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Dissertations / Theses on the topic 'Channel tracking'
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Mohanty, Nirode. "Phase Tracking Error in a Fading Channel." International Foundation for Telemetering, 1987. http://hdl.handle.net/10150/615322.
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International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, CaliforniaThe phase tracking error of the reception of a QPSK signal transmitted in a severe fading environment is derived. The phase estimate derived from the phase lock loop (PLL) will be used by a binary phase shift keying (BPSK) receiver for the recovery of the data. The resultant probability of bit error is analyzed, and is shoen to be significantly improved when the phase of the transmitted signal is tracked by a PLL separately and utilized in the coherent detection.
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Kho, Yau Hee. "MIMO Receiver Structures with Integrated Channel Estimation and Tracking." Thesis, University of Canterbury. Electrical and Computer Engineering, 2008. http://hdl.handle.net/10092/1264.
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This thesis looks at the problem of channel estimation and equalization in a multiple-input multiple-output (MIMO) dispersive fading environments. Two classes of MIMO receiver structure are proposed with integrated channel estimation and tracking. One is a symbol-by-symbol based receiver using a MIMO minimum mean square error (MMSE) decision feedback equalizer (DFE), and the other is a sequence-based receiver using a partitioned Viterbi algorithm (PVA) which approaches the performance of maximum likelihood sequence estimation (MLSE). A MIMO channel estimator capable of tracking the time and frequency selective channel impulse responses, known as the vector generalized recursive least squares (VGRLS) algorithm, is developed. It has comparable performance and a similar level of complexity as the optimum Kalman filter. However, it does not require any knowledge of the channel statistics to operate and as such it can be employed in a Rician fading channel readily. A reduced complexity form of the estimator, known as the vector generalized least mean squares (VGLMS) algorithm, is also developed. This is achieved by replacing the online recursive computation of the VGRLS algorithm's 'intermediate' Riccatti matrix with an offline pre-computed matrix. This reduces the complexity of the algorithm by an order of a magnitude, but at the expense of degraded performance. The estimators are integrated with the above-mentioned equalizers in a decision directed mode to form a receiver structure that can operate in continuously time-varying fading channels. Due to decision delays, the outputs from the equalizer are delayed and this then produces 'delayed' channel estimates. A simple polynomial-based channel prediction module is employed to provide up-to-date channel estimates required by the equalizers. However, simulation results show that the channel prediction module may be omitted for a very slowly fading channel where the channel responses do not vary much. In the case of the PVA- receiver, the zero-delay tentative decisions are used as feedback to the channel estimators with negligible loss.
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Mongol, Bayarpurev, Takaya Yamazato, and Masaaki Katayama. "Channel Estimation and Tracking Schemes for the Pulse-Shaping OFDM Systems." IEEE, 2009. http://hdl.handle.net/2237/13975.
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Tu, Chao-Cheng. "Subspace-based blind channel estimation and tracking for MIMO-OFDM systems." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94926.
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Multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) is now widely considered as a favored technology for emerging and future generation wireless systems. MIMO-OFDM aims to achieve increased channel capacity limit by exploiting the use of multiple antennas in combination with multi-carrier orthogonal modulation. While the possibility of achieving this limit is bestowed on the invention of capacity-achieving coding and decoding techniques, in reality, this prospect relies heavily on the existence and use of advanced channel estimation techniques. To facilitate fast and reliable channel estimation in MIMO-OFDM systems, pilot symbol insertion is usually considered; however, the channel capacity is greatly reduced by inserting those pilot symbols. Therefore, employing fast-converging and reliable blind channel estimation for MIMO-OFDM seems to be an attractive solution for future wireless systems. To this end, blind channel estimation based on second order statistics (SOS), instead of higher order statistics (HOS), has been widely considered as a suitable candidate. Amid SOS-based blind approaches, subspace-based estimation is attractive since reliable estimates can often be obtained in a simple form by optimizing a quadratic cost function. Nonetheless, the performance of the subspace-based blind channel estimators may still be seriously degraded under time-varying conditions. This problem can generally make overall performance unsatisfactory, especially in MIMO-OFDM systems whose number of subcarriers is large. In order to overcome this limitation and successfully employ subspace-based channel estimation in MIMO-OFDM systems, it is essential to minimize the required length of the underlying time averaging period. In this thesis, we propose a new subspace-based blind channel estimator that requires only a comparably short time averaging period. We consider the design of such an estimator directly in the frequency domain, as oLe multiplexage par répartition en fréquences orthogonales (orthogonal frequency division multiplexing, soit OFDM) à entrées et à sorties multiples (multiple-input multiple-output, soit MIMO) est maintenant généralement considéré comme une technologie à préconiser pour les nouveaux systèmes sans fil et ceux des générations ultérieures. Le MIMO-OFDM vise à augmenter la limite de capacité Shannon en combinant l'utilisation d'antennes multiples et la modulation orthogonale multiporteuse. Bien que la possibilité d'atteindre cette limite soit possible grâce à l'invention de techniques d'encodage et de décodage atteignant la capacité, en réalité, cette perspective d'avenir se base en grande partie sur l'existence et l'utilisation de techniques d'estimation de voie avancées. Pour faciliter l'estimation de voie rapide et fiable dans les systèmes MIMO-OFDM, on songe habituellement à l'insertion de symboles pilotes; cependant, la capacité de la voie est grandement réduite par leur insertion. L'utilisation d'estimation de voie aveugle fiable et à convergence rapide pour les MIMO-OFDM semble donc être une solution attrayante pour les futurs systèmes sans fil. À cette fin, l'estimation de voie aveugle basée sur des statistiques de deuxième ordre, au lieu des statistiques d'ordre supérieur, est généralement considérée comme une candidate acceptable. Parmi les approches aveugles basées sur les statistiques de deuxième ordre, l'estimation basée dans le sous-espace est attrayante, puisque des estimations fiables peuvent souvent être obtenues de façon simple en optimisant une fonction de coût quadratique. Néanmoins, la performance des estimateurs de voie aveugles basés dans le sous-espace peut être gravement dégradée dans des conditions instationnaires. Ce problème peut habituellement rendre la performance globalement insatisfaisante, surtout dans les systèmes MIMO-OFDM avec un nombre de sous-porteuses élevé. Afin de compen
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David, Radu Alin. "Improving Channel Estimation and Tracking Performance in Distributed MIMO Communication Systems." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/229.
