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1
Tshisaphungo, Mpho. "Validation of high frequency propagation prediction models over Africa." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1015239.
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The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.
2
Habarulema, John Bosco. "A contribution to TEC modelling over Southern Africa using GPS data." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005241.
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Modelling ionospheric total electron content (TEC) is an important area of interest for radio wave propagation, geodesy, surveying, the understanding of space weather dynamics and error correction in relation to Global Navigation Satellite Systems (GNNS) applications. With the utilisation of improved ionosonde technology coupled with the use of GNSS, the response of technological systems due to changes in the ionosphere during both quiet and disturbed conditions can be historically inferred. TEC values are usually derived from GNSS measurements using mathematically intensive algorithms. However, the techniques used to estimate these TEC values depend heavily on the availability of near-real time GNSS data, and therefore, are sometimes unable to generate complete datasets. This thesis investigated possibilities for the modelling of TEC values derived from the South African Global Positioning System (GPS)receiver network using linear regression methods and artificial neural networks (NNs). GPS TEC values were derived using the Adjusted Spherical Harmonic Analysis (ASHA) algorithm. Considering TEC and the factors that influence its variability as “dependent and independent variables” respectively, the capabilities of linear regression methods and NNs for TEC modelling were first investigated using a small dataset from two GPS receiver stations. NN and regression models were separately developed and used to reproduce TEC fluctuations at different stations not included in the models’ development. For this purpose, TEC was modelled as a function of diurnal variation, seasonal variation, solar and magnetic activities. Comparative analysis showed that NN models provide predictions of GPS TEC that were an improvement on those predicted by the regression models developed. A separate study to empirically investigate the effects of solar wind on GPS TEC was carried out. Quantitative results indicated that solar wind does not have a significant influence on TEC variability. The final TEC simulation model developed makes use of the NN technique to find the relationship between historical TEC data variations and factors that are known to influence TEC variability (such as solar and magnetic activities, diurnal and seasonal variations and the geographical locations of the respective GPS stations) for the purposes of regional TEC modelling and mapping. The NN technique in conjunction with interpolation and extrapolation methods makes it possible to construct ionospheric TEC maps and to analyse the spatial and temporal TEC behaviour over Southern Africa. For independent validation, modelled TEC values were compared to ionosonde TEC and the International Reference Ionosphere (IRI) generated TEC values during both quiet and disturbed conditions. This thesis provides a comprehensive guide on the development of TEC models for predicting ionospheric variability over the South African region, and forms a significant contribution to ionospheric modelling efforts in Africa.
3
Opperman, B. D. L. "Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005273.
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Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated.
4
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.
5
Rehman, F. (Faisal). "Radio wave propagation studies through modern windows." Master's thesis, University of Oulu, 2017. http://jultika.oulu.fi/Record/nbnfioulu-201709082871.
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Abstract. It is a growing trend in the modern housing construction especially in northern parts of Europe and America to use modern windows with selective glasses in order to achieve the adequate thermal isolation. The idea is to conserve the energy and discourage the excess use of it following the guidelines of European commission, which aims to achieve zero energy buildings by 2020. Even though the use of such windows do address the energy issue at hand, but on the other hand they cause problems to the radio wave propagation through these windows. The reason for this is the use of metallic coating made of titanium oxide or silver oxide in general on these windows because of their good properties to provide thermal isolation, but are susceptible to deterioration of radio wave propagation through them.
Various solutions to this problem have been addressed in this thesis along with their tradeoffs. The previous and current research being carried out to address this issue also have been discussed thoroughly including the research that worked as the motivation to pursue this issue. Amongst others, one solution is the use of passive repeater to achieve the power gain which have been focused on. A prototype repeater antenna developed earlier at CWC and tested through measurements addresses the problem considerably well. Measurements were taken at EMC chamber, University of Oulu, within the frequency range of 700 MHz to 10 GHz, and the results have been compared and analyzed in this thesis. According to our findings, the repeater antenna under the test has shown promising results. In the future work, the proposed repeater can be tested in real life scenarios and its performance can be analyzed within the real life environmental constraints.
6
Atefi, A. "An investigation of radio wave propagation in mobile radio frequency bands." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354537.
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7
Wang, Ying. "Site-specific modeling of indoor radio wave propagation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0020/NQ53522.pdf.
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8
Qing, Li. "GIS Aided Radio Wave Propagation Modeling and Analysis." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33287.
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The analysis of radio wave propagation is a crucial part in designing an efficient wireless communication system. The Geographic Information System (GIS) can be incorporated into this procedure because most of the factors in radio wave propagation are geographic features.
In this research, a commercial wireless planning software is tested in a field driving test carried out in Montgomery County, VA. The performance of current wireless planning software is evaluated based on field measurement. The received signal strength data collected during this driving test are then analyzed in a GIS environment in a statistical approach. The effects of local geographic features are modeled in GIS by appropriate spatial analyses.Master of Science
9
Östlin, Erik. "On Radio Wave Propagation Measurements and Modelling for Cellular Mobile Radio Networks." Doctoral thesis, Karlskrona : Blekinge Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00443.
