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Dissertations / Theses on the topic 'Digital communication channel'
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1
Clark, Alan Douglas. "Analysis and design of source/channel codes for noisy communication channels." Thesis, De Montfort University, 1987. http://hdl.handle.net/2086/4246.
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Sandberg, Sara. "Modulation and channel effects in digital communication /." Luleå : Luleå University of Technology, 2005. http://epubl.luth.se/1402-1757/2005/49.
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Jalali, Sammuel. "Wireless Channel Equalization in Digital Communication Systems." Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/cgu_etd/42.
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Our modern society has transformed to an information-demanding system, seeking voice, video, and data in quantities that could not be imagined even a decade ago. The mobility of communicators has added more challenges. One of the new challenges is to conceive highly reliable and fast communication system unaffected by the problems caused in the multipath fading wireless channels. Our quest is to remove one of the obstacles in the way of achieving ultimately fast and reliable wireless digital communication, namely Inter-Symbol Interference (ISI), the intensity of which makes the channel noise inconsequential.
The theoretical background for wireless channels modeling and adaptive signal processing are covered in first two chapters of dissertation.
The approach of this thesis is not based on one methodology but several algorithms and configurations that are proposed and examined to fight the ISI problem. There are two main categories of channel equalization techniques, supervised (training) and blind unsupervised (blind) modes. We have studied the application of a new and specially modified neural network requiring very short training period for the proper channel equalization in supervised mode. The promising performance in the graphs for this network is presented in chapter 4.
For blind modes two distinctive methodologies are presented and studied. Chapter 3 covers the concept of multiple "cooperative" algorithms for the cases of two and three cooperative algorithms. The "select absolutely larger equalized signal" and "majority vote" methods have been used in 2-and 3-algoirithm systems respectively. Many of the demonstrated results are encouraging for further research.
Chapter 5 involves the application of general concept of simulated annealing in blind mode equalization. A limited strategy of constant annealing noise is experimented for testing the simple algorithms used in multiple systems. Convergence to local stationary points of the cost function in parameter space is clearly demonstrated and that justifies the use of additional noise. The capability of the adding the random noise to release the algorithm from the local traps is established in several cases.
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Rizk, Ziad. "Digital data transmission over an HF channel." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7232.
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The thesis is concerned with detection, estimation techniques and a method of the adaptive adjustment of the equaliser, for use in a 4800bit/sec synchronous digital transmission system operating over a voice-band time-varying HF channel. Two main impairments are additive Gaussian noise and inter-symbol interference (ISI), which can be very severe at times. All techniques considered here are algorithms or processes that operate on sequences of sample values. Modern digital modems normally operate in this way, and the techniques described are of direct application to practical systems, and could be implemented using the new technology of high speed real-time digital signal processing (DSP). The performance of the various systems that employ the above techniques are obtained using the computer simulated model of three types of HF channels. The ionospheric propagation medium, the characteristics of HF channel and the signal distortion introduced by the channel are first described. The thesis then presents a suitable base-band model of the HF channel for computer simulation of quadrature amplitude modulation systems. A suitable method for the adjustment of the receiver is described next. This method is suitable both for the adjustment of a conventional decision feedback equaliser (DFE), and also for the adjustment of a linear feedforward filter that is employed ahead of a near-maximum likelihood (NML) detector. This method uses a minimum phase (root-finding) algorithm (MPA) to convert the channel response from being non-minimum phase to at least approximately minimum phase. The results of computer simulation tests of this algorithm are then presented over different types of HF channel models. The results demonstrate the algorithm's capability to make the channel response minimum (or near-minimum) phase. Various NML detectors, derived from the Viterbi detector, are discussed. Each detector is here preceded by an adaptive linear filter that is adjusted adaptively using an MPA. The performance of these detectors is compared with the conventional DFE, whose tap-gains are adjusted adaptively using an MPA, and the detector which gives the best compromise between performance and complexity is selected for combined receivers. These results are obtained using perfect estimation of the channel response. The estimation techniques studied in this thesis include both new and conventional estiniators, which are based on the least- mean-square (LMS) algorithm or recursive least-square(RLS) algorithm. The estimator provides an estimate of the sampled impulse response (SIR) of the channel, necessary for the NML detector or MPA. The performances of these estimators are compared using computer simulation tests. The results also demonstrate that the simpler LMS algorithm with adaptive step size gives a comparable level of accuracy with the more complex RLS algorithm. Finally the most promising of the detectors and estimators are connected with an adaptive equaliser, using an MPA, to form a new combined receiver. The details of the combined system structure with its computational complexity are given. Extensive computer simulation tests have been carried out on the different arrangements of the combined system including DFE, when all the functions of detection, estimation and MPA are present, in order to find the most cost effective system in terms of performance and complexity. A considerable reduction in the equipment complexity can be achieved by allowing a long period between successive adjustment of the adaptive filter and estimator.
5
Hum, Eddy N. (Eddy Ning) Carleton University Dissertation Engineering Electrical. "Burst-trapping codes for the land mobile data channel." Ottawa, 1988.
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6
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/.
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Dhanoa, Jasdeep Singh. "Acoustic digital communication systems for a doubly spread underwater channel." Thesis, Cranfield University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413403.
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Hickok, Tom. "Space Communication Channel Emulation Using Digital and Analog Signal Processing." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/398.
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New communication protocols intended for large distances, including low orbit and deep space, can be inherently difficult to evaluate since trial implementations are often impractical. In order to accurately measure the performance of a new protocol, it is important to evaluate it in an environment that most closely matchs that in which it will be used. This thesis demonstrates the ability to emulate a space communications channel through digitizing a transmission centered at an intermediate frequency of 70 MHz with a bandwidth of 24 MHz, digitally introducing the characteristics of a transmission through space, and reconstructing the digital data to its analog counterpart. Delay, Doppler shift, Gaussian noise, and fading are among the most prevalent characteristics of such a channel, and thus were the focus of this thesis. Special care was given to the design of each digital and analog component to maintain the integrity of the original signal by minimizing all undesired noise introduced. The final design can accurately produce a given dynamic transmission signature or continually output a static set of channel characteristic parameters to test new communication protocols.
9
Galvin, Ross. "Underwater fading channel simulator for a parametric communication system." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366764.
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鄭价昌 and Kai-cheong Chang. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31212888.
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Chang, Kai-cheong. "Adaptive channel equalisation technique for wideband time-division multiple access digital mobile radio communications systems /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B17590371.
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Narinian, Vartan. "Combined adaptive speech and channel coding for digital mobile radio communication." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314172.
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Deleu, Thibault. "Digital predistortion and equalization of the non-linear satellite communication channel." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209212.
