Dissertations / Theses on the topic 'Spatial channel'
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Lee, Hong Seng. "Spatial channel model /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426081.
Full textSasiakos, Christos. "A 3D spatial channel model for cellular radio." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA384906.
Full textKilfoyle, Daniel B. (Daniel Brian). "Spatial modulation in the underwater acoustic communication channel." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/29046.
Full textVita.
Includes bibliographical references (leaves 180-181).
A modulation technique for increasing the reliable data rate achievable by an underwater acoustic communication system is presented and demonstrated. The technique, termed spatial modulation, seeks to control the spatial distribution of signal energy such that multiple parallel communication channels are supported by the single, physical ocean channel. Results from several experiments successfully demonstrate higher obtainable data rates and power throughput. Given a signal energy constraint, a communication architecture with access to parallel channels will have increased capacity and reliability as compared to one with access to a single channel. Assuming the use of multiple element spatial arrays at both the transmitter and receiver, an analytic framework is developed that allows a multiple input, multiple output physical channel to be transformed into a set of virtual parallel channels. The continuous time, vector singular value decomposition is the primary vehicle for this transformation. Given knowledge of the channel impulse responses and assuming additive, white Gaussian noise as the only interference, the advantages of using spatial modulation over a deterministic channel may be exactly computed. Improving performance over an ensemble of channels using spatial modulation is approached by defining and then optimizing various average performance metrics including average signal to noise ratio, average signal to noise plus interference ratio, and minimum square error. Several field experiments were conducted. Detailed channel impulse response measurements were made enabling application of the decomposition methodology. The number, strength, and stability of the available parallel channels were analyzed. The parallel channels were readily interpreted in terms of the underlying sound propagation field. Acoustic communication tests were conducted comparing conventional coherent modulation to spatial modulation. In one case, a reliable data rate of 24000 bits per second with a 4 kHz bandwidth signal was achieved with spatial modulation when conventional signaling could not achieve that rate. In another test, the benefits of spatial modulation for a horizontally distributed communication system, such as an underwater network with autonomous underwater vehicles, were validated.
by Daniel Brian Kilfoyle.
Ph.D.
Downs, Peter William. "Spatial variations in river channel adjustments : implications for channel management in south-east England." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315506.
Full textWilliams, Ian E. "Channel Equalization and Spatial Diversity for Aeronautical Telemetry Applications." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605946.
Full textThis work explores aeronautical telemetry communication performance with the SOQPSK- TG ARTM waveforms when frequency-selective multipath corrupts received information symbols. A multi-antenna equalization scheme is presented where each antenna's unique multipath channel is equalized using a pilot-aided optimal linear minimum mean-square error filter. Following independent channel equalization, a maximal ratio combining technique is used to generate a single receiver output for detection. This multi-antenna equalization process is shown to improve detection performance over maximal ratio combining alone.
Stuart, Kenneth. "Wideband channel sounder development and investigation of spatial and temporal variations in wireless communication channels." Thesis, University of Portsmouth, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.478920.
Full textFu, Yu. "Performance investigation of spatial modulation systems under realistic channel models." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3032.
Full textYang, Yanling. "MIMO Channel Spatial Covariance Estimation: Analysis Using a Closed-Form Model." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2488.
Full textIannucci, Peter Anthony. "Wireless communication and localization systems under spatial and temporal channel variations." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121651.
Full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 209-218).
Wireless signals inevitably vary in time and space. The three chapters of this dissertation revolve around the exploitation of signal variations. This line of work has yielded new link-layer protocols for rateless codes on half-duplex additive white Gaussian noise channels; a new abstraction for short-range mobile-to-mobile and mobile-to-infrastructure "room-area" networks that adhere to the spatial boundaries of human conversation; a reduced-complexity tone reservation algorithm for optimizing signals to avoid amplifier non-linearities; and new tools for the study of physical-layer privacy and anonymity in wireless systems.
by Peter Anthony Iannucci.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
Wagenbrenner, Joseph William. "Post-fire stream channel processes| Changes in runoff rates, sediment delivery across spatial scales, and mitigation effectiveness." Thesis, Washington State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3598132.
Full textWildfires dramatically affect hydrologic processes including runoff and erosion, which in turn can impact society. Disturbance by fire creates ecosystem heterogeneity, prompting many species to adapt to fire cycles. Human impacts have altered fire frequency and affected natural systems to the point that additional landscape-scale disturbances may cause a disruption in ecosystem form and function. The altered ecosystems and increased development in forests may exacerbate post-fire impacts, affecting more of the population in fire-prone regions.
The following three studies will improve our understanding and management of post-fire impacts on stream channel processes. A catchment in eastern Arizona where runoff data were collected between 1962 and 1983 was subsequently burned by a wildfire in 2011. The direct comparison of pre and post-fire runoff showed that the fire made runoff more rapid, increased peak discharge rates, and compressed the time scale of storm hydrographs. These results can help improve post-fire runoff modeling and management efforts.
