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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.
21

Aufwandsgünstige Verfahren zur Vorcodierung bei nichtlinearen Übertragungssystemen

Siegrist, Michael January 2009 (has links)
Zugl.: Kaiserslautern, Techn. Univ., Diss., 2009
22

In-Flight Wireless Acquisition: an Experience

Guilot, Jean-Michel 10 1900 (has links)
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / The wireless acquisition system LISA has been designed for mechanical phenomenon analysis onboard aircrafts. It has been in use for more than one year now. This paper describes the organization of this equipment and the experiences related by first users.
23

Multilevel modulation formats for optical communication systems based on direct detection

Serbay, Murat January 2008 (has links)
Zugl.: Kiel, Univ., Diss., 2008
24

Synchronization of Distributed Units without Access to GPS

Carlsson, Erik January 2018 (has links)
Time synchronization between systems having no external reference can be an issue in small wireless node-based systems. In this thesis a transceiver is designed and implemented in two separate systems. Then the timing algorithm of "TwoWay Time Transfer" is then chosen to correct any timing error between the two free running clocks of the systems. In conclusion the results are compared towards having both systems get their timing based on GPS timing. / Tidssynkronisering mellan två system som saknar externa referenser kan bli ett problem i små nodbaserade system. I det här arbetet har en sändtagare designats och implementerats i två system. Sedan valdes algoritmen "TwoWay Time Transfer"för att rätta till de timing fel som uppstår mellan systemens separata klockor.I sammanfattningen så jämnförs uppkommna resultat med att ha systemens tid från GPS.
25

Simulace vysokorychlostních optických datových přenosů / Simulation of high-speed optical data transmissions

Chaloupka, Tomáš January 2019 (has links)
The aim of this master thesis is comparation of simulation tools OptSim™ and PHO- TOSS which are used to create simulations of data traffi cs in access and metropolitan networks. The outcome of this thesis is three laboratory exercises and their theoretical bases which should explain the way of working in diff erent simulation environments to students.
26

Simulace vysokorychlostních optických datových přenosů / Simulation of high-speed optical data transmissions

Chaloupka, Tomáš January 2019 (has links)
The aim of this master thesis is comparation of simulation tools OptSim™ and PHOTOSS which are used to create simulations of data traffi cs in access and metropolitan networks. The outcome of this thesis is three laboratory exercises and their theoretical bases which should explain the way of working in diff erent simulation environments to students.
27

Offset QPSK in SISO and MIMO Environments

Dang, Xiaoyu 10 July 2009 (has links) (PDF)
We demonstrate how the performance of offset quadrature phase-shift keying (OQPSK) and its variants of Feher-patented QPSK (FQPSK) and Shaped Offset QPSK (SOQPSK) (collectively known as the ARTM Tier-1 waveforms) in single input single output (SISO) system could change with the channel fading parameters. The bit error rate expression of offset QSPK and ATRM Tier-1 waveforms over the aeronautical telemetry multipath channel has been derived. Simulations show that for the case of a single multipath ray, the BER gets worse with increasing Γ for a fixed delay, and that the BER has a quasi-periodic property for fixed Γ and increasing τ. For the case of two multipath rays, the multipath component characterized by large amplitude and small delay is the main factor of the BER degradation, while the BER is not very sensitive to the change of multipath delay. Analysis of the average bit error probability shows that a relatively high error floor at approximately 10−2 occurs for |Γ1| ≥ 0.5. When offset quadrature phase-shift keying (OQPSK) is used in multiple input multiple output (MIMO) environment, orthogonal space-time block codes can be applied to waveforms to orthogonalize a space-time coded multiple-input, multiple output link. For offset QPSK, this technique has the advantage of eliminating the I/Q interference associated with simultaneous transmission of offset QPSK waveforms. In addition, orthogonalization presents uncorrelated noise samples to the space-time trellis decoder. As a consequence, a less complex space-time decoder (relative to what would be required without orthogonalization) can be used. It is demonstrated that a concatenated system based on an orthogonal space-time block code and a trellis code, optimized for single-input, single-output fading channel, outperforms a space-time trellis code for a 2x1 system. The space-time block code orthogonalizes the channel seen by the outer code and this simplifies the computations required for decoding. The advantages of orthogonalization are achieved at the expense of rate. In the examples presented, the codes were chosen to have roughly equivalent bit error rate performance and identical code rates: the complexity was compared.
28

Systèmes communicants haut-débit et bas coûts par guide d’ondes en plastique / Plastic waveguides for high speed communications