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In satellite communications, non-linear interference is created by the non-linear power amplifier aboard the satellite. Even in the case of a memoryless power amplifier, the channel is a non-linear system with memory due to the presence of linear filters on ground and aboard the satellite. The non-linear interference degrades the system performance, especially when considering high-order modulations or in case of several signals being amplified by the same power amplifier. In this thesis, we have proposed algorithms at the transmitter and at the receiver to digitally compensate this interference. In particular, a new predistortion algorithm has been proposed, which significantly improves state-of-the-art algorithms. Since the complexity of this algorithm is an issue, low-complexity algorithms have also been proposed and achieve almost the same performance as the initial algorithm. We have also proposed joint predistortion and turbo-equalization algorithms to further improve the system performance. / En communications par satellite, de l’interférence non-linéaire est créée par l’amplificateur de puissance non-linéaire à bord du satellite. Même si l’amplificateur peut être considéré comme sans mémoire, le canal est malgré tout un système non-linéaire avec mémoire de par la présence de filtres linéaires au sol ou à bord du satellite. L'interférence non-linéaire dégrade les performances du système, en particulier lorsqu’on considère des modulations d’ordre élevé ou plusieurs signaux amplifiés par le même amplificateur de puissance. Dans cette thèse, nous avons proposé des algorithmes à l’émetteur et au récepteur pour compenser numériquement cette interférence. En particulier, nous avons proposé un nouvel algorithme de prédistorsion qui améliore de façon significative les algorithmes de l’état-de-l’art. La complexité de l’algorithme étant très élevée, nous avons proposé des algorithmes de plus faible complexité atteignant pratiquement les mêmes performances par rapport à l’algorithme initial. Nous avons aussi proposé des algorithmes de prédistorsion et d’égalisation conjointes, permettant d'atteindre des performances plus élevées qu'avec la prédistorsion seule.<br>Doctorat en Sciences de l'ingénieur<br>info:eu-repo/semantics/nonPublished
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Zhu, Zhechen. "Automatic classification of digital communication signal modulations." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/9246.
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Automatic modulation classification detects the modulation type of received communication signals. It has important applications in military scenarios to facilitate jamming, intelligence, surveillance, and threat analysis. The renewed interest from civilian scenes has been fuelled by the development of intelligent communications systems such as cognitive radio and software defined radio. More specifically, it is complementary to adaptive modulation and coding where a modulation can be deployed from a set of candidates according to the channel condition and system specification for improved spectrum efficiency and link reliability. In this research, we started by improving some existing methods for higher classification accuracy but lower complexity. Machine learning techniques such as k-nearest neighbour and support vector machine have been adopted for simplified decision making using known features. Logistic regression, genetic algorithm and genetic programming have been incorporated for improved classification performance through feature selection and combination. We have also developed a new distribution test based classifier which is tailored for modulation classification with the inspiration from Kolmogorov-Smirnov test. The proposed classifier is shown to have improved accuracy and robustness over the standard distribution test. For blind classification in imperfect channels, we developed the combination of minimum distance centroid estimator and non-parametric likelihood function for blind modulation classification without the prior knowledge on channel noise. The centroid estimator provides joint estimation of channel gain and carrier phase o set where both can be compensated in the following nonparametric likelihood function. The non-parametric likelihood function, in the meantime, provide likelihood evaluation without a specifically assumed noise model. The combination has shown to have higher robustness when different noise types are considered. To push modulation classification techniques into a more timely setting, we also developed the principle for blind classification in MIMO systems. The classification is achieved through expectation maximization channel estimation and likelihood based classification. Early results have shown bright prospect for the method while more work is needed to further optimize the method and to provide a more thorough validation.
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Landqvist, Ronnie. "Signal processing techniques in mobile communication systems : signal separation, channel estimation and equalization /." Karlskrona : Blekinge Institute of Technology, 2005. http://www.bth.se/fou/Forskinfo.nsf/allfirst2/98bf8bfb44d67d86c1257099003e2fc1?OpenDocument.
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Anderson, Harry R. "Development and applications of site-specific microcell comunications channel modelling using ray tracing." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260848.
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Orellana, Francisco Watkins. "Concatened codes combined with deinterleaving and adaptive equalisation for fading channel." Thesis, Staffordshire University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341000.
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Bhattarai, Kripesh. "On the Use of a Digital Communication Channel for Feedback in a Position Control System." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353512595.
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Ferland, Guy J. M. "Error rate performance analysis of stream and block ciphers in a digital mobile communication channel." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6478.
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This thesis analyses the effect of encrypting data on the bit error rate at the receiver. Block and stream cipher modes based on the Data Encryption Standard (DES) are examined. More specifically, Electronic Code Book (ECB), Cipher Block Chaining (CBC), Output FeedBack (OFB) and Cipher FeedBack (CFB) modes are considered. The ability of binary BCH codes and of bit interleaving to reduce the error rate over fading channels is examined in detail. Experimental results are derived from computer simulations where the digital mobile communication channel is represented by the Gilbert and Fritchman models. Simulations are also carried out over memoryless binary symmetric channels (BSC) to illustrate the difference on the error rate at the receiver (after decryption) as a result of the presence or absence of channel memory.
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Richardson, A. J. "The effects of co-channel interference on digital transmission in mobile radio area coverage systems." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356289.
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Senol, Gokberk. "Performance Analysis Of A Digital Communication System On Sea Platforms." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615134/index.pdf.
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The transmission rate and reliability are the most crucial elements of a communication system on sea platforms. In this thesis, the performance of a high speed and reliable communication system that can be used on ship to ship sea
platforms will be evaluated.
The two ray channel model is used in order to characterize the channel considering the refraction and reflection. Using the channel model, the path loss and the Shannon channel capacities are obtained for different systems.
In order to increase the system performance, frequency diversity technique is used and a detailed comparison of diversity combining techniques is provided.
As an alternative to Shannon channel capacity, cut off rate analysis is considered to get more realistic results about the rate of the communication system in that it takes modulation into account and the results are compared with the channel capacity. Block fading model and jamming effects on the achievable rate of the system is considered for different linear modulation techniques.
Finally, an OFDM system design is given as an example using the tools obtained in this work.
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Franklin, Daniel Robert. "Enhancements to channel models, DMT modulation and coding for channels subject to impulsive noise." School of Electrical, Computer & Telecommunications Engineering - Faculty of Informatics, 2007. http://ro.uow.edu.au/theses/18.
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DMT modulation is an OFDM-based modulation scheme used in ADSL and proposed for various other high-speed broadband access systems. Existing mathematical models for transmission lines make a number of simplistic assumptions about the distribution of noise, in particular, the assumption that impulsive noise originates at either end of the transmission line. It is therefore desirable to improve the accuracy of the transmission-line model to allow better prediction of broadband modem performance, and to further improve the bit-allocation algorithms and equaliser designs used in DMT-based modems. This Thesis presents a new channel model particularly well-suited for simulation of high-speed digital subscriber line systems. The model extends a commonly-used physical channel model by distributing the points of noise ingress along the physical length of the transmission line. Simulation results are presented for a highspeed multicarrier modem operating on channels modelled with both the conventional and new models. Comparison with the same modem operating over a real channel demonstrates that the new model provides a better estimate of the bit error rates and temporal error distribution expected on actual telephone lines than is possible with the conventional model. A number of improvements to modulation and coding schemes for DMT modems are also presented in this Thesis, including a robust frequency-domain decision feedback equaliser, a new algorithm for allocating bits to sub-carriers based on a measurement of per-carrier BER, and a technique for encoding data with fractional numbers of bits ii Abstract iii per symbol, thereby providing additional channel capacity.
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Bäckström, Tove. "Large digital screen as a corporate communication channel : Enhancing the dissemination of information, administration and interaction." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-144285.
