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Tesi sul tema "Digital communications"
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1
Sen, Cem. "Digital communications jamming". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA383913.
Testo completoAbstract (sommario):
Thesis (M.S. in Systems Engineering) Naval Postgraduate School, Sept. 2000.Thesis advisor(s): Smith, Rasler W.; Lebaric, Jovan. Includes bibliographical references (p. 137-139). Also available online.
2
Michaels, Alan Jason. "Digital chaotic communications". Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34849.
Testo completoAbstract (sommario):
This dissertation provides the conceptual development, modeling and simulation, physical
implementation, and measured hardware results for a practicable digital coherent chaotic
communication system. Such systems are highly desirable for robust communications due to
the maximal entropy signal characteristics that satisfy Shannon's ideal noise-like waveform
and provide optimal data transmission across a flat communications channel. At the core of
the coherent chaotic communications system is a fully digital chaotic circuit, providing an
efficiently controllable mechanism that overcomes the traditional bottleneck of chaotic circuit
state synchronization. The analytical, simulation, and hardware results yield a generalization of direct sequence spread spectrum waveforms, that can be further extended to create a new class of maximal entropy waveforms suitable for optimized channel performance, maximal entropy transmission of chaotically spread amplitude modulated data constellations, and
permission-based multiple access systems.
3
Jiang, Xiaofeng. "Multipoint digital video communications". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239548.
Testo completo
4
Tsai, Tsung-Heng. "Time-interleaved analog-to-digital converters for digital communications /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
Testo completo
5
Schmelzer, Raymond Matthew. "Practical Wired Digital Communications Link Analysis". PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3143.
Testo completoAbstract (sommario):
This thesis deals with the analysis of a Wired High Speed Serial Data Link (PAM2) which is commonly used throughout the data-communications and tele-communications industry. The goal of this study is to build a scalable simulation tool using Matlab that ultimately uses Receiver Bit Error Ratio (BER) as the metric for data link health. This study is also designed to aid in link specification development.
The Matlab and theoretical development is broken up into three sections being Transmitter (TX), Channel (Hs) and Receiver (RX). Realistic noise impairments can be added to each section along the signal path creating signal stresses commonly seen in data center applications. The TX function is designed to create random and periodic timing jitter, voltage noise and deterministic pre-distortion filtering effects. For the channel response s-parameters are used as the model result for many commonly seen channel loss and reflection scenarios. The RX model uses signal to noise ratio and vertical eye margin to determine the equalized link BER.
The study results show many tradeoffs between noises, RX Equalizer, RX gain and RX BER. The simulation results also reveal that there is no closed form solution for converging the modern closed-eye PAM2 detector.
6
Talal, Mohammed. "Modem design for digital satellite communications". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/7442.
Testo completoAbstract (sommario):
The thesis is concerned with the design of a phase-shift keying system for a digital modem, operating over a satellite link. Computer simulation tests and theoretical analyses are used to assess the proposed design. The optimum design of both transmitter and receiver filters for the system to be used in the modem are discussed. Sinusoidal roll-off spectrum with different roll-off factor and optimum truncation lengths of the sample impulse response are designed for the proposed scheme to approximate to the theoretical ideal. It has used an EF bandpass filter to band limit the modulated signal, which forms part of the satellite channel modelling. The high power amplifier (HPA) at the earth station has been used in the satellite channel modelling due to its effect in introducing nonlinear AMAM and AM-PM conversion effects and distortion on the transmitted signal from the earth station. The satellite transponder is assumed to be operating in a linear mode. Different phase-shift keying signals such as differentially encoded quaternary phase-shift keying (DEQPSK), offset quaternary phase-shift keying (OQPSK) and convolutionally encoded 8PSK (CE8PSK) signals are analysed and discussed in the thesis, when the high power amplifier (HPA) at the earth station is operating in a nonlinear mode. Convolutional encoding is discussed when applied to the system used in the modem, and a Viterbi -algorithm decoder at the receiver has been used, for CE8PSK signals for a nonlinear satellite channel. A method of feed-forward synchronisation scheme is designed for carrier recovery in CE8PSK receiver. The thesis describes a method of baseband linearizing the baseband signal in order to reduce the nonlinear effects caused by the HPA at the earth station. The scheme which compensates for the nonlinear effects of the HPA by predistorting the baseband signal prior to modulation as opposed to correcting the distortion after modulation, thus reducing the effects of nonlinear distortion introduced by the HPA. The results of the improvement are presented. The advanced technology of digital signal processors (DSPs) has been used in the implementation of the demodulation and digital filtering parts of the modem replacing large parts of conventional circuits. The Viterbi-algorithm decoder for CE8PSK signals has been implemented using a digital signal processor chip, giving excellent performance and is a cost effective and easy way for future developments and any modifications, The results showed that, by using the various studied techniques, as well as the implementation of digital signal processor chip in parts of the modem, a potentially more cost effective modem can be obtained.
7
Waegemans, R. "Digital electronic predistortion for optical communications". Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20007/.
Testo completoAbstract (sommario):
The distortion of optical signals has long been an issue limiting the performance of communication systems. With the increase of transmission speeds the effects of distortion are becoming more prominent. Because of this, the use of methods known from digital signal processing (DSP) are being introduced to compensate for them. Applying DSP to improve optical signals has been limited by a discrepancy in digital signal processing speeds and optical transmission speeds. However high speed Field Programmable Gate Arrays (FPGA) which are sufficiently fast have now become available making DSP experiments without costly ASIC implementation possible for optical transmission experiments. This thesis focuses on Look Up Table (LUT) based digital Electronic Predistortion (EPD) for optical transmission. Because it is only one out of many possible implementations of EPD, it has to be placed in context with other EPD techniques and other distortion combating techniques in general, especially since it is possible to combine the different techniques. Building an actual transmitter means that compromises and decisions have to be made in the design and implementation of an EPD based system. These are based on balancing the desire to achieve optimal performance with technological and economic limitations. This is partly done using optical simulations to asses the performance. This thesis describes a novel experimental transmitter that has been built as part of this research applying LUT based EPD to an optical signal. The experimental transmitter consists of a digital design (using a hardware description language) for a pair of FPGAs and an analogue optical/electronic setup including two standard DAC integrated circuits. The DSP in the transmitter compensated for both chromatic dispersion and self phase modulation. We achieved transmission of 10.7 Gb/s non-return-to-zero (NRZ) signals with a +4 dBm launch power over 450 km keeping the required optical-signal-to-noise-ratio (OSNR) for a bit-error-rate of 2x10^{-3} below 11 dB. In doing so we showed experimentally, for the first time, that nonlinear effects can be compensated with this approach and that the combination of FPGA-DAC is a viable approach for an experimental setup.
8
Poirrier, Julien. "Electronic Mitigation of Polarization Mode Dispersion". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/34469.
Testo completoAbstract (sommario):
Polarization Mode Dispersion induces polarization dependent propagation. Consequently it generates a multiple imaging of the light pulse carrying the information. Its first order appears as a dual path fading channel of Maxwellian statistics. It results in harmful impairments that prevent the upgrade and installation of high bit-rate systems. The random process PMD exhibits a strong frequency dependence, so that its amelioration requires channel by channel, non-linear, adaptive mitigation. Electronic mitigation appears as a very attractive solution to overcome the limit set by the PMD.
Consequently, we considered the implementation of these solutions at the receiver in the electrical domain. We verified that these linear and non-linear equalization techniques can greatly reduce the power penalty due to PMD. Equalization's performance depends highly on the type of systems considered. For the two main types of systems: thermal noise limited systems and systems exhibiting ASE (systems using optical amplifiers), we demonstrated and quantified the induced improvement (measured as power penalty reduction). The most sophisticated technique that we considered (NLC+FDE) handles any kind of first order PMD within a 4 dB margin in the thermal noise limit. This extended to a 11 dB margin in the presence of ASE. This comes from the limitation set by the signal dependence of the noise. In fact, these DSP techniques do a better job at reducing very high penalty. Consequently, for a power and ISI limited link, it may be required to associate to electronic solutions optical compensation in order to reach acceptable performance. On the other hand, for links having large power margin or exhibiting reasonable PMD, electronic techniques appear as an easy, inexpensive and convenient solution.