Voineau, Florian 11 October 2018 (has links)
L’évolution actuelle de la société vers un monde de plus en plus numérique et connecté nécessite des liens de communication à la fois haut-débit et bas coûts. A cette fin, les guides d’ondes en plastique proposés ces dernières années visant les bandes de fréquences millimétriques (mm) offrent un compromis performance / coût très attractif.Profitant ainsi de larges bande-passantes de l’ordre de plusieurs gigahertz (GHz), des performances des technologies CMOS avancées aux fréquences mm mais également de tolérances d’assemblage relâchées, des systèmes de communication avec de tels guides d’ondes en plastique pourraient offrir des débits de plusieurs gigabits par seconde (Gb/s) sur des distances de plusieurs mètres de manière abordable.Dans ce travail, la conception d’un guide d’ondes en plastique est tout d’abord présentée en se basant à la fois sur des résultats théoriques et de simulation électromagnétique. Bien que les promesses de faible atténuation aient effectivement été confirmées, certaines limitations du confinement et de la robustesse aux contacts extérieurs sont également apparues. L’ajout d’une mousse protectrice est brièvement investiguée, mais une géométrie innovante de guide présentant des caractéristiques améliorées est principalement détaillée.Des thématiques « systèmes » sont ensuite explorées afin de construire un système de communication utilisant ce nouveau canal de propagation. Une architecture combinant la modulation de phase en quadrature (QPSK) et le multiplexage en fréquence est ainsi introduite. L’interface entre le circuit et le guide d’ondes a par ailleurs été identifiée comme une limitation potentielle à la bande-passante globale du système. Par conséquent, une transition très large-bande a été conçue et testée pour lever ce verrou. De même, en raison des inconvénients des techniques usuelles de démodulation de signaux mm QPSK, une topologie originale utilisant les non-linéarités des oscillateurs à injection a été développée.Enfin, la conception d’un émetteur mm en technologie silicium avancée (CMOS 28 nmFD-SOI) est décrite. Les contributions majeures incluent l’introduction de coupleurs hybrides intégrés à haute-performance ainsi que la réalisation d’un circuit de synchronisation. Celui-ci présente une large plage de capture et permet un fonctionnement à faible bruit de phase lorsque le système est verrouillé sur la cinquième harmonique du signal de référence. Des mesures sur signaux modulés ont également permis de mettre en évidence la capacité de l’émetteur à transmettre des débits très élevés de plusieurs Gb/s. / In a world willfully transitioning to the Digital Age, the thirst for connectivity demands high-speed communication links at low cost. In this context, affordable plastic waveguides have been proposed as a disruptive propagation channel in the millimeter-wave (mmW) range. Benefiting from multi gigahertz (GHz) bandwidths and mmW capabilities of advanced CMOS technologies as well as relaxed assembly tolerances requirements, cost-effective communication systems based on plastic waveguides could offer multi gigabits per second (Gb/s) data rates over several meters distances.In this work, the design of plastic waveguide channels is first discussed using both a theoretical approach and Electromagnetic (EM) simulations. Although low attenuation promises have been confirmed, some limitations are also highlighted, especially as regards confinement ability and robustness to external contacts. Solutions involving foam coating are briefly investigated and an innovative plastic waveguide design demonstrating improved characteristics is introduced.System-level topics are then explored in order to build a communication system using the previously presented channel. A new architecture, which combines Quadrature Phase Shift Keying (QPSK) and frequency multiplexing, is found to be much more suitable. The transition from the circuit to the plastic waveguide has also been identified as a potential bandwidth bottleneck. Consequently, a wideband microstrip to WR-12 transition has been designed. Another limitation concerning the demodulation of QPSK mmW signals is investigated and an original topology using the non-linearities of Injection Locked Oscillators (ILO) has been developed.Finally, the design of a mmW transmitter in an advanced silicon technology node (CMOS 28 nm FD-SOI) is described. Major contributions include the introduction of high-performance integrated hybrid couplers and the realization of a wide locking range synchronization circuit enabling low phase-noise operation when locked on the fifth harmonic of a reference signal. Measurements on modulated signals have validated the transmitter high data-rate capability of several Gb/s.
29

100 Gbps coherent MB-OFDM for long-haul WDM optical transmission / Transmission optique longue distance avec le format MB-OFDM cohérent à 100 Gbps