The second topic addressed the scaling of sediment delivery across hillslope and small catchment scales. Erosion data used in this study were from the Arizona site and five other sites across the western US. Results from five of the six sites showed that sediment delivery significantly decreased with increasing spatial extent, while the lack of trend at the sixth site illustrates the variability in erosion responses across ecosystems. The relationships developed in this study will help improve estimates of sediment delivery rates at the small-catchment scale using more easily acquired data from small plots.
The third study addressed whether straw bale check dams reduce post-fire sediment yields or affect ephemeral stream channel morphology. A series of laboratory flume experiments based on measured post-fire field conditions showed that check dams can store sediment from initial runoff events, but that a large number of check dams would be needed to reduce post-fire sediment yields. The stored sediment reduced the local channel gradient, but the check dams did not otherwise affect the channel morphology. These data and field observations were used to develop a check dam classification system that can be applied in ephemeral streams in burned or unburned areas.
Wanchaleam, Pora. "Algorithms and structures for spatial and temporal equalisation in TDMA mobile communications." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322203.
Full textStewart, Christopher B. "Spatial and temporal variability in recruitment timing, relative abundance, and mortality of juvenile red drum (Sciaenpos ocellatus) in southeastern North Carolina /." Electronic version (PDF), 2006. http://dl.uncw.edu/etd/2006/stewartc/christopherstewart.pdf.
Full textZeng, Shangyou. "Spatial distribution and function of ion channels on neural axon." Ohio : Ohio University, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1113855357.
Full textSultan, A. (Akmal). "Understanding the impact of spatial reuse on autonomous sensing order channel selection." Master's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201612103244.
Full textCabral, Mariza Castanheira de Moura da Costa. "Effects of spatial constraints on channel network topology : implications for geomorphological inference /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10147.
Full textMéndez, Real Maria. "Spatial Isolation against Logical Cache-based Side-Channel Attacks in Many-Core Architectures." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS454/document.
Full textThe technological evolution and the always increasing application performance demand have made of many-core architectures the necessary new trend in processor design. These architectures are composed of a large number of processing resources (hundreds or more) providing massive parallelism and high performance. Indeed, many-core architectures allow a wide number of applications coming from different sources, with a different level of sensitivity and trust, to be executed in parallel sharing physical resources such as computation, memory and communication infrastructure. However, this resource sharing introduces important security vulnerabilities. In particular, sensitive applications sharing cache memory with potentially malicious applications are vulnerable to logical cache-based side-channel attacks. These attacks allow an unprivileged application to access sensitive information manipulated by other applications despite partitioning methods such as memory protection and virtualization. While a lot of efforts on countering these attacks on multi-core architectures have been done, these have not been designed for recently emerged many-core architectures and require to be evaluated, and/or revisited in order to be practical for these new technologies. In this thesis work, we propose to enhance the operating system services with security-aware application deployment and resource allocation mechanisms in order to protect sensitive applications against cached-based attacks. Different application deployment strategies allowing spatial isolation are proposed and compared in terms of several performance indicators. Our proposal is evaluated through virtual prototyping based on SystemC and Open Virtual Platforms(OVP) technology
DIAS, MAURICIO HENRIQUE COSTA. "ACTUAL MOBILE RADIO PROPAGATION CHANNEL RESPONSES ESTIMATES IN THE SPATIAL AND TEMPORAL DOMAINS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3502@1.
Full textNo cenário atual das telecomunicações móveis, os arranjos de antenas voltaram a receber grande atenção dos pesquisadores, especialmente quando esquemas adaptativos de modificação de seus diagramas de radiação são utilizados. Uma das aplicações que exploram o potencial dos arranjos de antenas é o seu uso como forma de aumentar consideravelmente a eficiência espectral dos sistemas móveis atuais e da próxima geração. A outra aplicação em evidência está voltada para sistemas de localização de posição, pois algumas das técnicas conhecidas envolvem a estimação de ângulos-de-chegada usando arranjos de antenas. Diante destas possibilidades, cresce em importância o estudo das variações do canal de propagação rádio móvel no domínio em que o uso dos arranjos de antenas atua: o espacial. O presente trabalho procura contribuir para o contexto em questão, com uma investigação experimental do canal real rádio-móvel nos domínios temporal (retardos) e espacial (ângulos-de-chegada). No que se refere ao contexto nacional, contribuições similares baseadas em simulações já são encontradas; baseadas em medidas não. Em particular, sondagens na faixa de 1,8 GHz em ambientes internos típicos foram realizadas. Duas técnicas distintas de sondagem temporalespacial foram implementadas, tomando por base uma sonda de canal faixa-larga montada e testada com sucesso, como contribuição principal de uma dissertação de mestrado recentemente apresentada por um integrante do mesmo grupo de pesquisa ao qual esta tese está vinculada. Uma das técnicas sintetiza o arranjo realizando as sondagens com uma única antena que é sucessivamente deslocada para ocupar as posições correspondentes às dos elementos do arranjo. A outra técnica emprega um arranjo real. Em ambas, a configuração mais simples para um arranjo foi utilizada: a linear uniforme. As sondagens não forneciam diretamente os espectros espaciais-temporais. As estimativas dos espectros foram processadas posteriormente, aplicando técnicas como o correlograma para o domínio do retardo, e quatro técnicas distintas para o domínio espacial, que foi o foco principal deste trabalho: duas convencionais; e duas paramétricas, com potencial de aumentar a resolução das estimativas, assumindo hipóteses razoáveis sobre as respostas esperadas. De posse das respostas espectrais estimadas, comparações com estimativas teóricas permitiram uma análise de desempenho das técnicas utilizadas. Adicionalmente à investigação experimental do canal espacial, procurou-se verificar o potencial da aplicação da teoria de wavelets ao estudo do canal rádiomóvel. Em especial, uma das principais aplicações daquela teoria foi testada como técnica de pós-processamento das respostas espectrais no domínio do retardo. A supressão de ruído por decomposição wavelet foi aplicada a um vasto conjunto de medidas de canal disponíveis, fruto de trabalhos anteriores do grupo de pesquisa ao qual esta tese está vinculada, com resultados expressivos.