We derived in this work the bounds to NLC performance in the presence of ASE. Therefore, we extended the usual results of the thermal noise limit to the particular case of signal dependent noise. We also made clear that optical systems, because of their noise specificities can not be studied or designed as others links. Notions such as eye opening, SNR and ISI need to be carefully defined and adapted to this case.
We have provided in this work PMD dependent power penalty map for known systems. Given the link's statistics and characteristics, one can determine, following our structure, which mitigation techniques allow upgrade.Master of Science
9
Rockliff, Simon C. "Frequency hopping techniques for digital mobile radio /". Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phr683.pdf.
Testo completo
10
Lahey, Michael. "Soft control| Television's relationship to digital micromedia". Thesis, Indiana University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3607011.
Testo completoAbstract (sommario):
This dissertation explores the role soft control plays in the relationship between the television industry and short forms of digital media. Following James Beniger and Tizianna Terranova, I define soft control as the purposive movement by the television industry towards shaping audience attention toward predetermined goals through a range of interactions where development happens somewhat autonomously, while being interjected with commands over time. I define such things as media environment design, branding, and data collection as soft control practices. I focus on television as a way to understand how an industry historically patterned around more rigid forms of audience control deals with a digital media environment often cited for its lack of control features. And while there is already a robust discussion on the shifting strategies for the online distribution of shows, there is less of a focus on the increasing importance of shorter forms of digital media to the everyday operation of the television industry. Shorter forms of media include digitally circulated short videos, songs, casual digital games, and even social media, which is itself a platform for the distribution of shorter forms of media. I refer to all these forms of short media as "micromedia" and focus my interest on how various television companies are dealing with media environments saturated with it.
To do this I look at, for instance, how television companies use the data available on Twitter and appropriate the user-generated content of audiences, as well as how standard digital communication interfaces are utilized to more easily retrofit previous audience retention practices into new digital environments. Through the investigation of how television creates and appropriates micromedia as a way to reconfigure practices into the everyday lives of participatory audiences, I argue that we can see soft control elements at work in structuring the industry-audience relationship. These soft control features call into question the emancipatory role attributed to participatory audiences and digital technologies alike. If we think about media forms in their specific contexts, making sure to focus on their intermedial connections and their materiality, we can complicate ideas about what the categories of audience or industrial control mean.
11
Haj, Shir Mohammadi Atousa. "Application of Turbo-Codes in Digital Communications". Thesis, University of Waterloo, 2001. http://hdl.handle.net/10012/773.
Testo completoAbstract (sommario):
This thesis aims at providing results and insight towards the application of turbo-codes in digital communication systems, mainly in three parts. The first part considers systems of combined turbo-code and modulation. This section follows the pragmatic approach of the first proposed such system. It is shown that by optimizing the labeling method and/or modifying the puncturing pattern, improvements of more than 0. 5 dB insignal to noise ratio (SNR) are achieved at no extra cost of energy, complexity, or delay. Conventional turbo-codes with binary signaling divide the bit energy equally among the transmitted turbo-encoder output bits. The second part of this thesis proposes a turbo-code scheme with unequal power allocation to the encoder output bits. It is shown, both theoretically and by simulation, that by optimizing the power allocated to the systematic and parity check bits, improvements of around 0. 5 dB can be achieved over the conventional turbo-coding scheme. The third part of this thesis tackles the question of ``the sensitivity of the turbo-code performance towards the choice of the interleaver'', which was brought up since the early studies of these codes. This is the first theoretical approach taken towards this subject. The variance of the bound is evaluated. It is proven that the ratio of the standard deviation over the mean of the bound is asymptotically constant (for large interleaverlength, N), decreases with N, and increases with SNR. The distribution of the bound is also computationally developed. It is shown that as SNR increases, a very low percentage of the interleavers deviate quite significantly from the average bound but the majority of the random interleavers result in performances very close to the average. The contributions of input words of different weights in the variance of performance bound are also evaluated. Results show that these contributions vary significantly with SNR and N. These observations are important when developing interleaver design algorithms.
12
Borah, Deva Kanta, e dborah@nmsu edu. "Detection and Estimation in Digital Wireless Communications". The Australian National University. Research School of Information Sciences and Engineering, 2000. http://thesis.anu.edu.au./public/adt-ANU20050506.015503.
Testo completoAbstract (sommario):
This thesis investigates reliable data communication techniques for wireless channels. The problem of data detection at the receiver is considered and several novel detectors and parameter estimators are presented.¶
It is shown that by using a noise-limiting prefilter, with a spectral support at least equal to the signal part of the received signal, and sampling its output at the Nyquist rate, a set of sufficient statistics for maximum likelihood sequence detection (MLSD) is obtained.¶
Observing that the time-variations of the multipaths in a wireless channel are
bandlimited, channel taps are closely approximated as polynomials in time. Using this representation, detection techniques for frequency-flat and frequency-selective channels are obtained. The proposed polynomial predictor based sequence
detector (PPSD) for frequency-flat channels is similar in structure to the MLSD that employs channel prediction. However, the PPSD uses {\em a priori} known
polynomial based predictor taps. It is observed that the PPSD, without any explicit knowledge of the channel autocovariance, performs close to the Innovations based MLSD.¶
New techniques for frequency-selective channel estimation are presented. They are based on a rectangular windowed least squares algorithm, and they employ a
polynomial model of the channel taps. A recursive form of the least squares algorithm with orthonormal polynomial basis vectors is developed. Given the appropriate window size and polynomial model order, the proposed method outperforms the conventional least mean squares (LMS) and the exponentially weighted recursive least squares (EW-RLS) algorithms. Novel algorithms are proposed to obtain near optimal window size and polynomial model order.¶
The improved channel estimation techniques developed for frequency-selective channels are incorporated into sliding window and fixed block channel estimators. The sliding window estimator uses received samples over a time window to calculate the channel taps. Every symbol period, the window is moved along another symbol period and a new estimate is calculated. A fixed block estimator uses all
received samples to estimate the channel taps throughout a data packet, all at once. In fast fading and at a high signal-to-noise ratio (SNR), both techniques
outperform the MLSD receivers which employ the LMS algorithm for channel estimation.¶
An adaptive multiuser detector, optimal in the weighted least squares (WLS) sense, is derived for direct sequence code division multiple access (DS-CDMA) systems. In a multicellular configuration, this detector jointly detects the users within the cell of interest, while suppressing the intercell interferers in a WLS sense. In the absence of intercell interferers, the detector reduces to the well-known multiuser MLSD structure that employs a bank of matched filters. The relationship between the proposed detector and a centralized decision feedback detector is derived. The effects of narrowband interference are investigated and compared with the multiuser MLSD.¶
Since in a fast time-varying channel, the LMS or the EW-RLS algorithms cannot track the channel variations effectively, the receiver structures proposed for single user communications are extended to multiuser DS-CDMA systems. The fractionally-chip-spaced channel taps of the convolution of the chip waveform with the multipath channel are estimated. Linear equalizer, decision feedback equalizer
and MLSDs are studied, and under fast fading, as the SNR increases, they are found to outperform the LMS based adaptive minimum mean squared error (MMSE) linear receivers.
13
Weliwitegoda, Dhineth Chamara. "Equaliser performance optimisation for digital communications systems". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417191.
Testo completo
14
Sari, Hayri. "Underwater acoustic voice communications using digital techniques". Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/13854.
