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Guo, Zhijuan. "Implementation Of Wireless Channel Propagation Models In OPNET." Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-19750.
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In recent times, there has been a significant amount of research regarding the physical layer of wireless communications . The part of the physical layer, which cannot be ignored, is channel propagation. Different environments have different channels. Path loss, slow fading, fast fading and multipath fading are all involved in decisions regarding the condition of the channel . Based on related research, a number of empirical channel models are put forward to simulate a real environment with regards to communication and there are some simulation softwares that are able to implement those different channels. These include Matlab which is regarded as the best simulation software for the physical layer in wireless communication. OPNET is another network modeling simulation software, which could implement the entire process of the network communication, which Matlab is not able to complete . The network layer of OPNET is very mature and has the ability to implement different routing protocols. However, the description of the physical layer in OPNET is poor and there is only simple path loss model in pipeline modeling in OPNET. Thus, the objective of this thesis is to implement different channel models in OPNET and to make it capable to simulate in as close a manner as possible to a real environment.
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Yu, Kai. "Modeling of Multiple-Input Multiple-Output Radio Propagation Channels." Licentiate thesis, KTH, Signals, Sensors and Systems, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1478.
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In recent years, multiple-input multiple-output (MIMO)systems appear to be very promising since they can provide highdata rates in environments with sucient scattering byexploiting the spatial domain. To design a real MIMO wirelesssystem and predict its performance under certain circumstances,it is necessary to have accurate MIMO wireless channel modelsfor dierent scenarios. This thesis presents dierent models forindoor MIMO radio propagation channels based on 5.2 GHz indoorMIMO channel measurements.The recent research on MIMO radio channel modeling isbriey reviewed in this thesis. The models are categorized intonon-physical and physical models. The non-physical modelsprimarily rely on the statistical characteristics of MIMOchannels obtained from the measured data while the physicalmodels describe the MIMO channel (or its distribution) via somephysical parameters. The relationships between dierent modelsare also discussed.For the narrowband case, a non line-of-sight (NLOS)indoor MIMO channel model is presented. The model is based on aKronecker structure of the channel covariance matrix and thefact that the channel is complex Gaussian. It is extended tothe line-of-sight (LOS) scenario by estimating and modeling thedominant component separately.As for the wideband case, two NLOS MIMO channel modelsare proposed. The rst model uses the power delay prole and theKronecker structure of the second order moments of each channeltap to model the wideband MIMO channel while the second modelcombines a simple single-input single-output (SISO) model withthe same Kronecker structure of the second order moments.Monte-Carlo simulations are used to generate indoor MIMOchannel realizations according to the above models. The resultsare compared with the measured data and good agreement has beenobserved.
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Alonso, Javier. "M.I.M.O Channel Model for High Capacity Wireless Networks and Simulator for Performance Analysis." Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7784.
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The wireless communications have suffered, in these last years, one of the greater technological growth within the communications via radio. The application of multiple antennas, as much in transmission as in reception has taken to an impulse of the study of different models from propagation channels.
Taking this into consideration, the different types from mentioned models are going to be studied.
The work that the ISY department at the Institute of Technology of the Linköping University has proposed is to develop to a propagation channel model, with several antennas in reception and transmission, that one first approach allows a capacity of the channel study, in absence of measures of possible scenarios, as well as the development of a small simulator that allows to analyze its benefits.
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Hunter, Brandon. "Channel Probing for an Indoor Wireless Communications Channel." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/64.
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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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Xu, Hao. "Terrestrial radio wave propagation at millimeter-wave frequencies." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27522.
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This research focuses on radio wave propagation at millimeter-wave frequencies. A measurement based channel characterization approach is taken in the investigation.
First, measurement techniques are analyzed. Three types of measurement systems are designed, and implemented in measurement campaigns: a narrowband measurement system, a wideband measurement system based on Vector Network Analyzer, and sliding correlator systems at 5.8+AH4AXA-mbox{GHz}, 38+AH4AXA-mbox{GHz} and 60+AH4AXA-mbox{GHz}. The performances of these measurement systems are carefully compared both analytically and experimentally.
Next, radio wave propagation research is performed at 38+AH4AXA-mbox{GHz} for Local Multipoint Distribution Services (LMDS). Wideband measurements are taken on three cross-campus links at Virginia Tech. The goal is to determine weather effects on the wideband channel properties. The measurement results include multipath dispersion, short-term variation and signal attenuation under different weather conditions. A design technique is developed to estimate multipath characteristics based on antenna patterns and site-specific information.
Finally, indoor propagation channels at 60+AH4AXA-mbox{GHz} are studied for Next Generation Internet (NGI) applications. The research mainly focuses on the characterization of space-time channel structure. Multipath components are resolved both in time of arrival (TOA) and angle of arrival (AOA). Results show an excellent correlation between the propagation environments and the channel multipath structure.
The measurement results and models provide not only guidelines for wireless system design and installation, but also great insights in millimeter-wave propagation.Ph. D.
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Manan, Waqas. "Propagation channel models for 5G mobile networks. Simulation and measurements of 5G propagation channel models for indoor and outdoor environments covering both LOS and NLOS Scenarios." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17219.
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At present, the current 4G systems provide a universal platform for broadband mobile services; however, mobile traffic is still growing at an unprecedented rate and the need for more sophisticated broadband services is pushing the limits on current standards to provide even tighter integration between wireless technologies and higher speeds. This has led to the need for a new generation of mobile communications: the so-called 5G. Although 5G systems are not expected to penetrate the market until 2020, the evolution towards 5G is widely accepted to be the logical convergence of internet services with existing mobile networking standards leading to the commonly used term “mobile internet” over heterogeneous networks, with several Gbits/s data rate and very high connectivity speeds. Therefore, to support highly increasing traffic capacity and high data rates, the next generation mobile network (5G) should extend the range of frequency spectrum for mobile communication that is yet to be identified by the ITU-R. The mm-wave spectrum is the key enabling feature of the next-generation cellular system, for which the propagation channel models need to be predicted to enhance the design guidance and the practicality of the whole design transceiver system.
The present work addresses the main concepts of the propagation channel behaviour using ray tracing software package for simulation and then results were tested and compared against practical analysis in a real-time environment. The characteristics of Indoor-Indoor (LOS and NLOS), and indoor-outdoor (NLOS) propagations channels are intensively investigated at four different frequencies; 5.8 GHz, 26GHz, 28GHz and 60GHz for vertical polarized directional, omnidirectional and isotropic antennas patterns. The computed data achieved from the 3-D Shooting and Bouncing Ray (SBR) Wireless Insite based on the effect of frequency dependent electrical properties of building materials. Ray tracing technique has been utilized to predict multipath propagation characteristics in mm-wave bands at different propagation environments. Finally, the received signal power and delay spread were computed for outdoor-outdoor complex propagation channel model at 26 GHz, 28 GHz and 60GHz frequencies and results were compared to the theoretical models.
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Pirkl, Ryan J. "Measurement-based investigations of radio wave propagation: an exposé on building corner diffraction." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33961.
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Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channel's underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channel's impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-mpirical diffraction coefficient. Specific contributions of this thesis are:
* The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture.
* A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements.
* A wireless channel ``filming' technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region.
* High-resolution measurements of the space-time wireless channel near a right-angled brick building corner.
* The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel.
* An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge.
* The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data.
This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.
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Ho, Chung-Man Peter. "Antenna effects on indoor wireless channels and a deterministic wide-band propagation model for in-building personal communication systems." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-01102009-063157/.
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Hariri, Essamlali Kaoutar El. "Modélisation hybride du canal de propagation dans un contexte industriel." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2336/document.