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To support the continuously increasing number of mobile telephone users around the world, mobile communication systems have become more advanced and sophisticated in their designs. As a result of the great success with the second generation mobile radio networks, deployment of the third and development of fourth generations, the demand for higher data rates to support available services, such as internet connection, video telephony and personal navigation systems, is ever growing. To be able to meet the requirements regarding bandwidth and number of users, enhancements of existing systems and introductions of conceptually new technologies and techniques have been researched and developed. Although new proposed technologies in theory provide increased network capacity, the backbone of a successful roll-out of a mobile telephone system is inevitably the planning of the network’s cellular structure. Hence, the fundamental aspect to a reliable cellular planning is the knowledge about the physical radio channel for wide sets of different propagation scenarios. Therefore, to study radio wave propagation in typical Australian environments, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Australian Telecommunications Cooperative Research Centre (ATcrc) in collaboration developed a cellular code division multiple access (CDMA) pilot scanner. The pilot scanner measurement equipment enables for radio wave propagation measurements in available commercial CDMA mobile radio networks, which in Australia are usually deployed for extensive rural areas. Over time, the collected measurement data has been used to characterise many different types of mobile radio environments and some of the results are presented in this thesis. The thesis is divided into an introduction section and four parts based on peer-reviewed international research publications. The introduction section presents the reader with some relevant background on channel and propagation modelling. Also, the CDMA scanner measurement system that was developed in parallel with the research results founding this thesis is presented. The first part presents work on the evaluation and development of the different revisions of the Recommendation ITU-R P.1546 point-to-area radio wave propagation prediction model. In particular, the modified application of the terrain clearance angle (TCA) and the calculation method of the effective antenna height are scrutinized. In the second part, the correlation between the smallscale fading characteristics, described by the Ricean K-factor, and the vegetation density in the vicinity of the mobile receiving antenna is investigated. The third part presents an artificial neural network (ANN) based technique incorporated to predict path loss in rural macrocell environments. Obtained results, such as prediction accuracy and training time, are presented for different sized ANNs and different training approaches. Finally, the fourth part proposes an extension of the path loss ANN enabling the model to also predict small-scale fading characteristics.
10
Arshad, Kamran. "Modelling of radio wave propagation using Finite Element Analysis." Thesis, Middlesex University, 2007. http://eprints.mdx.ac.uk/9768/.
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Fourth generation (4G) wireless communication systems are intended to support high data rates which requires careful and accurate modelling of the radio environment. In this thesis, for the first time finite clement based accurate and computationally efficient models of wave propagation in different outdoor and indoor environments has been developed. Three different environments were considered: the troposphere, vegetation and tunnels and wave propagation in these environments were modelled using finite element analysis. Use of finite elements in wave propagation modelling is a novel idea although many propagation models and approaches were used in past. Coverage diagrams, path loss contours and power levels were calculated using developed models in the troposphere, vegetation and tunnels. Results obtained were compared with commercially available software Advanced Refractive Effects Prediction Software (AREPS) to validate the accuracy of the developed approach and it is shown that results were accurate with an accuracy of 3dB. The developed models were very flexible in handling complex geometries and similar analysis can be easily extended to other environments. A fully vectored finite element base propagation model was developed for straight and curved tunnels. An optimum range of values of different electrical parameters for tunnels of different shapes has been derived. The thesis delivered a novel approach to modelling radio channels that provided a fast and accurate solution of radio wave propagation in realistic environments. The results of this thesis will have a great impact in modelling and characterisation of future wireless communication systems.
11
Sheethalnath, Praveen T. "Novel Site-Specific Techniques for Predicting Radio Wave Propagation." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33016.
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This thesis addresses various aspects related to site-specific propagation prediction using ray tracing techniques. Propagation prediction based on ray tracing techniques requires that all the different physical objects, which affect the propagation of radio waves, be modeled. The first part of the thesis concentrates on modeling the buildings and the terrain for the above-mentioned application. A survey of the various geographic products that are available to model the environment is presented. The different methods used to model the terrain are analyzed and the most suitable method for a ray based application is suggested. A method to model the buildings in an environment from commercially available data is described. A novel method to combine the building information with the terrain information is presented.
An in depth discussion of deterministic propagation prediction using ray tracing is presented in the latter half of the thesis. An overview of the various ray based algorithms that exists in the literature are presented and the limitations and the computational complexity of ray based methods are discussed. All ray based algorithms model the receivers as point objects and predict the propagation characteristics at a particular point in space. However, to optimize the design of a wireless broadcast or a point to multi point system such as a Wireless LAN (WLAN) or a cellular system, propagation characteristics at multiple points in space need to be known. The standard ray tracing algorithms can be notoriously time consuming when used to predict the characteristics of multiple receivers. A new, computationally less intensive algorithm to predict the propagation characteristics of multiple receivers is described. This algorithm significantly reduces the computation time by using â grid modeâ predictions for broadcast channels.Master of Science
12
Finnie, James Smith. "Prediction of ground-wave radio propagation over irregular inhomogeneous terrain." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/46767.
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Caldeirinha, Rafael F. S. "Radio characterisation of single trees at micro- and millimetre wave frequencies." Thesis, University of South Wales, 2001. https://pure.southwales.ac.uk/en/studentthesis/radio-characterisation-of-single-trees-at-micro-and-millimetre-wave-frequencies(925a7a06-dc26-4ea4-ab20-68967467d7ee).html.