Testo completoAbstract (sommario):
An underwater acoustic voice communications system can provide a vital communication link between divers and surface supervisors. There are numerous situations in which a communication system is essential. In the event of an emergency, a diver's life may depend on fast and effective action at the surface. The design and implementation of a digital underwater acoustic voice communication system using a digital signal processor (DSP) is described. The use of a DSP enables the adoption of computationally complex speech signal processing algorithms and the transmission and reception of digital data through an underwater acoustic channel. The system is capable of operating in both transmitting and receiving modes by using a mode selection scheme. During the transmission mode, by using linear predictive coding (LPC), the speech signal is compressed whilst transmitting the compressed data in digital pulse position modulation (DPPM) format at a transmission rate of 2400 bps. At the receiver, a maximum energy detection technique is employed to identify the pulse position, enabling correct data decoding which in turn allows the speech signal to be reconstructed. The advantage of the system is to introduce advances in digital technology to underwater acoustic voice communications and update the present analogue systems employing AM and SSB modulation. Since the DSP-based system is designed in modular sections, the hardware and software can be modified if the performance of the system is inadequate. The communication system was tested successfully in a large indoor tank to simulate the effect of a short and very shallow underwater channel with severe multipath reverberation. The other objective of this study was to improve the quality of the transmitted speech signal. When the system is used by SCUBA divers, the speech signal is produced in a mask with a high pressure air environment, and bubble and breathing noise affect the speech clarity. Breathing noise is cancelled by implementing a combination of zero crossing rate and energy detection. In order to cancel bubble noise spectral subtraction and adaptive noise cancelling algorithms were simulated; the latter was found to be superior and was adopted for the current system.
15
Punskaya, Elena. "Sequential Monte Carlo methods for digital communications". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620013.
Testo completo
16
Vrcelj, Bojan Vaidyanathan P. P. "Multirate signal processing concepts in digital communications /". Diss., Pasadena, Calif. : California Institute of Technology, 2004. http://resolver.caltech.edu/CaltechETD:etd-06252003-115639.
Testo completo
17
Musonda, Evaristo. "Synthesis of filters for digital wireless communications". Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11750/.
Testo completoAbstract (sommario):
Firstly, a new synthesis method for the generation of the generalized Chebyshev characteristic polynomials has been presented. The general characteristic function is generated by a linear combination of Chebyshev basis characteristic functions. The basis functions for different filtering functions may easily be determined based on the number and position of reflection and transmission zeros. These basis functions enable direct synthesis of both lumped and distributed filter networks. Different filter functions including but not limited to low-pass, bandpass and dual bandpass filters, have been synthesised to demonstrate the general application of the synthesis method. Secondly, a new method for the design of a new class of distributed low-pass filter has been presented that enables exact realisation of the series short circuited transmission lines which are normally approximated via unit elements in other filter realisations. The filters are based on parallel coupled high impedance transmission lines which are terminated at one end in open-circuited stubs. The approach enables realisation of both finite and quarter-wave frequency transmission zeros hence giving improved stopband performance. A complete design is presented and the fabricated low-pass filter demonstrates excellent performance in good agreement with theory. Finally, design techniques for microwave bandpass filters using re-entrant resonators are presented. The key feature is that each re-entrant resonator in the filter generates a passband resonance and a finite frequency transmission zero, above the passband. Thus an Nth degree filter can have N finite frequency transmission zeros with a simple physical realization. A new synthesis technique for pseudo-elliptic low-pass filters suitable for designing re-entrant bandpass filter has also been show-cased. A physically symmetrical 5 pole re-entrant bandpass prototype filter with 5 transmission zeros above the passband was designed and fabricated. Measured results showed good correspondence with theories.
18
Morris, Jeremy. "Understanding the digital music commodity". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95108.
Testo completoAbstract (sommario):
This dissertation concentrates on the changing form of the music commodity over the last two decades. Specifically, it traces the transition from music on compact discs to music as a digital file on computers/mobile devices and the economic, industrial, aesthetic and cultural consequences this shift has for how we produce, present, and consume music. As computers became viable sources for the playback of popular music in the 1980s and 1990s, the roots of the digital music commodity took hold. Stripped of many of their previous attributes (i.e. album art, compressed sound, packaging, etc.), recordings as digital files were initially decontextualized commodities. On computers, music underwent an interface-lift, gradually getting redressed with new features (i.e. metadata, interfaces, digital packaging). This dissertation focuses on five technologies Winamp, Metadata, Napster, iTunes and Cloud Computing that were key to rehabilitating the music commodity in its digital environments. These technologies and the cultural practices that accompanied them gave music new paratexts and micromaterials that ultimately constituted the digital music commodity. Through case studies, generative archival research, and descriptive analysis, this study makes methodological and intellectual contributions to the field of communication and technology studies as well as to studies of new media and the cultural industries. By teasing out the differences between the commodity aspects of the CD and the digital file, this project offers fresh perspectives on materiality, aesthetics, labour and ownership in an era of digital goods. Digital music's fluid and ubiquitous nature seems to subvert those who seek to profit from it. But while digital music offers the potential to disrupt the traditional ways of doing business in music, it also affords new forms of control and power. This has not stopped artists, hobbyists and users from carrying out creative experiments that call into quesCette thèse de doctorat examine la transformation du produit musical au cours des deux dernières décennies. En particulier, elle illustre la transition de la musique inscrite sur disque compact en fichier numérique disponible sur ordinateurs ou appareils portables et s'intéresse aux conséquences économiques, industrielles, esthétiques et culturelles que cette transition a provoquées en regard aux manières avec lesquelles on produit, présente, et consomme la musique. Dès lors que les ordinateurs ont été en mesure de jouer de la musique populaire au cours des années 1980 et 1990, les bases d'un bien musical numérique ont pris racine. Dépourvue de nombre de ses anciennes caractéristiques (ex. les illustrations, l'information contextuelle, l'emballage, etc.), la musique de format de fichier numérique était, au départ, un bien décontextualisé. La musique présentée sur ordinateur est passée au travers un processus de mise à jour de l'interface marqué par l'insertion de nouvelles caractéristiques (ex. les métadonnées, les interfaces, « l'emballage » numérique). Cette thèse de doctorat focalise sur cinq technologies Winamp, les métadonnées, Napster, iTunes et l'infonuagique ayant joué un rôle central dans la réadaptation du bien musical dans son environnement numérique. Par l'entremise d'études de cas, de recherche en archive et d'a nalyses descriptives, cette étude propose une contribution méthodologique et intellectuelle aux domaines de la communication et de la technologie ainsi qu'aux études sur les nouveaux médias et les industries culturelles. En cernant les différences entre les aspects du disque compact et du fichier numérique les caractérisant comme biens, ce projet offre une nouvelle perspective sur la matérialité, l'esthétique, la main d'uvre et la propriété à l'ère des biens numériques. Bien que la musique numérique ait le potentiel de bouleverser les modèles d'affaires de l'industrie musicale
19
Monaghan, Joseph Francis. "Evaluation of digital communications using the Marine Corps Communications Architecture Analysis Model". Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23661.
Testo completoAbstract (sommario):
Approved for public release; distribution is unlimitedThe United States Marine Corps (USMC) is currently evolving to digital communications. This change has created a need for an analysis tool capable of analyzing digital architectures. Traditional communications are being supplemented, and in some cases, replaced by automated systems like the Marine Tactical Command and Control System (MTACCS) Older equipment, the PRC-77 and AN/VRC-12 family of radios, is being replaced by lighter, more efficient equipment like SINCGARS and the Digital Communications Terminal (DCT). Protocols like the Marine Tactical System (MTS) Broadcast Protocol are being implemented to orchestrate this new way of communicating. To assist in the transition, this thesis modified the Marine Corps Communications Architecture Analysis Model (MCCAAM) so it could measure the impact of changing from voice to digital communications. The Fidelity Enhancement Process (FEP) , a comprehensive methodology for model upgrades, was used to systematically modify the model. The model's usefulness is demonstrated in an analysis example by comparing three separate partially digital communications architectures.
20
Richardson, Iain Edward Garden. "Video coding for reliable communications". Thesis, Robert Gordon University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287763.
Testo completo
21
D'Aiello, Alan. "Communicating in the local : digital communications technology use in Brighton's gay pub scene". Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/61485/.