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This dissertation develops and analyzes several techniques for improving channel estimation and tracking performance in distributed multi-input multi-output (D-MIMO) wireless communication systems. D-MIMO communication systems have been studied for the last decade and are known to offer the benefits of antenna arrays, e.g., improved range and data rates, to systems of single-antenna devices. D-MIMO communication systems are considered a promising technology for future wireless standards including advanced cellular communication systems. This dissertation considers problems related to channel estimation and tracking in D-MIMO communication systems and is focused on three related topics: (i) characterizing oscillator stability for nodes in D-MIMO systems, (ii) the development of an optimal unified tracking framework and a performance comparison to previously considered sub-optimal tracking approaches, and (iii) incorporating independent kinematics into dynamic channel models and using accelerometers to improve channel tracking performance. A key challenge of D-MIMO systems is estimating and tracking the time-varying channels present between each pair of nodes in the system. Even if the propagation channel between a pair of nodes is time-invariant, the independent local oscillators in each node cause the carrier phases and frequencies and the effective channels between the nodes to have random time-varying phase offsets. The first part of this dissertation considers the problem of characterizing the stability parameters of the oscillators used as references for the transmitted waveforms. Having good estimates of these parameters is critical to facilitate optimal tracking of the phase and frequency offsets. We develop a new method for estimating these oscillator stability parameters based on Allan deviation measurements and compare this method to several previously developed parameter estimation techniques based on innovation covariance whitening. The Allan deviation method is validated with both simulations and experimental data from low-precision and high-precision oscillators. The second part of this dissertation considers a D-MIMO scenario with $N_t$ transmitters and $N_r$ receivers. While there are $N_t imes N_r$ node-to-node pairwise channels in such a system, there are only $N_t + N_r$ independent oscillators. We develop a new unified tracking model where one Kalman filter jointly tracks all of the pairwise channels and compare the performance of unified tracking to previously developed suboptimal local tracking approaches where the channels are not jointly tracked. Numerical results show that unified tracking tends to provide similar beamforming performance to local tracking but can provide significantly better nullforming performance in some scenarios. The third part of this dissertation considers a scenario where the transmit nodes in a D-MIMO system have independent kinematics. In general, this makes the channel tracking problem more difficult since the independent kinematics make the D-MIMO channels less predictable. We develop dynamics models which incorporate the effects of acceleration on oscillator frequency and displacement on propagation time. The tracking performance of a system with conventional feedback is compared to a system with conventional feedback and local accelerometer measurements. Numerical results show that the tracking performance is significantly improved with local accelerometer measurements.
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Atapattu, Lakmali Nadisha Kumari. "Channel tracking in SDMA-based multi-user MIMO-OFDM communications systems." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/65272/1/Lakmali_Atapattu_Thesis.pdf.
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Capacity of current and future high data rate wireless communications depend significantly on how well changes in the wireless channel are predicted and tracked. Generally, this can be estimated by transmitting known symbols. However, this increases overheads if the channel varies over time. Given today’s bandwidth demand and the increased necessity for mobile wireless devices, the contributions of this research are very significant. This study has developed a novel and efficient channel tracking algorithm that can recursively update the channel estimation for wireless broadband communications reducing overheads, therefore increasing the speed of wireless communication systems.
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Gupte, Abhishek. "A Method for Tracking the Accuracy of Channel Estimates in MIMO Receivers." International Foundation for Telemetering, 2009. http://hdl.handle.net/10150/605996.
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ITC/USA 2009 Conference Proceedings / The Forty-Fifth Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2009 / Riviera Hotel & Convention Center, Las Vegas, NevadaMultiple input multiple output communication systems offer significant advantages, but only if the receiver has an accurate estimate of the channel state information (CSI). To obtain a CSI estimate, the transmitter must stop sending data, and instead send a training sequence. To maximize throughput, the time spent sending training data should be minimized. This paper describes a method which allows the receiver to track the accuracy of its CSI estimate, so that it can request new training data only when necessary.
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Sung-hoon, Jang, Han Sung-hee, and Kim Heung-bum. "Auto-tracking antenna pattern effects on multipath channel model at test range." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/607672.
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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaTelemetry propagation channel is modeled to predict PCM/FM telemetry receiving signal level at APG(Anheung Proving Ground), ADD(Agency for Defense Development). Channel model is composed of direct wave and reflected wave in sea surface, so-called 2-ray model. Our 2-ray model includes transmitting antenna radiation pattern, auto-tracking antenna radiation pattern, sea surface reflection coefficient and phase depending on incident angle. Vertical and horizontal polarized receiving signal strength is obtained from pre-calculated flight trajectory of transmitter. Calculated results are compared with measured data in real flight test. 2-ray channel model can predict almost identical receiving signal level and calculate starting point of multi-path fading effect. Using these results, receiving system can be moved to more proper position before flight test.
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Champion, James. "A 3-CHANNEL MONOPULSE TRACKING RECEIVER SYSTEM USING COMMERCIAL OFF-THE-SHELF EQUIPMENT." International Foundation for Telemetering, 1998. http://hdl.handle.net/10150/607375.
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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, CaliforniaThree-channel monopulse tracking receiver systems are commonly used for high performance tracking of satellites, missiles, or aircraft to maximize the reception of data. Typically, the receiver in such systems are custom designed for their end purpose. This results in a high cost to cover the development, service, and support of a highly specialized piece of equipment. This paper covers the requirements and performance of a 3-channel monopulse tracking receiver assembled from commercial-off-the-shelf (COTS) equipment. Such a system provides an option for designing or upgrading tracking stations with the lower cost, larger support base, and greater system configuration choices that are available with COTS equipment.
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Hayman, Rebecca. "A DSP Algorithm for Multi-Channel Maximum Power Point Tracking in Photovoltaic Systems." Honors in the Major Thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/719.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucfBachelors
Engineering and Computer Science
Electrical Engineering
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Ehsani, Ali Reza 1963. "Design of a microprocessor based auto sun-tracking multi-channel solar radiometer system." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278092.
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A microprocessor controlled auto sun-tracking 10-channel solar radiometer system has been designed and fabricated. The instrument measurements are employed in determining the atmospheric optical depths at 10 discrete wavelengths through the visible and near IR regions. The solar radiometer consists of 10 parallel Field Of View (FOV) telescopes which are all pointed towards the sun via an active auto sun-tracking system. Each channel consists of a geometrical aperture-defined telescope, interference filter and silicon photodiode/op amp combination. The data is collected by a Data Acquisition System (DAS) controlled by an 8-bit microprocessor. The automated DAS tracks the sun, measures the temperature of detectors as well as the output of all 10 channels and writes these values to a RAM. At the end of data collection period the collected data can be serially transferred to an IBM compatible personal computer.
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Rey, Micolau Francesc. "Feedback-Channel and adaptative mimo coded-modulations." Doctoral thesis, Universitat Politècnica de Catalunya, 2006. http://hdl.handle.net/10803/6899.
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En els sistemes de comunicacions on el transmissor disposa de certa informació sobre l'estat del canal (CSI), es possible dissenyar esquemes lineals de precodificació que assignin la potència de manera òptima induint guanys considerables, sigui en termes de capacitat, sigui en termes de la fiabilitat de l'enllaç de comunicacions. A la pràctica, aquest coneixement del canal mai és perfecte i, per tant, el senyal transmès es veurà degradat degut al desajust entre la informació que el transmissor disposi del canal i el seu estat real.En aquest context, aquesta tesi estudia dos problemes diferents però alhora estretament relacionats: el disseny d'un esquema pràctic de seguiment del canal en transmissió per canals variants en temps, i el disseny d'esquemes lineals de precodificació que siguin robustos a la incertesa del canal.