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Wireless Communications are revolutionising personal and telecommunications services and the way in which they are utilised. Overall growth in cellular, fixed and satellite communication system markets in recent years has exceeded expectations. There is a widespread anticipation that customer demand for wireless telecommunication systems will continue to expand in the foreseeable future. Such systems rely in their planning, design and implementation on the availability of radiowave propagation models. These models are required to describe and characterise with sufficient accuracy the interaction of radiowaves with the environment, especially the various obstacles in the radio path. Prediction tools are highly desirable to radio planners in achieving appropriate coverage planning, determination of the propagation modes and the prediction and control of mutual co-channel interference between existing and new radio links. In the case of land mobile systems as well as wireless fixed access systems, trees, singly or in a group, are usually present in the radio cell environment, giving rise to both absorption and scatter of radio signals. An important part of the modelling process applied to vegetation effects is aimed at analysing the radio propagation modes and the identification of individual signal contributions to the scattered signal caused by various elements of the tree. Past research work on vegetation available in the literature does not account for the interaction between an incident plane wave and individual elements constituting the tree. The work reported in this thesis describes detailed studies aimed at the characterisation of propagation mechanisms arising in single trees of various types. It explores effects of geometrical and physical properties of the tree on radiowave propagation modes arising specifically, i.e. absorption, scatter and depolarisation. These have been addressed through a combination of analytical, computational and experimental modelling, based on thorough examination of the re-radiation functions of single trees. Appropriate measurements performed in both anechoic and outdoor environments at microwave and millimetre wave frequencies, covering frequency band from 2 to 62.4 GHz, provided both model validation and a deeper insight into the problem. Single tree scatter has been shown to be modelled adequately in terms of a re-radiation function with parameters which can be deduced from measured data. This is an important extension to the Radiative Energy Transfer (RET) model, which hitherto has been applied to a homogeneous forest half space. Forward, side and back scatter regions have been identified and characterised. Depolarisation effects were subjected to detailed study with the help of an idealised metallic structure. Analyses of measured results provided deep insight into the causes of depolarisation and the specific polarisation states likely to arise in vegetation. Reasons for signal fades or nulls in the re-radiated signals are established. Wideband channel measurements performed at 2 GHz provided valuable information on the dispersive effects of single trees, whose subsequent analyses revealed the sources of scattering, effects of tree elements, e.g. leaves and branches, and wind effects. The thesis provides also a novel method based on the Finite Difference Time Domain (FDTD) technique, used in studying the propagation modes due to interaction with single trees, starting from primary models for leaves, trunk and branches. Re-radiation fields in 3D of the entire tree are predicted by combining the effects of the single elements forming the tree. The model is shown to be capable of predicting the near-field radiated signal and the radar cross section (RCS). RCS predictions yielded good agreement with measurements and have provided a good basis for a planning model capable of accounting for single trees in the radio path. Overall, the thesis contributes new information, results and models which are very useful in radio system planning and design of broadband wireless communication services.
14
Ul-Haq, Syed Muhammad Naveed. "Outdoor to Indoor Radio Wave Propagation For Wireless in Buildings Solutions." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36195.
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A need for high data rates and reliable communication is required as we are moving from 2nd to 3rd and 4th generation of mobile communications. Therefore we see a tremendous rise in data rates. We know that most part of mobile users are indoor as compared to outdoor users, a new challenge for radio planners is to ensure proper coverage to indoor users so the prime focus is to ensure proper coverage and capacity requirements. There are various factors that account for poor coverage hence various techniques have been introduced to create a breakthrough in this process. This thesis basically focuses on indoor coverage for technologies like GSM 900MHz and 1800MHz as well as Tetra380MHz- 385MHz.I have tried different indoor models that could produce a feasible result. There is a lot of work that have been done in past that focus on outdoor models. Analysis of this thesis reveals that for the typical office environment with moderate amount of obstacle, 380MHz gives the best result as compared to 900MHz and 1800MHz. Observations reveals that 900MHz generates better results as compared to 1800MHz. All PLS coefficients used for 900MHz, 380MHz and 1800MHz are modified ones they are not taken from the standard table. focusing on PLS, Keenan Motley and Free Space models, a general summarization can be drawn that free space model generates least path loss but providing a poor coverage prediction, on the other hand path loss model generate higher loss as compared to free space model but provides good coverage while Keenan Motley model provides good coverage but shows the highest attenuation loss among all the selected models.
15
Simon, Reza Simon Reza. "Diffraction modelling of mobile radio wave propagation in built-up areas." Thesis, Brunel University, 1991. http://bura.brunel.ac.uk/handle/2438/5411.
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This thesis examines theoretical methods of modelling radio wave propagation in built-up areas, with particular application to mobile radio systems Theoretical approaches allow precise quantitative description of the environment in terms of parameters such as mean building heights and densities, in contrast to the ambiguous nature of more conventional empirical models. The models are constructed using both scalar and vector field analysis techniques. The vector analysis is accomplished using the Geometrical Theory of Diffraction to describe the detailed effects of building shape and positioning, particularly for short-range situations. Over longer ranges propagation can often be described in terms of multiple edge diffraction over building rooftops using a scalar field representation. This mechanism accounts well for measured field strength variations, but is time consuming to calculate accurately using standard methods. A rapid algorithm for calculating scalar diffraction over multiple building edges with arbitrary positioning is constructed. This model can be used for deterministic prediction of sector median field strengths including slow fading variations when appropriate building data exists. It is also applicable to terrain diffraction problems. For the case when only average building parameters are available a closed form solution to the problem of multiple diffraction over buildings of equal heights and spacings is derived. The solution is applicable to any antenna heights and so provides a rapid and efficient way to predict gross propagation characteristics. Both models are tested against measurements made in the UHF band and are found to yield good prediction accuracy.
