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1
Lee, Hong Seng. "Spatial channel model /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1426081.
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Sasiakos, 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.
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Kilfoyle, 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.
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Thesis (Ph. D.)--Joint Program in Oceanography and Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and the Woods Hole Oceanographic Institution), 2000.Vita.
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.
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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.
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Williams, Ian E. "Channel Equalization and Spatial Diversity for Aeronautical Telemetry Applications." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605946.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaThis 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.
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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.
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Fu, Yu. "Performance investigation of spatial modulation systems under realistic channel models." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3032.
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In order to fulfil the explosive demand for convenient wireless data access, novel wireless technologies such as the multiple-input-multiple-output (MIMO) have widely been used to improve the link reliability and capacity of wireless communication systems. In recent years, a new MIMO technology named the spatial modulation (SM) has attracted signi cant research interest due to its reported enhancement on the system performance with the reasonable system complexity. Before a new technology comes into real use, it is necessary to comprehensively evaluate its performance under different scenarios. In this thesis, we investigate the performance of SM systems under some important realistic scenarios for future wireless communications, such as the vehicle-to-vehicle (V2V), the high-speed train (HST), and the massive MIMO scenarios. Firstly, the bit error rate (BER) performance of SM systems under a novel threedimensional (3D) geometry based stochastic model (GBSM) for V2V MIMO channels is investigated by both theoretical analysis and system simulations. The impacts of vehicle tra c density (VTD), Doppler effect, and 3D feature on the BER performance of SM systems are thoroughly studied. In addition, other MIMO technologies, such as the vertical Bell Labs layered space-time (V-BLAST), the Alamouti scheme are compared with SM under different simulation settings. Secondly, the BER performance of SM systems is studied under a non-stationary wideband HST GBSM considering the non-ideal channel estimation case. The timevarying behaviour of the channel and its impact on the performance of SM systems are comprehensively investigated. The accurate theoretical BER expression of SM systems under a non-stationary wideband HST channels with non-ideal channel estimation is derived. A novel statistic property named stationary interval in terms of the space-time correlation function (STCF) is introduced in order to clearly explain all theoretical and simulation results. Thirdly, the performance of SM systems is evaluated under a Kroneck-based massive MIMO channel model. As a massive MIMO system employs large numbers of antennas, antenna elements are distributed over a wide range. Thus, different antenna elements may observe different sets of clusters. How this phenomenon affects the performance of SM systems is investigated by considering a survival probability of clusters, which abstracts the birth-death process of each cluster in the channel model. Moreover, the performance of SM systems is also compared with that of other MIMO technologies under the massive MIMO channel model. In summary, all research works in this thesis have considered realistic MIMO channel models, which are meaningful for the test, performance evaluation, and implementation of SM technology for future advanced wireless communications systems.
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Yang, Yanling. "MIMO Channel Spatial Covariance Estimation: Analysis Using a Closed-Form Model." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2488.
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Multiple-input Multiple-output (MIMO) wireless communication systems allow increased spectral efficiency and therefore promise significant improvement in performance. However, because of the rapid variation in channel state information (CSI) in networks with mobile nodes or scatterers, it is difficult both to maintain high communication performance and to create channel models that effectively represent the time-varying behavior of the channels. The spatial covariance of the MIMO channel describes the average power gain on each transmit-receive antenna pair as well as the correlation between the complex link gains and thus provides critical information for understanding the performance of the system and for creating models to accurately describe the interaction of the electromagnetic fields with the antennas. Furthermore, in many cases the MIMO signaling scheme uses knowledge of this spatial covariance. This thesis proposes a closed-form analytical model that allows estimation of the full MIMO channel covariance based on knowledge of the power angular spectrum (PAS) of the channel and the antenna radiation patterns. Comparison of covariance matrices computed using this model with those estimated from observed channel samples reveals the appropriate window over which the covariance should be estimated for non-WSS time-varying channels. Two approaches are developed to compare the covariance matrices in order to determine the appropriate window, both based on a metric, correlation matrix distance (CMD). Simulations based on both a two-ring propagation model and raytracing data in a three dimensional urban environment are included. The results reveal that with the optimal window size, the CMD of the estimated covariance is close to that of the analytical covariance. An average window size normalized by the scatterer circle radius is determined for practical estimation of covariance based on knowledge of the average distance to the scatterers. The impact of the number of scatterers on the optimal window size is analyzed as well. The results based on ray-tracing data show that the CMD of the estimated covariance using a 16 – 17λ window match the CMD of the analytical covariance.
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Iannucci, 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.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: 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
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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.
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Wildfires 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.
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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.
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Stewart, 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.
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Zeng, Shangyou. "Spatial distribution and function of ion channels on neural axon." Ohio : Ohio University, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1113855357.
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Sultan, 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.
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In wireless communication systems, there is a need to design efficient schemes in order to overcome the problem of spectrum scarcity. One technology to address the problem of spectrum scarcity is cognitive radio (CR), in which a network entity is able to adapt intelligently to the environment through observation, exploration and learning.
When multiple autonomous cognitive radios are searching for spectrum opportunities, they face competition from each other in order to access the available free channel. This will result in reduced throughput which occurs due to collision between cognitive radios, when they try to transmit in the same channel.
The purpose of this thesis is to study a smart adaptation scheme for efficient channel access which enable autonomous cognitive radios to improve their overall bandwidth efficiency in a distributed cognitive radio network with the help of spatial reuse.
An adaptive persistent strategy with efficient collision detection has been studied in this work for autonomous channel sensing order selection which enable distributed CRs to avoid collision and allow them to improve their overall system efficiency by increasing the average number of successful transmissions, especially, when number of available channels are less than the number of CRs competing to access these free channels.
The performance of the studied strategy is compared with random selection of sensing orders. Simulation results are presented, which indicate that the studied strategy with spatial reuse achieves the highest number of successful transmissions in a given time slot as compared to other strategies. Simulation results are also compared for the case with no spatial reuse and the results indicate that it degrades the system efficiency by reducing the average number of successful transmissions in a given time slot.
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Cabral, 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.
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Méndez, Real Maria. "Spatial Isolation against Logical Cache-based Side-Channel Attacks in Many-Core Architectures." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS454/document.