La primera part de la tesi proposa el disseny d'un esquema de seguiment de canal que, mitjançant un enllaç de retorn de baixa capacitat, proporcioni al transmissor una informació acurada sobre el seu estat. Històricament, aquest tipus d'esquemes han rebut fortes crítiques degut a la gran quantitat d'informació que és necessari transmetre des del receptor cap el transmissor. Aquesta tesi, doncs, posa especial èmfasi en el disseny d'aquest canal de retorn. La solució que es proposa, basada en el filtre de Kalman, utilitza un esquema que recorda al transmissor DPCM. Les variacions del canal són tractades mitjançant dos predictors lineals idèntics situats en el transmissor i en el receptor, i un canal de retorn que assisteix el transmissor amb l'error de predicció. L'interès d'aquest esquema diferencial és que permet seguir les variacions del canal amb només dos o quatre bits per coeficient complex, fins i tot en canals ràpidament variants.
La resta de la tesi cobreix el segon objectiu, l'estudi de diferents esquemes d'assignació de potències quan el coneixement del canal en transmissió no és perfecte. El problema es planteja per a un sistema MIMO OFDM com a formulació més general, incloent els casos d'una sola antena, de l'esquema beamforming i del canal multiplicatiu com a casos particulars.
Primerament s'ha plantejat l'optimització dels criteris de mínim error quadràtic mig (MMSE) i mínima BER sense codificar. La innovació en el treball presentat a la tesi, respecte a altres treballs que segueixen els mateixos criteris de disseny, ha estat la formulació Bayesiana del problema per al disseny dels algoritmes robustos.
La tesi continua amb el plantejament d'estratègies robustes d'assignació de potència destinades a minimitzar la BER codificada. Per aquesta tasca s'han utilitzat criteris de teoria de la informació. Possiblement una de les principals contribucions d'aquesta tesi ha estat el plantejament del cut-off rate com a paràmetre de disseny. Aquest criteri s'introdueix com alternativa a la capacitat de canal o a la informació mutual per al disseny del transmissor quan s'inclou codificació de canal.
La ultima part de la tesi proposa un interleaver adaptatiu de baixa complexitat que, utilitzant el coneixement del canal disponible en el transmissor, assigna estratègicament els bits no només per combatre les ràfegues d'errors, sinó també per lluitar contra els esvaïments que puguin presentar les diferents portadores del canal per a una realització concreta. El disseny d'aquest interleaver, anomenat "interleaver RCPC" està basat en els codis Rate-Compatible Punctured Convolutional Codes. Com s'il·lustra a partir del resultats numèrics, l'ús d'aquest interleaver millora les prestacions dels algoritmes quan es comparen amb les que s'obtindrien si s'utilitzes un interleaver de bloc o un interleaver pseudo-aleatori.
When the transmitter of a communication system disposes of some Channel State Information (CSI), it is possible to design linear precoders that optimally allocate the power inducing high gains either in terms of capacity or in terms of reliable communications. In practical scenarios, this channel knowledge is not perfect and thus the transmitted signal suffers from the mismatch between the CSI at the transmitter and the real channel.
In that context, this thesis deals with two different, but related, topics: the design of a feasible transmitter channel tracker for time varying channels, and the design of optimal linear precoders robust to imperfect channel estimates.
The first part of the thesis proposes the design of a channel tracker that provides an accurate CSI at the transmitter by means of a low capacity feedback link. Historically, those schemes have been criticized because of the large amount of information to be transmitted from the receiver to the transmitter. This thesis focuses, thus, the attention in an accurate design of the return link. The proposed solution is based on the Kalman filter and follows a scheme that reminds the well known DPCM transmitter. The channel variability is processed by two identical linear predictors located at the transmitter and at the receiver, and a feedback link that assists the transmitter with the prediction error. The interest of this differential scheme is that allows to track the channel variations with only two or four bits per complex channel coefficient even in fast time-varying channels.
The rest of the thesis covers the second topic, studying different robust power allocation algorithms when the CSI is not perfectly known at the transmitter. For the sake of generality, the problem is formulated for the general MIMO OFDM case, encompassing the single antenna transmission, the beamforming schemes and the frequency-flat fading channels as particular cases.
First, the minimum MSE and the minimum uncoded BER parameters are chosen to be optimized, evaluating the performance of the algorithms in terms of uncoded BER. The basic novelty with respect to previous works that considers the same strategies of design is the proposal of a Bayesian approach for the design of the robust algorithms.
Next the study is extended by proposing robust power allocation strategies focused on the minimization of the coded BER. For this purpose, information-theoretic criteria are used. Probably, one of the main contributions in the thesis is the proposal of the cut-off rate as a parameter of design whose maximization is directly related to the coded BER. This criterion is introduced as an alternative to the channel capacity and the mutual information for the design of optimal transceivers in the presence of any channel coding stage.
The last part of the thesis proposes a low complexity adaptive interleaver that, making use of the CSI available at the transmitter, reallocates the bits not only to combat the bursty channel errors but also to combat the specific distribution of the faded subcarriers as a function of the channel response. The design of this interleaver, named as "RCPC interleaver", is based on the Rate-Compatible Punctured Convolutional Codes. As shown by numerical results, the use of this interleaver improves the performance of the algorithms when they are compared with the classical block interleavers and pseudo-random interleavers.
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Yeh, ShihYuan. "Development of a digital tracking array with single-channel RSNS and monopulse digital beamforming." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/4956.
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Approved for public release; distribution is unlimitedUnmanned aerial vehicles (UAVs) are widely used in military applications, and one of the most common missions is remote sensing. Remote sensing requires UAVs equipped with different kinds of sensors. Information collected by remote sensors must be transmitted back to a ground control station (GCS) to conduct analysis. The majority of UAVs are controlled directly by GCS personnel using radio frequency (RF), line-of-sight (LOS) links. The ground antenna must acquire and then track the UAV signal. A digital phased array allows signal processing functions to be performed in the antenna processor as well as beamforming and tracking. The development of a digital tracking array with single-channel robust symmetrical number system (RSNS) and monopulse digital beamforming (DBF) to track a UAV's transmitted signal is described in this thesis. The RSNS is used as the direction finding (DF) algorithm and can provide high angle resolution with two closely spaced elements. However, as is typical for an array, the angle accuracy is reduced at the two ends of the field-of-view (FOV). The monopulse DBF is used to precisely track the signals. The monopulse tracking technique provides precise angle accuracy within a FOV of approximately ±45. The tracking system is developed in LabView, and the performance of a six-element prototype array is demonstrated by measurement in an anechoic chamber.
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Sanzhong, Li, Zhang Qishan, and L. L. Cheng. "DESIGN OF A PARALLEL MULTI-CHANNEL BPSK DIRECT-SEQUENCE SPREAD-SPECTRUM RECEIVER." International Foundation for Telemetering, 1997. http://hdl.handle.net/10150/609680.
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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, NevadaA parallel multi-channel receiver for binary phase shift keyed (BPSK) direct-sequence (DS) spread-spectrum (SS) is introduced in this paper. It adopts a Costas carrier frequency-tracking loop which maintains frequency lock rather than phase lock, and the delay-lock error can be noncoherently obtained to track the PN code. For airborne applications, this method will extend effectively the receiver’s tracking dynamics range for the carrier Doppler shift. A erasable programmable logic device (EPLD) is applied to get the advantage of smaller size and higher flexibility. A high speed microprocessor (TMS320C30) which acts as the processing unit of the receiver is used for acquiring and tracking of the carrier and PN code by digital signal processing algorithms. This receiver is more flexible and is easily improved by reconfiguring the EPLD and modifying the software algorithms. Its fundamental principle is described in the paper.