16
Nilsson, Månz. "Radio-wave propagation modelling over rough sea surfaces and inhomogeneous atmosphere." Thesis, Karlstads universitet, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-84595.
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Mousselon, Laure. "Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/10155.
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The performance of a mobile satellite communications link is conditioned by the characteristics of the propagation path between a satellite and mobile users. The most important propagation effect in land mobile satellite system is roadside attenuation of the signals due to vegetation or urban structures. System designers should have the most reliable information about the statistics of the propagation channel to build reliable systems that can compensate for bad propagation conditions.
In 1998, the Virginia Tech Antenna Group developed a simulator, PROSIM, to simulate a propagation channel in the case of roadside tree attenuation in land mobile satellite systems. This thesis describes some improvements to PROSIM, and the adaptation and validation of PROSIM for Digital Audio Radio Satellite systems operating at S-band frequencies. The performance of the simulator for S-band frequencies was evaluated through a measurement campaign conducted with the XM Radio signals at 2.33 GHz in various propagation environments. Finally, additional results on dual satellite systems and fade correlation are described.Master of Science
18
Ghobadi, Ch. "Indoor CM and MM wave propagation and diversity techniques." Thesis, University of Bath, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266471.
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Hawbaker, Dwayne Allen. "Indoor wide band radio wave propagation measurements and models at 1.3 ghz and 4.0 ghz /." This resource online, 1989. http://scholar.lib.vt.edu/theses/available/etd-08182009-040436/.
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Kim, Daeyoung. "Propagation measurements and system design for long-range RF tags." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13876.
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Sengul, Orhan. "Low Altitude Radar Wave Propagation Modelling." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608467/index.pdf.
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LOW ALTITUDE RADAR WAVE PROPAGATION MODELLING
In this PhD thesis, propagation aspects of low altitude radar performance have been modeled using geometrical optics. Both the path propagation factor and the radar clutter have been modeled. Such models already exist at various complexity levels, such as round earth specular reflection combined with knife edge hill diffraction [SEKE:IEEE,Ap-
34,No:8,1980] and round earth and slant plateau reflection combined with hill diffraction [RADCAL: 1988-2000,EE,METU]. In the proposed model we have considered an extension
to RADCAL&rsquos model to include convex and concave slant plateaus between hills and depressions (troughs). This propagation model uses a reflection model based on the Geometrical Theory of Reflection for the convex and concave surfaces. Also, back scattering from surface (clutter) is formulated for the new model of the terrain profile. The effects of the features of the terrain profile on the path propagation factor have been investigated. A real terrain data have been smoothed on the basis of the above study. In order to verify the formulation, the Divergence and Convergence Factors associated with the convex and concave plateaus, respectively are inserted into the RADCAL program. The chosen terrains have convex or concave plateaus in the model. The output of the RADCAL is compared with measured values and other propagation algorithms such as Forward-Backward Spectrally Accelerated (FBSA) [FBSA:IEEE Vol.53, No:9,2005] and Parabolic Equation Method [TPEM:IEEE Vol.42,No:1,1994]. Moreover, as the RADCAL Propagation model is based on the ray optics, the results are also compared with another ray optics based propagation model. For this purpose the results of SEKE [Lincoln Lab.] propagation model are used. SEKE model has been used to compute path loss for different types of terrain as a function of receiving antenna height at a fixed distance between transmit and receive antennas. For Beiseker W35 Terrain profile, the results of RADCAL, SEKE and measurements are compared. All results are in good agreement with those of RADCAL.
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Ngai, Hing-on. "A study of radiowave propagation at 900 MHz in the highly urbanised areas /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19667929.
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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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Fernandes, Telmo Rui C. C. "A discrete RET model for micro- and millimetre wave propagation through vegetation." Thesis, University of South Wales, 2007. https://pure.southwales.ac.uk/en/studentthesis/a-discrete-ret-model-for-micro-and-millimetre-wave-propagation-through-vegetation(0989dc1c-4bba-4653-b0aa-4d684f82033c).html.