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Public areas are more and more equipped with digital screens that are used to inform or promote a particular product. This is a way to communicate with the people on that area. The idea is to get people's attention, make them read and take in information and possibly buy the product that is marketed. This type of digital display is called digital signage and can also be used as an information channel of a company where information directed to employees and visitors is displayed. CGI Östersund has a screen placed in their office that works as such an information channel. This thesis is about investigating and analyzing the current presentation and creating a new solution with a custom interface that will be more effective and engage more people. The new solution is interactive and clickable with the help of a mouse. A user study has been done using a Kinect sensor to see how many people are watching the screen, how long they look at the screen and from what distance. This data was also supplemented by a survey sent to the employees at CGI Östersund. The result of the user study shows that there was no significant difference between the previous solution and the new one. This may be due to two main reasons: the lack of time in which the experiment was performed and the location of the digital screen that is not currently optimal.
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Blankenship, T. Keith III. "Design and Implementation of a Pilot Signal Scanning Receiver for CDMA Personal Communication Services Systems." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36682.
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In cellular and personal communications services (PCS)
systems based on code division multiple access (CDMA),
a pilot signal is used on the forward link for
synchronization, coherent detection, soft handoff,
maintaining orthogonality between base stations, and,
in the future, position location. It is critical that
the percentage of power allocated to the pilot signal
transmitted by each base station be fixed properly to
ensure the ability of the CDMA network to support
subscriber demand.
<p>
This thesis reports on the design and implementation
of a prototype receiver for measuring pilot signals
in CDMA PCS systems. Since the pseudonoise (PN) signal
of the pilot channel is a priori information, the
receiver searches for pilot signals by digitally
correlating the received signal with this known,
locally generated pilot signal. By systematically
changing the phase of this locally generated pilot
signal, the receiver scans the received signal to
identify all possible signs of pilot signal activity.
Large values of correlation indicate the presence of
a pilot signal at the particular phase of the locally
generated pilot signal. The receiver can also detect
multipath components of the pilot signal transmitted
from a given base station.
<p>
One issue associated with this receiver is its ability
to keep the signal power within the dynamic range of the
analog-to-digital (A/D) converter at its input. This
necessitated the design of an automatic gain control
(AGC) mechanism, which is digitally implemented in this
receiver.
<p>
Simulation studies were undertaken to assist in the
design and implementation of the pilot signal scanning
receiver. These simulations were used to quantify how
various non-idealities related to the radio frequency
(RF) front-end and A/D converter adversely affect the
ability of the digital signal processing algorithms to
detect and measure pilot signals.
<p>
Because the period of the pilot signal is relatively
long, methods were developed to keep the receiver's
update period as small as possible without compromising
its detection ability. Furthermore, the high sampling
rate required strains the ability of the digital logic
to produce outputs at a rate commensurate with
real-time operation. This thesis presents techniques
that allow the pilot signal scanning receiver to achieve
real-time operation. These techniques involve the
judicious use of partial correlations and windowing the
received signal to decrease the transfer rate from the
A/D converter to the digital signal processor. This
thesis provides a comprehensive discussion of these
and other issues associated with the actual hardware
implementation of the pilot signal scanning receiver.<br>Master of Science
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Hirschbeck, Martin [Verfasser], and Johannes [Gutachter] Huber. "Interference Mitigation and Channel Estimation for Digital Aeronautical Communication Systems based on OFDM / Martin Hirschbeck ; Gutachter: Johannes Huber." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1113876379/34.
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Pan, Zhaoyi. "Intra-channel nonlinearity mitigation of long-haul single-carrier coherent detection optical communication systems using digital signal processing." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104619.
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We live in the information era, where the ever increasing demand for data capacity is driven by the exponentially growing internet traffic worldwide. Since the optical fiber nonlinearity represents a key impairment that limits fiber capacity, the amount of fiber nonlinearity compensation determines the fiber channel capacity. In fact, advanced modulation formats and digital signal processing have recently been used to explore the nonlinear capacity of optical fibers in order to satisfy this capacity demand. The focus of this thesis is the compensation of intra-channel nonlinearities in single-carrier single-channel coherent detection optical communication transmission systems by using digital backpropagation and Volterra filter methods. These compensation methods are evaluated on a 112 Gbit/s optical transmission system over a distance of 1600 km, which employs dual-polarization 16 quadrature amplitude modulation and dual-polarization quadrature phase-shift keying modulation formats. Performance and computational complexity comparisons are presented.<br>Nous vivons dans l'ère informatique où la demande de la capacité d'information est propulsée par l'expansion exponentielle du trafic Internet. Étant donné que la non-linéarité de la fibre optique représente une dégradation qui limite la capacité de la fibre optique, le niveau de la compensation sur la non-linéarité de la fibre optique détermine la capacité du réseau de fibres optiques. En fait, les formats de modulation avancés et le traitement numérique du signal ont été utilisés récemment pour explorer la région non-linéaire de la capacité de la fibre optique. L'objectif de cette thèse est la compensation de la non-linéarité intra-canal dans les systèmes de communication optique uni-porteur et uni-canal à la détection cohérente en utilisant la méthode de la rétropropagation digitale et la méthode du filtre Volterra. Ces deux méthodes sont évaluées sur un système de 1600 km à 112 Gbit par seconde où la modulation en double polarisation et d'amplitude en quadrature 16 et la modulation en double polarisation par déplacement de phase quadrature sont utilisés. La performance et la complexité computationnelle de ces deux méthodes seront présentées.
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Hollis, Timothy Mowry. "Circuit and Modeling Solutions for High-Speed Chip-to-Chip Communication." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1067.
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This dissertation presents methods for modeling and mitigating voltage noise and timing jitter across high-speed chip-to-chip interconnects. Channel equalization and associated tuning schemes have been developed to target the distinct characteristics and signal degradation exhibited in the clock and data signals of multi-Gigabit/second digital communication links. Multiple methods for generating realistically degraded signals for the purpose of simulation are also presented and used to verify the proposed equalization and filtering topologies. Specifically, a new technique for modeling high-speed jittery clocks in the frequency domain is presented and shown to reduce transient simulation time and memory requirements, while simultaneously improving the timing resolution and accuracy of the simulation by minimizing the dependence on the transient simulation time-step. The technique is further developed to provide unprecedented control over the timing characteristics of the generated signals, and is then extended to the generation of random data signals with definable jitter statistics. Through these techniques,realistic clock and data waveforms are constructible, providing for the visualization of the combined effects of voltage and timing degradation, while at the same time tracking the phase relationship between the clock and data signals as they pass across their respective channels and through the receiving circuitry of the communication link. New methods for the automated tuning of second-order continuous-time channel equalizers are proposed based on the simulated or measured single pulse and double pulse responses of the transmission channel. Using only one degree of freedom, the methods target the reduction of inter-symbol interference (ISI) as identified in the single and double pulses. Through tuning either the circuit quality factor (Q), the peaking frequency, or the frequency zero, the methods are shown to adapt to a variety of channel lengths and datarates from the same original equalizer transfer function, implying a good degree of generality, while offering a simple, yet effective, method for ISI reduction. Finally, the design of an active 5 Gigahertz (GHz) bandpass filter, employed for high-speed clock conditioning, is presented and shown to address both random and deterministic components of the clock signal degradation. The bandpass transfer function is achieved through a combination of AC coupling and a resonant LC tank consisting of on-chip interleaved spiral inductors and a tunable capacitor array. Through adjusting the load capacitance in parallel with the inductors, the center frequency of the filter is tunable over a range of nearly 5GHz. The design targets a supply voltage of 1.2 volts and draws approximately 5.7 milliamps of current.