In the present mobile communications scenario, researchers have turned once again special attention to antennae arrays, particularly when adaptive schemes are employed to modify its radiation patterns. One of its main applications results in considerable increases to the spectral efficiency of present and next generation mobile systems. The other major application is headed towards position location systems, since some of the known techniques comprise angle-of-arrival estimation using antennae arrays. Under such possibilities, mobile radio propagation channel variations studies grow in relevance, specially regarding the antennae arrays main domain of action: the spatial domain. The present work tries to contribute to the overstated context, experimentally investigating the actual mobile radio channel over the temporal (delays) and spatial (angles of arrival) domains. Regionally speaking, similar contributions based on simulations are already found, but none based on measurements. In special, 1.8 GHz indoor soundings have been carried out. Two different temporal spatial sounding techniques have been deployed, based on na available wideband channel sounder successfully assembled and tested as the major contribution of a MSc. dissertation recently presented by a member of the same research team to which this thesis belongs. One of such techniques sinthesyzes the array carrying the sounding out with a single antenna, which is successively moved to occupy the spots corresponding to the array elements. The other method employs an actual array. For both cases, the simplest array configuration has been used: the uniform linear one. Space-time spectra were not directly available in real time during the soundings. Its estimates have been processed later, applying techniques such as the correlogram over the delay domain, and four distinct methods over the spatial domain, the main focus of the present work. Two conventional methods have been used, as well as two parametric ones, potentially capable to increase the estimates resolution, assuming reasonable hypotheses regarding the expected responses. With the estimated spectral responses in hands, comparisons with theoretical estimates allowed a performance assessment of the employed methods. In addition to the spatial channel experimental investigation, the wavelets theory potential of application to the mobile-radio channel study has been checked out. Notably, one of the wavelets theory major applications has been tested as a post-processing technique to improve delay-domain spectral responses. Wavelet decomposition based de-noising has been applied to a huge measurements ensemble, available as the product of previous works of the research group to which this thesis is attached, leading to remarkable results.
Meade, Benjamin K. "Spatial extent, timing, and causes of channel incision, Black Vermillion watershed, northeastern Kansas." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1451.
Full textBeckett, Kirsty A. "Multispectral analysis of high spatial resolution 256-channel radiometrics for soil and regolith mapping." Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/1434.
Full textBeckett, Kirsty A. "Multispectral analysis of high spatial resolution 256-channel radiometrics for soil and regolith mapping." Curtin University of Technology, Dept. of Exploration Geophysics, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17703.
Full textAdditionally, through the isolation of non-standard uranium channels 214 [superscript] Bi (1120 keV) and 214 [superscript] Bi (1253 keV), preferential attenuation of lower energy gamma-rays from 214 [superscript] Bi decay events are exploited to map variations in soil density and/or porosity. These variations are illustrated through the interpretation of uranium energy using ternary imagery [red: 214 [superscript] Bi (1764 keV), green: 214 [superscript] Bi (1120 keV), blue: 214 [superscript] Bi (1253 keV)] and uranium peak energy ratio [214 [superscript] Bi 1120 keV / 214 [superscript] Bi 1764 keV] pseudo colour imagery. Case studies examined in this thesis explore the characteristics of 256-channel radiometric spectrum from different resolution datasets from different Western Australian soil types, provide recommendations for acquiring radiometric data for soil mapping in different agricultural environments, demonstrate how high resolution 256-channel radiometric data can be used to model soil properties in three-dimensions, and illustrate how three-dimension soil models can be used to separate surface waterlogging influences from rising groundwater induced waterlogging.
Sterling, David L. "A Comparison of Spatial Interpolation Techniques for Determining Shoaling Rates of the Atlantic Ocean Channel." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/35072.
Full textThe United States of Army Corp of Engineers (USACE) closely monitors the changing depths of navigation channels throughout the U.S. and Western Europe. The main issue with their surveying methodology is that the USACE surveys in linear cross sections, perpendicular to the channel direction. Depending on the channel length and width, these cross sections are spaced 100 - 400 feet apart, which produces large unmapped areas within each cross section of a survey.