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Ce travail de thèse concerne la modélisation du canal de propagation dans les milieux industriels. Dans ce contexte, le canal de propagation a un comportement différent de celui classiquement rencontré en indoor. Cela est dû à l'aménagement des bâtiments qui sont plus grand et ouverts ainsi qu'à la présence de machines, d'objets mobiles et d'autres matériaux métalliques rencontrés dans ces environnements. Ainsi, les modèles de canaux indoor existants ne sont plus valides. L'utilisation de modèles déterministes comme alternative est possible mais limitée en raison du temps de calcul qui en découle.Pour répondre à cette problématique, nous proposons un modèle hybride de canal s'inspirant d'une méthode à tracer de rayons 3D et du modèle WINNER. L'originalité de ce modèle repose sur son caractère hybride consistant, en prétraitement, à partitionner l'environnement en zones de visibilité ou de non-visibilité «faible» et «forte» sur des critères déterministes liés à la propagation des ondes. Un modèle statistique, type WINNER, reprenant le concept de cluster est ensuite "joué" au sein de chacune des ces zones reproduisant ainsi fidèlement l'évolution des paramètres caractéristiques des clusters identifiés. Nous avons validé notre modèle en le comparant d'abord à un modèle déterministe et ensuite à la mesure. Sa robustesse ainsi que celle de WINNER sont testées en les simulant dans trois environnements différents et en les comparant au modèle déterministe à tracer de rayonsThis thesis focuses on the modeling of the propagation channel in industrial environments. In this context, the propagation channel has a different behavior than typically encountered in indoor. This is due to the construction of buildings that are larger and open and the presence of machines, moving objects and metal materials encountered in these environments. Thus, the existing indoor channel models are not valid. Using deterministic models as an alternative is possible, but limited by the computing time.To address this problem, we propose a hybrid channel model for communications in industrial environments inspired by a ray tracing method and Winner model. The originality of this model is its hybrid nature consisting, in preprocessing, in partitionning the environment in areas of visibility or non-visibility «weak» and «strong» based on deterministic criteria related to the wave propagation. A statistical model, as WINNER , using the concept of cluster is then played in each of these areas and faithfully reproducing the evolution of the characteristic parameters of the identified clusters. We have validated our model by comparing it firstly to a deterministic model and then to measurement. Its robustness as well that of WINNER are tested by simulating them in three different environments and by comparing them with the deterministic model
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Kacou, Marc Emmanuel Vivien-Marie Wozan. "Design of Models for the Planning of Indoor Multi-technology Wireless Networks." Thesis, Rennes, INSA, 2019. http://www.theses.fr/2019ISAR0010.
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L’évolution constante des technologies sans fil telles que le Wi-Fi, les normes de réseaux mobiles ou d’objets connectés, a donné naissance à de nouvelles applications et usages. Les possibilités offertes par cette multitude d’alternatives sont exploitées par les réseaux sans fil hétérogènes qui, en combinant au sein d’un réseau unique plusieurs technologies, permettent aux utilisateurs d’accéder à des services complémentaires de façon transparente. Cependant, pour bénéficier pleinement de ces avantages, plusieurs défis techniques sont à relever. L’un d’eux est relatif au déploiement de ces réseaux multi- technologies. En pratique, cette tâche s’appuie sur des règles et outils d’ingénierie afin de réaliser une planification optimale. Dans ce contexte, un objectif de la thèse a été d’établir des modèles sur lesquels peuvent se baser les outils d’ingénierie radio afin d’optimiser le déploiement de réseau locaux sans fil multi- technologies.Il s’agit principalement de calibrer des modèles de propagation pour l’estimation de couverture radio en environnement indoor résidentiel entre 800 MHz et 60 GHz; d’établir un modèle de débit pour l’estimation de capacité Wi-Fi en fonction du trafic montant et descendant; et de concevoir un modèle de résolution multi-objectif pour optimiser le positionnement de points d’accès opérant à 5 et 60 GHz. En complément, cette thèse a également proposé des recommandations pratiques visant à placer au mieux les points d’accès en phase de déploiement. Cela s’est fait par le biais d’études de sensibilité de couverture à divers facteurs, tels que l’environnement immédiat de l’émetteur ou encore la présence de personnes faisant obstructionThe constant evolution of wireless technologies such as Wi-Fi, mobile networks standards or IoT, has given rise to new applications and usages. The possibilities offered by this multitude of alternatives are exploited by heterogeneous wireless networks which, by combining within a single network several technologies, provide the users with a seamless access to complementary services. However, to take full advantage of these benefits, there are several technical issues to address. One of them is related to the deployment of these multi-technology networks. In practice, this task relies, most of the time, on radio network design software to achieve optimal planning. In such context, the main objective of this thesis is to establish models which can be used by radio network planning tools in order to the deployment of multi-technology wireless local area networks. This task has involved calibrating propagation models for radio coverage estimation, in residential indoor environments from 800 MHz to 60 GHz; developing a throughput model for Wi-Fi capacity estimation based on uplink and downlink traffic; and establishing a multi- objective resolution model to optimize the positioning of access points operating at 5 and 60 GHz. Moreover, this thesis also proposes practical recommendations for a better positioning of access points during deployment phases. This task has been achieved through coverage sensitivity studies to various factors, such as the transmitter surroundings or the presence of obstructing people
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Ahlehagh, Hasti. "Techniques for communication and geolocation using wireless ad hoc networks." Link to electronic thesis, 2004. http://www.wpi.edu/Pubs/ETD/Available/etd-0526104-111538/.
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Hunter, Brandon Rosel. "Channel probing for an indoor wireless communications channel /." Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd196.pdf.
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Alzaghal, Mohamad H. "Wireless sensor network channel propagation measurements and comparison with simulation." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion-image.exe/06Jun%5FAlzaghal.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2006.Thesis Advisor(s): Su, Weilian. "June 2006." Description based on title screen as viewed on March 12, 2008. Includes bibliographical references (p. 63-65). Also available in print.
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Kavak, Adnan. "Vector propagation channel studies for smart antenna wireless communication systems /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004302.
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Durgin, Gregory David. "Theory of Stochastic Local Area Channel Modeling for Wireless Communications." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29843.
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This dissertation outlines work accomplished in the pursuit of this degree. This report is also designed to be a general introduction to the concepts and techniques of small-scale radio channel modeling. At the present time, there does not exist a comprehensive introduction and overview of basic concepts in this field. Furthermore, as the wireless industry continues to mature and develop technology, the need is now greater than ever for more sophisticated channel modeling research.
Each chapter of this preliminary report is, in itself, a stand-alone topic in channel modeling theory. Culled from original reports and journal papers, each chapter makes a unique contribution to the field of channel modeling. Original contributions in this report include:
1. joint characterization of time-varying, space-varying, and frequency-varying channels under the rubric of duality
2. rules and definitions for constructing channel models that solve Maxwell's equations
3. overview of probability density functions that describe random small-scale fading
4. techniques for modeling a small-scale radio channel using an angle spectrum
5. overview of techniques for describing fading statistics in wireless channels
6. results from a wideband spatio-temporal measurement campaign
Together, the chapters provide a cohesive overview of basic principles. The discussion of the wideband spatio-temporal measurement campaign at 1920 MHz makes an excellent case study in applied channel modeling and ties together much of the theory developed in this dissertation.Ph. D.
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Zhang, Qian. "Wireless Near-ground Channel Characteristics in Several Unlicensed Bands." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1219170596.
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Ibraheem, Ali Ahmed Younis. "Implanted Antennas and Intra-Body Propagation Channel for Wireless Body Area Network." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50936.
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Implanted Devices are important components of the Wireless Body Area Network (WBAN) as a promising technology in biotelemetry, e-health care and hyperthermia applications. The design of WBAN faces many challenges, such as frequency band selection, channel modeling, antenna design, physical layer (PHY) protocol design, medium access control (MAC) protocol design and power source. This research focuses on the design of implanted antennas, channel modeling between implanted devices and Wireless Power Transfer (WPT) for implanted devices. An implanted antenna needs to be small while it maintains Specific Absorption Rate (SAR) and is able to cope with the detuning effect due to the electrical properties of human body tissues. Most of the proposed antennas for implanted applications are electric field antennas, which have a high near-zone electric field and, therefore, a high SAR and are sensitive to the detuning effect. This work is devoted to designing a miniaturized magnetic field antenna to overcome the above limitations. The proposed Electrically Coupled Loop Antenna (ECLA) has a low electric field in the near-zone and, therefore, has a small SAR and is less sensitive to the detuning effect. The performance of ECLA, channel model between implanted devices using Path Loss (PL) and WPT for implanted devices are studied inside different human body models using simulation software and validated using experimental work. The study is done at different frequency bands: Medical Implanted Communication Services (MICS) band, Industrial Scientific and Medical (ISM) band and 3.5 GHz band using ECLA. It was found that the proposed ECLA has a better performance compared to the previous designs of implanted antennas. Based on our study, the MICS band has the best propagation channel inside the human body model among the allowed frequency bands. The maximum PL inside the human body between an implanted antenna and a base station on the surface is about 90 dB. WPT for implanted devices has been investigated as well, and it has been shown that for a device located at 2 cm inside the human body with an antenna radius of 1 cm an efficiency of 63% can be achieved using the proposed ECLA.Ph. D.
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Chong, Chia-Chin. "Dynamic directional channel model for indoor wireless communications." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/13378.