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Hirschbeck, Martin [Verfasser]. "Interference Mitigation and Channel Estimation for Digital Aeronautical Communication Systems based on OFDM : Interferenzunterdrückung und Kanalschätzung für OFDM im digitalen Flugfunk / Martin Hirschbeck." Aachen : Shaker, 2017. http://d-nb.info/1138178055/34.
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Chan, Francis Chun Ngai Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Statistical methods on detecting superpositional signals in a wireless channel." Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/30596.
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The objective of the thesis is concerned on the problem of detecting superpositional signals in a wireless channel. In many wireless systems, an observed signal is commonly represented as a linear combination of the transmitted signal with the interfering signals dispersed in space and time. These systems are generally known as the interference-limited systems. The mathematical model of these systems is generally referred as a superpositional model. A distinguished characteristic of signal transmission in a time-varying wireless channel is that the channel process is not known a priori. Reliable signal reception inherently requires exploiting the structure of the interfering signals under channel uncertainty. Our goal is to design computational efficient receivers for various interference-limited systems by using advanced statistical signal processing techniques. The thesis consists of four main parts. Firstly, we have proposed a novel Multi-Input Multi-Output (MIMO) signal detector, known as the neighbourhood exploring detector (NED). According to the maximum likelihood principle, the space time MIMO detection problem is equivalent to a NP-hard combinatorial optimization problem. The proposed detector is a sub-optimal maximum likelihood detector which eliminates exhaustive multidimensional searches. Secondly, we address the problem of signal synchronization for Global Positioning System (GPS) in a multipath environment. The problem of multipath mitigation constitutes a joint estimation of the unknown amplitudes, phases and time delays of the linearly combined signals. The complexity of the nonlinear joint estimation problem increases exponentially with the number of signals. We have proposed two robust GPS code acquisition systems with low complexities. Thirdly, we deal with the problem of multipath mitigation in the spatial domain. A GPS receiver integrated with the Inertial Navigation System (INS) and a multiple antenna array is considered. We have designed a software based GPS receiver which effectively estimates the directions of arrival and the time of arrival of the linearly combined signals. Finally, the problem of communications with unknown channel state information is investigated. Conventionally, the information theoretical communication problem and the channel estimation problem are decoupled. However the training sequence, which facilitates the estimation of the channel, reduces the throughput of the channel. We have analytically derived the optimal length of the training sequence which maximizes the mutual information in a block fading channel.
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Geiser, Felix. "Social media as a communication channel : Is it possible to build a digital brand and generate revenue streams simultaneously by applying influencer marketing?" Thesis, KTH, Industriell Marknadsföring och Entreprenörskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210049.
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Fontes, Rodrigo Tadeu. "Sistema de comunicação digital em banda limitada baseado em sincronismo caótico." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-12072017-133122/.
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Nas últimas décadas, diversos sistemas de comunicação baseados em caos foram propostos. Dentre eles, vários utilizam uma função para codificar uma mensagem em um sinal caótico, que é caracterizado como um sinal de banda larga. Dado que o canal de transmissão é limitado em banda por natureza, é necessário determinar e controlar o espectro do sinal caótico transmitido por esse sistema. Nesse sentido, um sistema de comunicação em banda limitada, baseado em sincronismo caótico, foi proposto recentemente utilizando-se filtros digitais para controlar a largura de banda dos sinais transmitidos. Esses filtros, inseridos no sistema de comunicação, modificam o sistema original gerador do sinal caótico, tornando-se necessário analisar como essa inserção afeta o sincronismo caótico. Nessa tese, apresenta-se uma análise desse sistema de comunicação digital de tempo discreto, baseado em sincronismo caótico, considerando-se um canal com ruído aditivo branco gaussiano. As condições necessárias para a sincronização desse sistema são obtidas analiticamente, por meio de um teorema, para um mapa gerador de caos qualquer. O desempenho desse sistema é avaliado em termos da taxa de erro de bit, e, para melhorar seu desempenho, propõe-se filtrar o ruído fora da banda do sinal na entrada do receptor. Apesar das condições de sincronismo terem sido determinadas, a inserção dos filtros também pode modificar a natureza caótica dos sinais, e não há garantia que os sinais transmitidos sejam caóticos. Para analisar a natureza caótica dos sinais transmitidos pelo sistema de comunicação, o maior expoente de Lyapunov é obtido numericamente em função dos coeficientes dos filtros, dos parâmetros do mapa e da função de codificação da mensagem.<br>In recent decades, several chaos-based communication systems have been proposed. Many of them use a function to encode a message into a chaotic signal, which is characterized as wideband. Since every transmission channel is bandlimited in nature, it is necessary to determine and to control the spectrum of the chaotic signal transmitted by this system. This way, a bandlimited chaos-based communication system was recently proposed using digital filters and chaotic synchronization. These filters, inserted in the communication system, modify the original chaotic generator system, becoming necessary to study how their insertion affect chaotic synchronization. In this work, we present an analysis of this discrete-time chaos-based digital communication system considering an additive white Gaussian noise channel. The synchronization conditions of this system is analytically obtained, through a theorem, for a generic chaos generator map. The system performance is evaluated in terms of bit error rate, and, to obtain a performance improvement, it is also proposed to filter the out-of-band noise in the receiver. Although the conditions for chaotic synchronization have been determined, the filters insertion can also modify the chaotic nature of the signals, and there is no guarantee that the transmitted signals remain chaotic. To analyze the chaotic nature of the communication system transmitted signals, the largest Lyapunov exponent is numerically accessed as a function of the filters coefficients, the parameters of the map and the message coding function.
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Picorone, Antonio Angelo Missiaggia. "Comunicação digital em canais PLC: técnicas de transmissão, detecção e caracterização de canais PLC outdoor brasileiros." Universidade Federal de Juiz de Fora (UFJF), 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/4168.