Using a variety of spatial interpolation methods, depths of these unmapped areas were produced. The choice of spatial interpolator varied upon which method adequately produced surfaces from large hydrographic survey data sets with the lowest amount of prediction error. The data used for this research consisted of multibeam and singlebeam surveys. These surveys were taken in a systematic manner of linear cross-sections that produced tens of thousands of data points.
Nine interpolation techniques (inverse distance weighting, completely regularized spline, spline with tension, thin plate spline, multiquadratic spline, inverse multiquadratic spline, ordinary kriging, simple kriging, and universal kriging) were compared for their ability to accurately produce bathymetric surfaces of navigation channels. Each interpolation method was tested for effectiveness in determining depths at "unknown" areas. The level of accuracy was tested through validation and cross validation of training and test data sets for a particular hydrographic survey.
By using interpolation, grid surfaces were created at 15, 30, 60, and 90-meter resolution for each survey of the study site, the Atlantic Ocean Channel. These surfaces are used to produce shoaling amounts, which are taken in the form of volumes (yd.3). Because the Atlantic Ocean Channel is a large channel with a small gradual change in depth, a comparison of grid resolution was conducted to determine what difference, if any, exists between the calculated volumes from varying grid resolutions. Also, a comparison of TIN model volume calculations was compared to grid volume estimates.
Volumes are used to determine the amount of shoaling and at what rate shoaling is occurring in a navigation channel. Shoaling in each channel was calculated for the entire channel length. Volumes from varying grid resolutions were produced from the Atlantic Ocean Channel over a seven-year period from 1994-2001.
Using randomly arranged test and training datasets, spline with tension and thin plate spline produced the mean total error when interpolating using singlebeam and multibeam hydrographic data respectively. Thin plate spline and simple kriging produced the lowest mean total error in full cross validation testing of entire singlebeam and multibeam hydrographic datasets respectively.
Volume analysis of varying grid resolution indicates that finer grid resolution provides volume estimates comparable to TIN modeling, the USACE's technique for determining sediment volume estimates. The coarser the resolution, the less similar the volume estimates are in comparison to TIN modeling. All grid resolutions indicate that the Atlantic Ocean Channel is shoaling. Using a plan depth of 53 feet, TIN modeling displayed an annual average increase of 928,985 cubic yards of sediment from 1994 - 2001.
Master of Science
Bharadwaj, Vivek. "Ultra-Wideband for Communications: Spatial Characteristics and Interference Suppression." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33183.
Full textMaster of Science
Stavridis, Athanasios. "On the energy efficiency of spatial modulation concepts." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15951.
Full textLamahewa, Tharaka Anuradha, and tharaka lamahewa@anu edu au. "Space-Time Coding and Space-Time Channel Modelling for Wireless Communications." The Australian National University. Research School of Information Sciences and Engineering, 2007. http://thesis.anu.edu.au./public/adt-ANU20070816.152647.
Full textWarman, Craig S. "Understanding the spatial and temporal variation in anthropogenically induced channel response in the Irwin River catchment." University of Western Australia. School of Earth and Geographical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0214.
Full textBaykas, Tuncer. "Effects of spatial correlation and channel estimation errors on the performance of space-time block coded systems." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6147.
Full textThompson, Philip Jean-Paul. "The spatial and temporal variation of stratigraphic components within the San Fernando Channel System, Baja California, Mexico." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=158496.
Full textTsai, Chiou-Wei, Richard E. Cagley, and Ronald A. Iltis. "JOINT INTERFERENCE SUPPRESSION AND QRD-M DETECTION FOR SPATIAL MULTIPLEXING MIMO SYSTEMS IN A RAYLEIGH FADING CHANNEL." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604390.
Full textSpatial multiplexing (SM) systems have received significant attention because the architecture offers high spectral efficiency. However, relatively little research exists on optimization of SM systems in the presence of jamming. In a spatially uncoded SM system, such as V-BLAST, the channel state information is assumed to be unavailable a priori at both transmitter and receiver. Here, Kalman filtering is used to estimate the Rayleigh fading channel at the receiver. The spatial correlation of the jammer plus noise is also estimated, and spatial whitening to reject the jammers is employed in both the Kalman channel estimator and detector. To avoid the exponential complexity of maximum-likelihood (ML) detection, the QRD-M algorithm is employed. In contrast to sphere decoding, QRD-M has fixed decoding complexity of order O(M), and is thus attractive for hardware implementation. The performance of the joint Kalman filter channel estimator, spatial whitener and QRD-M detector is verfied by simulations.
Glenn, Dickins, and glenn dickins@dolby com. "Applications of Continuous Spatial Models in Multiple Antenna Signal Processing." The Australian National University. Research School of Information Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080702.222814.
Full textJiang, Jing. "Capacity-approaching data transmission in MIMO broadcast channels." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11208.
Full textPh. D.
Malmelöv, Tomas. "Implementation and Evaluation of Encoder Tools for Multi-Channel Audio." Thesis, Luleå tekniska universitet, Institutionen för system- och rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-71986.
Full textD'Alessandro, Maryann Marie. "The utility of intracranial EEG feature and channel synergy for evaluating the spatial and temporal behavior of seizure precursors." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/15789.