Testo completoAbstract (sommario):
This thesis is an analysis of the use and impact of digital communication technology (DCT) in the Gay pub scene in the Kemptown neighborhood of Brighton, East Sussex, UK. The purpose of this work is twofold: to create a snapshot record of the everyday activities in pub spaces at a particular point in the neighborhood's history from the point of view of an American gay man, and to develop an understanding of the impact of digital communications technology (DCT) on the activities in these spaces by investigating the impact of DCT on the idea of 'gay space'. This analysis is broken down into three distinct areas of enquiry: the implementation of DCT in pub spaces by the landlords/owners of the space, the use of DCT by the patrons of these spaces, and an analysis of those spaces that have not directly engaged DCT, neither implementing DCT as a feature of the location, nor limiting its use within the space. This thesis utilizes participant observations, auto ethnographic observations, and interviews made over a period of two years and engages with the theoretical arguments around gay space: its history both within the broad context of UK history, and also with Brighton's special historical status as a gay centre within the UK; its current uses; and the potential for its evolution. This investigation of hof DCT is impacting on gay space also questions to what extent 'gay space' is maintaining a sense of physicality and to what extent an extension of DCT-enabled virtual spaces is altering our relationship to these spaces. The work examines the notion of nostalgia, ownership, and control of space and attempts through its focus on several locations in Kemptown to catalogue the many changes in structure, clientele, locale, and business success that these spaces have gone through in a fairly short time and to determine to what extent the use and influences of DCT has driven these changes. The project includes interviews with landlords and patrons of eight current and former venues in Kemptown and encompasses a group of three key participants in detail through a series of scheduled interviews and group discussions conducted during the duration of the project, and details their particular relationships to the spaces in Kemptown as well as their uses of DCT in these spaces. These participants act as a focal point for the research by helping to create a frame of reference within the work balancing the author's auto ethnographic analysis with the point of view of a local Brighton gay male, as well as contribute to and support the broader narrative of the vicissitudes of smaller pub venues by helping to highlight the historical changes in the pubs being looked at. The specific questions that this research sets out to answer are: • How is digital communicative technology (DCT) affecting self defined gay spaces in Kemptown, Brighton? • How is DCT affecting the behaviours of the patrons and owners/operators in these spaces? • How are the owners/operators of these spaces adapting to DCT? Is there evidence of owners/operators conforming to Winston's theory on the suppression of disruptive potential of new and emerging media technology (1995)? • What are the implications, challenges and opportunities presented to those spaces which are not engaging with DCT in their spaces? • Are “gay spaces” in Kemptown still relevant with the intersection of digital and physical spaces? Do these spaces meet the same requirements as they have in the past? Does DCT have the ability on its own to maintain the relevance of a venue on its own when faced off against other pressures (such as commercial or demographic pressure)? The conclusions reached in this thesis draw attention to the potential for DCT: • Acting as a form of disruptive potential of new communication technologies (Winston, 1995). • The concerns that DCT is suppressing interpersonal communications in favor of mediated discourse (Turkle, 2011, 2012, 2015). • That automobility is creating a privatization of pub spaces, along with the creation of ‘non-places' (Bull, 2004) However, in the author's analysis, there is evidence of cohabitation, and adaptation towards DCT which is reminiscent of Winston's theory of the suppression of disruptive potential of emerging communication technology, as well as a resistance response with nostalgic overtones. The conclusions are also grounded in the larger narratives of pub culture within the UK and note the challenging culture that smaller, brewer-tied and non-tied gay venues have within these changing demographics and cultural acceptance of homosexuality in general. This research adds to the broader field of research into the adaptation of communications technology by drawing attention to the effects of DCT on both spaces and their users and also highlights their effects on a subculture.
22
Rugbeer, Hemduth. "Communicating by ordering electrons : the development of electronic communication as part of a secondary school Communication Science curriculum in the Language, Literacy and Communication learning area". Thesis, University of Zululand, 2001. http://hdl.handle.net/10530/314.
Testo completoAbstract (sommario):
A thesis submitted in fulfilment of the requirements for the Degree of MA in Communication Science, University of Zululand, 2001.In this thesis I focus on the introduction of Electronic Cornmunication as part of an envisaged Communication Science curriculum in the Language, Literacy and Communication Learning area of the Further Education and Training band. In the course of my thesis I will show that the requisite elements of verbal and written cornmunication are dispersed throughout the Language, Literacy and Communication learning area in the General Education and Training band, and that they can be utilised as basis for formally introducing Communication Science, as a subject in the Language, literacy and Communication learning area in the Further Education and Train¬ing band. I also show that electronic communication will form a crucial area of study in such a Communication Science curriculum. I argue that due to the diversity of cultures in South Africa, cross-cultural cornmunication is required in such a curriculum. I also argue that by the very na¬ture of Outcomes-Based Education it is necessary to have a subject into our school curriculum that will form an interface with conceptual learning and experiential learning, that will contextu-alise language study within the more comprehensive scope of forms of human communication, and that will form an interface between the humanities and science to prevent the humanities from becoming soft options in Further Education and Training band learning programmes. To this effect I focus on the crucial role of Constructivism as integrating theory to account for vari¬ous approaches to motivational learning, the primary form of learning required in Outcomes-Based Education. I examine the principles of curriculum construction in OBE and its associated culture of learn¬ing against the backdrop of the theory of Situated Cognition. This presents a platform to argue the case for Electronic Communication as part of Communication Science in the Further Edu¬cation and Training band curricula in South African schools.
National Research Foundation
23
Villares, Piera Javier. "Sample Covariance Based Parameter Estimation For Digital Communications". Doctoral thesis, Universitat Politècnica de Catalunya, 2005. http://hdl.handle.net/10803/6895.
Testo completoAbstract (sommario):
En aquesta tesi s'estudia el problema d'estimació cega de segon ordre en comunicacions digitals. En aquest camp, els símbols transmesos esdevenen paràmetres no desitjats (nuisance parameters) d'estadística no gaussiana que degraden les prestacions de l'estimador. En aquest context, l'estimador de màxima versemblança (ML) és normalment desconegut excepte si la relació senyal-soroll (SNR) és prou baixa. En aquest cas particular, l'estimador ML és una funció quadràtica del vector de dades rebudes o, equivalentment, una transformació lineal de la matriu de covariància mostral. Aquesta característica es compartida per altres estimadors importants basats en el principi de màxima versemblança com ara l'estimador ML gaussià (GML) i l'estimador ML condicional (CML). Així mateix, l'estimador MUSIC, i altres mètodes de subespai relacionats amb ell, es basen en la diagonalització de la matriu de covariància mostral. En aquest marc, l'aportació principal d'aquesta tesi és la deducció i avaluació de l'estimador òptim de segon ordre per qualsevol SNR i qualsevol distribució dels nuisance parameters.El disseny d'estimadors quadràtics en llaç obert i llaç tancat s'ha plantejat de forma unificada. Pel que fa als estimadors en llaç obert, s'han derivat els estimadors de mínim error quadràtic mig i mínima variància considerant que els paràmetres d'interès són variables aleatòries amb una distribució estadística coneguda a priori però, altrament, arbitrària. A partir d'aquest plantejament Bayesià, els estimadors en llaç tancat es poden obtenir suposant que la distribució a priori dels paràmetres és altament informativa. En aquest model de petit error, el millor estimador quadràtic no esbiaixat, anomenat BQUE, s'ha formulat sense convenir cap estadística particular pels nuisance parameters. Afegit a això, l'anàlisi de l'estimador BQUE ha permès calcular quina és la fita inferior que no pot millorar cap estimador cec que utilitzi la matriu de covariància mostral.
Probablement, el resultat principal de la tesi és la demostració de què els estimadors quadràtics són capaços d'utilitzar la informació estadística de quart ordre dels nuisance parameters. Més en concret, s'ha demostrat que tota la informació no gaussiana de les dades que els mètodes de segon ordre són capaços d'aprofitar apareix reflectida en els cumulants de quart ordre dels nuisance parameters. De fet, aquesta informació de quart ordre esdevé rellevant si el mòdul dels nuisance parameters és constant i la SNR és moderada o alta. En aquestes condicions, es demostra que la suposició gaussiana dels nuisance parameters dóna lloc a estimadors quadràtics no eficients.
Un altre resultat original que es presenta en aquesta memòria és la deducció del filtre de Kalman estès de segon ordre, anomenat QEKF. L'estudi del QEKF assenyala que els algoritmes de seguiment (trackers) de segon ordre poden millorar simultàniament les seves prestacions d'adquisició i seguiment si la informació estadística de quart ordre dels nuisance parameters es té en compte. Una vegada més, aquesta millora és significativa si els nuisance parameters tenen mòdul constant i la SNR és prou alta.
