spent of lots of money and time because we do not need terrestrial stations which modify the signals before the information is sent to the satellite.</p><p>For all this, we need an on board treatment of the information in the satellite. We design a frequency bank reallocation (FBR) network by using a filter bank system. This is the first step of the thesis. After we get FBR we introduce some different input signals and analyze the output, using parameters like symbol error rate and variance.</p><p>One important part in the thesis is the QAM signals used to test our system. For this, we design a modulator and a demodulator of QAM4, 16 and 64, paying more attention in the QAM64, cause is the modulation where more errors can appear due to we have got more possible chances which means more precision in the recovery of the signal.</p>
45

Extraction of radio frequency quality metric from digital video broadcast streams by cable using software defined radio

Eriksson, Viktor January 2013 (has links)
The purpose of this master thesis was to investigate how effiecient the extractionof radiofrequency quality metrics from digital video broadcast (DVB) streamscan become using software defined radio. Software defined radio (SDR) is a fairlynew technology that offers you the possibility of very flexible receivers and transmitters where it is possible to upgrade the modulation and demodulation overtime. Agama is interested in SDR for use in the Agama Analyzer, a widely deployedmonitoring probe running on top of standard services. Using SDR, Agama coulduse that in all deployments, such as DVB by cable/terrestrial/satellite (DVBC/T/S), which would simplify logistics. This thesis is an implementation of a SDR to be able to receive DVB-C. TheSDR must perform a number of adaptive algorithms in order to prevent the received symbols from being significantly different from the transmitted ones. Themain parts of the SDR include timing recovery, carrier recovery and equalization.Timing recovery performs synchronization between the transmitted and receivedsymbols and the carrier recovery performs synchronization between the carrierwave of the transmitter and the local oscillator in the receiver. The thesis discusses various methods to perform the different types of synchronizations andequalizations in order to find the most suitable methods.
46

Transparent Satellite Switching using Flexible Frequency-band Reallocation

Yagüe, Edgar Cámara, Carretero, José Manuel Menéndez January 2006 (has links)
The society expects a global interconected digital communication system offering multimedia services, information on demand and interchange of information with a high data rates and low cost. All this can not be realized with the terrestrial nets used nowadays cause it is necessary a high economic inversion to get a competitive capacity to interchange information between server and user. The next generation of satellite must have characteristics which improve the current generation, one important requirement is that the same satellite could make a treatment of the different input signals. With this we can avoid a spent of lots of money and time because we do not need terrestrial stations which modify the signals before the information is sent to the satellite. For all this, we need an on board treatment of the information in the satellite. We design a frequency bank reallocation (FBR) network by using a filter bank system. This is the first step of the thesis. After we get FBR we introduce some different input signals and analyze the output, using parameters like symbol error rate and variance. One important part in the thesis is the QAM signals used to test our system. For this, we design a modulator and a demodulator of QAM4, 16 and 64, paying more attention in the QAM64, cause is the modulation where more errors can appear due to we have got more possible chances which means more precision in the recovery of the signal.
47

M-PSK and M-QAM Modulation/Demodulation of UWB Signal Using Six-Port Correlator

A. Sani, Negar January 2010 (has links)
Nowadays high speed and high data rate communication are highly demanded. Consequently, wideband and high frequency transmitter and receivers should be designed. New transmitters and receivers should also have low power consumption, simple design and low manufacturing price in order to fulfill manufacturers’ requests for mass production. Having all above specifications, six-port correlator is a proper choice to be used as modulator and demodulator in transmitters and receivers. In this thesis the six-port correlator is introduced, modeled and simulated using Advanced Design System (ADS) software. A simple six-port transmitter/receiver system with a line of sight link is modeled and analyzed in BER, path length and noise terms. The modulation in this system is QAM, frequency is 7.5 GHz and symbol rate is 500 Msymbol/s. Furthermore two methods are proposed for high frequency and high symbol rate M-PSK and M-QAM modulation using six-port correlator. The 7.5 GHz modulators are modeled and simulated in ADS. Data streams generated by pseudo random bit generator with 1 GHz bandwidth are applied to modulators. Common source field effect transistors (FETs) with zero bias are used as controllable impedance termination to apply baseband data to modulator. Both modulators show good performance in M-PSK and M-QAM modulation.
48

Simulation and evaluation of a DVB System using Simulink (Vol. II)