Full textAlizadeh, Ardalan. "Cognitive Communications for Emerging Wireless Systems." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1470226402.
Full textHunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
Full textCrawford, Daniel E. "Simulation of spatial and temporal variability of methylmercury concentration within channel banks and surface waters of the Carson River, Nevada." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000856.
Full textCorbalán, García Maria Del Carmen. "Spatial distribution patterns of the sponge community in the Menorca Channel (Balearic Island), a new Marine Protected Area in the Western Mediterranean." Master's thesis, Universidade de Évora, 2014. http://hdl.handle.net/10174/18226.
Full textAl-Nu'aimi, Abdallah S. N. A. "Design, Implementation and Performance Evaluation of Robust and Secure Watermarking Techniques for Digital Coloured Images. Designing new adaptive and robust imaging techniques for embedding and extracting 2D watermarks in the spatial and transform domain using imaging and signal processing techniques." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4255.
Full textAl-Nu'aimi, Abdallah Saleem Na. "Design, implementation and performance evaluation of robust and secure watermarking techniques for digital coloured images : designing new adaptive and robust imaging techniques for embedding and extracting 2D watermarks in the spatial and transform domain using imaging and signal processing techniques." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4255.
Full textRaddadi, Bilel. "Récepteurs avancés et nouvelles formes d'ondes pour les communications aéronautiques." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0057/document.
Full textNowadays, several studies are launched for the design of reliable and safe communications systems that introduce Unmanned Aerial Vehicle (UAV), this paves the way for UAV communication systems to play an important role in a lot of applications for non-segregated military and civil airspaces. Until today, rules for integrating commercial UAVs in airspace still need to be defined, the design of secure, highly reliable and cost effective communications systems still a challenging task. This thesis is part of this communication context. Motivated by the rapid growth of UAV quantities and by the new generations of UAVs controlled by satellite, the thesis aims to study the various possible UAV links which connect UAV/aircraft to other communication system components (satellite, terrestrial networks, etc.). Three main links are considered: the Forward link, the Return link and the Mission link. Due to spectrum scarcity and higher concentration in aircraft density, spectral efficiency becomes a crucial parameter for largescale deployment of UAVs. In order to set up a spectrally efficient UAV communication system, a good understanding of transmission channel for each link is indispensable, as well as a judicious choice of the waveform. This thesis begins to study propagation channels for each link: a mutipath channels through radio Line-of-Sight (LOS) links, in a context of using Meduim Altitude Long drones Endurance (MALE) UAVs. The objective of this thesis is to maximize the solutions and the algorithms used for signal reception such as channel estimation and channel equalization. These algorithms will be used to estimate and to equalize the existing muti-path propagation channels. Furthermore, the proposed methods depend on the choosen waveform. Because of the presence of satellite link, in this thesis, we consider two low-papr linear waveforms: classical Single-Carrier (SC) waveform and Extented Weighted Single-Carrier Orthogonal Frequency-Division Multiplexing (EW-SC-OFDM) waveform. channel estimation and channel equalization are performed in the time-domain (SC) or in the frequency-domain (EW-SC-OFDM). UAV architecture envisages the implantation of two antennas placed at wings. These two antennas can be used to increase diversity gain (channel matrix gain). In order to reduce channel equalization complexity, the EWSC- OFDM waveform is proposed and studied in a muti-antennas context, also for the purpose of enhancing UAV endurance and also increasing spectral efficiency, a new modulation technique is considered: Spatial Modulation (SM). In SM, transmit antennas are activated in an alternating manner. The use of EW-SC-OFDM waveform combined to SM technique allows us to propose new modified structures which exploit exces bandwidth to improve antenna bit protection and thus enhancing system performances
Qurban, Mohammed Ali B. "An investigation of factors influencing the spatial and temporal distribution of surface phytoplankton in the English Channel and Bay of Biscay in 2003 and 2004." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/66340/.
Full textUsman, Muhammad. "Investigation, Design and Implementation of MIMO Antennas for Mobile Phones. Simulation and Measurement of MIMO Antennas for Mobile Handsets and Investigations of Channel Capacity of the Radiating Elements Using Spatial and Polarisation Diversity Strategies." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4279.
Full textSoccodato, Alice. "Spatial and temporal variation in settlement, growth and condition of the rockfish species Sebastes caurinus and Sebastes carnatus in the Channel Islands region, Santa Barbara, CA." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amslaurea.unibo.it/2125/.
Full textʿUs̲mān, Muḥammad. "Investigation, design and implementation of MIMO antennas for mobile phones : simulation and measurement of MIMO antennas for mobile handsets and investigations of channel capacity of the radiating elements using spatial and polarisation diversity strategies." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4279.
Full textCalatrava, Helena, and Mimmi Lindgren. "Simulation, Analysis and Detection of Indoor Multipath Fading Channels Using an SVM Classifier." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297677.