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Jain, Monika. "Regularized ensemble correlation filter tracking." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/229266/1/Monika_Jain_Thesis.pdf.
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Visual Object Tracking is the task of tracking an object within a video. Broadly, most tracking algorithms can be classified into neural network based, correlation filter based, and hybrid. This thesis investigates various methods to improve tracking using correlation filters. The thesis contributes four novel trackers. The first tracker uses an appearance model pool to avoid faulty filter updates. Next, the appearance feature channel weights are learned using the graph-based similarity followed by modelling sparse spatio-temporal variations. At last, non-linearity of the appearance features is captured. The thesis also presents extensive evaluation of the proposed trackers on standard datasets.
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Gurel, Ilker. "Channel Estimation For Ofdm Systems." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606940/index.pdf.
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In this thesis, various pilot symbol aided channel estimation and tracking methods are investigated and their performances are compared for an OFDM system with packet based communication on HF channel. For the HF channel, Watterson HF channel model is used. The compared methods are least squares (LS) channel estimation, linear minimum mean square error (LMMSE) channel estimation, least mean squares (LMS) channel tracking, recursive least squares (RLS) channel tracking, constant position model based Kalman filter channel tracking, and constant velocity model based Kalman filter channel tracking. For LMS and RLS methods some adaptive approaches are also investigated.
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Hankin, Barry Gwyn. "Modelling the dispersion of a passive tracer in complex open channel flows using random walk, particle tracking techniques." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296886.
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Wu, Mingyang. "Pitch tracking and speech enhancement in noisy and reverberant environments." Columbus, Ohio : Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1064341479.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xvi, 149 p.; also includes graphics. Includes abstract and vita. Advisor: DeLiang Wang, Dept. of Computer and Information Science. Includes bibliographical references (p. 136-149).
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Jakubisin, Daniel J. "Array Processing for Mobile Wireless Communication in the 60 GHz Band." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/31130.
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In 2001, the Federal Communications Commission made available a large block of spectrum known as the 60 GHz band. The 60 GHz band is attractive because it provides the opportunity of multi-Gbps data rates with unlicensed commercial use. One of the main challenges facing the use of this band is poor propagation characteristics including high path loss and strong attenuation due to oxygen absorption. Antenna arrays have been proposed as a means of combating these effects. This thesis provides an analysis of array processing for communication systems operating in the 60 GHz band. Based on measurement campaigns at 60 GHz, deterministic modeling of the channel through ray tracing is proposed. We conduct a site-specific study using ray tracing to model an outdoor and an indoor environment on the Virginia Tech campus. Because arrays are required for antenna gain and adaptability, we explore the use of arrays as a form of equalization in the presence of channel-induced intersymbol interference. The first contribution of this thesis is to establish the expected performance achieved by arrays in the outdoor environment. The second contribution is to analyze the performance of adaptive algorithms applied to array processing in mobile indoor and outdoor environments.Master of Science
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Feldman, Chris R. "Evolutionary Genetics of Tetrodotoxin (TTX) Resistance in Snakes: Tracking a Feeding Adaptation from Populations Through Clades." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/159.
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Understanding the nature of adaptive evolution has been the recent focus of research detailing the genetic basis of adaptation and theoretical work describing the mechanics of adaptive evolution. Nevertheless, key questions regarding the process of adaptive evolution remain. Ultimately, a detailed description of the ecological context, evolutionary history, and genetic basis of adaptations is required to advance our understanding of adaptive evolution. To address some of the contemporary issues surrounding adaptive evolution, I examine phenotypic and genotypic changes in a snake feeding adaptation. Adaptations can arise through fixation of novel mutations or recruitment of existing variation. Some populations of the garter snakes Thamnophis sirtalis, T. couchii, and T. atratus possess elevated resistance to tetrodotoxin (TTX), the lethal toxin of their newt prey. I show that TTX resistance has evolved independently through amino acid changes at critical sites in a voltage-gated sodium channel protein (Nav1.4) targeted by TTX. Thus, adaptive evolution has occurred multiple times in garter snakes via de novo acquisition of beneficial mutations. Detailing the genetic basis of adaptive variation in natural populations is the first step towards understanding the tempo and mode of adaptive evolution. I evaluate the contribution of Nav1.4 alleles to TTX resistance in two garter snake species from central coastal California. Allelic variation in Nav1.4 explains 29% and 98% of the variation in TTX resistance in T. atratus and T. sirtalis, respectively, demonstrating that Nav1.4 is a major effect locus. The simple genetic architecture of TTX resistance in garter snakes may significantly impact the dynamics of trait change and coevolution. Patterns of convergent evolution are cited as some of the most compelling examples of the strength of natural selection in shaping organismal diversity. Yet repeated patterns may tell us as much about the constraints that restrict evolution as about the importance of natural selection. I present data on convergent molecular adaptations in parallel arms races between diverse snakes and amphibians from across the globe. Six snake species that prey on TTX bearing amphibians have independently acquired amino acid changes in Nav1.4. The derived mutations are clustered in two portions of the gene, often involving the same sites and substitutions. While a number of amino acid changes can make Nav1.4 insensitive to TTX, most of these negatively impact or abolish the ion-conducting function of the protein. Thus, intramolecular pleiotropy likely prevents most replacements from becoming fixed and imposes limits on protein evolution.
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Shah, Anant Pankaj. "Development and application of a dispersed two-phase flow capability in a general multi-block Navier Stokes solver." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/36101.
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Gas turbines for military applications, when operating in harsh environments like deserts often encounter unexpected operation faults. Such performance deterioration of the gas turbine decreases the mission readiness of the Air Force and simultaneously increases the maintenance costs. Some of the major factors responsible for the reduced performance are ingestion of debris during take off and landing, distorted intake flows during low altitude maneuvers, and hot gas ingestion during artillery firing. The focus of this thesis is to study ingestion of debris; specifically sand. The region of interest being the internal cooling ribbed duct of the turbine blade. The presence of serpentine passages and strong localized cross flow components makes this region prone to deposition, erosion, and corrosion (DEC) by sand particles.
A Lagrangian particle tracking technique was implemented in a generalized coordinate multi-block Navier-Stokes solver in a distributed parallel framework. The developed algorithm was validated by comparing the computed particle statistics for 28 microns lycopodium, 50 microns glass, and 70 microns copper with available data [2] for a turbulent channel flow at Ret=180.
Computations were performed for a particle-laden turbulent flow through a stationary ribbed square duct (rib pitch / rib height = 10, rib height / hydraulic diameter = 0.1) using an Eulerian-Lagrangian framework. Particle sizes of 10, 50, and 100 microns with response times (normalized by friction velocity and hydraulic diameter) of 0.06875, 1.71875, and 6.875 respectively are considered. The calculations are performed for a nominal bulk Reynolds number of 20,000 under fully developed conditions. The carrier phase was solved using Large Eddy Simulation (LES) with Dynamic Smagorinsky Model [1]. Due to low volume fraction of the particles, one-way fluid-particle coupling was assumed.