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The frequency-domain space alternating generalised expectation-maximisation (FD-SAGE) algorithm is proposed and used in conjunction with the serial interference cancellation (SIC) technique for joint detection and estimation of multipath channel parameters. The SIC technique demonstrates more stable performance than the parallel interference cancellation (PIC) technique used in the time-domain SAGE algorithm especially in a multipath rich environment. The performance of the FD-SAGE algorithm is demonstrated by using real indoor channel measurement data and its functionality is verified through comparison with unitary estimation of signal parameter via rotational invariance technique (ESPRIT) algorithm. The first channel model is derived from data collected during a static measurement campaign. This model incorporates both the clustering of MPCs and the correlation between the spatial and temporal domains. The clustering effect relies on two classes of parameters (intercluster and intracluster parameters) and two classes of power density spectra (PDS) (intercluster and intracluster PDS) which characterise the cluster and MPC, respectively. All parameters are described by empirical probability density (pdfs) derived from the measured data and the correlation properties are incorporated in two joint pdfs for cluster and MPC positions. Data analysis shows that the intercluster and intracluster PDS exhibit exponential and Laplacian functions in the delay and angular domains, respectively. The second channel model is derived based on data collected during a dynamic measurement campaign. This model incorporates both the spatial-temporal properties as well as the dynamic evolution of paths due to motion of the MT. An M-step, 4-state Markov channel model (MCM) is proposed in order to account for the correlation between the number of births and deaths and multiple births and deaths that can occur at any time instant. The power and spatio-temporal variation of paths within their lifespan are modelled by a low-pass-filter and a Gaussian distributed spatio-temporal vector, respectively. Due to the distinction in the birth-death statistics and the spatio-temporal dispersion and correlation properties for line-of-sight (LOS) and non-LOS (NLOS) scenarios, the model can be generalised, and parameterised by two sets of Markov parameters for these two scenarios.
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Al-Wajeeh, Taha. "Efficient radio channel modeling for urban wireless sensors networks." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2314.
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Le canal de propagation est un élément important pour la fiabilité des simulations et la conception des systèmes sans fil. Les modèles déterministes offrent un bon niveau de précision au prix d'une complexité croissante de calcul, ce qui les rend prohibitifs pour les simulateurs de réseaux de capteurs sans fil (RdC) car ils impliquent de nombreux nœuds distribués à l'échelle d’une ville. Dans ce contexte, l'objectif de cette thèse est de proposer des méthodes déterministes rapides et précises pour modéliser le comportement des ondes électromagnétiques en garantissant le juste compromis entre la précision et le temps de calcul. L’étude a d’abord été subdivisée en deux modes selon le mécanisme dominant de propagation. Dans une configuration microcellule, l'approche proposée est basée sur un modèle de lancer de rayons reposant sur la technique de la visibilité qui adopte un ensemble de techniques d'accélération pour réduire la complexité sans perte significative de la précision. Dans le même objectif, la propagation verticale a été abordée en incluant les contributions les plus significatives. Enfin, ces modèles ont été intégrés dans un simulateur de RdC pour fournir des résultats réalistes dans le contexte d'une ‘smart city’. L'impact des modèles précis dans les simulateurs est illustré par certains paramètres du réseauModeling the radio channel in an accurate way is a key element of any wireless systems. Deterministic models offer a good degree of precision at the cost of high computational complexity, which is prohibitive for wireless sensor network (WSN) simulators because they involve many sensor nodes in a city-wide scale. Within this context, the objective of this thesis is to propose efficient, fast, and accurate deterministic methods for modeling electromagnetic waves by finding the best time-accuracy trade-offs that guarantee accuracy under tight time constraints. The study was first subdivided into two modes according to the dominant propagation mechanism. In microcell configurations, the proposed approach is a ray-tracing model based on the visibility technique. It adopts a set of acceleration techniques to reduce the complexity with a minimal loss of precision. With the same objective, the vertical propagation was addressed to include the most significant contributions. Finally, these models were integrated into a WSN simulator to provide realistic and accurate results for smart city applications. The importance of using accurate models in WSN simulators is illustrated in terms of some network parameters
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Fang, Cheng. "The characterisation and modelling of the wireless propagation channel in small cells scenarios." Thesis, University of Bedfordshire, 2015. http://hdl.handle.net/10547/595693.
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The rapid growth in wireless data traffic in recent years has placed a great strain on the wireless spectrum and the capacity of current wireless networks. In addition, the makeup of the typical wireless propagation environment is rapidly changing as a greater percentage of data traffic moves indoors, where the coverage of radio signals is poor. This dual fronted assault on coverage and capacity has meant that the tradition cellular model is no longer sustainable, as the gains from constructing new macrocells falls short of the increasing cost. The key emerging concept that can solve the aforementioned challenges is smaller base stations such as micro-, pico- and femto-cells collectively known as small cells. However with this solution come new challenges: while small cells are efficient at improving the indoor coverage and capacity; they compound the lack of spectrum even more and cause high levels of interference. Current channel models are not suited to characterise this interference as the small cells propagation environment is vast different. The result is that overall efficiency of the networks suffers. This thesis presents an investigation into the characteristics of the wireless propagation channel in small cell environments, including measurement, analysis, modelling, validation and extraction of channel data. Two comprehensive data collection campaigns were carried out, one of them employed a RUSK channel sounder and featured dual-polarised MIMO antennas. From the first dataset an empirical path loss model, adapted to typical indoor and outdoor scenarios found in small cell environments, was constructed using regression analysis and was validated using the second dataset. The model shows good accuracy for small cell environments and can be implemented in system level simulations quickly without much requirements.
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Andreu, Estellés Carlos. "UWB radio channel and diversity characterization for wireless implanted devices." Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/111836.
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Las redes de área corporal permiten la interconexión de nodos independientes situados dentro o fuera de la superficie corporal o, incluso, alejados de dicha superficie. En cuanto a las comunicaciones intracorporales, el establecimiento de un enlace robusto con una cápsula endoscópica o con un marcapasos, son ejemplos de los avances tecnológicos conseguidos en las últimas décadas. A pesar
de estos desarrollos en asistencia sanitaria, los estándares actuales para este tipo de comunicaciones no permiten conexiones inalámbricas de alta velocidad de transmisión, las cuales son comunes en los servicios actuales de telecomunicaciones. Los sistemas UWB han surgido como potencial candidato para las futuras redes de comunicaciones inalámbricas intracorporales. No obstante, el principal obstáculo de la tecnología UWB para aplicaciones intracorporales es la alta atenuación que sufren las señales transmitidas al atravesar los distintos tejidos corporales, que aumenta drásticamente con el aumento de la frecuencia. Por tanto, es importante una caracterización precisa del canal UWB intracorporal a la hora de validar dicha banda como la adecuada para este propósito.Esta tesis se centra en el análisis de la tecnología UWB para posibilitar comunicaciones intracorporales inalámbricas desde un punto de vista experimental. Para conseguir este objetivo, se ha empleado un novedoso sistema
de medidas experimental basado en fantomas en diversos escenarios de propagación intracorporal. De esta forma, se pueden comprobar las pérdidas de propagación en el medio así como la diversidad del canal de una forma fiable. Con el fin de validar los valores obtenidos en el laboratorio, se han comparado y analizado con los obtenidos en un experimento in vivo. Por otro lado, se han diseñado y fabricado nuevas antenas UWB candidatas para comunicaciones intracorporales, empleando técnicas existentes y nuevas de miniaturización y optimización. Finalmente, se han usado técnicas basadas en diversidad para mejorar el rendimiento del canal de propagación en dos escenarios intracorporales diferentes.Wireless Body Area Networks allow the interconnection between independent nodes located either inside or over the body skin or further. Regarding in-body communications, establishing a proper link with a capsule endoscope or with a pacemaker are examples of technological advances achieved in the last decades. In spite of these healthcare developments, current standards for these kind of communications do not allow high data rate wireless connections, which are common in the current telecommunication services. UWB systems have emerged as a potential solution for future wireless in-body communications. Nevertheless, the main drawback of UWB for in-body applications is the high attenuation of human body tissues which increases dramatically with the increment of frequency. Hence, an accurate UWB in-body channel characterization is relevant in order validate UWB frequency band as the best candidate for future networks of implantable nodes. This thesis is devoted to test UWB technology for in-body communications from an experimental point of view. To achieve this goal, a novel spatial phantom-based measurement setup is used in several in-body propagation scenarios. Thus, the losses in the propagation medium and the channel diversity are checked in a reliable way. In order to check the values obtained in laboratory, they are compared and discussed with those obtained in an in vivo experiment. On the other hand, new UWB antenna candidates for inbody communications are designed and manufactured by using typical and new miniaturization and antenna optimization techniques for this purpose. Finally, diversity-based techniques are used to improve the performance of the propagation channel in two different in-body scenarios.