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Previous issue date: 2014-08-22<br>Esta tese discute a medição e a caracterização das redes de distribuição de energia elétrica de baixa tensão (RDE-BT) e externa (outdoor) como meio de comunicação de dados para sistemas power line communication (PLC). São apresentados e discutidos diversos parâmetros obtidos a partir de uma campanha de medição realizada na RDE-BT de uma concessionária brasileira. Dentre os parâmetros analisados destacam-se o tempo de coerência, banda de coerência, espalhamento do atraso, comprimento da resposta ao impulso do canal e capacidade do canal, quando se considera as bandas de frequências de 1,7 a 30 MHz, 1,7 a 50 MHz e 1,7 a 100 MHz. As análises estatísticas evidenciam o potencial da rede de energia elétrica como meio de comunicação e discute os limites dessa potencialidade. Além disso, são propostos modelos de densidade espectral de potência dos ruídos, caracterização esparsa de canais PLC e proposto um modelo para geração de canais PLC variantes no tempo, cujo tempo de coerência entre as realizações dos canais é controlado. A estimação de canais PLC é apresentada como uma oportunidade de aplicação das técnicas de amostragem compressiva. Os resultados relacionados com as modelagens propostas constituem um ferramental de grande utilidade para projetar e analisar o desempenho de sistemas PLC.<br>This dissertation aims at discussing the measurement and characterization of outdoor electric power grid of low voltage as communication medium (power line communication - PLC). Statistical analyses carried out on several parameters such as average channel gain, coherence time, coherence bandwidth, delay spread, length of the channel impulse response, and channel capacity, when it is considered the frequency bands from 1.7 to 30 MHz, from 1.7 up to 50 MHz, and from 1.7 up to 100 MHz, are presented. These analyses reveal the circumstances in which outdoor and low-voltage electric power grids can be advantageous to support a reliable and efficient PLC system operation. Moreover, power spectral density models of additive noise and sparse representation of PLC channels are proposed. Also, a PLC time-varying channels model generator that makes use of coherence time is introduced. The proposed model generator, which is validated with measured PLC channels, is an effective tool to carry out performance analysis of PLC systems. Finally, PLC channel estimation is highlighted as an opportunity for the application of compressive sampling-based techniques. The use of traditional OFDM - based channel estimation techniques and the ones based on compressive sensing gives some directions for advancing channel estimation techniques for PLC channels.
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Abu-Al-Saud, Wajih Abdul-Elah. "Efficient Wideband Digital Front-End Transceivers for Software Radio Systems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5257.
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Software radios (SWR) have been proposed for wireless communication systems to enable them to operate according to incompatible wireless communication standards by implementing most analog functions in the digital section on software-reprogrammable hardware. However, this significantly increases the required computations for SWR functionality, mainly because of the digital front-end computationally intensive filtering functions, such as sample rate conversion (SRC), channelization, and equalization. For increasing the computational efficiency of SWR systems, two new SRC methods with better performance than conventional SRC methods are presented. In the first SRC method, we modify the conventional CIC filters to enable them to perform SRC on slightly oversampled signals efficiently. We also describe a SRC method with high efficiency for SRC by factors greater than unity at which SRC in SWR systems may be computationally demanding. This SRC method efficiently increases the sample rate of wideband signals, especially in SWR base station transmitters, by applying Lagrange interpolation for evaluating output samples hierarchically using a low-rate signal that is computed with low cost from the input signal.
A new channelizer/synthesizer is also developed for extracting/combining frequency multiplexed channels in SWR transceivers. The efficiency of this channelizer/synthesizer, which uses modulated perfect reconstruction (PR) filter banks, is higher than polyphase filter banks (when applicable) for processing few channels, and significantly higher than discrete filter banks for processing any number of variable-bandwidth channels where polyphase filter banks are inapplicable. Because the available methods for designing modulated PR filter banks are inapplicable due to the required number of subchannels and stopband attenuation of the prototype filters, a new design method for these filter banks is introduced. This method is reliable and significantly faster than the existing methods.
Modulated PR filter banks are also considered for implementing a frequency-domain block blind equalizer capable of equalizing SWR signals transmitted though channels with long impulse responses and severe intersymbol interference (ISI). This blind equalizer adapts by using separate sets of weights to correct for the magnitude and phase distortion of the channel. The adaptation of this blind equalizer is significantly more reliable and its computational requirements increase at a lower rate compared to conventional time-domain equalizers making it efficient for equalizing long channels that exhibit severe ISI.
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Isautier, Pierre Paul Roger. "Autonomous receivers for next-generation of high-speed optical communication networks." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54418.
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Advances in fiber optic communications and the convergence of the optical-wireless network will dramatically increase the network heterogeneity and complexity. The goal of our research is to create smart receivers that can autonomously identify and demodulate, without prior knowledge, nearly any signal emerging from the next-generation of high-speed optical communication networks.
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Antoja, Lleonart Guillem. "New Generation 4-Channel GNSS Receiver : Design, Production, and Testing." Thesis, Luleå tekniska universitet, Rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67420.
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Due to the current research needs and the lack of commercial multi-channel, multi-constellation GNSS receivers, a two-board solution has been developed so it can be mated with and take advantage of the processing power of the FPGA board branded as MicroZed. In order to achieve the proposed goals, an initial phase for assessing and updating the older design, building, and testing of SiGe modules (including both the electronics and casings) has been carried out. The results included demonstrate performances at logging GPS-L1 data with similar C/N0 and AGC values as the previous versions of the modules and offering navigation solutions with accuracies of a few meters. Secondly, a first iteration and design proposal for the new generation receiver has been proposed for GPS and GLONASS L1 and L2, which has been manufactured and tested. Partial tests have been performed due to the flaws of the current revision of the MicroZed Board in regards to its communication peripherals, and the results have validated the receiver’s design provided certain modifications are considered for future iterations. Furthermore, voltage and frequency tests have provided results with an error of less than 7%, and signal tests have provided C/N0 values similar to those of the SiGe modules of around 47[dB-Hz] which will be a useful baseline for future iterations. Finally, a design proposal for an Interface Board used between the older NT1065_PMOD Board and other FPGA boards carrying the standardized FMC connectors has been added to the report and negotiations with manufacturers have been engaged.
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Kallin, Maria. "Community Policing with support of digitalcommunication channels." Thesis, Mittuniversitetet, Avdelningen för data- och systemvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-36851.
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While today's police forces are decreasing in number and their resources are limited, population is at the same time increasing. This means that other types of efforts and strategies are needed to fight crime. There are different strategies to do this, one of which is called community policing that involves proactive cooperation between citizens and the police to deal with the problems. Traditionally, community policing meant that a local police in the neighbourhood called for physical meetings, where citizens and police together raised problems and discussed solutions to these. With today's limited resources, there is little possibilities for the police to execute this kind of physical collaboration and meetings. On the other hand, another meeting place has been added (the one online) and an alternative way to implement community policing may be online. With digital channels for this purpose, there may also be an opportunity to reach groups of citizens that the police have not reached before, but in order to do so, it requires work and a use of these digital channels in the right way according to community policing. The purpose of this paper is to investigate what challenges and requirements that needs to be taken into consideration when implementing community policing with the support of digital communication channels. For this purpose, qualitative research in the form of literature studies and semi-structured interviews were conducted. Findings show there are a lot of challenges and requirements to consider and there are guidelines in the analysis and discussion section, to help begin to implement this way of working. The practical implications for this thesis may help police improving their relationships with citizens in vulnerable areas to be able to cooperate according to community policing to make these areas a better and safer place to live.
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Hennschen, Lill. "A single case study exploring mediatized activism: How, why and with what consequences does the Danish activist movement #hvorerderenvoksen make use of Facebook as their primary communication channel?" Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-22564.