Full textNu för tiden så är identifiering av fejkad data en svår utmaning som ofta kräver maskininlärningstekniker. Detta beror på den stora mängden data och att komplexiteten i datat gör att skillnaderna kan vara svår att se även för ett tränat öga. I det här projektet använder vi oss av MATLABs systemobjekt wlanTGnChannel för att simulera flervägs fädningskanaler som kan jämföras med riktiga impulssvarsmätningar gjorda av Ericsson AB av ett innomhus 8 X 8 MIMO(Multiple Input Multiple Output) system. Vi använde en SVM (stödvektormaskins) klassificerare för att jämföra egenvärdena av deras korrelationskovariansmatriser, vilket erhåller en noggranhet på 84%. Att jämföra deras power delay profiles (PDP) råkar vara ett klassificeringsproblem av låg svårighetsgrad på grund av tidsupplösningsbegränsningar för de riktiga mätningarna. Vi vill påstå att den tilltänkta MATLAB- modellen aviker mycket från den givna datan.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
Komulainen, P. (Petri). "Coordinated multi-antenna techniques for cellular networks:Pilot signaling and decentralized optimization in TDD mode." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202815.
Full textTiivistelmä Tämä väitöskirja keskittyy lineaarisella lähetys- ja vastaanottoprosessoinnilla toteutettavien tilajakomonikäyttömenetelmien suunnitteluun ja arviointiin langattomissa moniantennisissa solukkoverkoissa, jotka hyödyntävät aikajakodupleksointia (TDD). Erityisesti tarkastellaan efektiivisen kanavatiedon hankintaa, joka mahdollistaa hajautetun prosessoinnin siten että verkkoelementit – tukiasemat ja terminaalit, jotka kukin hyödyntävät useaa antennielementtiä – voivat osallistua paikallisesti verkon adaptaatioon. Esitetyt menetelmät perustuvat ylä- ja alalinkin kanavien resiprookkisuuteen ja tilatasossa esikoodattuun opetus- eli pilottisignalointiin ilmarajapinnan yli. Yksisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään ylälinkin koordinoituja nollaanpakottavia lähetys- ja vastaanottomenetelmiä. Tukiasema laskee lähetysparametrit keskitetysti ja käyttää pilottisignaaleja kertomaan millaista lähetyskeilanmuodostusta terminaalien tulee käyttää. Alalinkin nollaanpakotuksen yhteydessä esikoodattuja demodulaatiopilotteja voidaan uudelleenkäyttää ylälinkin lähetyskeilojen allokointiin, ja esikoodattuja ylälinkin demodulaatiopilotteja uudelleenkäytetään puolestaan osittaiseen kanavan luotaukseen (sounding). Näin ollen molempiin suuntiin tarvitaan vain esikoodatut pilotit. Lisäksi työssä esitetään menetelmä ylälinkin luotauspilottiresurssitarpeen vähentämiseksi. Kanavatietoon perustuen moniantenniset terminaalit muodostavat tilatasossa esikoodattuja pilottilähetyskeiloja, joita tarvitaan vähemmän kuin perinteisiä antennikohtaisia pilotteja. Kun otetaan huomioon kanavanestimointivirhe tukiasemassa, resurssiensäästömenetelmä parantaa häiriösietoisuutta ja nostaa järjestelmän keskimääräistä kapasiteettia alalinkin nollaanpakotuksen yhteydessä. Monisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään hajautettuja koordinoituja alalinkin keilanmuodostusstrategioita, jotka perustuvat painotetun summadatanopeuden (WSR) maksimointiin. Valitussa optimointikehyksessä WSR:n maksimointi toteutetaan painotetun summaneliövirheen minimoinnin kautta, ja työssä menettelytapa yleistetään antennikohtaisten lähetystehorajoitusten tapaukseen. Iteratiivinen prosessointi koostuu optimointiaskelista, jotka tukiasemat paikallisesti suorittavat. Yhdessä esitetyssä strategiassa yhteistoiminnalliset solut päivittävät lähettimensä ja vastaanottimensa yksi solu kerrallaan, mikä takaa verkonlaajuisen ongelmanratkaisun monotonisen konvergenssin. Tämä strategia käyttää erillisiä ylälinkin luotaussignaaleja sekä varattu-signaaleja ilmaistakseen terminaalien efektiiviset kanavat naapuritukiasemille. Toisessa strategiassa monotoninen konvergenssi uhrataan ja kehitetään nopeammin adaptoituva menetelmä, jossa tukiasemat saavat optimoida muuttujansa rinnakkain, perustuen vain luotaussignaaleihin ja tukiasemien väliseen informaationvaihtoon. Numeeriset tulokset osoittavat, että WSR:n maksimointi toteuttaa aktiivisten käyttäjien valinnan tilatasossa implisiittisesti. Lopuksi esitetään menetelmiä luotauspilottiresurssitarpeen vähentämiseksi ja käsitellään kanavatiedon epävarmuuden vaikutusta
Mungara, Ratheesh Kumar. "System-level performance of interference-aware spatial frequency reuse." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/400869.