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The overall growth in cellular, fixed and satellite communications markets, has exceeded many expectations and there is a widespread anticipation that the demand for wireless telecommunication systems will continue to expand in the foreseeable future. Such systems rely in their planning, design and implementation on the availability of radiowave propagation models. In the particular case of land mobile radio systems and wireless fixed access systems, obstacles in the form of vegetation volumes, e.g formations of trees, are likely to influence radio propagation, giving rise to absorption and scattering of radio signals. In this context, this thesis investigates suitable techniques to characterise and model the effects of inhomogeneous volumes of vegetation on the propagation modes of radiowaves. The thesis proposes an enhanced model based on the Radiative Energy Transfer theory (RET) which was discretised to accommodate forests formed by different vegetation species with their distinct propagation characteristics. The discretised model computational structure, comprises several element cells, whose characteristic propagation parameters may be assigned independently. The discretised RET (dRET), is therefore capable of gathering the interactive responses between the element cells comprising the computational structure, leading to the determination of the received signal inside or around a given illuminated vegetation medium. The performance of the proposed model, was assessed utilising results from an extended range of measurements, carried out in different environments. Such measurements comprised those necessary for the model input parameters extraction. Others enabled the model assessment through comparison between the model predictions and the actual directional profile of the measured received signal results. An initial assessment of the model was carried out in the laboratory, using an idealised test forest formation placed inside an anechoic chamber, whereas the final model assessment was performed in an outdoor tree groupings formed by several different full size trees. Both indoor and outdoor measurements, confirmed good overall model performance and predictions of both absorption and scattering propagation modes caused by the presence of vegetation in the radio path. This was demonstrated at micro- and millimetre wave frequency bands, centered at 11.2, 20, 40 and 62.4 GHz frequencies. The thesis provides a valid tested method to evaluate the dRET propagation parameters for various isolated volumes of vegetation. Such parameters, may subsequently be utilized into the proposed propagation model, which is shown to be capable of dealing with typical and non homogeneous forests thereby effectively predicting the received signal directional profile at several locations inside and around the inhomogeneous forest. The thesis has many novel features. These include the development and extension of the basic dRET model removing many limitations. The parameter extraction including the effects of the receive antenna radiation pattern is another novel contribution. Further novelty lies in the application of the dRET model to mixed, finite and inhomogeneous vegetation formations. As a result of these refinements and extensions, the dRET propagation model has been shown to yield predicted results which agree well with measurements.
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Ryan, Patrick L. "Radio frequency propagation differences through various transmissive materials." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc5801/.
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The purpose of this research was to determine which of the commonly used wireless telecommunication site concealment materials has the least effect on signal potency. The tested materials were Tuff Span® fiberglass panels manufactured by Enduro Composite Systems, Lexan® XL-1 polycarbonate plastic manufactured by GE Corporation and Styrofoam polystyrene board manufactured by The Dow Chemical Company. Testing was conducted in a double electrically isolated copper mesh screen room at the University of North Texas Engineering Technology Building in Denton, Texas. Analysis of the data found no differences exist between the radio frequency transmissiveness of these products at broadband personal communication service frequencies. However, differences in the signal do exist with regards to the angle of incidence between the material and the transmitting antenna.
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Cui, Huajian. "Extraction of input parameters for the theory of radiative energy transfer using deconvolution." Thesis, University of South Wales, 2009. https://pure.southwales.ac.uk/en/studentthesis/extraction-of-input-parameters-for-the-theory-of-radiative-energy-transfer-using-deconvolution(4eb05b79-5ef1-4a06-8cba-471d9fb82431).html.
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The ever growing application of wireless communication systems requires accurate models for characterising radiowave propagation when affected by the presence of a variety of obstacles. In particular if the obstacles take the shape of vegetation volumes, like single trees or groups of trees and are present in the radio path, they give rise to absorption and scattering of radio signals. This thesis presents a literature review of common models for radiowave propagation through vegetation, the theory of Radiative Energy Transfer (RET) is one of these models and provides an accurate analysis of radiowave propagation through a vegetation media. Extensive measurements have been designed and conducted in a controlled indoor environment to provide valuable measurement data for later development of deconvolution approaches. It can be shown that the measured directional spectra are convolution products of the phase function pattern and the receiver antenna radiation patterns, which impacts determination of the RET input parameters. Consequently, in order to achieve more accurate determination of the RET input parameters, the adverse influence caused by receiver antenna radiation patterns have to be removed from measured directional spectra by implementing a process of deconvolution. This thesis provides successful implementation of two iterative based deconvolution techniques on the measurement directional spectra. To the author's knowledge, this is its first kind of application to eliminate distortion caused by the receiver antenna radiation pattern during measurements. This thesis reports a number of novel approaches. These include the further development and extension of deconvolution techniques such as combining the Bennia-Riad criterion and an error function to determine optimal parameters, as well as using pre-filtering techniques to improve the deconvolution results. Development of clearly defined criteria based on the knowledge of the central-limit theorem and discussion of loss of information avoidance during convolution is another novel contribution. Further novelty lies in the modification of the two methods to suit implementation on the measurement data from radiowaves impacting on vegetation volumes. As a result of these refinements, extracted RET input parameters from the restored patterns after applying the deconvolution processes show evident improvements compared to those extracted from directly measured patterns. Early stage results of this project are published in the IEEE Proceedings on Next Generation Applications, Services and Technologies.
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Mercer, Christopher Crossley. "The search for an ionospheric model suitable for real-time applications in HF radio communications." Thesis, Rhodes University, 1994. http://hdl.handle.net/10962/d1005274.
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Statement of work: In essence the research work was to focus on the development of an ionospheric model suitable for real time HF frequency prediction and direction finding applications. The modelling of the ionosphere had to be generic in nature, sufficient to ensure that the CSIR could simultaneously secure commercial competitiveness in each of the three niche market areas aforementioned, while requiring only minimal changes to software architecture in the case of each application. A little research quickly showed that the development of an ionospheric model capable of driving a HFDFSSL system in "real time" would result in one having to make only slight re-structuring of the software to facilitate application of the same model in the areas of real time frequency prediction and spectrum management. The decision made at the outset of the project to slant the research toward the development of a model best suited for HF direction finding applications is reflected in the avenues followed during the course of the modelling process
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Tharek, A. R. "Propagation and bit error rate measurements in the millimetre wave band about 60GHz." Thesis, University of Bristol, 1988. http://hdl.handle.net/1983/1b39cd0b-e371-46a5-9ce4-463e2167a6b5.