Finalment, la teoria dels estimadors quadràtics plantejada s'ha aplicat en alguns problemes d'estimació clàssics en l'àmbit de les comunicacions digitals com ara la sincronització digital no assistida per dades, el problema de l'estimació del temps d'arribada en entorns amb propagació multicamí, la identificació cega de la resposta impulsional del canal i, per últim, l'estimació de l'angle d'arribada en sistemes de comunicacions mòbils amb múltiples antenes. Per cadascuna d'aquestes aplicacions, s'ha realitzat un anàlisi intensiu, tant numèric com asimptòtic, de les prestacions que es poden aconseguir amb mètodes d'estimació de segon ordre.
This thesis deals with the problem of blind second-order estimation in digital communications. In this field, the transmitted symbols appear as non-Gaussian nuisance parameters degrading the estimator performance. In this context, the Maximum Likelihood (ML) estimator is generally unknown unless the signal-to-noise (SNR) is very low. In this particular case, if the SNR is asymptotically low, the ML solution is quadratic in the received data or, equivalently, linear in the sample covariance matrix. This significant feature is shared by other important ML-based estimators such as, for example, the Gaussian and Conditional ML estimators. Likewise, MUSIC and other related subspace methods are based on the eigendecomposition of the sample covariance matrix. From this background, the main contribution of this thesis is the deduction and evaluation of the optimal second-order parameter estimator for any SNR and any distribution of the nuisance parameters.
A unified framework is provided for the design of open- and closed-loop second-order estimators. In the first case, the minimum mean square error and minimum variance second-order estimators are deduced considering that the wanted parameters are random variables of known but arbitrary prior distribution. From this Bayesian approach, closed-loop estimators are derived by imposing an asymptotically informative prior. In this small-error scenario, the best quadratic unbiased estimator (BQUE) is obtained without adopting any assumption about the statistics of the nuisance parameters. In addition, the BQUE analysis yields the lower bound on the performance of any blind estimator based on the sample covariance matrix.
Probably, the main result in this thesis is the proof that quadratic estimators are able to exploit the fourth-order statistical information about the nuisance parameters. Specifically, the nuisance parameters fourth-order cumulants are shown to provide all the non-Gaussian information that is utilizable for second-order estimation. This fourth-order information becomes relevant in case of constant modulus nuisance parameters and medium-to-high SNRs. In this situation, the Gaussian assumption is proved to yield inefficient second-order estimates.
Another original result in this thesis is the deduction of the quadratic extended Kalman filter (QEKF). The QEKF study concludes that second-order trackers can improve simultaneously the acquisition and steady-state performance if the fourth-order statistical information about the nuisance parameters is taken into account. Once again, this improvement is significant in case of constant modulus nuisance parameters and medium-to-high SNRs.
Finally, the proposed second-order estimation theory is applied to some classical estimation problems in the field of digital communications such as non-data-aided digital synchronization, the related problem of time-of-arrival estimation in multipath channels, blind channel impulse response identification, and direction-of-arrival estimation in mobile multi-antenna communication systems. In these applications, an intensive asymptotic and numerical analysis is carried out in order to evaluate the ultimate limits of second-order estimation.
24
Shiu, Wan Yi. "Noniterative digital beamforming in CDMA cellular communications systems". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36081.pdf.
Testo completo
25
Vigneron, Philip J. "Interference in single carrier and multicarrier digital communications". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/NQ54439.pdf.
Testo completo
26
Clarke, Richard. "On Synchronisation Issues in Wireless Mobile Digital Communications". Thesis, University of Canterbury. School of Engineering, 2002. http://hdl.handle.net/10092/1156.
Testo completoAbstract (sommario):
Symbol timing recovery is an important function of any digital receiver. In the wireless mobile data field the task of establishing accurate symbol timing at the receiver is complicated by the time varying channel. This time varying channel also makes the use of coherent modulation schemes significantly more difficult. This is one of the major reasons that almost all existing mobile wireless digital standards utilise some form of differential modulation and detection. This thesis takes a primarily practical approach to the investigation of timing and phase estimation problems. The main focus of the work is on the comparison of three existing all digital timing synchronisation algorithms, two of which were originally designed for the AWGN channel, and the third was designed from ML principles for the Rayleigh fading channel. In order to test these sub-systems in the wider context of receiver performance, a pilot symbol assisted (PSAM) receiver was simulated to compare the effects of the different synchronisers on receiver steady state performance. Finally, because the real time implementation aspects of software radio are of considerable interest to the author, some attempt has been made to migrate the MATLAB synchronisation simulations to a real time DSP platform, specifically the TMS320C6701 Texas Instruments floating point device.
27
Zenteno, Efrain. "Digital Compensation Techniques for Transmitters inWireless Communications Networks". Doctoral thesis, KTH, Signalbehandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-167971.
Testo completoAbstract (sommario):
Since they appeared, wireless technologies have deeply transformed our society. Today, wireless internet access and other wireless applications demandincreasingly more traffic. However, the continuous traffic increase can be unbearableand requires rethinking and redesigning the wireless technologies inmany different aspects. Aiming to respond to the increasing needs of wirelesstraffic, we are witnessing a rapidly evolving wireless technology scenario.This thesis addresses various aspects of the transmitters used in wireless communications.Transmitters present several hardware (HW) impairments thatcreate distortions, polluting the radio spectrum and decreasing the achievabletraffic in the network. Digital platforms are now flexible, robust and cheapenough to enable compensation of HW impairments at the digital base-bandsignal. This has been coined as ’dirty radio’. Dirty radio is expected in future transmitters where HW impairments may arise to reduce transmitter cost or to enhance power efficiency. This thesis covers the software (SW) compensation schemes of dirty radio developed for wireless transmitters. As describedin the thesis, these schemes can be further enhanced with knowledge of thespecific signal transmission or scenarios, e.g., developing cognitive digital compensationschemes. This can be valuable in today’s rapidly evolving scenarioswhere multiple signals may co-exist, sharing the resources at the same radiofrequency (RF) front-end. In the first part, this thesis focuses on the instrumentation challenges andHWimpairments encountered at the transmitter. A synthetic instrument (SI)that performs network analysis is designed to suit the instrumentation needs.Furthermore, how to perform nonlinear network analysis using the developedinstrument is discussed. Two transmitter HW impairments are studied: themeasurement noise and the load impedance mismatch at the transmitter, asis their coupling with the state-of-the-art digital compensation techniques.These two studied impairments are inherent to measurement systems and areexpected in future wireless transmitters. In the second part, the thesis surveys the area of behavioral modeling and digital compensation techniques for wireless transmitters. Emphasis is placed on low computational complexity techniques. The low complexity is motivated by a predicted increase in the number of transmitters deployed in the network, from base stations (BS), access points and hand-held devices. A modeling methodology is developed that allows modeling transmitters to achieve both reduced computational complexity and low modeling error. Finally, the thesis discusses the emerging architectures of multi-channel transmittersand describes their digital compensation techniques. It revises the MIMOVolterra series formulation to address the general modeling problem anddrafts possible solutions to tackle its dimensionality. In the framework of multi-channel transmitters, a technique to compensate nonlinear multi-carrier satellite transponders is presented. This technique is cognitive because it uses the frequency link planning and the pulse-shaping filters of the individual carriers. This technique shows enhanced compensation ability at reduced computational complexity compared to the state-of-the-art techniques and enables the efficient operation of satellite transponders.QC 20150526
28
Wren, Timothy J. "Orthogonal chaotic vector shift keying in digital communications". Thesis, University of Sussex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442424.
Testo completo
29
Onochie, Francis Chukwuemeka. "Digital data communications over voice-band telephone channels". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47598.
Testo completo
30
Millar, D. S. "Digital signal processing for coherent optical fibre communications". Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1333248/.