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L’évolution technologique ainsi que l’augmentation incessante de la puissance de calcul requise par les applications font des architectures ”many-core” la nouvelle tendance dans la conception des processeurs. Ces architectures sont composées d’un grand nombre de ressources de calcul (des centaines ou davantage) ce qui offre du parallélisme massif et un niveau de performance très élevé. En effet, les architectures many-core permettent d’exécuter en parallèle un grand nombre d’applications, venant d’origines diverses et de niveaux de sensibilité et de confiance différents, tout en partageant des ressources physiques telles que des ressources de calcul, de mémoire et de communication. Cependant, ce partage de ressources introduit également des vulnérabilités importantes en termes de sécurité. En particulier, les applications sensibles partageant des mémoires cache avec d’autres applications, potentiellement malveillantes, sont vulnérables à des attaques logiques de type canaux cachés basées sur le cache. Ces attaques, permettent à des applications non privilégiées d’accéder à des informations secrètes sensibles appartenant à d’autres applications et cela malgré des méthodes de partitionnement existantes telles que la protection de la mémoire et la virtualisation. Alors que d’importants efforts ont été faits afin de développer des contremesures à ces attaques sur des architectures multicoeurs, ces solutions n’ont pas été originellement conçues pour des architectures many-core récemment apparues et nécessitent d’être évaluées et/ou revisitées afin d’être applicables et efficaces pour ces nouvelles technologies. Dans ce travail de thèse, nous proposons d’étendre les services du système d’exploitation avec des mécanismes de déploiement d’applications et d’allocation de ressources afin de protéger les applications s’exécutant sur des architectures many-core contre les attaques logiques basées sur le cache. Plusieurs stratégies de déploiement sont proposées et comparées à travers différents indicateurs de performance. Ces contributions ont été implémentées et évaluées par prototypage virtuel basé sur SystemC et sur la technologie ”Open Virtual Platforms” (OVP)The 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
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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.
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INSTITUTO MILITAR DE ENGENHARIANo 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.
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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.
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Beckett, 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.
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Over the past decade studies into the application of radiometrics for soil and regolith mapping have met with mixed response. While the use of radiometric data for regolith mapping has been generally well received, radiometric methods have not commonly been adopted to assist and improve soil mapping. This thesis contributes to the development of radiometric techniques as soil and regolith mapping tools by examining soil characteristics and radiometric response using non-standard radiometric methods. This is accomplished through the development of new data processing methodologies, which extracts additional information from standard radiometric data that is unattainable using standard processing methods, and development of a new interpretation approach to soil and regolith mapping employing the multispectral processed radiometric data. The new multispectral processing methodology resolves seven gamma ray peaks from standard 256-channel NaI radiometric data to produce new radiometric uranium ternary, thorium ternary and uranium ratio imagery. Changes in the gamma ray relationships, identified through the new imagery, identify changes in soil and/or environmental conditions that are absent or difficult to identify in the standard radiometric imagery. With the isolation of non-standard thorium channels 228 [superscript] Ac (900 keV) and 228 [superscript] Ac (1600 keV), case studies in this thesis demonstrate how the difference of 1.9 years (half-life) between thorium 228 [superscript] Ac and 232 [superscript] Th decay daughter products can be mapped through the interpretation of thorium energy using ternary imagery [red: 208 [superscript] Tl (1764 keV), green: 228 [superscript] Ac (900 keV), blue: 228 [superscript] Ac (1600 keV)]. Energy peak differences may be be linked to local variations in soil chemistry, soil movement, and water movement.Additionally, 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.
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Beckett, 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.
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Over the past decade studies into the application of radiometrics for soil and regolith mapping have met with mixed response. While the use of radiometric data for regolith mapping has been generally well received, radiometric methods have not commonly been adopted to assist and improve soil mapping. This thesis contributes to the development of radiometric techniques as soil and regolith mapping tools by examining soil characteristics and radiometric response using non-standard radiometric methods. This is accomplished through the development of new data processing methodologies, which extracts additional information from standard radiometric data that is unattainable using standard processing methods, and development of a new interpretation approach to soil and regolith mapping employing the multispectral processed radiometric data. The new multispectral processing methodology resolves seven gamma ray peaks from standard 256-channel NaI radiometric data to produce new radiometric uranium ternary, thorium ternary and uranium ratio imagery. Changes in the gamma ray relationships, identified through the new imagery, identify changes in soil and/or environmental conditions that are absent or difficult to identify in the standard radiometric imagery. With the isolation of non-standard thorium channels 228 [superscript] Ac (900 keV) and 228 [superscript] Ac (1600 keV), case studies in this thesis demonstrate how the difference of 1.9 years (half-life) between thorium 228 [superscript] Ac and 232 [superscript] Th decay daughter products can be mapped through the interpretation of thorium energy using ternary imagery [red: 208 [superscript] Tl (1764 keV), green: 228 [superscript] Ac (900 keV), blue: 228 [superscript] Ac (1600 keV)]. Energy peak differences may be be linked to local variations in soil chemistry, soil movement, and water movement.Additionally, 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.
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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.
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The 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
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Bharadwaj, Vivek. "Ultra-Wideband for Communications: Spatial Characteristics and Interference Suppression." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33183.
Full textAbstract:
Ultra-Wideband Communication is increasingly being considered as an attractive solution for high data rate short range wireless and position location applications. Knowledge of the statistical nature of the channel is necessary to design wireless systems that provide optimum performance. This thesis investigates the spatial characteristics of the channel based on measurements conducted using UWB pulses in an indoor office environment. The statistics of the received signal energy illustrate the low spatial fading of UWB signals. The distribution of the Angle of arrival (AOA) of the multipath components is obtained using a two-dimensional deconvolution algorithm called the Sensor-CLEAN algorithm. A spatial channel model that incorporates the spatial and temporal features of the channel is developed based on the AOA statistics. The performance of the Sensor-CLEAN algorithm is evaluated briefly by application to known artificial channels.
UWB systems co-exist with narrowband and other wideband systems. Even though they enjoy the advantage of processing gain (the ratio of bandwidth to data rate) the low energy per pulse may cause these narrow band interferers (NBI) to severely degrade the UWB system's performance. A technique to suppress NBI using multiple antennas is presented in this thesis which exploits the spatial fading characteristics. This method exploits the vast difference in fading characteristics between UWB signals and NBI by implementing a simple selection diversity scheme. It is shown that this simple scheme can provide strong benefits in performance.Master of Science
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Stavridis, Athanasios. "On the energy efficiency of spatial modulation concepts." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15951.
Full textAbstract:
Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results.
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Lamahewa, 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 textAbstract:
In this thesis we investigate the effects of the physical
constraints such as antenna aperture size, antenna geometry and
non-isotropic scattering distribution parameters (angle of
arrival/departure and angular spread) on the performance of coherent
and non-coherent space-time coded wireless communication systems.