It is found that at any given instant in time about 40% of the total number of 10 micron particles are concentrated in the vicinity (within 0.05 Dh) of the duct surfaces, compared to 26% of the 50 and 100 micron particles. The 10 micron particles are more sensitive to the flow features and are prone to preferential concentration more so than the larger particles. At the side walls of the duct, the 10 micron particles exhibit a high potential to erode the region in the vicinity of the rib due to secondary flow impingement. The larger particles are more prone to eroding the area between the ribs and towards the center of the duct. At the ribbed walls, while the 10 micron particles exhibit a fairly uniform propensity for erosion, the 100 micron particles show a much higher tendency to erode the surface in the vicinity of the reattachment region. The rib face facing the flow is by far the most susceptible to erosion and deposition for all particle sizes. While the top of the rib does not exhibit a large propensity to be eroded, the back of the rib is as susceptible as the other duct surfaces because of particles which are entrained into the recirculation zone behind the rib.Master of Science
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Stynsberg, John. "Incorporating Scene Depth in Discriminative Correlation Filters for Visual Tracking." Thesis, Linköpings universitet, Datorseende, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-153110.
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Visual tracking is a computer vision problem where the task is to follow a targetthrough a video sequence. Tracking has many important real-world applications in several fields such as autonomous vehicles and robot-vision. Since visual tracking does not assume any prior knowledge about the target, it faces different challenges such occlusion, appearance change, background clutter and scale change. In this thesis we try to improve the capabilities of tracking frameworks using discriminative correlation filters by incorporating scene depth information. We utilize scene depth information on three main levels. First, we use raw depth information to segment the target from its surroundings enabling occlusion detection and scale estimation. Second, we investigate different visual features calculated from depth data to decide which features are good at encoding geometric information available solely in depth data. Third, we investigate handling missing data in the depth maps using a modified version of the normalized convolution framework. Finally, we introduce a novel approach for parameter search using genetic algorithms to find the best hyperparameters for our tracking framework. Experiments show that depth data can be used to estimate scale changes and handle occlusions. In addition, visual features calculated from depth are more representative if they were combined with color features. It is also shown that utilizing normalized convolution improves the overall performance in some cases. Lastly, the usage of genetic algorithms for hyperparameter search leads to accuracy gains as well as some insights on the performance of different components within the framework.
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Celik, Ahmet Ozan. "Experimental Investigation of the Role of Turbulence Fluctuations on Incipient Motion of Sediment." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28731.
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The movement of granular material along a streambed has been a challenging subject for researchers for more than a century. Predicting the limiting case of nearly zero bedload transport, usually referred to as threshold of motion or critical condition, is even more challenging due to the highly fluctuating nature of turbulent flow. Numerous works have advocated that the peak turbulent forces, randomly occurring in time and space with magnitudes higher than the average, initiate the bed material motion. More recent findings have shown that not only the magnitude of the peak turbulent forces acting on individual grains but their duration as well have to be considered for determining the incipient conditions. Their product, or impulse, is better suited for specifying such conditions.
The goal of this study was to investigate the mechanism responsible for initiation of sediment motion under turbulent flow conditions. The impulse concept was investigated by utilizing appropriate measurement methods in the laboratory for determining the condition of incipient motion. The experimental program included measurements of particle entrainment rates of a mobile grain and turbulence induced forces acting upon a fixed grain for a range of flow conditions. In addition, near bed flow velocities were measured synchronously with both the entrainment and pressure measurements at turbulent resolving frequencies.
Results of this work covered the limitations and uncertainties associated with the experimental methods employed, and the description of the inadequacies of existing incipient motion models via the impulse framework. The extreme sensitivity of bed material activity to minute adjustments in flow conditions was explained by the associated change in the frequency of impulse events. The probability density function proposed for impulse was used together with the critical impulse to estimate the particle entrainment rate for a range of flow conditions. It was shown that the impulse events with potential to dislodge the grain were occurring mostly during sweep type of flow structures. The impulse events were also typically accompanied by positive lift forces. The force patterns showed that the positive peaks in the lift consistently occurred before and after the impulse events in the drag force. The magnitude of these lift forces were significantly higher in the wake of a cylinder compared to that of uniform flow conditions. The time average lift force in the wake of a cylinder was also observed to be positive with magnitudes reaching more than 30% of the submerged weight of the particle. The cylinder caused the downstream turbulence intensity to increase slightly but the particle entrainment rate to increase significantly. This finding provided a physically based explanation for the modification of turbulent force fluctuations and resulting changes in the particle movement rates by such unsteady flow conditions.Ph. D.
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Shuaieb, Wafa S. A. "Radio-Location Techniques for Localization and Monitoring Applications. A study of localisation techniques, using OFDM system under adverse channel conditions and radio frequency identification for object identification and movement tracking." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/18185.
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A wide range of services and applications become possible when accurate position
information for a radio terminal is available. These include: location-based services;
navigation; safety and security applications. The commercial, industrial and military value
of radio-location is such that considerable research effort has been directed towards
developing related technologies, using satellite, cellular or local area network
infrastructures or stand-alone equipment.
This work studies and investigates two location techniques. The first one presents an
implementation scheme for a wideband transmission and direction finding system using
OFDM multi-carrier communications systems. This approach takes advantage of delay
discrimination to improve angle-of-arrival estimation in a multipath channel with high
levels of additive white Gaussian noise. A new methodology is interpreted over the multi carrier modulation scheme in which the simulation results of the estimated channel
improves the performance of OFDM signal by mitigating the effect of frequency offset
synchronization to give error-free data at the receiver, good angle of arrival accuracy and
improved SNR performance. The full system simulation to explore optimum values such
as channel estimation and AoA including the antenna array model and prove the
operational performance of the OFDM system as implemented in MATLAB.
The second technique proposes a low cost-effective method of tracking and monitoring
objects (examples: patient, device, medicine, document) by employing passive radio
frequency identification (RFID) systems. A multi-tag, (totalling fifty-six tags) with known
ID values are attached to the whole patient’s body to achieve better tracking and
monitoring precision and higher accuracy. Several tests with different positions and
movements are implemented on six patients. The aim is to be able to track the patient if
he/she is walking or sitting; therefore, the tests considered six possible movements for
the patient including walking, standing, sitting, resting, laying on the floor and laying on
the bed, these placements are important to monitor the status of the patient like if he
collapsed and fall on the ground so that the help will be quick. The collected data from
the RFID Reader in terms of Time Stamp, RSS, Tag ID, and a number of channels are
processed using the MATLAB code.
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Melle, Christophe, David Chaimbault, Fabien Peleau, and Alain Karas. "A Tri-Band L, S, C Prime Focus Feed: Concept, Design and Performance." International Foundation for Telemetering, 2013. http://hdl.handle.net/10150/579680.