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This study aims to explore how the Danish grassroots movement #hvorerderenvoksen is shaped through the usage of Facebook as their primary communication tool. Using the embedded case study method, this thesis describes in detail how and why the movement arose and explains the role of Facebook’s features, primarily groups and sites, for the movements external communication. As such, it will become clear that using Facebook is not merely a means to an end. Being an activist on Facebook means using and being used, it entails the acceleration of mobilisation, but also disciplining activist action in accordance with Facebook’s terms and conditions. This thesis will draw upon modern communication theories such as mediatization and network media logic and analyse #hvorerderenvoksen as a digital social phenomenon. As will become clear, digitalisation and even more so datafication processes play a role when critically examining contemporary activism. To sum up, this thesis aims to show how an activist movement is mediatized and strongly emphasizes the role of digitalization and media hybridity in this process. It suggests that future research will focus more on the influence datafication, and especially the collection of human data and its untransparent processing, has on mediatized activism.
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Jiang, Jeng-Shiann. "Measurement, Modeling, and Performance, of Indoor MIMO Channels." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5035.
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The objective of this dissertation is to investigate the performance of the recently proposed MIMO technology in real indoor environments based on channel measurements centered at 5.8 GHz. First, a MIMO channel measurement system is implemented based on the virtual antenna array infrastructure. This measurement testbed can acquire the wideband channel matrices of MIMO systems with arbitrary array geometries. The measurement system structure and measurement procedure are described in detail in the first part. The second part is about MIMO channel modeling. Two novel number-of-sources detection algorithms, which are more robust and suitable for practical applications than traditional methods, are proposed. The MIMO path parameters, including delay, DOA, and DOD are estimated from measured data by several estimation schemes based on the ESPRIT algorithm. The accuracies of these estimation schemes are evaluated in terms of the estimation error between the capacities of the directly measured and the reconstructed channels. Moreover, based on ray tracing and measurement results, the spherical wave model is suggested to replace conventional plane wave model in order to prevent the capacity underestimation of short-range MIMO channels. An important observation is that short-range MIMO can achieve full capacity in free space channel. A threshold distance is derived to determine whether the spherical wave model is necessary. In the final part, measurements conducted in the Residential Laboratory are used to investigate the impact of element spacing, LOS, interference, spatial correlation between the interfering and data links, and stream control. A capacity enhancement scheme, which improves the performance by adapting the element locations, is implemented using our measurement system. Finally, the performances of beam selection and antenna selection in combination with MIMO technologies are compared in both narrowband and wideband channels.
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Poikolainen, Rosén Anton. "Tidningen Maskinentreprenören blir digital : En möjlighet till normkreativt tänkande i en digitaliseringsprocess." Thesis, Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-30459.
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Denna rapport beskriver ett examensarbete som gått ut på att skapa en ny hemsida till den tryckta tidningen Maskinentreprenören. Projektet resulterade i detaljerade skisser för en webbtidning anpassad för desktop, surfplattor och mobiler. Teoretiska ingångar till projektet är begreppen användbarhet, användarupplevelse, designprinciper, teorier om flerkanalspublicering samt normkritisk design. Stor vikt har lagts på en process enligt modellen Design Thinking, där metoder som enkät, intervju, användartest och personas använts för att skapa förståelse för användarna och tjänsten som skall utformas. Dessa metoder har även kopplats till en normkreativ praktik. Syftet med detta har varit att förstå de nuvarande användarna, men även förstå de potentiella användare som tidigare eventuellt uteslutits.<br>This report describes a practical exam work on creating a new website for the printed magazine Maskinentreprenören. The project resulted in detailed sketches for an online magazine designed for desktop, tablet and mobile. Theoretical frame work in the project are the concepts of usability, User Experience, design principles, theories of multi-channel publishing and norm critical design. A Design Thinking process has been applied during the project, where methods such as survey, interview, user test and personas were used to create an understanding of the users and the service to be developed. These methods have also been linked to a ”norm creative” practice. The purpose of this has been to understand the current users, but also understand the potential users that previously might have been excluded.
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Gineste, Mathieu. "Spécification d'un cadre générique pour l'expression et le déploiement de la Qualité de Service dans les architectures de communication : application à une architecture de communication par satellite." Paris 6, 2006. http://www.theses.fr/2006PA066267.
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L’évolution des applications vers le multimédia et des réseaux vers une hétérogénéité d’architectures protocolaires, a placé la notion de Qualité de Service au cœur des architectures de communication émergentes ; Ceci soulève la question de l’expression de la QdS et de l’adaptation aux besoins applicatifs de la diversité des services disponibles. Cette thèse propose un cadre sémantique et syntaxique pour décrire les contraintes applicatives et les services sous-jacents, et sélectionner et composer les services de communication, répondant aux besoins applicatifs. Les systèmes satellitaires intègrent une propriété naturelle de diffusion de l’information, ce qui en fait un composant de l’Internet de nouvelle génération. Nous montrons comment, grâce au cadre générique, les services orientés gestion de QdS spécifiques d’une architecture de communication satellitaire peuvent être composés, afin de délivrer une adaptation efficace entre les ressources satellitaires et les besoins applicatifs.
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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.
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Seehathao, Titti, and Gustavsson Helena Levin. "Att kommunicera hållbarhet inom turism : Hur kommunicerar aktörer inom besöksnäringen hållbarhet i digitala kanaler? Om det inte syns, hur vet vi att det finns?" Thesis, Karlstads universitet, Institutionen för geografi, medier och kommunikation (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-78823.
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Denna studie har som syfte att undersöka hur aktörer inom besöksnäringen i Värmland arbetar med att kommunicera hållbarhet i digitala kanaler. Vi har valt att använda oss av en kvalitativ metod med socialkonstruktivism och diskursanalys som vetenskaplig inriktning samt ett abduktivt angreppssätt. I metoden använde vi oss av textanalys för att se hur de utvalda aktörerna kommunicerar hållbarhet med texter, bilder och filmer. Urvalet av aktörerna har vi valt utifrån turismens tre delar som är inom kategorierna äta, göra och bo, där en aktör valdes ut i varje kategori. Det teoretiska ramverk grundar sig på hållbar turism och marknadsföring, där vi beskriver tidigare forskning kring hållbarhet inom sociala, ekologiska och ekonomiska aspekter, samt olika marknadsföringsstrategier inom digitala kanaler. Studien visar att aktörer använder sig av digital marknadsföring och med deras aktiva närvaro i digitala kanaler indikerar på att det bidrar till varumärkesbyggande. Studien visar också att de kommunicerar hållbar turism främst inom den sociala och ekologiska aspekten och mindre visar kommunikation av ekonomisk hållbarhet.<br>The purpose of this study is to analyze how companies in the hospitality industry in Värmland work to communicate sustainable tourism on digital channels. We have chosen to use a qualitative method with social constructivism and discourse analysis as a scientific approach and an abductive approach. In the method, we used text analysis to define how the selected companies communicate sustainability with texts, images and videos. The selection of the tourist company we’ve used was based on the tourism three category äta-göra-bo, where one company was selected in each category. Our theoretical framework is based on sustainable tourism and marketing, where we describe previous research on sustainability in social, ecological and economic aspects, as well as various marketing strategies in digital channels. The study shows that the companies use digital marketing and their active presence on digital channels indicates to the contribution of branding. The study also shows that companies communicate sustainable tourism in primarily the social and ecological aspects and less show communication of economic sustainability.