Les xarxes d'àrea corporal permeten la interconnexió de nodes independents situats, o bé dins, o bé sobre la pell, o inclús allunyats del propi cos. Pel que fa a les comunicacions intracorporals, l'establiment d'un bon enllaç amb una càpsula endoscòpica o amb un marcapassos, són exemples dels avanços tecnològics aconseguits les darreres dècades. A pesar d'aquests desenvolupaments en assistència sanitària, els estàndards actuals per a aquests tipus de comunicacions no permeten connexions sense fil d'alta velocitat de transmissió, que són habituals als serveis actuals de telecomunicacions. Els sistemes UWB han sorgit com una solució potencial per a les futures comunicacions sense fill intracorporals. No obstant, el principal obstacle de la tecnologia UWB per a les aplicacions intracorporals és l'alta atenuació dels teixits del cos humà, que augmenta dràsticament amb l'increment de freqüència. Per tant, és important una caracterització acurada del canal UWB intracorporal a l'hora de validar la banda de freqüència UWB com a la millor candidata per a les futures xarxes de nodes implantats.Aquesta tesi se centra en l'anàlisi de la tecnologia UWB per a comunicacions intracorporals des d'un punt de vista experimental. Per a aconseguir aquest objectiu s'ha emprat un sistema novedós de mesures experimentals, basat en fantomes, en diversos escenaris de propagació intracorporal. D'aquesta manera es poden comprovar les pèrdues de propagació en el medi i la diversitat del canal d'una forma fiable. Per tal d'avaluar els valors obtinguts al laboratori, s'han comparat i analitzat amb aquells obtinguts en un experiment in vivo. Per altra banda, s'han dissenyat i fabricat noves antenes UWB candidates per a comunicacions intracorporals emprant tècniques típiques i noves de miniaturització i optimització d'antenes per a aquest propòsit. Finalment s'han usat tècniques basades en diversitat per a millorar el rendiment del canal de propagació en dos escenaris intracorporals diferents.
Andreu Estellés, C. (2018). UWB radio channel and diversity characterization for wireless implanted devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/111836
TESIS
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Ha, Sean Anthony. "3.5 GHz Indoor Propagation Modeling and Channel Characterization." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53949.
Full textAbstract:
In the push for spectrum sharing and open spectrum access, the 3.5 GHz frequency band is under consideration for small cells and general Wireless Local Area Networks (WLAN) in the United States. The same band is beginning to see deployment in China, Japan, and South Korea, for the 4G Long Term Evolution (LTE) cellular standard to increase coverage and capacity in urban areas through small cell deployment. However, since the adoption of this band is new, there is a distinct shortage of propagation data and accurate channel modeling at 3.5 GHz in indoor environments. These models are necessary for cellular coverage planning and evaluating the performance and feasibility of wireless systems.
This report presents the results of a fixed wireless channel measurement campaign at 3.5 GHz. Measurements were taken in environments typical of indoor wireless deployment: traditional urban indoor office, hallway, classroom, computer laboratory, and atrium areas, as well as within a hospital. Primarily Non Line of Sight (NLOS) experiments were carried out in areas with a controllable amount of partitions separating the transmitter and receiver in order to document material-based attenuation values. Indoor-to-outdoor measurements were carried out, focusing on attenuation due to common exterior building materials such as concrete, brick, wood, and reinforced glass.
Documented metrics include large scale path loss, log-normal shadowing, and channel power delay profiles combined with delay spread characteristics for multipath analysis. The statistical multi-antenna diversity gain was evaluated to gauge the benefit of using multi-antenna systems in an indoor environment, which has much greater spatial diversity than an outdoor environment. Measurements were compared to indoor path loss models used for WLAN planning in the low GHz range to investigate the applicability of extending these models to 3.5 GHz.Master of Science
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Vig, Jyotika. "ISM Band Indoor Wireless Channel Amplitude Characteristics: Path Loss and Gain vs. Distance and Frequency." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1091111060.
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Ketprom, Urachada. "Line-of-sight propagation of optical wave through multiple-scatter channel in optical wireless communication system /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6057.
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Shigueta, Roni. "Channel Allocation in Mobile Wireless Networks." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX037/document.
Full textAbstract:
L'utilisation intensive des services de données mobiles a de plus en plus augmenté la consommation de ressources sur les réseaux sans fil. La ressource principale utilisée pour la communication sans fil est le spectre de fréquence. À mesure que le trafic de données augmente brusquement, de nouvelles bandes du spectre de fréquences ne sont pas disponibles dans la même proportion, ce qui rend le spectre de fréquence de plus en plus rare et saturé. Plusieurs propositions ont été présentées pour optimiser l'allocation des canaux de fréquences afin d'atténuer les interférences entre les liaisons proches qui transmettent des données. Beaucoup d'entre eux utilisent un critère unique et ne considèrent pas le comportement de l'utilisateur pour guider le processus d'allocation de canaux. Les utilisateurs ont des cycles de routine et un comportement social. Ils passent au travail, à l'école, utilisent leurs appareils mobiles générant du trafic de données, et rencontrent des amis formant des groupes. Ces caractéristiques peuvent être explorées pour optimiser le processus d'allocation des canaux.Cette thèse présente une stratégie d'allocation de canaux pour les réseaux sans fil basée sur le comportement de l'utilisateur. Notre contribution principale consiste à considérer certaines caractéristiques du comportement de l'utilisateur, telles que la mobilité, le trafic et la popularité dans le processus d'allocation des canaux. De cette façon, nous priorisons l'allocation de canaux pour les nœuds qui resteront dans le réseau dans une fenêtre de temps future, avec un trafic plus élevé dans le réseau, et avec plus de popularité. Nous adoptons une approche distribuée qui permet de limiter le nombre de messages échangés dans le réseau tout en répondant rapidement aux changements de la topologie du réseau. Dans notre évaluation des performances, nous considérons des scénarios dans des réseaux ad hoc et véhiculaires, et nous utilisons des modèles de mobilité synthétique, tels que SLAW et Manhattan grid, et l'ensemble de données de traces de ville de Cologne. Dans les scénarios, nous comparons notre mécanisme avec différents types de techniques : une centralisée (nommée TABU), une autre aléatoire (nommée RANDOM), une avec la plus grande distance spectrale (appelée LD) et une avec un seul canal (appelée SC). Nous évaluons les métriques telles que le débit agrégé, le débit de livraison des paquets et le délai de bout en bout.Les simulations envisageant un scénario ad hoc avec un routage monodiffusion montrent que notre stratégie présente des améliorations en termes de débit de l'ordre de 14,81% par rapport à RANDOM et de 16,28% par rapport à l'allocation de canal LD. Dans le scénario véhiculaire, notre stratégie montre des gains de taux de livraison de paquets de l'ordre de 11,65% et de 17,18% par rapport aux méthodes RANDOM et SC, respectivement. Dans ces deux scénarios, la performance de notre stratégie est proche de la limite supérieure donnée par l'approche centralisée de TABU, mais avec l’envoie de moins des messagesThe intensive use of mobile data services has increasingly increased resource consumption over wireless networks. The main resource used for wireless communication is the frequency spectrum. As data traffic rises sharply, new bands of the frequency spectrum are not available in the same proportion, making the frequency spectrum increasingly scarce and saturated. Several proposals have been presented to optimize frequency channel allocation in order to mitigate interference between nearby links that are transmitting data. Many of them use a single criterion and does not consider the user behavior to guide the channel allocation process. Users have routine cycles and social behavior. They routinary move to work, to school, use their mobile devices generating data traffic, and they meet with friends forming clusters. These characteristics can be explored to optimize the channel allocation process.This thesis presents a channel allocation strategy for wireless networks based on user behavior. Our main contribution is to consider some characteristics of the user behavior, such as mobility, traffic, and popularity in the channel allocation process. In this way, we prioritize the channel allocation for the nodes that will remain in the network in a future time window, with higher traffic in the network, and with more popularity. We adopt a distributed approach that allows limiting the number of messages exchanged in the network while quickly responding to changes in the network topology. In our performance evaluation, we consider scenarios in ad hoc and vehicular networks, and we use some synthetic mobility models, such as SLAW and Manhattan grid, and the traces dataset of Cologne city. In the scenarios, we compare our mechanism with different types of approaches: i.e., a centralized (named TABU), a random (named RANDOM), a with largest spectral distance (named LD), and a with single channel (named SC). We evaluate metrics such as aggregated throughput, packet delivery rate, and end-to-end delay. Simulations considering ad hoc scenario with unicast routing show that our strategy presents improvements in terms of throughput at the order of 14.81% than RANDOM and 16.28% than LD channel allocation. In vehicular scenario, our strategy shows gains of packet delivery rate at the order of 11.65% and 17.18% when compared to RANDOM and SC methods, respectively. In both scenarios, the performance of our strategy is close to the upper bound search of the TABU centralized approach, but with lower overhead
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Hibbard, Daniel James. "The Impact of Signal Bandwidth on Indoor Wireless Systems in Dense Multipath Environments." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/9945.