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ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NVThe flight test mission services need higher data rates due to increased system complexity and the need for more accurate, higher rate, and better data acquisition. The existing L or S band frequency spectrum allocation was a limiting factor to meet this increased data rate requirement. The World Radio-communication Conference (WRC 2007) attributed new additional frequency spectrum allocations in the C band for Aeronautical Mobile Telemetry (AMT). The international flight test community has taken this opportunity to immediately take advantage of the new C-band range 5091-5250MHz. This paper presents the multi-band feed product designed by the RF & Antenna Laboratory of ZODIAC DATA SYSTEMS company. This feed is foreseen to be used in prime focus configuration on any diameter parabola dish providing telemetry and tracking channels in three L, S, and C bands. Here, are described the concept and the technology achieved taking into consideration the performance and industrial constraints. Moreover, this contribution focuses on the electromagnetic simulations of radiating elements, the feed network and RF system integration. This paper is structured as follows: firstly, the objectives and the motivation for developing a prime focus feed which works in L, S, C bands are presented. In particular, the market constraints and approach to find the best solution satisfying the feed RF requirements, and mechanical constraints, such as weight, size and cost, are discussed. The second section describes the 5 step development cycle: principle and technology, design of the telemetry channels and tracking function, cohabitation of the different radiating elements, and problems of the channels isolations. The third section discusses the performance achieved using electromagnetic simulations. The fourth section talks about the integration of RF system feed. The paper concludes by discussing future work using the same concept that is applied to other telecommunication or telemetry frequency bands.
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Kerndl, Michal. "Automatický systém pro sledování polohy pohybujících se objektů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220084.
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There is suggestion of obtaining exact position in this work, based on GPS and GSM modules controlled by PIC microcontroller. Layout of this work is electronic schematic, PCB footprint and theoretical analysis of used modules. The practical part of work is also dealing with software for both microprocessor and web interface. The function prototype will be created and tested in next phases of this project.
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Shang, Lei, and lei shang@ieee org. "Modelling of Mobile Fading Channels with Fading Mitigation Techniques." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20061222.113303.
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This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.
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Li, Weichang. "Estimation and tracking of rapidly time-varying broadband acoustic communication channels /." Cambridge, Mass. : Woods Hole, Mass. : Massachusetts Institute of Technology ; Woods Hole Oceanographic Institution, 2006. http://hdl.handle.net/1912/1509.
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Originally issued as the author's thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2006."February 2006". "Doctoral dissertation." "Department of origin: Applied Ocean Physics and Engineering." "Joint Program in Oceanography/Applied Ocean Science and Engineering"--Cover. Bibliography: p. 197-206.
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Eitel, Emna [Verfasser]. "Tracking of Time-Varying Multiple Input Multiple Output Channels / Emna Eitel." München : Verlag Dr. Hut, 2014. http://d-nb.info/1047994879/34.
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Li, Weichang 1972. "Estimation and tracking of rapidly time-varying broadband acoustic communication channels." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39205.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2006.Includes bibliographical references (p. 197-206).
This thesis develops methods for estimating wideband shallow-water acoustic communication channels. The very shallow water wideband channel has three distinct features: large dimension caused by extensive delay spread; limited number of degrees of freedom (DOF) due to resolvable paths and inter-path correlations; and rapid fluctuations induced by scattering from the moving sea surface. Traditional LS estimation techniques often fail to reconcile the rapid fluctuations with the large dimensionality. Subspace based approaches with DOF reduction are confronted with unstable subspace structure subject to significant changes over a short period of time. Based on state-space channel modeling, the first part of this thesis develops algorithms that jointly estimate the channel as well as its dynamics. Algorithms based on the Extended Kalman Filter (EKF) and the Expectation Maximization (EM) approach respectively are developed.
(cont.) Analysis shows conceptual parallels, including an identical second-order innovation form shared by the EKF modification and the suboptimal EM, and the shared issue of parameter identifiability due to channel structure, reflected as parameter unobservability in EKF and insufficient excitation in EM. Modifications of both algorithms, including a two-model based EKF and a subspace EM algorithm which selectively track dominant taps and reduce prediction error, are proposed to overcome the identifiability issue. The second part of the thesis develops algorithms that explicitly find the sparse estimate of the delay-Doppler spread function. The study contributes to a better understanding of the channel physical constraints on algorithm design and potential performance improvement. It may also be generalized to other applications where dimensionality and variability collide.
by Weichang Li.
Ph.D.
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Cohen, Tal. "A data approach to tracking and evaluating engineering changes." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17971.
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Segkos, Michail. "Advanced techniques to improve the performance of OFDM Wireless LAN." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSegkos.pdf.
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Thesis (M.S. in Electrical Engineering and M.S. in Applied Physics)--Naval Postgraduate School, June 2004.Thesis advisor(s): Tri T. Ha, Brett H. Borden. Includes bibliographical references (p. 107-109). Also available online.
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Harrington, Edward, and edwardharrington@homemail com au. "Aspects of Online Learning." The Australian National University. Research School of Information Sciences and Engineering, 2004. http://thesis.anu.edu.au./public/adt-ANU20060328.160810.
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Online learning algorithms have several key advantages compared to their batch learning algorithm counterparts: they are generally more memory efficient, and computationally mor efficient; they are simpler to implement; and they are able to adapt to changes where the learning model is time varying. Online algorithms because of their simplicity are very appealing to practitioners. his thesis investigates several online learning algorithms and their application. The thesis has an underlying theme of the idea of combining several simple algorithms to give better performance. In this thesis we investigate: combining weights, combining hypothesis, and (sort of) hierarchical combining.¶
Firstly, we propose a new online variant of the Bayes point machine (BPM), called the online Bayes point machine (OBPM). We study the theoretical and empirical performance of the OBPm algorithm. We show that the empirical performance of the OBPM algorithm is comparable with other large margin classifier methods such as the approximately large margin algorithm (ALMA) and methods which maximise the margin explicitly, like the support vector machine (SVM). The OBPM algorithm when used with a parallel architecture offers potential computational savings compared to ALMA. We compare the test error performance of the OBPM algorithm with other online algorithms: the Perceptron, the voted-Perceptron, and Bagging. We demonstrate that the combinationof the voted-Perceptron algorithm and the OBPM algorithm, called voted-OBPM algorithm has better test error performance than the voted-Perceptron and Bagging algorithms. We investigate the use of various online voting methods against the problem of ranking, and the problem of collaborative filtering of instances. We look at the application of online Bagging and OBPM algorithms to the telecommunications problem of channel equalization. We show that both online methods were successful at reducing the effect on the test error of label flipping and additive noise.¶
Secondly, we introduce a new mixture of experts algorithm, the fixed-share hierarchy (FSH) algorithm. The FSH algorithm is able to track the mixture of experts when the switching rate between the best experts may not be constant. We study the theoretical aspects of the FSH and the practical application of it to adaptive equalization. Using simulations we show that the FSH algorithm is able to track the best expert, or mixture of experts, in both the case where the switching rate is constant and the case where the switching rate is time varying.
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Heusser, Peter Andreas. "Modelling and simulation of boiling channels with a general front tracking approach /." [S.l.] : [s.n.], 1996. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11736.