Full textLa reutilització de la freqüència espacial és l’aproximació més acceptada per tal de millorar la capacitat dels sistemes wireless mitjançant l'increment de l'eficiència espectral (bits per segon per unitat d'ample de banda). S'espera que la futura cinquena generació de sistemes wireless incorpori diverses formes de reutilització de freqüència. Això inclou la comunicació multi-input multi-output (MIMO) que permet la reutilització a través d'antenes, densificació dispositiu-a-dispositiu (D2D) que permet reutilitzar l'espectre a través d’enllaços de comunicació directa, així com un full-dúplex emprant el mateix espectre per a la comunicació en la transmissió i recepció de direccions. Aquest treball pretén determinar els límits de rendiment dels sistemes wireless emergents, basats en una densa reutilització de la freqüència espacial i en la supressió d'interferències, així com espigolar coneixement clau per al disseny de sistemes d'aquest tipus. La geometria estocàstica és l'eina que s'aplicarà a l'anàlisi que es durà a terme, modelitzant les localitzacions dins la xarxa com a punts d'un procés de Poisson. La introducció d'un ajust Gaussià a la interferència, conjuntament amb la consideració de nivells variables d'expectació espacial, han permès definir un nou marc matemàtic que fa possible unes expressions més compactes i uns resultats més significatius en comparació amb els anàlisis existents. Dins d'aquest marc, en primer lloc es prenen en consideració la multiplexació MIMO i l'aliniament d'interferència (IA, en les seves sigles en anglès). El primer esquema empra totes les dimensions espacials disponibles per a la senyalització i el segon minimitza la interferència a costa de conèixer els estats de esvaïment instantani dels transmissors i receptors, i d'una reducció en les dimensions de senyalització espacial. Malgrat l'intens treball en l'IA i la multiplexació espacial, s'ha prestat escassa atenció a tractar de comprendre el seu balanç d’enginyeria en el context d'xarxes cel.lulars de rellevància pràctica, com els de propagació de pèrdues, o les dinàmiques de esvaïment degudes a la mobilitat de l'usuari i al coneixement imperfecte dels estats de esvaïment. En aquest treball s'ha estudiat en profunditat aquest problema a través d'anàlisis tant a nivell dels enllaços com del sistema. Fins i tot en condicions de coneixement perfecte del esvaïment, l'IA resulta beneficiós sobre la multiplexació només en situacions de xarxa molt específiques i relativament infreqüents, mentre que perd tots els seus avantatges a velocitats vehiculars quan el coneixement del esvaïment és imperfecte. En segon lloc, el treball es centra en el ITLinQ i el FlashLinQ, els dos principals esquemes de canalització proposats fins al moment per controlar la interferència en xarxes D2D. S'ofereix una caracterització analítica de l'esquema ITLinQ, obrint així la porta a l'optimització dels seus paràmetres controlables. Es mostra que tots dos esquemes de canalització aconsegueixen millors resultats que l'esquema no canalitzat, amb un lleuger avantatge per al ITLinQ. Considerant la geometria de xarxa més desfavorable, el ITLinQ produeix millores múltiples en l'eficiència espectral en comparació amb la xarxa no canalitzada. Finalment, el treball introdueix els transreceptors full-dúplex en xarxes cel.lulars i caracteritza l'impacte de la interferència incrementada en el seu funcionament. A través d'anàlisis i de simulacions complementàries en una xarxa de test de Vodafone LTE, s'estableix que la interferència d'usuari a usuari té un impacte poc significatiu mentre que la interferència de base a base faria inviable l'operació full-dúplex en xarxes microcell.lulars sense gestió de les interferències. En resum, aquest tesis doctoral aporta evidència de que el multiplexat MIMO i la densificació basada en D2D juguen un paper vital en la millora de la capacitat dels sistemes wireless mentre que el IA i el full-dúplex resulten inefectius.
Phan, Phong Thanh. "Development of a multi-distance, multi-channel broadband near-infrared spectroscopy system to investigate the spatial variation in cellular oxygen metabolism in the healthy and injured adult human brains." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10042965/.
Full textBourdaud, Pierre. "Impact of a landing obligation on coupled dynamics ecosystem-fishers : individual-based modelling approach applied to Eastern English Channel." Thesis, Littoral, 2018. http://www.theses.fr/2018DUNK0474/document.
Full textThe objective of this thesis was to anticipate the effects if the EU Landing Obligation (LO) implemented since the beginning of 2015 in the Eastern English Channel (EEC). To achieve these objectives, it was planned to : i) better understand seasonal spatial distribution of commercial species using on-board commercial vessels observation data, ii) compare them with the final scale fishing effort distribution of EEC bottom otter trawlers (OTB), and iii) develop an individual-based model of fleet-dynamics, DSVM, to be integrated within the ecosystem model OSMOSE to simulate a LO. The usefulness of on-board observation data was proved for a main part of a species sample, using validation from the literature and a geostatistical indicator. Then the comparison of fine scale fishing effort provided an improvement of the quantification of effective fishing effort and emphasized the importance of cuttlefish and red mullet for the global distribution of EEC OTB. In addition, the targeting intensity of OTB was quantified in October using a newly-developed indicator, and demonstrated the attractiveness of the same species, but also the constraint of low cod quota for fishers. Results of the OSMOSE-DSVM coupling show that the LO would have short-term negative effects on fishers' revenue, induced by a large reallocation of their fishing effort to avoid quota over-shooting, but would be profitable in the medium-term. However, the LO would induce an increase of the predatory pressure operated by cod and withing on the other species, which would not improve the overall ecosystem health
Skalak, Katherine Joanne. "Fine-grained channel margin deposits in a typical gravel bed river spatial and temporal controls on the distribution, quantity, and residence time and implications for centennial-scale sediment and mercury cycling /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 437 p, 2009. http://proquest.umi.com/pqdweb?did=1885693201&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full textBarrachina, Muñoz Sergio. "Responsive spectrum management for wireless local area networks: from heuristic-based policies to model-free reinforcement learning." Doctoral thesis, Universitat Pompeu Fabra, 2021. http://hdl.handle.net/10803/670782.