Full textAbstract:
Recently there has been a significant amount of interest in the area of wideband and ultra-wideband (UWB) signaling for use in indoor wireless systems. This interest is in part motivated by the notion that the use of large bandwidth signals makes systems less sensitive to the degrading effects of multipath propagation. By reducing the sensitivity to multipath, more robust and higher capacity systems can be realized. However, as signal bandwidth is increased, the complexity of a Rake receiver (or other receiver structure) required to capture the available power also increases. In addition, accurate channel estimation is required to realize this performance, which becomes increasingly difficult as energy is dispersed among more multipath components.
In this thesis we quantify the channel response for six signal bandwidths ranging from continuous wave (CW) to 1 GHz transmission bandwidths. We present large scale and small scale fading statistics for both LOS and NLOS indoor channels based on an indoor measurement campaign conducted in Durham Hall at Virginia Tech. Using newly developed antenna positioning equipment we also quantify the spatial correlation of these signals. It is shown that the incremental performance gains due to reduced fading of large bandwidths level off as signals approach UWB bandwidths. Furthermore, we analyze the performance of Rake receivers for the different signal bandwidths and compare their performance for binary phase modulation (BPSK). It is shown that the receiver structure and performance is critical in realizing the reduced fading benefit of large signal bandwidths. We show practical channel estimation degrades performance more for larger bandwidths. We also demonstrate for a fixed finger Rake receiver there is an optimal signal bandwidth beyond which increased signal bandwidth produces degrading results.Master of Science
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Habib, Bachir. "MIMO Channel Hardware Simulator for LTE and 802.11ac Wireless Communication Systems." Thesis, Rennes, INSA, 2013. http://www.theses.fr/2013ISAR0023.
Full textAbstract:
Pour évaluer les performances des systèmes de communications sans fil, un simulateur matériel de canal MIMO (Multiple-Input Multiple-Output) est réalisé pour les nouveaux systèmes de communication. Il fournit la vitesse de traitement nécessaire et permet d’évaluer les performances en temps réel. Il permet de comparer les différents systèmes dans les mêmes conditions souhaitées. Les objectifs de ce travail concernent principalement les modèles de canal MIMO et l'architecture de bloc numérique du simulateur matériel.Le simulateur matériel conçu peut être configuré avec les nouveaux réseaux radio-mobiles (LTE) et les réseaux locaux sans fil (WLAN 802.11ac). Il utilise des modèles de canaux standardisés, comme le TGn IEEE 802.11n et le 3GPP-LTE, ou des résultats de mesures effectuées avec un sondeur de canalMIMO conçu et réalisé dans notre laboratoire. Récemment, le sondeur de canal a été utilisé au cours de campagnes de mesure pour des environnements à bord d’un navire et de l’extérieur-vers-l’intérieur (outdoor-to-indoor). Un algorithme est proposé pour que les réponses impulsionnelles mesurées soient compatibles avec la bande des signaux LTE. En outre, le modèle de Kronecker avec des évanouissements de Rayleigh est utilisé pour obtenir un canal variant dans le temps.Le simulateur doit être capable de reproduire différents types d'environnement. Dans ce contexte, de nombreux scénarios ont été proposés. Ils considèrent le mouvement à l'intérieur et à l'extérieur pour des environnements et des réseaux hétérogènes. Un algorithme est proposé et analysé pour basculer entre les environnements d’une manière continue. Ces réseaux offrent des services à travers un réseau cellulaire à l'aide du LTE et sont capables de maintenir le service lors du passage à un réseau local sans fil WLAN 802.11ac.Deux architectures pour le bloc numérique du simulateur matériel sont proposées. La première opère dans le domaine fréquentiel en utilisant des modules de transformée de Fourier rapide (FFT/IFFT). Dans ce contexte, une nouvelle architecture fréquentielle améliorée qui fonctionne avec des signaux d'entrée de longue durée est proposée. La seconde opère dans le domaine temporel en utilisant des filtres à Réponse Impulsionnelle Finie (FIR).Les architectures ont été implémentées sur des circuits programmables (FPGA : Field Programmable Gate Array) Virtex-IV de Xilinx. Leurs occupations sur FPGA, la précision des signaux de sortie et leur latence sont analysées et comparées. De plus, une solution basée sur un facteur d’échelle automatique (ASF: Auto-Scale Factor) est introduite pour augmenter la précision des signaux de sortieTo evaluate the performance of the emerging mobile and wireless communication systems, a Multiple-Input Multiple-Output (MIMO) channel hardware simulator is designed and implemented using the recent communication standards. It provides the processing speed required to the real-time performance evaluation and allows comparing various systems in the same test conditions. The objectives of this work mainly concern the MIMO channel models and the digital block architecture of the hardware simulator. The hardware simulator can be configured with Long Term Evolution (LTE) and Wireless Local Area Network (WLAN) 802.11ac signals. It uses standard channel models, as 3GPP LTE and TGn IEEE 802.11n. It also allows replaying measurement results obtained with the MIMO channel sounder designed and realized at our laboratory. In fact, data obtained during measurement campaigns onboard a ship and for outdoor-to-indoor environments were used. The measured impulse responses are pre-processed in order to make them compatible with LTE or 802.11ac signals. Moreover, timevarying channel models are obtained using Kronecker model with Rayleigh fading.The simulator must be able to reproduce different types of environment. In this context, many scenarios considering realistic people movements have been proposed. They involve movements in outdoor, indoor, outdoor-to-indoor or heterogeneous environments. An algorithm is proposed and described to switch between the environments in a continuous manner. Heterogeneous wireless communication systems are also considered. These systems provide service through a cellular network using LTE standard and are able to maintain the service when switching to a WLAN 802.11ac, for example.Two architectures for the digital block of the hardware simulator are proposed. The first operates in the frequency domain using Fast Fourier Transform (FFT/IFFT) modules. A new improved frequency architecture that works for streaming mode input signals is proposed. The second operates in time domain using Finite Impulse Response (FIR) filters.The architectures of the digital block of the hardware simulator are implemented on a Field Programmable Gate Array (FPGA) Virtex-IV from Xilinx. Their occupation on the FPGA, the accuracy of the output signals and their latency are analyzed and compared. Moreover, a new algorithm, based on an Auto-Scale Factor (ASF), is added for the time domain architecture. This algorithm improves the precision of the output signals
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Bombino, Andrea. "Machine Learning Aided Methods for Resilient Industrial Wireless Sensor Network." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17636/.
Full textAbstract:
Le Wireless Sensor Network (WSN) possono essere definite come un’ infrastruttura
composta da sensori/dispositivi in grado di calcolare comunicare e
effettuare sensing sul ambiente che gli circonda processando e analizzando i
dati in modo da reagire a eventi e fenomeni che possono occorrere durante
la comunicazione. Questo motiva un enorme effort nella ricerca, standardizzazione
e investimento industriale in questo campo, nell’ultimo decennio.
L’uso delle WSN nell’ambiente industriale è soggetto a diverse problematiche,
dovuto all’ostilità dell’ambiente, come rumore, shadwoing, multi-percorso e
interferenze.
Nel nostro progetto, proponiamo un meccanismo basato sulle condizioni
di propagazione del canale e algoritmi di machine learning che ci permettono
di classificare lo stato del canale (LOS o NLOS) e migliorare qualità, sicurezza
e in particolar modo l’affidabilità del sistema radio link da noi esaminato in
differenti ambienti.
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Sakarai, Deesha S. "Wireless Channel Characterization for Large Indoor Environments at 5 GHz." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1338494030.
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Fu, Weihuang. "Analytical Model for Capacity and Delay Optimization in Wireless Mesh Networks." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1289937944.
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Adegoke, Elijah. "Radio frequency channel characterization for energy harvesting in factory environments." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/33412.
Full textAbstract:
This thesis presents ambient energy data obtained from a measurement campaign carried out at an automobile plant. At the automobile plant, ambient light, ambient temperature and ambient radio frequency were measured during the day time over two days. The measurement results showed that ambient light generated the highest DC power. For plant and operation managers at the automobile plant, the measurement data can be used in system design considerations for future energy harvesting wireless sensor nodes at the plant. In addition, wideband measurements obtained from a machine workshop are presented in this thesis. The power delay profile of the wireless channel was obtained by using a frequency domain channel sounding technique. The measurements were compared with an equivalent ray tracing model in order to validate the suitability of the commercial propagation software used in this work. Furthermore, a novel technique for mathematically recreating the time dispersion created by factory inventory in a radio frequency channel is discussed. As a wireless receiver design parameter, delay spread characterizes the amplitude and phase response of the radio channel. In wireless sensor devices, this becomes paramount, as it determines the complexity of the receiver. In reality, it is sometimes difficult to obtain full detail floor plans of factories for deterministic modelling or carry out spot measurements during building construction. As a result, radio provision may be suboptimal. The method presented in this thesis is based on 3-D fractal geometry. By employing the fractal overlaying algorithm presented, metallic objects can be placed on a floor plan so as to obtain similar radio frequency channel effects. The environment created using the fractal approach was used to estimate the amount of energy a harvesting device can accumulate in a University machine workshop space.