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Norouzi, Mehdi. "Tracking Long-Term Changes in Bridges using Multivariate Correlational Data Analysis." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1416570591.
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Kaiser, Julius A., and Fredrick W. Herold. "Simultaneous Tracking of Multiple Signals Using a Thinned Array Antenna System." International Foundation for Telemetering, 2001. http://hdl.handle.net/10150/606413.
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International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, NevadaMultiple same-frequency signals including direct/multipath signals are distinguished and individually tracked by measuring phase differences between sum and error channels of thinned array systems.
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Feng, Xiaoming. "On-line tracking of external topology changes using tie-line flow measurements." Ohio : Ohio University, 1986. http://www.ohiolink.edu/etd/view.cgi?ohiou1183131338.
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Wu, Yating. "Code tracking for direct-sequence spread-spectrum systems under multiuser environment and multipath fading channels /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ee-b30082602f.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 105-111)
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Lassami, Nacerredine. "Représentations parcimonieuses et analyse multidimensionnelle : méthodes aveugles et adaptatives." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2019. http://www.theses.fr/2019IMTA0139.
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Au cours de la dernière décennie, l’étude mathématique et statistique des représentations parcimonieuses de signaux et de leurs applications en traitement du signal audio, en traitement d’image, en vidéo et en séparation de sources a connu une activité intensive. Cependant, l'exploitation de la parcimonie dans des contextes de traitement multidimensionnel comme les communications numériques reste largement ouverte. Au même temps, les méthodes aveugles semblent être la réponse à énormément de problèmes rencontrés récemment par la communauté du traitement du signal et des communications numériques tels que l'efficacité spectrale. Aussi, dans un contexte de mobilité et de non-stationnarité, il est important de pouvoir mettre en oeuvre des solutions de traitement adaptatives de faible complexité algorithmique en vue d'assurer une consommation réduite des appareils. L'objectif de cette thèse est d'aborder ces challenges de traitement multidimensionnel en proposant des solutions aveugles de faible coût de calcul en utilisant l'à priori de parcimonie. Notre travail s'articule autour de trois axes principaux : la poursuite de sous-espace principal parcimonieux, la séparation adaptative aveugle de sources parcimonieuses et l'identification aveugle des systèmes parcimonieux. Dans chaque problème, nous avons proposé de nouvelles solutions adaptatives en intégrant l'information de parcimonie aux méthodes classiques de manière à améliorer leurs performances. Des simulations numériques ont été effectuées pour confirmer l’intérêt des méthodes proposées par rapport à l'état de l'art en termes de qualité d’estimation et de complexité calculatoireDuring the last decade, the mathematical and statistical study of sparse signal representations and their applications in audio, image, video processing and source separation has been intensively active. However, exploiting sparsity in multidimensional processing contexts such as digital communications remains a largely open problem. At the same time, the blind methods seem to be the answer to a lot of problems recently encountered by the signal processing and the communications communities such as the spectral efficiency. Furthermore, in a context of mobility and non-stationarity, it is important to be able to implement adaptive processing solutions of low algorithmic complexity to ensure reduced consumption of devices. The objective of this thesis is to address these challenges of multidimensional processing by proposing blind solutions of low computational cost by using the sparsity a priori. Our work revolves around three main axes: sparse principal subspace tracking, adaptive sparse source separation and identification of sparse systems. For each problem, we propose new adaptive solutions by integrating the sparsity information to the classical methods in order to improve their performance. Numerical simulations have been conducted to confirm the superiority of the proposed methods compared to the state of the art
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Nandikotkur, Giridhar. "Tracking spectral changes in blazars with the energetic gamma ray experiment telescope (EGRET)." College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7747.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Lami, Pietro. "Verso la convergenza tra Operational Transformation e Change Tracking." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16813/.
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In questa tesi sono state analizzate le fondamenta teoriche di Operational Transformation e Change Tracking che sono state successivamente confrontate sia teoricamente sia tramite l'implementazione e la discussione dell'editor collaborativo DOTT (Document Operational Transformation Tracking). Questa analisi è stata eseguita al fine di dimostrare che Operational Transformation e Change Tracking siano fondamentalmente modi diversi per rappresentare una stessa organizzazione dei dati basata sulla rappresentazione sequenziale delle operazioni su un documento.
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Alhakim, Rshdee. "Optimisation des performances de réseaux de capteurs dynamiques par le contrôle de synchronisation dans les systèmes ultra large bande." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENT101/document.
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Dans cette thèse nous nous sommes principalement concentrés sur les transmissions impulsion radio Ultra Large Bande (UWB-IR) qui a plusieurs avantages grâce à la nature de sa bande très large (entre 3.1GHZ et 10.6GHz) qui permet un débit élevé et une très bonne résolution temporelle. Ainsi, la très courte durée des impulsions émises assure une transmission robuste dans un canal multi-trajets dense. Enfin la faible densité spectrale de puissance du signal permet au système UWB de coexister avec les applications existantes. En raison de toutes ces caractéristiques, la technologie UWB a été considérée comme une technologie prometteuse pour les applications WSN. Cependant, il existe plusieurs défis technologiques pour l'implémentation des systèmes UWB. A savoir, une distorsion différente de la forme d'onde du signal reçu pour chaque trajet, la conception d'antennes très larges bandes de petites dimensions et non coûteuses, la synchronisation d'un signal impulsionnel, l'utilisation de modulation d'onde d'ordre élevé pour améliorer le débit etc. Dans ce travail, Nous allons nous intéresser à l'étude et l'amélioration de la synchronisation temporelle dans les systèmes ULBThe basic concept of Impulse-Radio UWB (IR-UWB) technology is to transmit and receive baseband impulse waveform streams of very low power density and ultra-short duration pulses (typically at nanosecond scale). These properties of UWB give rise to fine time-domain resolution, rich multipath diversity, low power and low cost on-chip implementation facility, high secure and safety, enhanced penetration capability, high user capacity, and potential spectrum compatibility with existing narrowband systems. Due to all these features, UWB technology has been considered as a feasible technology for WSN applications. While UWB has many reasons to make it a useful and exciting technology for wireless sensor networks and many other applications, it also has some challenges which must be overcome for it to become a popular approach, such as interference from other UWB users, accurate modelling of the UWB channel in various environments, wideband RF component (antennas, low noise amplifiers) designs, accurate synchronization, high sampling rate for digital implementations, and so on. In this thesis, we will focus only on one of the most critical issues in ultra wideband systems: Timing Synchronization
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Gaspar, Fontes Elaine. "Tracking the effects of limnological changes using chironomids and Chaoborus from Lake Annie, Florida." FIU Digital Commons, 2008. http://digitalcommons.fiu.edu/etd/3333.
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Water transparency decrease and dissolved oxygen concentration are some of the limnological trends observed in Lake Annie. Chemical and physical alterations are well documented; associations between environmental variables and the aquatic biota are however unknown. The goal of this research is to assess the relationships of physical variables with chironomids and Chaoborus. During a period of one year, samples were collected every month from 2 sites, and t-tests and correlations were used to compare the assembled data. A sediment core dating back to 1938 was also analyzed for midge remains.