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Katz, Ettie. "Trellis codes for multipath fading ISI channels with sequential detection." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/13908.
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Ortiz, Sosa Joel. "Design of a digital baseband transceiver for wireless network-on-chip architectures." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S081.
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Le parallélisme massif dans les applications émergentes de calcul haute performance (HPC) nécessite l'utilisation des architectures multi-cœur reposant sur un système d'interconnexion efficace. Les technologies d'interconnexion sans fil sur un réseau sur puce (WiNoC) offrent une solution prometteuse pour ces architectures, permettant principalement des liaisons efficaces et prenant en charge de façon naturelle les communications broadcastand multicast. Cette thèse se concentre sur la couche physique des WiNoC, en particulier sur la conception d'un émetteur-récepteur numérique capable de fournir le meilleur compromis entre performances et efficacité énergétique. Afin de concevoir l'émetteur-récepteur numérique le plus approprié, nous avons tout d'abord étudié la dégradation des canaux en prenant en considération les phénomènes parasites courants appartenant à n'importe quel canal sans fil, contrairement au modèle idéal utilisé par la littérature sur les WiNoC. Par la suite, nous avons proposé une première solution capable de fournir une résilience aux interférences de canal, offrant également un accès à plusieurs canaux. Cette conception a ensuite été modifiée pour pouvoir s?adapter aux modèles de trafic de NoC existants. De plus, afin de fournir une communication à haut débit sans compromis significatif sur le plan énergétique, un émetteur-récepteur haute vitesse basé sur une architecture multi-porteuses a été proposé, surmontant les limites des émetteurs-récepteurs monoporteuses classiques en WiNoC. Finalement, un simulateur de réseau a été développé pour calculer le pourcentage d'utilisation des liaisons sans fil en fonction de la configuration et du placement de l'interface sans fil. Ce simulateur calcule également l'énergie dynamique consommée par un NoC électrique par rapport à un WiNoC utilisant plusieurs interfaces sans fil<br>Massive parallelism in emerging high-performance computing (HPC) applications requires the use of manycore architectures relying on an efficient on-chip interconnection system. Wireless Network-on-Chip (WiNoC) offers a promising solution for interconnection architectures, mainly providing efficient communication links and supporting natural broadcast/multicast communicatioAn. This thesis focuses on the physical layer of WiNoC, particularly on the design of a digital transceiver capable of providing the best trade-off between performance and energy efficiency. In order to design the most appropriate digital transceiver, we first study the channel degradation carried out by common parasitic phenomena belonging to any wireless channel, contrasting with the ideal channel models used by most of the WiNoC research papers. Subsequently, we propose a first solution capable of providing channel interference resilience, while offering multiple channel access. This design is later enhanced to be able to adapt to the existing NoC traffic patterns. Then, in order to provide a high speed communication without a significant compromise in energy, a high-speed transceiver based on a multi-carrier architecture is proposed, overcoming the limitations of conventional single-carrier WiNoC transceivers. Finally, a network simulator is developed to calculate the percentage of wireless link utilization according to the wireless interface configuration and placement. This simulator further computes the dynamic energy consumed by an electrical NoC compared with a WiNoC using multiple wireless interfaces
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Bradley, Martin James. "Adaptive equalisation for fading digital communication channels." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/5177/.
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This thesis considers the design of new adaptive equalisers for fading digital communication channels. The role of equalisation is discussed in the context of the functions of a digital radio communication system and both conventional and more recent novel equaliser designs are described. The application of recurrent neural networks to the problem of equalisation is developed from a theoretical study of a single node structure to the design of multinode structures. These neural networks are shown to cancel intersymbol interference in a manner mimicking conventional techniques and simulations demonstrate their sensitivity to symbol estimation errors. In addition the error mechanisms of conventional maximum likelihood equalisers operating on rapidly time-varying channels are investigated and highlight the problems of channel estimation using delayed and often incorrect symbol estimates. The relative sensitivity of Bayesian equalisation techniques to errors in the channel estimate is studied and demonstrates that the structure's equalisation capability is also susceptible to such errors. Applications of multiple channel estimator methods are developed, leading to reduced complexity structures which trade performance for a smaller computational load. These novel structures are shown to provide an improvement over the conventional techniques, especially for rapidly time-varying channels, by reducing the time delay in the channel estimation process. Finally, the use of confidence measures of the equaliser's symbol estimates in order to improve channel estimation is studied and isolates the critical areas in the development of the technique — the production of reliable confidence measures by the equalisers and the statistics of symbol estimation error bursts.
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盧志明 and Chi-ming Lo. "Analytical evaluation of wireless digital communication performance over fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B3124208X.
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Міська, Ігор Васильвич, та Ihor Mis’ka. "Методи та засоби структурно-параметричного моделювання цифрових каналів зв’язку". Master's thesis, Тернопільський національний технічний університет імені Івана Пулюя, 2020. http://elartu.tntu.edu.ua/handle/lib/33324.
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в кваліфікаційній роботі магістра досліджено методи та засоби структурнопараметричного моделювання цифрових каналів зв’язку, які уможливлюють імітаційне
моделювання та визначення критеріїв ефективності цифрових каналів зв’язку, які
використовуються у вбудованих комп’ютерних системах. Визначено структурні та
функціональні елементи цифрових каналів зв’язку, наведено їх математичні описи та методи
їх моделювання. Таке розбиття на елементи уможливлює коректну побудову їх математичних
моделей та вибір засобів моделювання. Визначено засоби за допомогою яких можливе
моделювання структурних та функціональних елементів цифрових каналів зв’язку та їх
параметри, шляхом їх ідентифікації із відповідними інструментами Matlab Simulink.