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Wang, Xiaohui. "Environment Models for Realistic Simulation and Emulation of Wireless Networks." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/322.
Full textAbstract:
Wireless research and development requires effective and efficient simulation and emulation tools to validate and evaluate wireless designs. Wireless channel models are used in the tools to simulate signal propagation properties in the real physical world. However, due to practical issues, these models are often too generalized and simplified in large scale experiments, and they only provide limited realism.
In this thesis, a novel world model is proposed for simulation and emulation of wireless networks. The proposed model includes the design and implementation of a variety of environment models that enhance realism in simulation. These models capture realistic signal propagation properties across multiple connections, and over time: first, the impact of realistic physical world features, such as channel dynamics and cross link correlation are characterized at different time scales; then, both geometrical and statistical simulation models are developed to recreate desired channel dynamics among wireless network links efficiently.
Three major components of the proposed design are described in this thesis: 1) a flexible channel simulation model, 2) improvement of parameter accuracy in geometric channel models, and 3) wireless link correlation models with a case study in vehicular networks. The flexible channel simulation model supports fast generation of channel updates for complicated channel models, including small-scale fast fading, large-scale path loss and multi-path delay and attenuation. To achieve high realism, a variety of techniques are developed to obtain high parameter accuracy in geographic channel models. Link correlation models are developed for simulating wireless channels within a network context, where adjacent wireless links share the same propagation medium. The wireless link correlation model handles both temporal and spatial correlations, to reflect properties at different time scales and location-based similarities.
A case study in vehicular networks illustrates the effectiveness of using the proposed environment model to improve the realism of wireless simulation and emulation platforms. Simulation results from implemented models are compared against the measurement data from physical world vehicle-to-vehicle channels, and show good approximation to reality. The evaluation results of correlated channel models show improved realism in channel properties and corresponding impact on the performance of a gossip protocol.
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Herbert, Steven John. "Wireless communication in vehicles." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/280675.
Full textAbstract:
There is an increasing interest in the deployment of wireless communication systems in vehicles. The motivation for this work is to provide a fundamental characterisation of the in-vehicle Electromagnetic (EM) wave propagation environment, and to demonstrate how this can be used to aid the deployment of wireless communication systems in vehicles. The fundamental characterisation of the in-vehicle EM wave propagation environment presented in this dissertation yields a number of useful outcomes. The instantaneous impulse response of the in-vehicle channel is characterised, which is presented in the form of a statistical model for arriving rays. Noticing that it is impractical to undertake a full statistical characterisation of the time-varying impulse response, the time variation of the in-vehicle channel is instead characterised as a Doppler spread. This approach provides parameters which are sufficient to perform an information theoretic analysis to lower bound the capacity of the in-vehicle channel. For typical operating conditions, it is found that the channel capacity is approximately equal to that of the same channel with perfect channel state information available at the receiver. Having established the fundamental EM wave propagation characteristics for a single in-vehicle wireless channel, the EM properties of the cavity itself are characterised. This is achieved through a thorough investigation into the analogy between vehicle cavities and reverberation chambers, specifically considering the quality factor (and hence time constant), EM isolation, and electric field uniformity of typical vehicle cavities. This approach yields the important insight that the root mean square delay spread is approximately the same for all wireless links in a typical vehicle cavity. Also, that the angular spread of energy received at any given location (away from the cavity boundaries) is approximately uniform, and that over short distances the coherence distance is well defined, and hence Multiple Input Multiple Output antenna arrays should work well in vehicles. To what extent a typical wireless system can exploit this characterisation depends on how well the parameters can be estimated by a typical wireless communication system. This is also addressed, specifically investigating the estimation of the cavity time constant, and channel time variation. It is found that both of these can be estimated well using a typical wireless sensor network system.
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Liechty, Lorne Christopher. "Path Loss Measurements and Model Analysis of a 2.4 GHz Wireless Network in an Outdoor Environment." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16308.
Full textAbstract:
Careful network planning has become increasingly critical with the rising deployment, coverage, and congestion of wireless local area networks (WLANs). This thesis outlines the achieved prediction accuracy of a direct-ray, single path loss exponent, adapted Seidel-Rappaport propagation model as determined through measurements and analysis of the established 2.4 GHz, 802.11g outdoor WiFi network deployed on the campus of the Georgia Institute of Technology. Additionally, the viability of using the obtained model parameters as a means for planning future network deployment is discussed. Analysis of measured data shows that accurate predictive planning for network coverage is possible without the need for overly complicated modeling techniques such as ray tracing. The proposed model performs with accuracy comparable to other commonly accepted, more complicated models and is offered as a simple, yet strong predictive model for network planning having both speed and accuracy. Results show, that for the area under study, the standard deviation of the prediction error for the proposed model is below 6.8dB in all analyzed environments, and is approximately 5.5dB on average. Further, the accuracy of model predictions in new environments is shown to be satisfactory for network planning.
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Wu, Jingqi. "Cooperative Jamming in Wireless Networks - Turning Attacks into Privacy Protection." ScholarWorks@UNO, 2008. http://scholarworks.uno.edu/td/885.
Full textAbstract:
Generally, collisions between packets are undesired in wireless networks. We design this scheme, Cooperative Jamming in Wireless Networks (CJWN), to make use of collision to protect secret DATA packets from being sniffed by a nearby eavesdropper. We are intending to greatly increase the Packet Error Rate (PER) at the eavesdropper when the PER at the receiver is maintained at an acceptable level. This scheme is not intended to completely take the place of various encryption/decryption schemes which are working based on successfully received packets. Adding CJWN to the popular CSMA/CA adopted in IEEE 802.11 will add more security even the key for encryption/decryption is already exposed. Because the overhead of CJWN is very big, we do not suggest using it on every transmission. When some secret packets have a high requirement of confidentiality, CJWN is worth trying at the cost of throughput performance and power.
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Rowe, Christopher D. "Channel Propagation Model for Train to Vehicle Alert System at 5.9 GHz using Dedicated Short Range Communication." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73178.
Full textAbstract:
The most common railroad accidents today involve collisions between trains and passenger vehicles at railroad grade crossings [1][2]. Due to the size and speed of a train, these collisions generally result in significant damage and serious injury. Despite recent efforts by projects such as Operation Lifesaver to install safety features at grade crossings, up to 80% of the United States railroad grade crossings are classified as 'unprotected' with no lights, warnings, or crossing gates [2]. Further, from January to September 2012, nearly 10% of all reported vehicle accidents were a result of train-to-vehicle collisions. These collisions also accounted for nearly 95% of all reported fatalities from vehicular accidents [2].
To help provide a more rapidly deployable safety system, advanced dedicated short range communication (DSRC) systems are being developed. DSRC is an emerging technology that is currently being explored by the automotive safety industry for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications to provide intelligent transportation services (ITS). DSRC uses WAVE protocols and the IEEE 1609 standards. Among the many features of DSRC systems is the ability to sense and then provide an early warning of a potential collision [6]. One potential adaption for this technology is for use as a train-to-vehicle collision warning system for unprotected grade crossings. These new protocols pose an interesting opportunity for enhancing cybersecurity since terrorists will undoubtedly eventually identify these types of mass disasters as targets of opportunity.
To provide a thorough channel model of the train to vehicle communication environment that is proposed above, large-scale path loss and small scale fading will both be analyzed to characterize the propagation environment. Measurements were collected at TTCI in Pueblo Colorado to measure the received signal strength in a train to vehicle communication environment. From the received signal strength, different channel models can be developed to characterize the communication environment.
Documented metrics include large scale path loss, Rician small scale fading, Delay spread, and Doppler spread. An analysis of the DSRC performance based on Packet Error Rate is also included.Master of Science
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Cash, Jason M. "Using Light Detection and Ranging (LiDAR) Imagery to Model Radio Wave Propagation." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31615.