Chaoborus larvae from modem dataset were con-elated to environmental variables; however some correlations were low and sediment type could be an important factor driving their abundance and distribution. Chironomid remains which are indicators of warm taxa and eutrophication showed highest percent abundances at the 10 cm interval, which corresponds to 1976. All Chaoborus remains were from the same species, which suggests that fish assemblages haven’t changed much through the years in Lake Annie.
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Smith, Dana-Jean C. "A pentadic analysis of Alaskan reality television| Tracking the changes within America's frontier myth." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527588.
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Utilizing Kenneth Burke's dramatistic pentad, I argue that the rhetoric of Alaskan reality television produces a new strain of the American frontier myth wherein agents struggle to live within an omnipotent scene. After tracing the evolution of the pentadic elements in literature and film embodying the eastern and western variations of the myth, I analyze Deadliest Catch, Flying Wild Alaska, and Gold Rush and thereby discover that the discourse does not revive older versions, but instead formulates a contemporary iteration that diminishes tension between the dialectical values of individualism and community. As the United States faces daunting exigencies concerning the economy, technology, and the environment in the new millennium, the myth of the Alaskan frontier offers ways for people to cope with their anxieties. This thesis concludes with a discussion of implications and ideas for future research.
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Sadowski, Pawel Grzegorz. "Dynamic LOPIT, new proteomics tool for tracking changes in sub-cellular localisation of proteins." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608797.
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Huang, Sheng-Yeh, and 黃聖曄. "Subspace-Tracking Channel Estimation for IEEE 802.11p." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9dmw83.
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碩士國立交通大學
電子研究所
106
In this thesis, we study downlink channel estimation based on the IEEE 802.11p system designed for vehicular communications. We investigate the performance of subspace-tracking channel estimation method in a IEEE 802.11p downlink system. And we simulate the channel estimation method with MATLAB. We use subspace-tracking channel estimation method as an intermediate step after obtaining the least-squares (LS) estimate over the pilot subcarriers, whose purpose is to increase the accuracy of the estimate over the pilot subcarriers. And this preliminary estimate is interpolated/smoothed over the entire frequency-time grid to obtain the channel estimate of the corresponding symbol. In subspace-tracking channel estimator, we parameterize the channel frequency response into the multiplication of delay matrix and amplitude vector. Since the temporal variation characteristic of these two parameters are different, we use subspace-tracking and least mean square (LMS) methods to estimate them respectively. We show the performance of subspace-tracking estimator in additive white Gaussian noise (AWGN) channel and Rayleigh fading channel for IEEE 802.11p system. In this thesis, we first introduce the system structure of IEEE 802.11p standard. Then we describe the channel estimation method we use. Next, we introduce the common channel estimators for IEEE 802.11p system. Finally, we do the simulation and discuss the performance in each transmission condition.
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Hsu, Yu-Hao, and 許育豪. "Aanlysis of Complex Code Tracking with Channel Estimation in Bandlimited Rayleigh Fading Channels." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/46398150184767396833.
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碩士國立交通大學
電信工程系
89
This thesis investigates the structures and performance of coherent bandlimited digital delay-locked loops (BL-DDLL) for complex-spread direct sequence spread spectrum (DS/SS) signals in either AWGN and Rayleigh fading channels. These loops use either the pilot channel alone or the pilot channel plus other data or control channels that are separated by orthogonal Walsh channelization codes. We consider a RAKE receiver with each RAKE finger suffers from independent Jakes flat Rayleigh fading. Tracking in the presence fading necessitates an auxiliary circuit to generate a channel estimate in real-time. We suggest a simple channel estimate derived from low-pass-filtering the de-spread pilot channel signal. The low pass filter is used to approximate the optimal Wiener filter for estimating the embedded low-pass fading process. The resulting loop actually performs code phase and carrier phase estimates simultaneously. Computer simulation is carried out to validate our analysis on the root-mean-squared (rms) tracking error (jitter) performance of various code tracking schemes. Numerical results also point out the limitation imposed by the self-interference and demonstrate that impressive performance improvement is attained by using non-pilot channel signal in a decision-directed manner.
48
Lin, Wen-Jun, and 林玟君. "A Rapid Channel-Tracking Structure for TH-UWB Systems over Time-Varying Multipath Channels." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/50683846754940847492.
Full textAbstract:
碩士國立中正大學
通訊工程研究所
93
In this thesis, we will focus on the multiuser detection of UWB systems. In the multiuser transmission environment, multiple access interference (MAI) becomes a serious issue and results in the degradation of system performance. To efficiently suppress MAI, a subspace-based blind adaptive linear detector which was first proposed by H.V. Poor is chosen. Besides, since the UWB system is mainly operated in an indoor environment, it also causes a serious inter-symbol interference (ISI). Therefore, the Rake receiver is adopted in this thesis to mitigate the multipath distortion. In addition, we consider a mobile UWB transceiver. Changing the transmission position will sometimes suffer the transition of the channel models because of different transmission distance or characteristics. However, the subspace-based blind adaptive linear detector proposed by H. V. Poor is highly sensitive to the sudden change of the channel environment over a time-varying channel, eventually results in a large performance degradation and a slow convergence speed to the steady state. In order to overcome this shortcoming, we propose a low complexity decision mechanism, termed the decision timing instant (DTI). Simulation results show that DTI is able to fast and precisely trace the variation of the channel environment and to improve the performance of the blind adaptive multiuser detection with a subspace approach over time-varying channels.
49
Tsou, Tien-Chi, and 鄒典齊. "An Efficient Channel Tracking Method for Mobile OFDM System." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/96332095128201070953.
Full textAbstract:
碩士元智大學
通訊工程學系
95
The channel variation and Doppler Effect should be solved in a mobile communication environment. Two methods of channel estimation have been proposed from two facts in this thesis. First, an efficient channel tracking method is proposed to estimate the channel variation in the vehicle to vehicle communication environment under the IEEE 802.11p standard. Second, we proposed an iterative method which joints channel estimation and LDPC decoding by using Expectation Maximization (EM) and Sum-Product Algorithm (SPA). In our simulation that based on normalized Doppler environment, we can obtain good system performance after several iteration.
50
WU, CHIA-MU, and 吳珈穆. "The OFDM System with a Semi-Blind Channel Tracking Algorithm." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/54138595340853363385.
Full textAbstract:
碩士國立中央大學
通訊工程研究所
96
To deal with the channel effect in an OFDM time-varying channel, channel tracking is an important issue. We can have two methods to solve the channel effect problem. First, we use pilots to be inserted in transmitted signals, which significantly reduce the bandwidth efficiency. Second, we use a preamble along with decision feedback methods, which has better bandwidth efficiency than the first method. However, the drawback of the latter method is the requirement of a preamble between two successive data payloads. If the length of the frame is small, the bandwidth efficiency is also restricted. Therefore, we propose a semi-blind channel tracking method to improve the bandwidth efficiency. It is well-known that the decision feedback channel tracking method has the error propagation problem which can degrade the system performance. In contrast, the semi-blind channel tracking method applies a decision error criterion to change the use of the error control signal without the error propagation problem. Simulation results show that the proposed semi-blind channel tracking scheme has better BER performance than the decision feedback method.