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Durgin, Gregory David. "Advanced Site-Specific Propagation Prediction Techniques." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36746.
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This thesis describes advanced techniques for site-specific propagation prediction. The need for accurate site-specific propagation is discussed in the context of current trends in the wireless industry. The first half of the report is dedicated to measuring and modeling continuous wave (CW) local-area path loss. Specifically, the text uses examples from a 5.85 GHz CW measurement campaign in and around suburban homes. Not only do these measurements demonstrate the validity of the original models and techniques presented in the thesis, but the results themselves may prove particularly useful for developing in-home wireless devices operating in the National Information Infrastructure band. This unlicensed spectrum was allocated in January of 1997 and holds promising applications for public and private telecommunications, home-based wireless internet, wireless local loops, and any number of wideband wireless applications.
There is an in-depth development of deterministic propagation prediction techniques in the latter half of the thesis. The use of geometrical optics for terrestrial microwave propagation is discussed as well as an overview of the numerous ray tracing techniques that exist in the literature. Finally, a new 3D ray launching method is presented which improves upon many of the existing ray tracing algorithms. The thesis demonstrates how this algorithm is capable of recovering very detailed channel information from a wideband deterministic propagation prediction.Master of Science
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Ängskog, Per. "Measurement and Analysis of Radio Wave Coverage in Industrial Environments." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-13615.
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Several studies have characterized the path loss properties in industrial environments. However most of them have focused on one frequency, and some two or maximum three frequencies, usually cellular telephone frequencies or the unlicensed ISM bands that are commonly used in various industries. Few, if any, have characterized a larger part of the useable frequency range.This thesis is taking that challenge and investigates the path loss characteristics over a large frequency range, 300 MHz – 3 GHz, in industrial environments. First a measurement system suitable for the harsh environments found in industries is designed and verified. The measurement system is designed as two asynchronous stand-alone units that can be positioned at an arbitrary position to measure the path loss characteristics in any environment without interfering with the normal activities at the location. After that a measurement campaign involving three different types of environments is carried out. The environment types are: first, one highly absorbing – a paper warehouse at a paper mill; second, one highly reflective – a furnace building filled with metal objects and constructions and third, a mine tunnel – located 1 km below the surface of earth which is neither highly reflective nor absorbing but exhibits somewhat wave-guide like characteristics. The environments are shown to have very different behavior when it comes to propagation characteristics. Observations in the first environment reveal an environment that almost cancels out certain frequency bands and only line-of-sight communication is possible, hence no improvement will be achieved if installing systems that take multipath propagation into account, like MIMO. In the second environment reflections are legion; there are so many reflecting surfaces at different angles so any polarization of the signal is almost completely eliminated. Large fading variations were observed.The third environment is the underground mine where signals propagate inside the tunnels like in waveguides. It is shown that there are regions in the spectrum where the path loss dips and that these dips at least partly can be modeled with a simple two-beam propagation model normally used for outdoor propagation over infinite fields. The overall conclusion is that industrial environments are more heterogeneous regarding propagation characteristics than commonly assumed when selecting communication solutions. And that the only way to really know if a radio system will work at a certain location is to measure and characterize the environment.
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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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Lindquist, Tim. "Wave Propagation Models in the Troposphere for Long-Range UHF/SHF Radio Connections." Thesis, Karlstads universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-80679.
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Bradley, W. Scott. "Propagation modeling for land mobile satellite communications." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/74511.
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Satellite systems are being planned for two-way communication with mobile vehicles using UHF and L-band frequencies. Of special concern in the system design are the characteristics of propagation in suburban and rural areas where fading occurs due to multipath effects and vegetative shadowing. A review of the literature was performed to study these propagation impairments. Available experimental data are examined, compared, and summarized. Propagation through vegetation is studied in order to compare reported modeling efforts and to determine the parameter dependences of path loss. A simple deterministic path model is then presented to estimate vegetative path loss. An overall statistical model is also proposed to describe the signal level fading statistics. The statistical model is compared to data, and the deterministic path model is used to determine the mean of signal level distribution functions in the presence of shadowing.Master of Science
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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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Boukraa, Lotfi. "Simulation of wireless propagation in a high-rise building." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FBoukraa.pdf.
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Hawbaker, Dwayne Allen. "Indoor wide band radio wave propagation measurements and models at 1.3 ghz and 4.0 ghz." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/44287.
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An extensive radio wave propagation measurement campaign was conducted at 1.3 GHz and 4.0 GHz inside four buildings, including a sports arena, a modern closed-plan office building, and two dissimilar, open-plan factories. Measurements were recorded at 57 locations using base station antenna heights of 1.7 meters and 4.0 meters. Results were obtained for mean and maximum excess delay, rms delay spread, time delay jitter, differential delay jitter, and path loss through analyses of impulse response estimates, which were obtained via repetitive 5 ns probing pulses. The effects of frequency, antenna height, topography (line-of-sight or obstructed direct path), and building environment on delay spread and path loss are quantified. Results indicate that, on average, the frequencies and antenna heights used in this study have minimal impact on rms delay spread and path loss. However, topography and building environment significantly affect these parameters. RMS delay spread values as high as 230 ns were observed in open plan factories. Computed path loss power law exponents are 1.84 and 2.35 for line-of-sight and obstructed topographies, respectively. A second campaign was conducted to determine the effects of antenna directivity and polarization on propagation parameters. On average, line-of-sight indoor channels offer 8 dB of cross-polarization discrimination, whereas obstructed environments offer less than 3 dB. Directional antennas provide a significant reduction in rms delay spread over omni-directional antennas. In line-of-sight environments, circular polarization provides an additional delay spread reduction.Master of Science
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Baldé, Mamadou Dialounké. "Millimeter wave radio channel characterization and site-specific simulation for 5G systems." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S134/document.