First, we derive analytical expressions for the exact pairwise error
probability (PEP) and PEP upper-bound of coherent and non-coherent
space-time coded systems operating over spatially correlated fading
channels using a moment-generating function-based approach. These
analytical expressions account for antenna spacing, antenna
geometries and scattering distribution models. Using these new PEP
expressions, the degree of the effect of antenna spacing, antenna
geometry and angular spread is quantified on the diversity advantage
(robustness) given by a space-time code. It is shown that the number
of antennas that can be employed in a fixed antenna aperture without
diminishing the diversity advantage of a space-time code is
determined by the size of the antenna aperture, antenna geometry and
the richness of the scattering environment.
¶
In realistic channel environments the performance of space-time
coded multiple-input multiple output (MIMO) systems is significantly
reduced due to non-ideal antenna placement and non-isotropic
scattering. In this thesis, by exploiting the spatial dimension of a
MIMO channel we introduce the novel use of linear spatial precoding
(or power-loading) based on fixed and known parameters of MIMO
channels to ameliorate the effects of non-ideal antenna placement on
the performance of coherent and non-coherent space-time codes. The
spatial precoder virtually arranges the antennas into an optimal
configuration so that the spatial correlation between all antenna
elements is minimum. With this design, the precoder is fixed for
fixed antenna placement and the transmitter does not require any
feedback of channel state information (partial or full) from the
receiver. We also derive precoding schemes to exploit non-isotropic
scattering distribution parameters of the scattering channel to
improve the performance of space-time codes applied on MIMO systems
in non-isotropic scattering environments. However, these schemes
require the receiver to estimate the non-isotropic parameters and
feed them back to the transmitter.
¶
The idea of precoding based on fixed parameters of MIMO channels is
extended to maximize the capacity of spatially constrained dense
antenna arrays. It is shown that the theoretical maximum capacity
available from a fixed region of space can be achieved by power
loading based on previously unutilized channel state information
contained in the antenna locations. We analyzed the correlation
between different modal orders generated at the transmitter region
due to spatially constrained antenna arrays in non-isotropic
scattering environments, and showed that adjacent modes contribute
to higher correlation at the transmitter region. Based on this
result, a power loading scheme is proposed which reduces the effects
of correlation between adjacent modes at the transmitter region by
nulling power onto adjacent transmit modes.
¶
Furthermore, in this thesis a general space-time channel model for
down-link transmission in a mobile multiple antenna communication
system is developed. The model incorporates deterministic
quantities such as physical antenna positions and the motion of the
mobile unit (velocity and the direction), and random quantities to
capture random scattering environment modeled using a bi-angular
power distribution and, in the simplest case, the covariance between
transmit and receive angles which captures statistical
interdependency. The Kronecker model is shown to be a special case
when the power distribution is separable and is shown to
overestimate MIMO system performance whenever there is more than one
scattering cluster. Expressions for space-time cross correlations
and space-frequency cross spectra are given for a number of
scattering distributions using Gaussian and Morgenstern's family of
multivariate distributions. These new expressions extend the
classical Jake's and Clarke's correlation models to general
non-isotropic scattering environments.
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Warman, 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 textAbstract:
The Irwin River catchment, located in the central western region of Western Australia, has been the scene of significant geomorphological change over both historical and geological timescales. This thesis focuses on the most recent of these changes, the anthropogenic imprint, through the development of a catchment-scale understanding of system behaviour. Analysis and modelling of changes in the hydrological behaviour of the system indicates that while the Irwin River has displayed a natural susceptibility to large flood events, these have been exacerbated by the widespread clearing of native vegetation throughout the catchment. As a result, when such events do occur, the catchment response is now larger, more direct and has a greater ability to cause erosion. However, the nature and detail of sediment yield processes and stream channel response varies markedly throughout the system. A series of representative channel reaches, as defined by their planform characteristics, geometry and architecture, are presented to illustrate spatial changes in stream channel behaviour. A distinct variation in river morphotypes is seen both downstream throughout the system as well as across the tributary sub-catchments of the Irwin River, Lockier River and Green Brook. This inter and intra sub-catchment variation in stream channel response can be attributed to changes in the boundary conditions and coupling mechanisms in operation throughout the Irwin River system. The pronounced spatial variability in response to human disturbance and the changing nature of catchment-scale connectivity seen in the Irwin River system differs markedly to that reported elsewhere in the literature. Appreciation of the variability in form, behaviour and evolutionary history throughout the Irwin River catchment not only provides the foundation for effective management but also contributes to a wider understanding of fluvial system behaviour. Unlike the majority of existing literature, which tends to identify and measure channel changes in a single catchment where historical variation to the sediment and discharge regime is well known, this study demonstrates the role of boundary conditions in determining the response of the fluvial system to changing environmental controls.
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Baykas, 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 textAbstract:
Today's wireless communication systems require more efficiency in terms of data rate. One of the ways to improve channel capacity of such systems is to utilize diversity. Space-time block codes provide transmit diversity gain without any significant increase in complexity of systems. However in some cases, the gain by utilizing diversity decreases due to some factors. In this work we studied two of these factors and their effects to several space-time block coded systems. The first factor is the spatial correlation among channels and the second factor is channel estimation errors. Both of these factors are experienced in real life situations. The systems under consideration are 2, 3 and 4 antenna orthogonal and quasi-orthogonal space-time block coded systems. We have also compared the results with the maximum ratio combining schemes with 2 and 4 receiver antennas.
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Thompson, 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 textAbstract:
The San Fernando Channel System is a superbly exposed submarine channel system of late Cretaceous age located on the Pacific coast of Baja California, Mexico. High-resolution mapping and extensive system-wide correlation panels coupled with detailed sedimentology studies and interpretation of high-resolution photomosaics have shown that the system comprises a distinct hierarchy of stratigraphy components. Extensive outcrops have allowed a detailed submarine channel model to be proposed which describes architecture and facies spanning outcrop to seismic scales. Channel complex sets are the largest mappable component within the system and are bounded by basal system-wide erosion surfaces. Each set shows a consistent stratigraphic evolution comprising 3 distinct stages each characterised by distinct channel complexes. Channel complexes in Stage 1 are predominantly coarse-grained, highly amalgamated and confined within an extensive composite erosion surface. Stage 2 is dominated by channel complexes which are finer-grained, less amalgamated and laterally flanked by internal levee deposits. Stage 3 relates to the shutdown and gradual abandonment of the system and is dominated by fine-grained turbidites and well developed condensed intervals. The stratigraphic variation observed within the channel system is linked to sea-level fluctuations. However, throughout the system, local contemporaneous faulting is shown to have a high degree of control on the location of sedimentation and commonly overrides the normal sea-level influenced depositional evolution. Local faulting is also shown to profoundly affect both the local channel-fill type and the stacking patterns of architectural elements and channel complexes. Stacking patterns of individual channel complexes are generally more predictable in Stage 2 than in Stage 1 which is attributed to the variation in relative confinement of the individual channel complexes.