Testo completoAbstract (sommario):
In this thesis investigations were performed into digital signal processing (DSP) algorithms for coherent optical fibre transmission systems, which provide improved performance with respect to conventional systems and algorithms. Firstly, an overview of coherent detection and coherent transmission systems is given. Experimental investigations were then performed into the performance of digital backpropagation for mitigating fibre nonlinearities in a dual-polarization quadrature phase shift keying (DP-QPSK) system over 7780 km and a dual-polarization 16- level quadrature amplitude modulation (DP-QAM16) system over 1600 km. It is noted that significant improvements in performance may be achieved for a nonlinear step-size greater than one span. An approximately exponential relationship was found between performance improvement in Q-factor and the number for required complex multipliers. DSP algorithms for polarization-switched quadrature phase shift keying (PS-QPSK) are then investigated. A novel two-part equalisation algorithm is proposed which provides singularity-free convergence and blind equalisation of PS-QPSK. This algorithm is characterised and its application to wavelength division multiplexed (WDM) transmission systems is discussed. The thesis concludes with an experimental comparison between a PS-QPSK transmission system and a conventional DP-QPSK system. For a 42.9 Gb/s WDM system, the use of PS-QPSK enabled an increase of reach of more than 30%. The resultant reach of 13,640 km was, at the time of publication, the longest transmission distance reported for 40 Gb/s transmission over an uncompensated link with standard fibre and optical amplification.
31
Rice, Michael. "IRIG-106: A Design Exercise for Digital Communications". International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/607601.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper describes a design project which combines the simulation capabilities of the Communications Tool Box in SIMULINK® with the IRIG-106 standard. The design project is part of a senior level digital communications course offered in the Department of Electrical & Computer Engineering at Brigham Young University and functions as an introduction to the Telemetering Program at BYU which is funded by the International Foundation for Telemetering.
32
Ng, Wai-Hung. "A Time-Variant Approach for Encrypted Digital Communications". International Foundation for Telemetering, 1989. http://hdl.handle.net/10150/614624.
Testo completoAbstract (sommario):
International Telemetering Conference Proceedings / October 30-November 02, 1989 / Town & Country Hotel & Convention Center, San Diego, CaliforniaTwo new approaches, a time-variant key and a random transmission rate, are introduced to strengthen the security of encrypted digital communications in which a "black-box" type of crypto-device is employed. These approaches not only further upgrade present crypto-methodology, but may also secure the system against the possibility of the cryptographic key's falling into the hands of an unauthorized listener after initial communication has begun. Therefore, communication privacy could be maintained even under the most scrutinizing post-recorded ciphertext attack.
33
Hassanien, Mohamed A. M. "Error rate performance metrics for digital communications systems". Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42497.
Testo completoAbstract (sommario):
In this thesis, novel error rate performance metrics and transmission solutions are investigated for delay limited communication systems and for co-channel interference scenarios. The following four research problems in particular were considered. The first research problem is devoted to analysis of the higher order ergodic moments of error rates for digital communication systems with time- unlimited ergodic transmissions and the statistics of the conditional error rates of digital modulations over fading channels are considered. The probability density function and the higher order moments of the conditional error rates are obtained. Non-monotonic behavior of the moments of the conditional bit error rates versus some channel model parameters is observed for a Ricean distributed channel fading amplitude at the detector input. Properties and possible applications of the second central moments are proposed. The second research problem is the non-ergodic error rate analysis and signaling design for communication systems processing a single finite length received sequence. A framework to analyze the error rate properties of non-ergodic transmissions is established. The Bayesian credible intervals are used to estimate the instantaneous bit error rate. A novel degree of ergodicity measure is introduced using the credible interval estimates to quantify the level of ergodicity of the received sequence with respect to the instantaneous bit error rate and to describe the transition of the data detector from the non-ergodic to ergodic zone of operation. The developed non-ergodic analysis is used to define adaptive forward error correction control and adaptive power control policies that can guarantee, with a given probability, the worst case instantaneous bit error rate performance of the detector in its transition fi'om the non-ergodic to ergodic zone of operation. In the third research problem, novel retransmission schemes are developed for delay-limited retransmissions. The proposed scheme relies on a reliable reverse link for the error-free feedback message delivery. Unlike the conventional automatic repeat request schemes, the proposed scheme does not require the use of cyclic redundancy check bits for error detection. In the proposed scheme, random permutations are exploited to locate the bits for retransmission in the predefined window within the packet. The retransmitted bits are combined using the maximal-ratio combining. The complexity-performance trade-offs of the proposed scheme is investigated by mathematical analysis as well as computer simulations. The bit error rate of the proposed scheme is independent of the packet length while the throughput is dependent on the packet length. Three practical techniques suitable for implementation are proposed. The performance of the proposed retransmission scheme was compared to the block repetition code corresponding to a conventional ARQ retransmission strategy. It was shown that, for the same number of retransmissions, and the same packet length, the proposed scheme always outperforms such repetition coding, and, in some scenarios, the performance improvement is found to be significant. Most of our analysis has been done for the case of AWGN channel, however, the case of a slow Rayleigh block fading channel was also investigated. The proposed scheme appears to provide the throughput and the BER reduction gains only for the medium to large SNR values. Finally, the last research problem investigates the link error rate performance with a single co-channel interference. A novel metric to assess whether the standard Gaussian approximation of a single interferer underestimates or overestimates the link bit error rate is derived. This metric is a function of the interference channel fading statistics. However, it is otherwise independent of the statistics of the desired signal. The key step in derivation of the proposed metric is to construct the standard Gaussian approximation of the interference by a non-linear transformation. A closed form expression of the metric is obtained for a Nakagami distributed interference fading amplitude. Numerical results for the case of Nakagami and lognormal distributed interference fading amplitude confirm the validity of the proposed metric. The higher moments, interval estimators and non-linear transformations were investigated to evaluate the error rate performance for different wireless communication scenarios. The synchronization channel is also used jointly with the communication link to form a transmission diversity and subsequently, to improve the error rate performance.
34
Hernandez, Jose H. "Digital communications over non-fading and fading channels". Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Sept/08Sep%5FHernandez.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2008.Thesis Advisor(s): Robertson, Clark R. "September 2008." Description based on title screen as viewed on November 5, 2008. Includes bibliographical references (p. 75). Also available in print.
35
DOVIS, Fabio. "Wavelet based design of digital multichannel communications systems". Doctoral thesis, Politecnico di Torino, 1999. http://hdl.handle.net/11583/2500808.
Testo completoAbstract (sommario):
The huge penetration of the personal communications systems
in the market is constantly presenting new challenges to the research,
aimed at satisfying people's needs and requirements for effective communication systems.
At present, the cellular telephone network is perhaps the most evident example of communication system that has had a great impact on the lives of ordinary people and, at the same time,
is the subject of interest of many researchers both at academic and
industrial level.
For the future, one of the main challenges
in telecommunications will be the provision of ubiquitous broadband tetherless integrated services to mobile users. Such a pretentious goal cannot be achieved without a continuous research facing such problems as service quality, complete mobility support, and affordable
complexity that are still open problems.
However, present telecommunication problems are not only a matter
of implementation or development of new services, exploiting a totally assessed doctrine.
In order to respond to the mobility of the users personal communication systems have to deal with the wireless communication channel whereby
mobility and non-stationarity of the propagation conditions require a stochastic description of the channel
parameters.
While this fact can be viewed as strong limitation to the development of
a solid theory whose validity can be assesed in practice,
on the other hand allows for an investigation and study of novel
communication schemes, sometimes encompassing basic aspects of digital
communications.
This thesis, is the result of a research work that has investigated one
of the basic building block of every communication systems, the modulation
scheme, and the design of the pulse shape carrying the digital
information.
We have studied the design of multichannel communication scheme
exploiting the mathematical theory of wavelets. Such a theory,
developed recently, has had a great impact in many fields of
engineering and of other
scientific disciplines. In particular, wavelet theory has become very popular
in the signal processing area; in fact it is a flexible toolbox for signal analysis allowing effective representation of signals for features extraction purposes.
The main features that make wavelet waveforms
suitable to be used as shaping pulses
for modulation are their substantial compact support both in the time and frequency domains, and the fact that they are ISI-free pulses over frequency flat channels. The study presented in this thesis is focused on application of wavelet theory to design high-efficiency multichannel communication schemes and to the performance
evaluation over linear and non-linear channels.
We present a general method to design wavelet based multichannel
communication schemes that we denoted
Wavelet
Orthogonal Frequency Division Multiplexing (WOFDM).