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Cette thèse a apporté une contribution au défi de la caractérisation des canaux radios en bandes millimétriques ainsi que la validation d'un outil de simulation déterministe à travers un grand nombre de campagnes de mesures réalisées dans divers scénarios représentatives. Des questions de recherche liées à la caractérisation des canaux radio en bandes millimétriques et sa prédiction à travers un outil de simulation déterministe ont été abordées. Fournir des résultats précis et reproductibles est nécessaire dans le développement d'un système de communication. Ce défi peut être relevé en réalisant des campagnes de mesures qui capturent la réalité du canal de propagation constituant le point de départ. Dans cette thèse, les principales motivations scientifiques derrière ces campagnes de mesures étaient d'étudier la variabilité dans le temps et l'effet de l'environnement sur le canal de propagation dans les bandes millimétriques. Les bandes de fréquences adressées dans cette thèse sont identifiées comme étant importantes par l'UIT en vue d'un futur déploiement de la 5G à savoir 15, 28, 32 et 83 GHz. Les environnements considérés sont une conférence room, bureau, bibliothèque et micro-cellulaire. Les campagnes de mesures ont été menées en utilisant un sondage de canal fréquentiel avec l'utilisation d'un analyseur de réseau. L'exploitation des résultats de mesures ont permis d'apporter des éléments de réponses concernant le canal de propagation dans ces bandes de fréquences. D'autre part, les données de mesures ont été utilisés pour évaluer les performances et contribuer à la calibration d’un simulateur de canal radio à tracé de rayons (RT) reposant sur une approche déterministe. Le simulateur de canal déterministe utilisé dans cette thèse incorpore les mécanismes de propagation tels que le LOS, la réflexion et la diffraction. Le RT a permis de prédire le canal de propagation dans les bandes millimétriques avec une concordance acceptable avec les données de mesures. Ces résultats démontrent que le canal de propagation en bandes millimétriques a pour avantage d'être prédit avec de simple outil déterministeThis thesis has contributed to the challenge of the radio channel characterizations in millimeter wave bands as well as the validation of a deterministic simulation tool through a large number of measurement campaigns carried out in various representative scenarios. Research questions related to the characterization of radio channels in millimetric bands and its prediction through a deterministic simulation tool were discussed. Providing accurate and repeatable results is necessary for the development of a communication system. This challenge can be meet by conducting measurement campaigns that capture the reality of the propagation channel and therefore constituting the starting point. In this thesis, the main scientific motivations behind these measurement campaigns were to study the time variability and the effect of the scattering environment of the propagation channel in the millimetric bands. The frequency bands addressed in this thesis are identified as important by the ITU for a future deployment of 5G, namely 15, 28, 32 and 83 GHz. The environments considered are a conference room, office, library and microcellular. The measurement campaigns were conducted using a frequency channel sounding technique with the use of a vector network analyzer. The exploitation of the measurement data provided some answers about the radio chennel propagation in these frequency bands. On the other hand, the measurements data were used to evaluate the performance and to contribute to the calibration of the ray-tracing tool (RT) based on a deterministic approach. The RT used in this thesis incorporates propagation mechanisms such as LOS, reflection and diffraction. The RT predicted the propagation channel in the millimeter bands with an acceptable level of agreement with respect to the measurement data. These results demonstrate that the propagation channel in millimetric bands has the advantage of being predicted with a simple deterministic tool
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Mason, Samuel P. "Atmospheric effects on radio frequency (RF) wave propagation in a humid, near-surface environment." Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5353.
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Approved for public release; distribution is unlimitedCurrently, the meteorological and physical phenomena associated with the various dynamic processes in the very near surface environment (for example, within the surface layer), are poorly understood. By properly characterizing what is happening in the real world, there is potential for obtaining an empirical formula that correlates well with real world data, and thus can be used as a means of quantifying these physical processes. This, in turn, can be used to more accurately model the effects of the atmosphere on RF waves. This thesis is an analysis of the propagation loss measurements taken from the Near Earth Propagation-6 (NEP-6), Panama City, FL, experiment in Aug 2009, where propagation loss was measured at 1768 MHz within a few wavelengths approximately (0.5 meters) of the surface. The results support and extend the near-surface, short range RF propagation conclusions drawn by Merrill et al. (2004). In particular, we focus on a novel technique that takes advantage of tidal sea level variation to continuously vary antenna height above the surface. Results confirm a strong dependence of propagation loss on antenna height similar to Merrill et al. (2004) observations.
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Lock, Wai Lek Willy. "Effects of radio wave propagation in urbanized areas on UAV-GCS command and control." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FLock.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2003.Thesis advisor(s): David C. Jenn, Jeffrey B. Knorr. Includes bibliographical references (p. 85-87). Also available online.
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Mason, Sammuel P. "Atmospheric effects on radio frequency (RF) wave propagation in a humid, near-surface environment." Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Mar/10Mar%5FMason.pdf.