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Tsai, 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 textAbstract:
ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, CaliforniaSpatial 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.
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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 textAbstract:
This thesis covers the investigation and application of continuous spatial models for multiple antenna signal processing. The use of antenna arrays for advanced sensing and communications systems has been facilitated by the rapid increase in the capabilities of digital signal processing systems. The wireless communications channel will vary across space as different signal paths from the same source combine and interfere. This creates a level of spatial diversity that can be exploited to improve the robustness and overall capacity of the wireless channel. Conventional approaches to using spatial diversity have centered on smart, adaptive antennas and spatial beam forming. Recently, the more general theory of multiple input, multiple output (MIMO) systems has been developed to utilise the independent spatial communication modes offered in a scattering environment.¶
Underlying any multiple antenna system is the basic physics of electromagnetic wave propagation. Whilst a MIMO system may present a set of discrete inputs and outputs, each antenna element must interact with the underlying continuous spatial field. Since an electromagnetic disturbance will propagate through space, the field at different positions in the space will be interrelated. In this way, each position in the field cannot assume an arbitrary independent value and the nature of wave propagation places a constraint on the allowable complexity of a wave-field over space. To take advantage of this underlying physical constraint, it is necessary to have a model that incorporates the continuous nature of the spatial wave-field. ¶This thesis investigates continuous spatial models for the wave-field. The wave equation constraint is introduced by considering a natural basis expansion for the space of physically valid wave-fields. This approach demonstrates that a wave-field over a finite spatial region has an effective finite dimensionality. The optimal basis for representing such a field is dependent on the shape of the region of interest and the angular power distribution of the incident field. By applying the continuous spatial model to the problem of direction of arrival estimation, it is shown that the spatial region occupied by the receiver places a fundamental limit on the number and accuracy with which sources can be resolved. Continuous spatial models also provide a parsimonious representation for modelling the spatial communications channel independent of specific antenna array configurations. The continuous spatial model is also applied to consider limits to the problem of wireless source direction and range localisation.
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Jiang, Jing. "Capacity-approaching data transmission in MIMO broadcast channels." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11208.
Full textAbstract:
This dissertation focuses on downlink multi-antenna transmission with packet scheduling in a wireless packet data network. The topic is viewed as a critical system design problem for future high-speed packet networks requiring extremely high spectral efficiency. Our aim is to illustrate the interaction between transmission schemes at the physical layer and scheduling algorithms at the medium access control (MAC) layer from a sum-capacity perspective. Various roles of multiple antennas are studied under channel-aware scheduling, including diversity, beamforming and spatial multiplexing. At a system performance level, our work shows that downlink throughput can be optimized by joint precoding across multiple transmit antennas and exploiting small-scale fading of distributed multiple input and multiple output (MIMO) channels.
There are three major results in this dissertation. First, it is shown that over a MIMO Gaussian broadcast channel, and under channel-aware scheduling, open-loop transmit antenna diversity actually reduces the achievable sum rate. This reveals a negative interaction between open-loop antenna diversity and the closed-loop multiuser diversity through scheduling. Second, a suboptimal dirty paper coding (DPC) approach benefits greatly from multiuser diversity by an efficient packet scheduling algorithm. Performance analysis of a suboptimal greedy scheduling algorithm indicates that, compared with the receiver-centric V-BLAST method, it can achieve a much larger scheduling gain over a distributed MIMO channel. Further, pre-interference cancellation allows for transmissions free of error propagation. A practical solution, termed Tomlinson-Harashima precoding (THP), is studied under this suboptimal scheduling algorithm. Similar to V-BLAST, a reordering is applied to minimize the average error rate, which introduces only a negligible sum-rate loss in the scenarios investigated. Third, for an orthogonal frequency division multiplexing (OFDM) system using MIMO precoding, it is shown that a DPC-based approach is readily applicable and can be easily generalized to reduce the peak-to-average power ratio (PAR) up to 5 dB without affecting the receiver design. Simulations show that in an interference-limited multi-cell scenario, greater performance improvement can be achieved by interference avoidance through adaptive packet scheduling, rather than by interference diversity or averaging alone. These findings suggest that, coordinated with channel-aware scheduling, adaptive multiplexing in both spatial and frequency domains provides an attractive downlink solution from a total capacity point of view.Ph. D.
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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 textAbstract:
The increasing interest for immersive experiences in areas such as augmented and virtual reality makes high quality 3D sound more important than ever before. A technique for capturing and rendering 3D audio which has received more attention during the last twenty years are Higher Order Ambisonics (HOA). Higher Order Ambisonics is a scene based audio format which has a lot of advantages compared to other standard formats. Hovever, one problem with HOA is that it requires a lot of bandwidth. For example, sending an uncoded high quality HOA signal requires 49 channels to be transmitted at the same time which requires a bandwidth of about 40 Mbps. A lot of effort has been made in the last ten years on coding HOA signals. In this thesis, two different approaches are taken on coding HOA signals. In one approach, called Sound Field Rotation (SFR) in this thesis, the microphone that records the sound field is virtually rotated to see if it is possible to make some of the channels zero. The second approach, called Sound Field Decomposition (SFD) in this thesis, use Principal component analysis to decompose a sound field into a foreground and background component. The Sound Field Decomposition approach is inspired by the emerging MPEG-H 3D Audio standard for coding HOA signals. The result shows that the Sound Field Rotation method only works for very simple sound scenes. It has also been shown that a 49 channels HOA signal can be reduced to as little as 7 channels if the sound scene consists of a point source. The Sound Field Deomposition method worked for more complex sound scenes. It was shown that a MPEG similar system could be improved. Result from MUSHRA (Multiple stimuli with hidden reference and anchor) listening tests showed that an improved MPEG similar system reached a MUSHRA score about 78 while the MPEG similar system reached 55 at a bitrate of 256 kbps. Without coding each monochannels with the 3GPP EVS (Enhanced voice services) codec, the improved MPEG similar system reached the MUSHRA score 85. At 256 kbps, the improved MPEG similar system coded the HOA signal into six channels instead of 49 for the uncoded signal. From objective results, it was shown that the improved MPEG similar system had largest effect at low bitrates.
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D'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.
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Alizadeh, Ardalan. "Cognitive Communications for Emerging Wireless Systems." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1470226402.
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
Full textAbstract:
The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated.
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Crawford, 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.