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The purpose of this study was to determine if light detection and ranging (LiDAR) imagery could provide a significantly more accurate data set for modeling near line-of-sight (LOS) propagation at higher frequencies, specifically 27.810 GHz. than a USGS digital elevation model (DEM). In addition, the study tested for significant differences in LiDAR elevation data created at various resolutions ranging from 1 to 100 meters. Finally, this study examined the effects of various classification thresholds for transforming continuous signal strength measurements into LOS or non-LOS (NLOS) classifications used in determining prediction accuracy. The capability to transmit information via higher frequency wireless equipment requires a near LOS path between the transmitter and the antenna receiving the signal. USGS DEMs, commonly used in GIS programs to predict communication viewsheds (commsheds), represent the bare earth topography and do not reflect surface features such as vegetation and buildings. In actuality these surface features can significantly influence near LOS paths and therefore a data set that contains these features can greatly improve the ability to predict commshed areas. LiDAR is a form of active imagery that records both the bare-earth as well as these surface features, at a high resolution, making it well suited for wireless modeling applications. Results indicate that signal strength threshold classification has a direct influence on the accuracy of predicted commsheds across all resolutions. Secondly, LiDAR resolutions lower than 40m as well as bare-earth DEMs were unsuccessful in predicting an accurate commshed while LiDAR resolutions coarser than 15m provided significant predictions of equal accuracy. These results indicate that high resolution LiDAR is needed to accurately model commsheds but signal strength threshold classification determines which of these higher resolutions are significant.Master of Science
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Bhorgay, Ketaki D. "A Generalized Extended Suzuki Model for Land Mobile Satellite Channels." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108759154.
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Spencer, Quentin H. "Transmission Strategies for Wireless Multi-user, Multiple-Input, Multiple-Output Communication Channels." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd378.pdf.
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Anderson, Christopher R. "Design and Implementation of an Ultrabroadband Millimeter-Wavelength Vector Sliding Correlator Channel Sounder and In-Building Multipath Measurements at 2.5 & 60 GHz." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32415.
Full textAbstract:
Over the past decade, the market for wireless service has grown at an unprecedented rate. The industry has grown from cellular phones and pagers to broadband and ultra-broadband (also called ultra-wideband) wireless services that can provide voice, data, and full-motion video in real time. This growing hunger for faster data rates and larger bandwidths has prompted a need for a deeper understanding of the wireless channels upon which these devices communicate. In order for the visions of real time full-motion video, multimedia, and high speed data delivery inherent in the 3rd and 4th generations of wireless communication standards to be fully realized, system design engineers must have a thorough understanding of the wireless channels upon which these devices operate. Additionally, for these networks to deliver their promised data rates, they must operate at very high microwave and millimeter-wave frequencies, where large segments of spectrum are readily obtained.
Unfortunately, little is known about the propagation characteristics at these frequencies and bandwidths. As a consequence, there has been a significant demand for wireless test equipment that is capable of characterizing these new wireless channels. The objective of this research was to design and develop a wireless test instrument that can not only characterize these new wireless channels, but has the portability to be quickly and easily re-located to various measurement sites, as well as the flexibility to characterize a wide variety of frequencies and bandwidths in addition to the ultrawideband channels investigated in this work. This measurement system is also designed to be capable of characterizing both the magnitude and phase response of these wireless channels, which not only provides a more complete channel characteristic, but the potential capability to measure the Doppler spectrum introduced by a dynamic channel.Master of Science
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Gunyan, Scott Nathan. "An Examination into the Statistics of the Singular Vectors for the Multi-User MIMO Wireless Channel." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd539.pdf.
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Wells, Derek A. "Simulation of a Wireless Communication Channel to Determine a Best Topology for a Base Station Array Antenna." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31230.
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This thesis presents simulation data on array operation in wideband
communication systems. It is shown that array structures with closer
inter-element spacing outperform structures with much larger
inter-element spacing. It is also shown that circular structures
outperform linear structures. This performance difference between the
classifications of arrays is due largely to the circular array's
ability to handle high levels of interference. Even though a
diversity combining scheme (MRC) was used in the simulator, the
arrays provided interference rejection capabilities due to the closely
spaced antenna elements. Though diversity does provide a gain in received
signal, relative to the faded signal, realized diversity gain only
comes about once interference has been mitigated. This thesis
work showed that in an environment with a lot of interferers, the
rejection of those interferers by an array is of utmost importance,
even more than fading mitigation.Master of Science
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Fernandes, Victor. "Analyses of a low-bit rate hybrid PLC-wireless single-relay channel." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/5504.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Essa dissertação tem por objetivo mostrar os benefícios em termos de desempenho e confiabilidade de um modelo de canal híbrido de baixa taxa de dados que pode ser aplicado a smart grids e internet das coisas. Esse modelo é chamado de hybrid power line communication-wireless single-relay channel (HSRC), que consiste do uso paralelo e mútuo dos modelos single-relay channel baseado em transmissão de dados via rede elétrica e sem fio. Para mostrar os benefícios do mesmo, foi considerado que a posição do nó de retransmissão é variável, também foi assumida alocação de potência uniforme e ótima sob restrição de potência, bem como o uso de dois protocolos de cooperação: amplify-andforward (AF) e decode-and-forward (DF). Além disso, essa dissertação discute o modelo HSRC incompleto, que é caracterizado pela perda de um enlace de comunicação de dados ou uma interface de comunicação de um nó no modelo HSRC. Primeiramente, foi apresentada a formulação matemática no que tange a taxa de dados ergódica e probabilidade de outage dos dois modelos mencionados. Em seguida, foi realizada a análise numérica dos mesmos. Por fim, os resultados numéricos foram analisados e mostraram que tanto o HSRC quanto o HSRC incompleto têm performance melhores do que o single-relay channel baseado em transmissão de dados via rede elétrica ou sem fio para todas as posições do nó de retransmissão e protocolos de cooperação considerados. Também, os resultados mostraram que a posição relativa entre os nós de fonte, destino e de retransmissão impactam significativamente na taxa de dados ergódica bem como na probabilidade de outage. Ainda, foi mostrado o impacto da perda de cada enlace de comunicação de dados ou interface de comunicação de um nó (HSRC incompleto) quando a posição relativa do nó de retransmissão muda. Por último, é mostrado que a diferença de desempenho entre os protocolos de cooperação AF e DF reduz quando o modelo HSRC é utilizado e que a melhor posição para o nó de retransmissão é entre os nós fonte e destino em termos de taxa de dados ergódica.
This dissertation aims at discussing improvements of performance and reliability of lowbit rate data communication technologies applied to smart grids and internet of things. In this regard, a comprehensive analysis of the ergodic achievable data rate and the outage probability of the so-called low-bit rate hybrid power line communication-wireless singlerelay channel (HSRC) model, which jointly and in parallel uses power line and wireless channels for data transmission, is presented. In order to highlight the benefits of such hybrid channel model for the target applications when the relative position of relay node changes, optimal and uniform power allocations under sum power constraint, amplifyand-forward (AF) and decode-and-forward (DF) cooperative protocols are taken into account. Moreover, this dissertation discusses the so-called incomplete HSRC which is characterized by the loss of one data communication link or node communication interface in a HSRC. Numerical results show that the HSRC and incomplete HSRC remarkably outperform power line or wireless single-relay channels for all considered positions of the relay node and the chosen cooperative protocols. Furthermore, these results show that the relative distances among source, relay and destination nodes significantly impact the achievable data rate and outage probabilities. In addition, the impact of each missing data communication link or node communication interface (incomplete HSRC) when the relay position, relative to source and destination nodes, changes is quantified. Finally, but not the least, it is shown that the performance difference between AF and DF protocols reduces when the HSRC model is taken into account and that the best relay position is in the middle between source and destination nodes.
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Ivan. "Vehicle to vehicle communication systems performance evaluation : A simulation approcach combining physical layer implementation, propagation channel model and antenna properties." Rennes, INSA, 2012. http://www.theses.fr/2012ISAR0009.
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V2X est un système de communication entre les véhicules (ou V2V) et entre les véhicules et l'infrastructure routière (véhicule à l'infrastructure, ou V2I) fonctionnant à 5,9 GHz, avec pour principal objectif d'améliorer la sécurité routière et d'augmenter la fluidité du trafic. L'évaluation des performances du système V2X par simulation numérique, reposant sur des modèles précis et éprouvés, constitue une étape fondamentale dans une logique de conception-validation avant l'intégration sur véhicule réel. Le travail présenté dans ce document se concentre sur les techniques de simulation pour l'évaluation des performances du système de communication V2X dans différents environnements d'exploitation, avec différents types de récepteur, et avec différentes antennes au niveau du récepteur. Des résultats de mesure sur banc d’essai avec des prototypes de modems V2X et avec un émulateur de canal RF, valident certaines de nos techniques et résultats de simulationV2X is a communication system between vehicles (vehicle to vehicle, or V2V) and between vehicles and the infrastructure (vehicle to infrastructure, or V2I) operating at 5. 9 GHz, with main purpose to improve road safety and to increase traffic efficiency. The computer performance evaluation of the V2X system, while employing accurate simulation models, represents an important preliminary step before its integration into vehicles and thus a possible large-scale deployment. The work presented in this document focuses on simulation techniques for realistic performance evaluation of the V2X communication system in different operating environments, with different types of receiver implementations, and with different antennas at the receiver. On-bench measurement results with V2X prototypes and with a RF channel emulator validated some of our computer simulation techniques and results
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Matcha, Chaitanya Kumar, Mohsen Bahrami, Shounak Roy, Shayan Garani Srinivasa, and Bane Vasic. "Generalized belief propagation based TDMR detector and decoder." IEEE, 2016. http://hdl.handle.net/10150/622831.