Full textEn aquesta tesi ens centrem en el problema conjunt de la gestió de l'espectre: assignació de canals primaris i secundaris a xarxes d'àrea local sense fils (WLAN) amb channel bonding. Des de l'estàndard IEEE 802.11n fins a estàndards més recents com el 802.11ac, el 802.11ax i el 802.11be, s'han anat proposant amplades de banda més grans per permetre agrupar canals, augmentant així l'amplada de banda total per transmissió. Tot i que aquest augment en l'amplada de banda afavoreix la capacitat potencial de les xarxes, suportant així els requeriments de les noves aplicacions Wi-Fi, també redueix la potència per Hertz i accentua els problemes de contenció i interferència entre nodes veïns. En resum, si les xarxes WLANs ja eren complexes per se, s'estan tornant encara més complexes a causa de l'augment de la densitat de nodes i de les noves prestacions incloses als darrers estàndards. Primer proposem un model analític basat en xarxes Markov en temps continu (CTMN) per caracteritzar channel bonding en WLANs saturades. Aquest model es basa en un nou algorisme que genera CTMNs a partir d'escenaris distribuïts espaialment, on no és necessari que els nodes estiguin dins del rang de contenció de la resta. Identifiquem els factors claus que afecten el rendiment i l'equitat de les diferents polítiques de channel bonding i mostrem l'existència d'interrelacions crítiques entre nodes en forma de reacció en cadena. D'això se'n desprèn que no hi ha una política channel bonding òptima única per a cada escenari. En ampliar el model analític per donar suport a règims no saturats, destaquem els avantatges d'assignar els canals tan amplis com sigui possible a les WLAN i implementar polítiques d'accés adaptatiu per fer front a les situacions que poden aparèixer tant en termes de rendiment com d'equitat. A part dels models analítics, aquesta tesi es basa en simulacions per generalitzar escenaris evitant costosos bancs de proves experimentals, de vegades inviables. Malauradament, els simuladors de xarxes sense fils existents solen ser massa simplistes o molt costosos computacionalment. És per això que desenvolupem el simulador de xarxes sense fils Komondor, concebut com una eina de codi obert accessible (llesta per utilitzar) per a la investigació de xarxes sense fils. L’avantatge essencial de Komondor respecte d’altres simuladors sense fils coneguts rau en la seva elevada velocitat de processament d’esdeveniments. A continuació ens desviem de models analítics i simulacions i abordem mesures reals a través del Wi-Fi All-Channel Analyzer (WACA), el primer sistema que mesura simultàniament l'energia de tots els 24 canals que permeten channel bonding a la banda Wi-Fi dels 5 GHz. Amb WACA, realitzem un estudi únic de localitzacions que inclouen nuclis urbans, barris residencials, universitats i fins i tot un partit a al Camp Nou, un estadi ple amb 98.000 aficionats i 12.000 connexions Wi-Fi simultànies. Les dades experimentals revelen els factors fonamentals que controlen el guany de rendiment, a partir dels quals ressaltem la correlació entre canals. També mostrem la importància del conjunt de dades recopilades per trobar nous factors claus, que d'una altra manera no seria possible, atès que els models d'ocupació de canals simples subestimen els guanys potencials. Pel que fa a solucions, primer discutim propostes basades en heurístiques per trobar configuracions satisfactòries ràpidament. En aquest sentit, proposem dinàmicament (DyWi), un algorisme de selecció de canal primari en línia, descentralitzat i eficient per xarxes channel bonding. DyWi millora el rendiment esperat tenint en compte no només l’ocupació del canal primari objectiu, sinó també l’activitat dels canals secundaris. Fins i tot quan suposem retards significatius a causa del canvi de canal primari, observem millores importants en termes de rendiment i retard. Finalment, identifiquem els enfocaments d’aprenentatge automàtic (o machine learning) aplicables al problema de la gestió de l’espectre a les WLAN i justifiquem per què l'aprenentatge del tipus reinforcement learning (RL) és el més adient. En particular, ens centrem en el rendiment adequat de les variacions d'RL sense estats i proposem multi-armed bandits com la solució adequada, ja que i) necessitem una adaptabilitat ràpida per millorar l’experiència d’usuari en escenaris Wi-Fi dinàmics i ii) el nombre de configuracions multicanal que una xarxa pot adoptar és limitat; per tant, els agents poden explorar completament l’espai d’acció en un temps raonable.