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Corbalán, 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 textAbstract:
O projeto INDEMARES produziu uma extensa base de dados obtida a partir das análises de 73 transectos de vídeo gravados com ROV e submersíveis tripulados durante os cruzeiros INDEMARES 3-‐4-‐5-‐6 e 0811 (período de 2010-‐2012) no Canal de Menorca, localizado entre as ilhas de Mallorca e Menorca. A informação proveniente dos transectos de vídeo foi processado e analisado pela equipa ICM durante os últimos anos. No âmbito da presente dissertação de mestrado, os dados sobre as várias espécies de esponjas foram processados com enfoque na distribuição espacial e batimétrica na plataforma e talude continental. O padrão de distribuição de cada espécie de esponja foi diferente, no entanto, houve uma acentuada preferência para a plataforma continental profunda norte e talude onde as espécies ocorrem com maior frequência e abundância. Os resultados deste estudo são destinadas a completar o conhecimento científico sobre as diferentes espécies de esponjas, a fim de definir as bases para a gestão e proteção eficiente do ecossistema do Canal de Menorca; ABSTRACT: The INDEMARES project has produced an extensive database obtained from the analyses of 73 video transects recorded with ROV and manned submersible during the cruises INDEMARES 3-‐4-‐5-‐6 and 0811 (years 2010 to 2012) in the Menorca Channel, located between the islands of Mallorca and Menorca. The information derived from the video transects has been processed and analyzed by the ICM team during the past years. Within the framework of my thesis, data concerning several sponge species was processed focusing in the spatial and bathymetric distribution on the continental shelf and slope. The distribution pattern of each sponge species was different, however there was a marked preference for the northern deep continental shelf and slope where species reach highest occurrence and abundances. The results of this study are aimed to complete the scientific knowledge about the different sponge species in order to set the bases toward efficient management and protection of the Menorca Channel ecosystem.
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Al-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 textAbstract:
The tremendous spreading of multimedia via Internet motivates the watermarking as a new promising technology for copyright protection. This work is concerned with the design and development of novel algorithms in the spatial and transform domains for robust and secure watermarking of coloured images. These algorithms are adaptive, content-dependent and compatible with the Human Visual System (HVS). The host channels have the ability to host a large information payload. Furthermore, it has enough capacity to accept multiple watermarks.
Abstract
This work achieves several contributions in the area of coloured images watermarking. The most challenging problem is to get a robust algorithm that can overcome geometric attacks, which is solved in this work. Also, the search for a very secure algorithm has been achieved via using double secret keys. In addition, the problem of multiple claims of ownership is solved here using an unusual approach. Furthermore, this work differentiates between terms, which are usually confusing the researchers and lead to misunderstanding in most of the previous algorithms.
One of the drawbacks in most of the previous algorithms is that the watermark consists of a small numbers of bits without strict meaning. This work overcomes this weakness
III
in using meaningful images and text with large amounts of data. Contrary to what is found in literature, this work shows that the green-channel is better than the blue-channel to host the watermarks.
A more general and comprehensive test bed besides a broad band of performance evaluation is used to fairly judge the algorithms.
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Al-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 textAbstract:
The tremendous spreading of multimedia via Internet motivates the watermarking as a new promising technology for copyright protection. This work is concerned with the design and development of novel algorithms in the spatial and transform domains for robust and secure watermarking of coloured images. These algorithms are adaptive, content-dependent and compatible with the Human Visual System (HVS). The host channels have the ability to host a large information payload. Furthermore, it has enough capacity to accept multiple watermarks. Abstract This work achieves several contributions in the area of coloured images watermarking. The most challenging problem is to get a robust algorithm that can overcome geometric attacks, which is solved in this work. Also, the search for a very secure algorithm has been achieved via using double secret keys. In addition, the problem of multiple claims of ownership is solved here using an unusual approach. Furthermore, this work differentiates between terms, which are usually confusing the researchers and lead to misunderstanding in most of the previous algorithms. One of the drawbacks in most of the previous algorithms is that the watermark consists of a small numbers of bits without strict meaning. This work overcomes this weakness III in using meaningful images and text with large amounts of data. Contrary to what is found in literature, this work shows that the green-channel is better than the blue-channel to host the watermarks. A more general and comprehensive test bed besides a broad band of performance evaluation is used to fairly judge the algorithms.
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Raddadi, Bilel. "Récepteurs avancés et nouvelles formes d'ondes pour les communications aéronautiques." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0057/document.
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De nos jours, l'utilisation des drones ne cesse d'augmenter et de nombreuses études sont réalisées afin de mettre en place des systèmes de communication dronique destinés à des applications non seulement militaires mais aussi civiles. Pour le moment, les règles d'intégration des drones commerciaux dans l’espace aérien doivent encore être définies et le principal enjeu occupation est d'assurer une communication fiable et sécurisée. Cette thèse s’inscrit dans ce contexte de communication. Motivée par la croissance rapide du nombre des drones et par les nouvelles générations des drones commandés par satellite, la thèse vise à étudier les différents liens possibles qui relient le drone aux autres composants du système de communication. Trois principaux liens sont à mettre en place : le lien de contrôle, le lien de retour et le lien de mission. En raison de la rareté des ressources fréquentielles déjà allouées pour les futurs systèmes droniques, l'efficacité spectrale devient un paramètre crucial pour leur déploiement à grande échelle. Afin de mettre en place un système de communication par drones spectralement efficace, une bonne compréhension des canaux de transmission pour chacune des trois liaisons est indispensable, ainsi qu’un choix judicieux de la forme d’onde. Cette thèse commence par étudier les canaux de propagation pour chaque liaison : canaux de type muti-trajets avec ligne de vue directe, dans un contexte d’utilisation de drones à moyenne altitude et longue endurance (drones MALE). L’objectif de cette thèse est de proposer de nouveaux algorithmes de réception permettant d’estimer et égaliser ces canaux de propagation muti-trajets. Les méthodes proposées dépendent du choix de la forme d’onde. Du fait de la présence d’un lien satellite, les formes d’onde considérées sont de type mono-porteuse (avec un faible facteur de crête) : SC et EW-SCOFDM. L’égalisation est réalisée dans le domaine temporel (SC) ou fréquentiel (EW-SC-OFDM). L'architecture UAV prévoit l'implantation de deux antennes placées aux ailes. Ces deux antennes peuvent être utilisées pour augmenter le gain de diversité (gain de matrice de canal). Afin de réduire la complexité de l'égalisation des canaux, la forme d'onde EW-SC-OFDM est proposée et étudiée dans un contexte muti-antennes, dans le but d'améliorer l'endurance de l'UAV et d'accroître l'efficacité spectrale, une nouvelle technique de modulation est considérée: Modulation spatiale ( SM). Dans SM, les antennes de transmission sont activées en alternance. L'utilisation de la forme d'onde EW-SC-OFDM combinée à la technique SM nous permet de proposer de nouvelles structures modifiées qui exploitent l’étalement spectrale pour mieux protéger des bits de sélection des antennes émettrices et ainsi améliorer les performances du systèmeNowadays, 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