Karaki, Julie 12 April 2013 (has links)
Aujourd'hui, le format « Quadrature Phase Shift Keying » avec multiplexage de polarisation (DP-QPSK) opérant à 100 Gbps est devenue un standard pour la transmission WDM longue distance. Une alternative au format DP-QPSK permettant d’atteindre des débits de 100 Gbps et plus (400 G & 1Tbps) est l’ « Orthogonal Frequency Division Multiplexing » (OFDM). Mais, des interrogations subsistent quant à sa robustesse aux effets non linéaires. Dans cette thèse nous avons étudié le potentiel de la technologie OFDM pour la transmission WDM longue distance à 100 Gbps. Le traitement du signal est détaillé ainsi que la mise en œuvre du transmetteur et récepteur OFDM cohérent. Nous présentons aussi les résultats expérimentaux de la transmission obtenus dans plusieurs configurations. Dans l’une de ces configurations, le canal modulé avec le format DP-OFDM coherent (Co-DP-OFDM) est multiplexé avec 40 canaux modulés en DP-QPSK à 100 Gbps. Les canaux ont ensuite été transmis sur 1000 km de fibre G.652 sans gestion de dispersion chromatique. Dans une autre configuration, les canaux Co-DP-OFDM et Co-DP-QPSK sont combinés avec 78 canaux 10 Gbps NRZ-OOK et transmis sur 1000 km de fibre G.652 avec gestion de dispersion. Nous avons montré que le Co-DP-OFDM et Co-DP-QPSK ont des performances similaires après une transmission de 1000 km sur une ligne sans gestion de dispersion, et nous avons aussi montré que la transmission de ces formats sur une infrastructure de fibre deployée est possible à condition de réduire de 5 dB la puissance des canaux 10 Gbps NRZ-OOK par rapport aux canaux à100 Gbps. Ces résultats sont précieux pour la prochaine génération de systèmes WDM à 400 Gbps ou 1 Tbps. / Today the 100 Gbps coherent dual polarization quadrature phase shift keying (Co-DP-QPSK) is standardized as the industrial solution for long-haul WDM transmission. Another alternative format to DP-QPSK that permits also to reach a data rate of 100 Gbps and beyond is the coherent orthogonal frequency division multiplexing (OFDM) format. However a doubt exists over the ability of OFDM to be as efficient as QPSK for long-haul WDM transmission due to its supposed higher sensitivity to nonlinear effects . In this thesis, we have investigated the potential of Co-DP-OFDM for 100 Gbps WDM transport. The digital signal processing algorithms are detailed as well as the various experimental set-ups required to carry out and validate the 100 Gbps transceiver. We also present the transmission results obtained with several configurations. In one of these configurations, the 100 Gbps Co-DP-OFDM channel is multiplexed with forty 100 Gbps DP-QPSK channels and all these channels are transmitted over 1000 km of DCF-free G.652 fiber, while in another configuration, the Co-DP-OFDM and Co-DP-QPSK channels are combined with seventy eight 10 Gbps NRZ-OOK channels and transmitted over 1000 km of dispersion managed G.652 fiber line. We have demonstrated that OFDM and QPSK have nearly the same performance after a transmission over 1000 km, and also we have demonstrated that the transmission of these two formats over legacy fiber infrastructure is possible under the condition of decreasing by 5 dB the 10 Gbps NRZ-OOK channel power with respect to the 100 Gbps channels. The results presented in this thesis are very valuable when considering the next generation of 400 Gbps or 1 Tbps for WDM systems.
30

FQPSK-L: An Improved Constant Envelope Modulation Scheme for QPSK

Lee, Tong-Fu, Wang, Shih-Ho, Liu, Chia-Liang, Bao, Liu 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A new constant envelope modulation scheme and architecture for QPSK by cubic spline interpolation methods which increase spectral efficiency and power efficiency, named FQPSK-L, is presented. This modulation technique is an extension of the Feher Quadrature Shift Keying (FQPSK) patented technologies, see Ref [1]. Being a constant envelope modulation, FQPSK-L can operate with class C power amplifier without spectrum regrowth. We achieve a more compact spectrum with comparable bit error rate performance. For example, FQPSK-L is about 20% more spectral efficient than GMSK BTb=0.3 from 40 to 70 dB attenuation point. Moreover, FQPSK-L intrinsically has spikes at fc ± 0.5fb, fc ± 1.0fb, fc ± 1.5fb, ... which are useful for carrier recovery, symbol time recovery and fading compensation. In Rayleigh fading channel, FQPSK-L outperform GMSK BTb=0.3 by 0.8 dB. FQPSK-L is an excellent scheme for wireless and satellite communications which require high spectral and power efficiency.

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