Проведено імітаційне моделювання цифрових каналів зв’язку та визначено їх параметри на
практичному прикладі цифрового модему V.32bis який використовується у комп’ютерних та
вбудованих системах. Отримані результати свідчать про адекватність моделювання та
можливість застосування методів та засобів структурно-параметричного моделювання
цифрових каналів зв’язку у практичних задачах побудови вбудованих систем.<br>in the qualification work of the master the methods and means of structure-parameter
modeling of digital communication channels are investigated, which enable simulation modeling and
determination of efficiency criteria of digital communication channels used in embedded computer
systems. The structural and functional elements of digital communication channels are determined,
their mathematical descriptions and methods of their modeling are given. This division into elements
allows the correct construction of their mathematical models and the choice of modeling tools. The
means by which it is possible to model the structural and functional elements of digital
communication channels and their parameters by identifying them with the appropriate Matlab
Simulink tools are identified. Simulation of digital communication channels is carried out and their
parameters are determined on a practical example of digital modem V.32bis used in computer and
embedded systems. The obtained results testify to the adequacy of modeling and the possibility of
applying methods and means of structure-parameter modeling of digital communication channels in
the practical problems of building embedded systems.<br>ВСТУП...8
РОЗДІЛ 1 ОСНОВИ СИСТЕМ ПЕРЕДАЧІ ДАНИХ ....11
1.1. Призначення та особливості системи Matlab ...11
1.2. Особливості проектування систем зв’язку в середовищі Matlab...12
1.3. Пакет Communications Toolbox ...14
1.4. Поняття моделі ...16
1.5. Співвідношення між системою та моделлю ...19
1.6. Структурно-параметричне моделювання ...20
1.6.1. Двовимірне та тривимірне параметричне моделювання ...20
1.6.2. Типи параметризації ...22
1.6.3. Метод багатовимірного параметричного моделювання ...23
РОЗДІЛ 2 МОДЕЛЮВАННЯ СИСТЕМ ПЕРЕДАЧІ ДАНИХ...26
2.1. Функції моделювання й аналізу сигналів ...26
2.2. Функції кодування/декодування джерела...27
2.2.1. Нерівномірне квантування...27
2.2.2. Логарифмічне й експонентне перетворення...27
2.3. Функції завадостійкого кодування/декодування ...28
2.3.1. Блокові коди..29
2.3.2. Згорткові коди ...30
2.4. Модуляція і демодуляція ...32
2.4.1. Поняття та види модуляції та демодуляції ...32
2.4.2. Фазова модуляція ...33
2.4.3. Частотна модуляція ...34
2.4.4. Амплітудна модуляція ...35
2.5. Моделювання каналів зв'язку ...36
2.6. Спеціальні фільтри...36
2.7. Функції обчислень у полях Галуа ...37
2.8. Допоміжні функції ...38
РОЗДІЛ 3 МОДЕЛЮВАННЯ СИСТЕМИ ПЕРЕДАЧІ ДАНИХ ІЗ
ЗАСТОСУВАННЯМ МОДЕМУ V.32BIS...39
3.1. Моделювання модему V.32bis використовуючи пакет Communications ...39
3.1.1. Функція моделювання передавача модему V.32bis...41
3.1.2. Функція моделювання приймача модему V.32bis...45
3.2. Моделювання системи зв’язку використовуючи набір блоків Communications
Blockset ...50
3.2.1. Comm Sources (джерела повідомлень)...51
3.2.2. Comm Sinks (одержувачі повідомлень)... 51
3.2.3. Source Coding (кодування й декодування джерела).... 51
3.2.4. Channel Coding (завадостійке кодування/декодування)....51
3.2.5. Modulation (модуляція/демодуляція) ...51
РОЗДІЛ 4 ОХОРОНА ПРАЦІ ТА БЕЗПЕКА В НАДЗВИЧАЙНИХ СИТУАЦІЯХ...55
4.1. Охорона праці.... 55
4.2. Оцінка стійкості роботи об’єкту економіки до впливу вражаючих факторів ядерної зброї...57
ВИСНОВКИ .... 62
СПИСОК ВИКОРИСТАНИХ ДЖЕРЕЛ...63
Додаток А ...65
Додаток Б ...69
48
Ruiz, Svensson Erik, and Emma Rådhall. "Social responsibility in the digital era : Digital communication agencies social responsibility in digital channels." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Datateknik och informatik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-46404.
Full textAbstract:
Purpose and problem discussion: Nowadays, it is crucial to implement social responsibility to business operations to succeed as a business. Companies face increased demands from customers and stakeholders to show their actions regarding social responsibility. At the same time, digital development is shaping the communication industry, creating new communication platforms in the world. The purpose of this study is to explore digital communication agencies role in the production and implementation of digital products within digital channels to best understand digital social responsibility. The study aims to answer the research questions: What social responsibilities does a digital communication agency have in regard to the products and messages they produce for digital channels? and How do digital communication agencies become socially responsible when using digital channels? Method: An abductive analysis method was applied to semi-structured interviews with digital communication agencies in Jönköping, Sweden. The analysis of the empirical findings has resulted in deeper understanding of social responsibility in digital environments; a study area that has not been explored before. Four digital communication agencies represent the average digital social responsibility mindset and business culture in Jönköping, Sweden. This gave us the possibility to research social responsibility on digital channels. Results, discussion and conclusions: The results show that the digital communication agencies clients are entirely responsible for the digital material published on their own digital channels. Although, the agencies do need to make sure they produce the best possible material for their clients to avoid bad relationships with stakeholders and a bad reputation. The results also show that social responsibility is not first priority for any company; profitability always comes first. The key to digital social responsibility is to work with the right clients and thoroughly analyse the client’s business operations to bring out the best in each case and to be prepared for backlashes. The digital communication agencies could also benefit from a crisis plan, to minimise stress and optimize the problem solving if a crisis would occur. If doing this correctly,the agencies enable genuine and honest digital communication, which minimises the risk of being perceived unfairly on digital platforms. This is especially of importance on digital platforms, where the speed, great reach and two-way communication makes it even easier to receive negativity and face backlashes. A digital communication agency can become socially responsible by working with the right clients, as well as producing and publishing genuine and honest digital communication.
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Frisch, Yannik Felix, and Jaakko Alarik Tawast. "Digital Sports Sponsorship : The Impact of Digital Communication Channels on Sponsorship Relationships." Thesis, Umeå universitet, Företagsekonomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-164732.
Full textAbstract:
Supporters and spectators of sports club matches are often exposed to advertising of sponsors of the respective club. The most common exposure is to billboard ads, such as, e.g. LED screens on the side of the football pitch, the logo of sponsors embedded in the ice of an ice hockey rink or the logo of the sponsor on the athletes' jerseys. However, exposure does not mean engagement and engagement is what sponsors seek as it can increase the purchase intention of the supporters and spectators engaging with the company. With classical sponsorship approaches, it is hard to measure the number of supporters that actually engage with and eventually purchase from the sponsoring companies. Furthermore, the engagement approach that companies choose besides classical offline sponsorship is limited to occasional news updates or - at the most - highlights of matches. Therefore, the distance between sponsors and supporters is perceived as very wide by the latter. Digital communication channels and especially social media generally poses a good way to engage with supporters, but many companies fail to implement a strategic approach to social media communication.This study is aimed at analysing sports sponsorship in the light of digitalisation and wants to contribute to the scarce literature in the field. Sponsorship is a generally widely investigated and researched topic, and so is digital marketing. In current literature, these topics rarely appear closely linked to each other. Although many companies recognise the importance of digital communication tools for their sponsorship agreements, many fail to integrate it properly. Also, sports clubs often neglect the strategic implementation of digital communication. To fill this research gap, the study at hand wants to answer the following research question.“How is sports sponsorship effectiveness enhanced by the use of digital communication channels and by restructuring the relationships among all three stakeholders within the respective agreement?”An exploratory mixed methods study, which includes 115 questionnaire respondents as well as six expert interviews, was conducted to address this research question as well as the novelty of the research topic. The research was undertaken with a focus on Swedish football and ice hockey teams in professional divisions as well as their sponsors. The study yielded several results which contribute to the literature and show relevance for practice. Firstly, the study showed that all the stakeholders lack the knowledge of the aspiration of each other as well as structured communication strategies in digital channels. Secondly, the communication between clubs and sponsors is insufficient, and wishes, ideas and assumptions concerning a sponsorship agreement remain hidden to the other parties. Thirdly, the clubs, as well as the sponsors, fail to integrate the supporters' wishes and needs into the sponsorship approach, which impedes the effectiveness and the success of this agreement. Fourthly, clubs and sponsors fail to implement precise indicators for the success of a sponsorship deal.
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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.
Full textAbstract:
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2008.<br>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.