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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 textAbstract:
Throughout 2003 and 2004 continuous autonomous observations of surface temperature, conductivity and chlorophyll fluorescence were recorded on the P&O "Pride of Bilbao" ferry between Portsmouth, UK and Bilbao Spain. Different conditions over the shelf, slope and deep waters along the route were detected and studied - from eutrophic harbour waters to the southern Bay of Biscay, which is oligotrophic in summer. During the two years, 21 manned crossings on the ferry provided information on nutrients, phytoplankton biomass and speciation. Measurements include chlorophyll a concentrations (calibration of the fluorimeter is discussed), High Performance Liquid Chromatography (HPLC) determined pigments concentrations, phytoplankton species abundance (biomass and identification) and nutrients. Data was also available from satellite images for estimates of chlorophyll (SeaWIFS), zooplankton abundance from CPR (Continuous Plankton Recorder) tows, wind speed and direction and irradiance. This has enabled phytoplankton populations to be related to-: (1) nutrient supply (2) grazing pressure (3) fresh water influences, (4) hydrography and (5) climatic conditions. The distributions of hydrographic properties and of plankton were analysed on the basis of four generalised regions (i) well-mixed, (ii) northern summer stratified, and (iii) southern summer stratified on the shelf and (iv) oceanic region in the Bay of Biscay water. There were differences between the two years in the timing of seasonal changes and in the abundance of phytoplankton species. Chlorophyll a values were generally higher in shelf waters compared to oceanic water in both years. The spring phytoplankton bloom reached its peak during March 2003 in the Bay of Biscay and during April on the continental shelf with maximum chlorophyll values of 2- 4 mg m-3. Whereas, the strong SW wind in Bay of Biscay in winter 2004 may have delayed growth in this region. In the shelf regions in 2004 low salinity values off western France and high solar irradiance in the north are likely to have led to earlier phytoplankton biomass than in 2003. During early summer, the coccolithophore, Emiliania huxlyei (>1000 cells ml-1) was widespread in northern stratified regions, more so in 2003 than in 2004. In the summer of 2003 an exceptional dinoflagellate bloom occurred in the western English Channel. The bloom was composed of a monspecific surface population of Karenia mikimotoi, giving cell densities up to 8000 cells ml-1 and chlorophyll a concentrations up to 70 mg m-3. Development of this dinoflagellate bloom in the western English Channel could be explained in terms of physical stability, and ii low wind speed together with sufficient light and a supply of inorganic nutrients favouring growth of the cells. By contrast, in 2004, the abundance of diatoms was higher than 2003 and K. mikimotoi was common but not at bloom levels (chlorophyll a ~4.0 mg m-3). A mixed diatom-dinoflagellate community was the dominant the final stage in the succession, as the summer thermocline was less well developed. The phytoplankton biomass and composition in 2003 matches the classical model of phytoplankton seasonal succession in temperate waters (Margalef, 1978; Smayda, 1980) but this was not obvious in 2004. In general, the FerryBox system on the Pride of Bilbao in 2003 and 2004 was successful and improved understanding of the relationship between the phytoplankton population and hydrographic regimes in 2003 and 2004 between Portsmouth and Bilbao. Improvements in future might include continuous observations of oxygen and nutrients and more work can be done to link FerryBox data, satellite and CPR based observations.
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Usman, 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 textAbstract:
The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest.
A comprehensive study of MIMO antenna configurations such as 2 × 1, 3 × 1, 2 × 2 and 3 × 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 × 2 and 3 × 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger.
A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands.
A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity.
In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally.
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Soccodato, 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 textAbstract:
Survival during the early life stages of marine species, including nearshore temperate reef fishes, is typically very low, and small changes in mortality rates, due to physiological and environmental conditions, can have marked effects on survival of a cohort and, on a larger scale, on the success of a recruitment season. Moreover, trade offs between larval growth and accumulation of energetic resources prior to settlement are likely to influence growth and survival until this critical period and afterwards.
Rockfish recruitment rates are notoriously variable between years and across geographic locations. Monitoring of rates of onshore delivery of pelagic juveniles (defined here as settlement) of two species of nearshore rockfishes, Sebastes caurinus and Sebastes carnatus, was done between 2003-2009 years using artificial collectors placed at San Miguel and Santa Cruz Island, off Southern California coast.
I investigated spatiotemporal variation in settlement rate, lipid content, pelagic larval duration and larval growth of the newly settled fishes; I assessed relationships between birth date, larval growth, early life-history characteristics and lipid content at settlement, considering also interspecific differences; finally, I attempt to relate interannual patterns of settlement and of early life history traits to easily accessible, local and regional indices of ocean conditions including in situ ocean temperature and regional upwelling, sea surface temperature (SST) and Chlorophyll-a (Chl-a) concentration.
Spatial variations appeared to be of low relevance, while significant interannual differences were detected in settlement rate, pelagic larval duration and larval growth. The amount of lipid content of the newly settled fishes was highly variable in space and time, but did not differ between the two species and did not show any relationships with early life history traits, indicating that no trade off involved these physiological processes or they were masked by high individual variability in different periods of larval life.
Significant interspecific differences were found in the timing of parturition and settlement and in larval growth rates, with S. carnatus growing faster and breeding and settling later than S. caurinus. The two species exhibited also different patterns of correlations between larval growth rates and larval duration. S. carnatus larval duration was longer when the growth in the first two weeks post-hatch was faster, while S. caurinus had a shorter larval duration when grew fast in the middle and in the end of larval life, suggesting different larval strategies. Fishes with longer larval durations were longer in size at settlement and exhibited longer planktonic phase in periods of favourable environmental conditions.
Ocean conditions had a low explanatory power for interannual variation in early life history traits, but a very high explanatory power for settlement fluctuations, with regional upwelling strength being the principal indicator. Nonetheless, interannual variability in larval duration and growth were related to great phenological changes in upwelling happened during the period of this study and that caused negative consequences at all trophic levels along the California coast. Despite the low explanatory power of the environmental variables used in this study on the variation of larval biological traits, environmental processes were differently related with early life history characteristics analyzed to species, indicating possible species-specific susceptibility to ocean conditions and local environmental adaptation, which should be further investigated.