We show that such schemes,
having a largerspectral efficiency for a small number of channels,
are a valid alternative to the classical OFDM.
Potential advantage of wavelet modulation are shown presenting other
applications examined in this thesis: a joint use of WOFDM and Trellis Coded
Modulation to shape the power spectrum in order to match a frequency selective channel and minimize distortion,
and application to spread spectrum modulation.
Particular attention has been
devoted to the timing recovery problem in multichannel communication schemes, exploiting the timing information of the different
subchannels to improve the error variance in estimation of the
sampling instant leading to a reduction of the
adjacent channels interference.
36
Lo, Chi-ming. "Analytical evaluation of wireless digital communication performance over fading channels". Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23295211.
Testo completo
37
Paradise, Richard A. "Modeling and simulation of the physical layer of the single channel ground and airborne radio system (SINCGARS)". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Jun%5FParadise.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2005.Thesis Advisor(s): Frank Kragh, Herschel H. Loomis. Includes bibliographical references (p. 55-56). Also available online.
38
Bornestav, Eric. "Digital detox – människans räddning i den digitala eran? : En etnografisk studie om digital detox". Thesis, Södertörns högskola, Institutionen för kultur och lärande, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-35726.
Testo completoAbstract (sommario):
Uppsatsens syfte är att få en djupare förståelse för fenomenet digital detox och hur problem knutna till det alltmer digitalt uppkopplade samhället framställs samt hur dessa är tänkta att lösas inom detox-trenden. Följande frågeställningar är utformade för att besvara syftet: 1. Hur framställs problem knutna till det alltmer digitalt uppkopplade samhället inom digital detoxtrenden? 2. Hur är dessa problem tänkta att lösas? Det vill säga, vad innebär det egentligen att göra en digital detox? Uppsatsens teoretiska ramverk kretsar runt det accelererande samhället samt de effekter som de digitala medierna har inneburit för människan. Däribland redogörs det för upplevelsen av tid, tidspress, medierad interaktion och digital bundenhet. Studien genomfördes med en deltagande observation på digital detox-lägret Villa Insikt i norra Sverige den 17-19 november 2017. Materialet består bland annat av en intervju med kursledaren, informella samtal med densamme och övriga deltagare, fältanteckningar samt analys av broschyrer och lägrets hemsida. Resultatet visar att digitala medier, enligt detox-lägret, har inneburit en rad olika problem för människor. Trots detta ges inga konstruktiva förslag för hur dessa problem ska lösas. Uppsatsens huvudsakliga slutsats är således att detoxen enbart fungerar som ett konstaterande över att människors bundenhet och förhållningssätt till de digitala medierna är problematisk samt att detoxen inte innebär någon större förändring för deltagarna som istället individuellt måste försöka att lösa de problem som detoxen påvisar genom insikt och digital strategi.
39
Taylor, Gregory. "Canadian broadcasting regulation and the digital television transition". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86874.
Testo completoAbstract (sommario):
This thesis examines the evolution of Canadian broadcasting regulation since the adoption of the 1991 Broadcasting Act with a specific focus on the digital television transition. For Canada, this technological shift exemplifies many of the greater changes in public policy in the last two decades: a faith in market mechanisms, light-touch regulation, co-regulatory approaches, and the powerful influence of new technologies. This dissertation will address the following central question: does the policy surrounding the transition to digital television broadcasting pose a challenge to traditional concerns of the role of broadcasting in Canadian democracy? Utilizing the approach of institutional political economy, this study is informed by primary government and industry documents and interviews conducted with key actors within Canadian broadcasting. This dissertation offers a unique contribution to knowledge in three areas: establishing clear parameters for the differences between policy and regulations in Canadian broadcasting; offering the first comprehensive study of the Canadian digital television transition; and analyzing the growth and impact of self and co-regulation in Canadian broadcasting policy. The results of this study speak to the power dynamics amid the range of actors involved in the Canadian policy process, the influence of new technologies, and the greater prevailing policy directions in broadcasting since the 1991 Broadcasting Act was adopted.Cette thèse examine l'évolution de la réglementation canadienne de la radiodiffusion depuis l'adoption de la Loi sur la radiodiffusion (fédérale) en 1991 en se concentrant plus particulièrement sur la transition à la télévision numérique. Pour le Canada, ce changement de cap est révélateur des grandes modifications que les politiques publiques ont connues dans les deux dernières décennies : une foi dans les mécanismes de marché, une réglementation en pointillé, des approches axées sur la coréglementation et la puissante influence des nouvelles technologies. La question centrale étudiée dans ce mémoire est la suivante : la politique sous-jacente à la transition à la télédiffusion numérique constitue-t-elle un défi en regard des préoccupations traditionnelles afférentes au rôle de la radiodiffusion dans la démocratie canadienne ? Adoptant une approche de économie politique institutionnelle, cette étude se fonde sur l'étude de documents gouvernementaux ou provenant des entreprises privées oeuvrant dans le secteur ainsi que sur des entretiens effectués avec certains acteurs clés de la radiodiffusion canadienne. Cette thèse offre une contribution unique au savoir quant à trois aspects : établir des paramètres clairs permettant de différencier les politiques de la réglementation dans le domaine de la radiodiffusion ; offrir la première étude détaillée sur la transition canadienne à la télévision numérique, et présenter une analyse du développement et de l'impact de l'autoréglementation et de la coréglementation dans les politiques canadiennes relatives à la radiodiffusion. Les conclusions de cette étude mettent en lumière les dynamiques de pouvoir existant entre les divers acteurs engagés dans le processus d'élaboration et d'adoption des politiques canadiennes, l'influence des nouvelles technologies et les grandes orientations politiques ayant prévalu dans le domaine de la radiodiffusion depuis l'adoption d
40
Malan, Estian. "Multi-dimensional direct-sequence spread spectrum multiple-access communication with adaptive channel coding". Pretoria : [S.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-10252007-142715/.
Testo completo
41
Katz, Ettie. "Trellis codes for multipath fading ISI channels with sequential detection". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/13908.
Testo completo
42
Diniz, Júlio César Medeiros 1987. "Estimador de desvio de frequência para receptores ópticos coerentes digitais". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261926.
Testo completoAbstract (sommario):
Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Sistemas de comunicações ópticas coerentes digitais permitem a utilização de formatos de modulação que carregam informação através de fase, amplitude e polarização do sinal óptico. Com o processamento digital dos sinais ópticos, é possível compensar as distorções inerentes à transmissão óptica, bem como realizar o sincronismo entre transmissor e receptor. Assim, junto ao avanço da eletrônica digital, a transmissão e recepção de sinais a centenas de gigabits por segundo se torna possível. Dentro desse cenário, os métodos comuns para a estimação de fase da portadora que chega ao receptor possuem baixa tolerância à dessintonia em frequência entre a portadora transmitida e o laser oscilador local. Nesta dissertação, é proposto e experimentalmente demonstrado um método de estimação de desvios de frequência de alimentação direta, com amplo alcance de estimação, eficiente, no ponto de vista de hardware, e compatível com os requisitos definidos pelo Fórum de Interconexões Ópticas (OIF ¿ Optical Internetworking Forum). Resultados obtidos experimentalmente mostram que o método proposto possui alta tolerância à assimetria espectral causada por filtragens no sinal
Abstract: Digital coherent optical systems allow the use of modulation formats that carry information through optical signal phase, amplitude and polarization. With digital processing of optical signals it is possible to compensate for distortions associated with optical transmission, as well as to perform timing and carrier synchronization. Thus, by also taking into account the current high speed electronic progress, transmission and reception of signals at hundreds gigabits per second has became possible. In this scenario, common carrier phase estimation methods have low tolerance to frequency offsets between transmitted carrier and local oscillator laser. This dissertation proposes and experimentally demonstrates a hardware-efficient, feed-forward, wide-range frequency offset estimator, compliant with Optical Internetworking Forum (OIF) requirements. Experimental results show that this method has high tolerance to the spectrum asymmetry caused by signal filtering
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
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Carrion, Betancourt Carlos Enrique 1982. "Sincronização de portadora em modo rajada para receptores ópticos coerentes". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258898.