Prieto, Alberto Pastor January 2005 (has links)
DVB (Digital Video Broadcasting) is the television digital system. It's however much more than a simple replacement for existing analogue television transmission, this system has many advantages such as picture quality and allows you a range of new features and services including subtitling, multiple audio tracks, interactive content, multimedia content. The system is based in the OFDM technology, which allows DVB system to exploit the spectrum frequencies in a better way, saving spectrum, but OFDM has an important drawback that is the peak to average power ratio problem. OFDM is based on the FFT algorithms generating orthogonal subcarriers. This thesis talks about the improvement of the PAPR problem using the soft compression method. The simulation has been developed in Simulink® and Matlab®. With all the information presented in this thesis, any user can simulate the system. Thus, this thesis can be improved using other techniques to solve the PAPR problem.
49

Sistema de videovigilancia mediante radioenlaces para el distrito de Santiago de Cusco

Asencios Rodriguez, Aldo Williams, Vergaray Mayo, Manuel Accel January 2015 (has links)
El presente proyecto de investigación tiene como finalidad presentar una solución a la problemática que se tiene en la Región Cusco, Provincia Cusco, Distrito de Santiago. Como se detalla el presente proyecto, existen diversos factores que determinan el tipo de problemática en el ámbito de seguridad que presenta el distrito de Santiago, por ejemplo, lugares de riñas frecuentes, puntos de mayor incidencia delictiva, lugares con nula o escasa iluminación, lugares de concentración de alcohólicos o drogadictos, todo esto a raíz de la falta de coordinación entre las instituciones a quienes les compete el ámbito de seguridad. Santiago es uno de los distritos principales de la ciudad del Cusco, por lo tanto, planteamos la propuesta de tener un sistema de seguridad integrado, el cual consiste en emplear cámaras de videovigilancia que estarán interconectadas mediante el uso de radio enlaces hacia un punto central o centro de control, desde dicho lugar se podrán monitorear las principales calles y avenidas con altos índices mayor incidencia. Se espera como resultado, disminuir los índices de inseguridad que actualmente presenta el distrito, con ayuda de la propuesta planteada.
50

Geometrical and dimensional Measurement Planning : - a systematic and holistic approach

Lindqvist, Richard January 2011 (has links)
För att försäkra sig om den slutliga kvaliteten på maskinbearbetade komponenter måste tillverkande företag mäta och verifiera de geometriska och dimensionella egenskaperna på komponenter innan dem skickas vidare nedströms till den mer värdeskapande monteringen. Det är idag vanligt att den geometriska och dimensionella mätningen och verifieringen uppstår varje gång då en maskin ställs om, när man startar om eller startar upp en ny produktionslina eller då en produktionsprocess ändras. Produktionsteknisk mätteknik och resultat från utförda mätningar används sedan som indata för statistisk processtyrning och övervakning av produktionsprocesser. Syftet med vår forskning har varit att först ta fram en nulägesbild av mätteknisk beredning inom fordons- och flygindustrin och utifrån den identifiera framtida trender med behovsanalys och gap. Utifrån analysen har vi sedan utforskat och utvecklat en modell och metodik för mätteknisk mät- och styrbarhetsberedning. I denna licentiat avhandling har vi utforskat området geometrisk och dimensionell mät- och styrbarhetsberedning (GMCP - Geometrical and dimensional Measurement and Controllability Planning). Vi presenterar en nulägesanalys av området och vi presenterar en teori med modell och ramverk för GMCP. Vidare har vi utforskat en metodik och verktyg benämnd kvalitetssäkringsmatris (QAM - Quality Assurance Matrix) och som vi lyfter fram i denna avhandling. I slutet av avhandlingen presenteras och diskuteras dem hittills uppnådda resultaten från forskningen och i det sista kapitlet dras slutsatser och den fortsatta forskningen inom ”SIMET-GICP” projektet presenteras. / In order to ensure final product quality on machined components, manufacturing enterprises must measure and inspect the geometrical and dimensional characteristics of components before they go into higher-value assemblies. Commonly, the geometrical and dimensional measurement and inspection occurs every time at machine tool set-up, when a line is restarted or if the production process is changed. Production metrology and results from production measurements is used as input data for statistical process control and monitoring of production processes. The purpose of our research has been to firstly perform a state of the art analysis in the area of measurement planning applied in the automotive and aerospace industry. The output from the state of the art study has then been used to identify future trends and needs including a gap analysis. Then we used the analysis to explore and develop a model and methodology for measurement and controllability planning.   In this licentiate thesis we have explored the area of GMCP (Geometrical and dimensional Measurement and Controllability Planning). As a major result in this thesis a state of the art survey on GMCP is presented. Based on the state of the art study a theory and model framework for GMCP has been explored and a methodology and tool called QAM (Quality Assurance Matrix) is highlighted in this thesis. In the end of the thesis we present and discuss the present research results we have accomplished and in the final chapter we draw conclusions and outline the continued research within the SIMET-GICP project. / QC 20111027 / SIMET 1

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