These results have implications for understanding the processes influencing larval and juvenile survival, and consequently recruitment variability, which may be dependent on biological characteristics and environmental conditions.
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ʿUs̲mān, 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 textAbstract:
The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest. A comprehensive study of MIMO antenna configurations such as 2 × 1, 3 × 1, 2 × 2 and 3 × 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 × 2 and 3 × 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger. A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands. A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity. In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally.
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Calatrava, 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 textAbstract:
Nowadays, identification of fake data is an elaboratechallenge that calls for the use of machine learning techniques.This is due to the huge amount of data and its complexity makesthe differences indistinguishable even for the trained eye. In thisproject we use the MATLAB wlanTGnChannel System objectto simulate multipath fading channels that are comparable toreal impulse response measurements made by Ericsson AB of anindoor8×8MIMO (Multiple Input Multiple Output) system.We use an SVM classifier to compare the eigenvalues of theircorrelation covariance matrices, obtaining an accuracy of 84%.Comparing their power delay profiles (PDPs) happens to bea classification task of low complexity due to time resolutionlimitation in the real measurements. We suggest that the proposedMATLAB model strongly differs from the real data we have beenprovided with.Nu 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
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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 textAbstract:
Abstract This thesis concentrates on the design and evaluation of spatial user multiplexing methods via linear transmit-receive processing for wireless cellular multi-user multiple-input multiple-output (MIMO) communication systems operating in the time-division duplexing (TDD) mode. The main focus is on the acquisition of effective channel state information (CSI) that facilitates decentralized processing so that the network nodes – base stations (BS) and user terminals (UT), each employing an arbitrary number of antenna elements – are able to locally participate in the network adaptation. The proposed methods rely on the uplink-downlink channel reciprocity and spatially precoded over-the-air pilot signaling. Considering (single-cell) multi-user MIMO systems, coordinated zero-forcing transmit-receive processing schemes for the uplink (UL) are proposed. The BS computes the transmission parameters in a centralized manner and employs downlink (DL) pilot signals to convey the information of the beamformers to be used by the UTs. When coexisting with the DL zero-forcing, the precoded DL demodulation pilots can be reused for UL beam allocation, and the precoded UL demodulation pilots are reused in turn for partial channel sounding (CS). As a result, only the precoded pilot symbols are needed in both UL and DL. Moreover, a concept for reducing the number of the required orthogonal UL CS pilot resources is presented. Based on their DL channel knowledge, the multi-antenna UTs form fewer pilot beams by spatial precoding than conventionally needed when transmitting antenna-specific pilots. In the context of DL zero-forcing, when taking into account the CSI estimation error at the BS, the overhead reduction turns out to improve robustness and increase the average system capacity. Considering multi-cell multi-user MIMO systems, decentralized coordinated DL beamforming strategies based on weighted sum rate (WSR) maximization are proposed. An optimization framework where the WSR maximization is carried out via weighted sum mean-squared-error minimization is utilized, and the approach is generalized by employing antenna-specific transmit power constraints. The iterative processing consists of optimization steps that are run locally by the BSs. In one novel strategy, the coordinating cells update their transmit precoders and receivers one cell at a time, which guarantees monotonic convergence of the network-wide problem. The strategy employs separate uplink CS and busy burst pilot signaling to reveal the effective channels of the UTs to the neighboring BSs. In another novel strategy, the monotonic convergence is sacrificed to devise a faster scheme where the BSs are allowed to optimize their variables in parallel based on just the CS responses and additional low-rate backhaul information exchange. The numerical results demonstrate that WSR maximization has the desirable property that spatial user scheduling is carried out implicitly. Finally, methods for UL CS overhead reduction are presented, and the effect of CSI uncertainty is addressedTiivistelmä 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
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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 textAbstract:
Spatial frequency reuse is a long-established approach for enhancing the capacity of wireless systems through increased spectral efficiency (bits per second per unit bandwidth). The future 5th generation of wireless systems is expected to incorporate various forms of frequency reuse. This includes multiple-input multiple-output (MIMO) communication enabling frequency reuse across antennas, device-to-device (D2D)-based densification allowing spectrum reuse across direct communication links, and full duplexing utilizing the same spectrum for communication in the transmit and receive directions.
This dissertation aims at determining the performance limits of emerging wireless systems underpinned by dense spatial frequency reuse and interference suppression, and to glean key system design insights. Stochastic geometry is the toolbox invoked to conduct the analysis, with network locations modeled as points of a Poisson process. A new framework is developed by introducing a Gaussian fit to the interference and variable degrees of spatial averaging, which enable more meaningful results and compact expressions compared to those of existing analyses.
Within this framework, we first consider MIMO spatial multiplexing and interference alignment (IA). The former scheme utilizes all available spatial dimensions for signaling and the latter minimizes interference at the expense of knowing the instantaneous fading states at both transmitters and receivers and of a reduction in spatial signaling dimensions. Despite the intense work on IA and spatial multiplexing, there is limited work aimed at understanding their engineering tradeoff in the context of practically relevant cellular settings such as propagation losses, fading dynamics due to user mobility and imperfect knowledge of the fading states. We have studied this problem in depth through both system- and link-level analyses. Even under perfect knowledge of the fading, IA is seen to be beneficial over spatial multiplexing only in very specific and relatively infrequent network situations, and IA loses all its advantages at vehicular speeds when the fading knowledge is imperfect.
Second, we focus on ITLinQ and FlashLinQ, the two principal channelization schemes proposed to date for controlling the interference in D2D networks. An analytical characterization of ITLinQ scheme is provided, opening the door to optimizing its controllable parameters. It is shown that both channelization schemes outperform the unchannelized baseline, with a slight edge for ITLinQ. On the most unfavorable network geometries, ITLinQ yields multiple-fold improvements in spectral efficiency with respect to an unchannelized network.
Finally, we introduce full-duplex transceivers in cellular networks and characterize the impact of increased interference on their performance. It is established through analysis and complemented by simulations on a Vodafone LTE field test network that additional user-to-user interference only has a minor impact while base-to-base interference would render full-duplex operation unfeasible in dense microcellular networks without any interference management.
In summary, MIMO spatial multiplexing and D2D-based densification are seen to play a vital role in improving wireless system capacity while IA and full duplexing are found to be ineffective.La 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.
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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/.