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Two dimensional magnetic recording (TDMR) achieves high areal densities by reducing the size of a bit comparable to the size of the magnetic grains resulting in two dimensional (2D) inter symbol interference (ISI) and very high media noise. Therefore, it is critical to handle the media noise along with the 2D ISI detection. In this paper, we tune the generalized belief propagation (GBP) algorithm to handle the media noise seen in TDMR. We also provide an intuition into the nature of hard decisions provided by the GBP algorithm. The performance of the GBP algorithm is evaluated over a Voronoi based TDMR channel model where the soft outputs from the GBP algorithm are used by a belief propagation (BP) algorithm to decode low-density parity check (LDPC) codes.
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Ricci, Eugenio. "Multiscale analysis of a HCN4 channel double mutation in a human sinoatrial computational model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19966/.
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The Double Mutation (DM) I479V/A485E has been reported (Servatius et al., 2018) to determine a loss of function of the funny current (If), which is a key player of the onset of the action potential in the Sinoatrial Node (SAN). Thus, the DM can result in bradycardia. This work presents a multiscale study that links the DM (i.e. genotype) to the bradycardia (i.e. phenotype). To do this, first a tool to display and analyse electrophysiological data was developed. Thanks to it, the decrease in If conductance was quantified and used as an input for a computational model of a human SAN cell. The simulation of the action potential of this model gave a Cycle Length (CL) of 1019 ms (compared to 814 ms of the Wild Type condition, +20.1 %). After this, a 1D and 2D model of the SAN were implemented, in order to test the behaviour of more complex systems (fibre and tissue), since these can show phenomena not present at the channel or single cell level. Several values of cellular heterogeneity (σ) and coupling (ρ) were considered, in order to investigate the most physiologic degree of these properties. This was assessed relying on the most realistic results obtained for CL, Action Potential Amplitude (APA) and Conduction Velocity (CV). The results show that: I) increasing σ leads to shorter mean CLs and wider CL and APA distributions; II) increasing ρ provides wider CL and APA distributions, whereas their mean values are the highest for ρ = 1000 MΩ·m. A complete synchronization is therefore a trade-off between σ and ρ; III) for physiologic values of σ (0.1873) and ρ (~ 100 MΩ·m) cells manage to synchronize their pacing frequency and show a conduction velocity similar to that reported in literature (~ 11 cm/s) in both 1D and 2D models. This is true for both WT and DM but, in the last case, the mean CL is significantly shorter. This fact proves the detrimental effect of these mutations: in 2D, the heart rate drops from 75.6 bpm (WT) to 60.2 bpm (DM, -18.3 %).
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Muqaibel, Ali Hussein. "Characterization of Ultra Wideband Communication Channels." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26398.
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Ultra-wideband (UWB) communication has been the subject of extensive research in recent years due to its unique capabilities and potential applications, particularly in short-range multiple access wireless communications. However, many important aspects of UWB-based communication systems have not yet been thoroughly investigated. The propagation of UWB signals in indoor environments is the single most important issue with significant impacts on the future direction, scope, and generally the extent of the success of UWB technology. The objective of this dissertation is to obtain a more thorough and comprehensive understanding of the potentials of UWB technology by characterizing the UWB communication channels. Channel characterization refers to extracting the channel parameters from measured data. The extracted parameters are used to quantify the effect of the channel on communication UWB systems using this channel as signal transmission medium. Data are measured in different ways using a variety of time-domain and frequency-domain techniques. The experimental setups used in channel characterization effort also include pulse generators and antennas as integral parts of the channel, since the pulse shape and antenna characteristics have significant impact on channel parameters.
At a fundamental level, the propagation of UWB signals, as any electromagnetic wave, is governed, among other things, by the properties of materials in the propagation medium. One of the objectives of this research is to examine propagation through walls made of typical building materials and thereby acquire ultra-wideband characterization of these materials. The loss and the dielectric constant of each material are measured over a frequency range of 1 to 15 GHz. Ten commonly used building materials are chosen for this investigation. These include, dry wall, wallboard, structure wood, glass sheet, bricks, concrete blocks, reinforced concrete (as pillar), cloth office partition, wooden door, and styrofoam slab. The work on ultra-wideband characterization of building materials resulted in an additional interesting contribution. A new formulation for evaluating the complex dielectric constant of low-loss materials, which involves solving real equations and thus requiring only one-dimensional root searching techniques, was found. The results derived from the exact complex equation and from the new formulation are in excellent agreement.
Following the characterization of building materials, an indoor UWB measurement campaign is undertaken. Typical indoor scenarios, including line-of-sight (LOS), non-line-of-sight (NLOS), room-to-room, within-the-room, and hallways, are considered. Results for indoor propagation measurements are presented for local power delay profiles (local-PDP) and small-scale averaged power delay profiles (SSA-PDP). Site-specific trends and general observations are discussed. The results for pathloss exponent and time dispersion parameters are presented. The analyses results indicate the immunity of UWB signals to multipath fading. The results also clearly show that UWB signals, unlike narrowband signals, do not suffer from small scale fading, unless the receiver is too close to walls. Multipath components are further studies by employing a deconvolution technique. The application of deconvolution results in resolving multipath components with waveforms different from those of the sounding pulse. Resolving more components can improve the design of the rake receiver. The final part of this research elaborates on the nature of multiple access interference and illustrates the application of multi-user detection to improve the performance of impulse radio systems. Measured dispersion parameters and their effects on the multiple access parameters are discussed.Ph. D.
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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.
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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.
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Newhall, William George. "Radio Channel Measurements and Modeling for Smart Antenna Array Systems Using a Software Radio Receiver." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27115.
Full textAbstract:
This dissertation presents research performed in the areas of radio wave propagation measurement and modeling, smart antenna arrays, and software-defined radio development. A four-channel, wideband, software-defined receiver was developed to serve as a test bed for wideband measurements and antenna array experiments. This receiver was used to perform vector channel measurements in terrestrial and air-to-ground environments using an antenna array. ent results served as input to radio channel simulations based on three geometric channel models. The simulation results were compared to measurement results to evaluate the performance of the radio channel models under test. Criteria for evaluation include RMS delay spread, excess delay spread, signal envelope fading, antenna diversity gain, and gain achieved through the use of a two-dimensional rake receiver.
This research makes contributions to the wireless communications field through analysis, development, measurement, and simulation that builds upon past theoretical and experimental results. Contributions include a software-defined radio architecture, based on object oriented techniques, that has been developed and successfully demonstrated using the wideband receiver. This research has produced new wideband vector channel measurements to provide extensive characterization results facilitating simulation of emerging wireless technology for commercial and military communications systems. Original ways of interpreting multipath component strength and correlation for antenna arrays have been developed and investigated. A novel geometric air-to-ground ellipsoidal channel model has been developed, simulated, and evaluated. Other contributions include an evaluation of two popular radio channel models, a geometric channel simulator for producing channel impulse responses, and analytical derivation results related to channel modeling geometries and multipath channel measurement processing.
In addition to new results, existing theory and earlier research results are discussed. Fundamental theory for antenna arrays, vector channels, multipath characterization, and channel modeling is presented. Contemporary issues in software radio and object orientation are described, and measurement results from other propagation research are summarized.Ph. D.
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ISLAM, MD JAHERUL. "Performance Analysis of Diversity Techniques for Wireless Communication System." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-1962.
Full textAbstract:
Different diversity techniques such as Maximal-Ratio Combining (MRC), Equal-Gain Combining (EGC) and Selection Combining (SC) are described and analyzed. Two branches (N=2) diversity systems that are used for pre-detection combining have been investigated and computed. The statistics of carrier to noise ratio (CNR) and carrier to interference ratio (CIR) without diversity assuming Rayleigh fading model have been examined and then measured for diversity systems. The probability of error (p_e) vs CNR and (p_e) versus CIR have also been obtained. The fading dynamic range of the instantaneous CNR and CIR is reduced remarkably when diversity systems are used [1]. For a certain average probability of error, a higher valued average CNR and CIR is in need for non-diversity systems [1]. But a smaller valued of CNR and CIR are compared to diversity systems. The overall conclusion is that maximal-ratio combining (MRC) achieves the best performance improvement compared to other combining methods. Diversity techniques are very useful to improve the performance of high speed wireless channel to transmit data and information. The problems which considered in this thesis are not new but I have tried to organize, prove and analyze in new ways.