Testo completoAbstract (sommario):
Orientadores: Dalton Soares Arantes, Fábio Lumertz GarciaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-26T08:19:51Z (GMT). No. of bitstreams: 1 CarrionBetancourt_CarlosEnrique_M.pdf: 2602148 bytes, checksum: d14588789c8a464595b34613eb4822aa (MD5) Previous issue date: 2014
Resumo: Esta dissertação estuda as técnicas de recuperação de frequência e fase de portadora em receptores ópticos coerentes, operando no modo rajada. Inicialmente, abordam-se a análise e modelagem das duas principais degradações que afetam a portadora, quais sejam, os desvios de frequência, que são produto da diferença de frequência entre o laser emissor e o oscilador local no receptor, e de ruídos de fase dos dispositivos a laser usados em comunicações ópticas coerentes. Usando os modelos de passeio aleatório (random walk) para o ruído de fase, os principais algoritmos de recuperação de frequência e de fase são revisados. Os estudos levam em consideração as novas tecnologias de lasers para comunicações, que asseguram alta estabilidade de frequência de curto prazo (short-term), para uso em receptores ópticos coerentes operando a taxas acima de 100 Gbps. Um projeto de preâmbulo especial foi concebido, a fim de viabilizar a obtenção de expressões analíticas para um estimador ótimo, no sentido do Mínimo Erro Quadrático Médio (MMSE). Resultados de simulações em MatLab/Simulink são apresentados para a validação dos resultados teóricos
Abstract: Frequency and phase estimation for carrier recovery in burst-mode coherent optical receivers are studied in this dissertation. Accurate models for frequency and phase deviations in communication lasers are initially studied, in order to present a tutorial study on frequency mismatch and phase recovery algorithms. Our studies take into account the current laser technology for optical communications using coherent receivers, especially the high short-term laser frequency stability for receivers operating above 100 Gbps. A special preamble design is presented for which an optimum estimator using the Minimum Mean-Square Error criterion is obtained. The estimator is given in closed-form solution with low computational space- and time-complexity. Simulation results in MatLab/Simulink are presented to validate the theoretical results.
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
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Ekvetchavit, Thunyachate 1974. "Phase-locked loop digital FM receiver for wireless communications". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46528.
Testo completoAbstract (sommario):
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 77-79).
by Thunyachate Ekvetchavit.
S.B.and M.Eng.
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Liu, Zaifei. "Monte Carlo methods for Bayesian inference in digital communications". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613099.
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Wong, Wai-ki. "Adaptive equalizers for multipath compensation in digital microwave communications". Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/11600.
Testo completo
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Glade, William Daniel. "Way-Finding: A New Approach to Studying Digital Communications". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/8554.
Testo completoAbstract (sommario):
This work further develops the way-finding model first proposed by Pearson and Kosicki (2017) which examines the flow of information in the digital age. Way-finding systems are online systems that help individuals find information—i.e. social media, search engines, email, etc. Using a grounded theory methodology, this new framework was explored in greater detail. Way-finding theory was created using the context of the elaboration likelihood model, gatekeeping theory, algorithmic gatekeepers, and the existence of the filter bubble phenomenon. This study establishes the three basic pillars of way-finding theory: the user’s mindset when accessing way-finding systems, the perception of how popular way-finding systems function, and the perception of the information personalization process—particularly regarding algorithmic gatekeepers and their roles in creating the filter bubble phenomenon. These pillars and the relationships that exist between each constitute way-finding theory.
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Miranda, Gabriela Dischinger. "As teorias da comunicação aplicadas à narrativa transmídia". Pontifícia Universidade Católica de São Paulo, 2017. https://tede2.pucsp.br/handle/handle/20322.
Testo completoAbstract (sommario):
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Gabriela Dischinger Miranda.pdf: 9361011 bytes, checksum: 6de1bfd60b91a107b8b069cc79027a3c (MD5)Made available in DSpace on 2017-08-30T12:55:55Z (GMT). No. of bitstreams: 1 Gabriela Dischinger Miranda.pdf: 9361011 bytes, checksum: 6de1bfd60b91a107b8b069cc79027a3c (MD5) Previous issue date: 2017-08-21
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
From a brief overview of the main communication theories we can see that many that are still used today were thought between the decades of 1930 and 29160, based on mass communication; media that assumes asymmetric communication and one to many. Communication on digital media, on the other hand, is two way, in which the individual not only has the possibility to send their own messages, bus also respond to those they receive. Therefore, new digital media changed radically the communication environment, making it important to review the main communication theories seeking to identify those that can still explain multimedia and transmedia communication. In this dissertation, we mapped these main communication theories and detailed how digital and transmedia communication works. With four case studies we illustrated how communication happens today and looked for those communications theories that still fits in this scenario
A partir de um breve panorama das principais teorias da comunicação percebemos que a maioria das teorias que perduram até hoje foram pensadas entre 1930 e 1960 baseadas nos meios de comunicação de massa; meios esses que preveem uma comunicação assimétrica e de um para muitos. A comunicação nos meios digitais, por outro lado, é uma via de mão dupla, por meio da qual o indivíduo não apenas passou a ter a possibilidade de transmitir suas próprias mensagens, mas também responder àquelas que recebe. Dessa forma, as novas mídias digitais trouxeram uma grande mudança no ambiente comunicacional, o que torna importante a revisão das principais teorias da comunicação com o objetivo de identificar aquelas que ainda conseguem explicar a comunicação multimeios e transmidiática. Nessa dissertação mapeamos as principais teorias da comunicação e detalhamos a comunicação digital e transmidiática. Através quatro de estudos de caso ilustramos a comunicação hoje e buscamos as principais teorias da comunicação que ainda se encaixam nesse cenário
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Iyer, Gopal Balakrishnan. "Digital communication and control circuits for 60ghz fully integrated CMOS digital radio". Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39589.
Testo completoAbstract (sommario):
Emerging "bandwidth hungry" applications such as high definition video distribution and ultra fast multimedia side-loading have extended the need for multi-gigabit wireless solutions beyond the reach of conventional WLAN technology or even more recently emerging UWB and MIMO systems. The availability of 7GHz of unlicensed bandwidth in the 60GHz spectrum, represents a unique opportunity to address such data-throughput requirements. The 60GHz Integrated CMOS digital radio chipset comprises of PHY and MAC layers, RF transceiver, High-Speed Digital Interface and an underlying Serial Communication Fabric.
To have a complete communication solution compliant with the latest ECMA-369, ISO/DIS 13156 and IEEE 802.15.3c standards, we build a million gate digital implementation of MAC and PHY. The Serial Peripheral Interface (SPI) serves as the bridge between the higher layers in the communication stack (PAL-MAC) and the lower layers like PHY-RF Front End. The MAC module can setup the communication link on the fly by tuning parameters such as operating channel, channel bonding and bandwidth, data rates, error correction mechanisms, handshaking mechanisms, etc, by using the SPI to communicate with internal components. The SPI interface plays a crucial rule in not only this, but also during the testing and debug phase. Operation of each of the RF modules is monitored through the serial interface using local SPI slaves which are hooked up to the 4-wire serial bus running all through the chip. The SPI host controller emulates an embedded protocol analyzer. For calibration and fine tuning purposes, digital settings can also be loaded onto these modules through the SPI interface. R-2R DACs are used to convert these commands into analog voltages which then provide a tunable bias to the RF and mixed-signal modules. Other key functions of this serial communication and control interface are: Initialization of all of the RF and mixed signal modules, DC calibration of data converter, PLL and other mixed-signal modules, data acquisition, parametric tuning for digital modules such as linear equalizer, Gain Control loops (AGC, VGA), etc.
Ultra high speed digital Input-Output buffers are used to provide an external data interface to the radio chipset. These high speed I/Os are also used in the gbps (gigabit-per-second) link for data transfer between the RF transceiver chip and the PHY-MAC baseband chip. The IOs are expected to comply with different signaling standards such as LVDS, SLVS200, SLVS400, etc. A robust system involves a meticulous pad ring design with proper power domains and power cuts. Full-chip integration of the digital PHY, MAC, peripheral logic and IO ring is done in a semi-custom fashion.
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雷靜 e Jing Lei. "Frequency synchronization methods for digital broadband receivers". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31244427.
Testo completo