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This PhD thesis describes the progressive development of a multi-channel, multi-distance broadband NIRS system designed to measure the concentration changes in oxygenated haemoglobin (HbO2), deoxygenated haemoglobin (HHb), and especially the oxidation state of cytochrome-c-oxidase (oxCCO) across multiple regions of the adult human brain. The system was developed using an iterative approach, through two major iterations. At each iteration, in vivo tests in healthy adult volunteers were performed to test the system capability. The first iteration was the pseudo broadband diffuse optical tomography system, achieved by physically moving one source fibre and eight detector fibres across multiple positions in a fixed 3D printed probe holder. A functional activation task involving the visual cortex was used as an in vivo test of this approach. The second iteration was the full multi-channel, multi-distance broadband NIRS system, achieved by increasing the number of source and detector fibres and integrating a time-multiplexing mechanism for the sources. The capability of this system was tested using functional activation tasks involving both the visual and frontal cortices. The final version of the system was then used in the neurointensive care unit to monitor the frontal regions of patients with acute brain injury, demonstrating the capability for monitoring the temporal and spatial variations in cerebral haemodynamics and oxygen metabolism. The multi-channel, multi-distance broadband NIRS measurements acquired from various functional activation studies and the clinical study have provided evidence for the existence of spatially dependent changes in [oxCCO] signal. More importantly, they show that the spatial variation in the changes in [oxCCO] can be monitored using a multi-channel broadband NIRS approach. The measurements collected during various stages of system development have allowed the implementation of the oxCCO image reconstruction algorithm, reconstructing 3D tomographic images of oxCCO for the first time. The combined developments in hardware engineering, data acquisition, clinical studies and image reconstruction open up a whole new avenue for the investigation of cerebral oxygen metabolism in the healthy and injured adult human brain.
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Bourdaud, 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 textAbstract:
L'objectif de cette thèse était d'anticiper les effets de l'Obligation de Débarquement (OD) mise en place en UE depuis début 2015 en Manche Orientale (MO). Pour accomplir ces objectifs, il a été prévu de : i) mieux comprendre la distribution spatiale saisonnière d'espèces commerciales à l'aide d'observations embarquées sur des navires commerciaux, ii) les comparer avec la distribution de l'effort de pêche à fine échelle des chalutiers de fonds (OTB), et iii) développer un modèle individu-centré de dynamique des flotilles, DSVM, à intégrer avec le modèle écosystémique OSMOSE pour simuler l'OD. L'utilité des données d'observations embarquées a été prouvée pour une majeure partie des espèces échantillonnées, en utilisant une validation par la bibliographie et un indicateur géostatique. Ensuite la comparaison de l'effort de pêche à fine échelle a fourni une amélioration de la quantification de l'effort de pêche effectif et mis en valeur l'importance de la seiche et du rouget barbet pour la distribution des OTB en MO. De plus, l'intensité de ciblage des OTB a été quantifiée en octobre à l'aide d'un nouvel indicateur, et démontré l'intérêt pour les mêmes espèces, mais aussi la contrainte d'un faible quota de cabillaud pour les pêcheurs. Les résultats du couplage OSMOSE-DSVM montrent que k'OD aurait des effets négatifs à court terme pour le revenu des pêcheurs, induits par le déplacement de l'effort de pêche afin d'éviter les dépassements de quota, mais serait profitable à moyen terme. Cependant, l'OD provoquerait une hausse de la pression de prédation produite par le cabillaud et le merlan sur les autres espèces, ce qui n'améliorerait pas l'état global de l'écosystèmeThe 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
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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.
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Barrachina, 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 textAbstract:
In this thesis, we focus on the so-called spectrum management's joint problem: efficient
allocation of primary and secondary channels in channel bonding wireless local area networks
(WLANs). From IEEE 802.11n to more recent standards like 802.11ax and 802.11be, bonding
channels together is permitted to increase transmissions' bandwidth. While such an increase
favors the potential network capacity and the activation of higher transmission rates, it comes at
the price of reduced power per Hertz and accentuated issues on contention and interference
with neighboring nodes. So, if WLANs were per se complex deployments, they are becoming
even more complicated due to the increasing node density and the new technical features
required by novel highly bandwidth-demanding applications. This dissertation provides an
in-depth study of channel allocation and channel bonding in WLANs and discusses the
suitability of solutions ranging from heuristic-based to reinforcement learning (RL)-based.
To characterize channel bonding in saturated WLANs, we first propose an analytical model
based on continuous-time Markov networks (CTMNs). This model relies on a novel,
purpose-designed algorithm that generates CTMNs from spatially distributed scenarios, where
nodes are not required to be within the carrier sense range of each other. We identify the key
factors affecting the throughput and fairness of different channel bonding policies and expose
critical interrelations among nodes in the spatial domain. By extending the analytical model to
support unsaturated regimes, we highlight the benefits of allocating channels as wide as
possible all together with adaptive policies to cope with unfair situations.
Apart from the analytical model, this thesis relies on simulations to generalize channel bonding
in dense scenarios while avoiding costly, sometimes unfeasible, experimental testbeds.
Unfortunately, existing wireless network simulators tend to be too simplistic or too computational
demanding. That is why we develop the Komondor wireless network simulator, with the
essential advantage over other well-known simulators lying in its high event processing rate.
We then deviate from analytical models and simulations and tackle real measurements through
the Wi-Fi All-Channel Analyzer (WACA), the first system specifically designed to simultaneously
measure the energy in all the 24 bondable Wi-Fi channels at the 5 GHz band. With WACA, we
perform a first-of-its-kind spectrum measurement in areas including urban hotspots, residential
neighborhoods, universities, and even a football match in Futbol Club Barcelona’s Camp Nou
stadium. Our experimental findings reveal the underpinning factors controlling throughput gain,
from which we highlight the inter-channel correlation. %We show the significance of the
gathered dataset for finding new insights, which would not be possible otherwise, given that
simple channel occupancy models severely underestimate the potential gains.
As for solution proposals, we first cover heuristic-based approaches to find satisfactory
configurations quickly. In this regard, we propose dynamic-wise (DyWi), a lightweight,
decentralized, online primary channel selection algorithm for dynamic channel bonding. DyWi
improves the expected WLAN throughput by considering not only the occupancy of the target
primary channel but also the activity in the secondary channels. Even when assuming
significant delays due to primary channel switching, simulations reveal important throughput and
delay improvements.
Finally, we identify machine learning (ML) approaches applicable to the spectrum management
problem in WLANs and justify why model-free RL suits it the most. In particular, we put the
focus on the adequate performance of stateless variations of RL and anticipate multi-armed
bandits as the right solution since i) we need fast adaptability to suit user experience in dynamic
Wi-Fi scenarios and ii) the number of multichannel configurations a network can adopt is limited;
thus, agents can fully explore the action space in a reasonable time.En 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.