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Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2010.Thesis Advisor(s): Guest, Peter S. ; Goroch, Andreas K. "March 2010." Author(s) subject terms: Electromagnetic propagation, electromagnetic scattering, groundwave propagation, mathematical techniques, variance reduction. Includes bibliographical references (p. 67-68). Also available in print.
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Rose, Scott Michael. "The Effect of Digital Elevation Model Resolution on Wave Propagation Predictions at 24Ghz." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32355.
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Digital Elevation Models (DEMs) are computer-generated representations of the earth's surface. These surfaces can be used to predicted Line-of-Sight (LOS) radio propagation. DEM resolution can affect the results of this prediction. This study examines the effect of DEM resolution on accuracy by comparing varied resolution terrain data for a portion of Blacksburg, Virginia using the prediction of ESRI's ArcView® viewshed algorithm. Results show that resolutions between one-meter and thirty-meters have little effect on the aggregate accuracy of the viewshed.Master of Science
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Fragoulis, Ioannis. "An investigation of two broadband HF shipboard communication antennas." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA245608.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Adler, Richard W. Second Reader: Vincent, Wilbur R. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Ship Antennas, Communication Antennas, Antenna Radiation Patterns, High Frequency, Multiwire Antennas, Theses. Author(s) subject terms: Inverted Cone Antenna, Computer Antenna Modeling, NEC, HF Antennas, Shipboard Antenna. Includes bibliographical references (p. 95). Also available in print.
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Wallace, Jon. "Modeling Electromagnetic Wave Propagation in Electrically Large Structures." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/91.
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Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of snow, (2) modeling an optical Bragg resonator, and (3) modeling the MIMO wireless channel.
First, complex snow media is analyzed with a hybrid FDTD/radiative transfer model. FDTD is used to compute phase matrices and extinction coefficients required for radiative transfer. Comparison with exact analytical methods proves the validity of the FDTD method for modest domain sizes ([5λ^3]) and number of Monte Carlo realizations (32). The method is used to illustrate a penetrating sphere model, which is not possible with existing analysis techniques. Backscatter from the resulting model is about 3 times higher than that of existing dense-medium theories, underlying the importance of exact characterization of the media.
Second, a hybrid FD/FDTD/S-parameter analysis is developed to model a large (10^4 section) optical Bragg resonator: a simple FD method computes propagation constants and field profiles, FDTD analysis provides reflection and transmission coefficients for the single section, and S-parameter analysis combines the sections to obtain the complete device response. A detailed study on error suggests that the method provides better than 2% accuracy in reflection and transmission response.
Third, a hybrid electromagnetic/SVA model is developed to study the indoor MIMO wireless channel. A MIMO measurement platform is discussed for simultaneous probing of up to 16 transmit and receive antennas, which was required to assess the validity of later modeling. FDTD or MOM antenna analysis coupled with the SVA model gives capacity predictions which match measured data. The model is used to explore the impact of antenna spacing, directivity, and polarization on channel capacity. Closely spaced antennas lead to an approximate halving of receive power. Directivity effectively doubles receive power for aligned transmit and receive. Dual polarization increases system capacity anywhere from 10% to 70%, depending on the spacing of elements and the amount of multipath richness. This analysis of MIMO systems underlines the need for models that describe both multipath richness and average receive power.
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Li, Kuo-Hui. "RF beamformers for high-speed wireless communications." Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/14768.
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De, Larquier Sebastien. "The mid-latitude ionosphere under quiet geomagnetic conditions: propagation analysis of SuperDARN radar observations from large ionospheric perturbations." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24770.
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The Earth's ionosphere is a dynamic environment strongly coupled to the neutral atmosphere, magnetosphere and solar activity. In the context of this research, we restrict our interest to the mid-latitude (a.k.a., sub-auroral) ionosphere during quiet geomagnetic conditions. The Super Dual Auroral Radar Network (SuperDARN) is composed of more than 30 low-power High Frequency (HF, from 8-18 MHz) Doppler radars covering the sub-auroral, auroral and polar ionosphere in both hemispheres. SuperDARN radars rely on the dispersive properties of the ionosphere at HF to monitor dynamic features of the ionosphere. Though originally designed to follow auroral expansion during active periods, mid-latitude SuperDARN radars have observed ground and ionospheric scatter revealing several interesting features of the mid-latitude ionosphere during periods of moderate to low geomagnetic activity. The past 7 years' expansion of SuperDARN to mid-latitudes, combined with the recent extended solar minimum, provides large-scale continuous views of the sub-auroral ionosphere for the first time. We have leveraged these circumstances to study prominent and recurring features of the mid-latitude ionosphere under quiet geomagnetic conditions.
First, we seek to establish a better model of HF propagation effects on SuperDARN observations. To do so, we developed a ray-tracing model coupled with the International Reference Ionosphere (IRI). This model is tested against another well established ray-tracing model, then optimized to be compared to SuperDARN observations (Chapter 2).
The first prominent ionospheric feature studied is an anomaly in the standard ionospheric model of photo-ionization and recombination. This type of event provides an ideal candidate for testing the ray-tracing model and analyzing propagation effects in SuperDARN observations. The anomaly was first observed in ground backscatter occurring around sunset for the Blackstone, VA SuperDARN radar. We established that it is related to an unexpected enhancement in electron densities that leads to increased refraction of the HF signals. Using the ray-tracing, IRI model, and measurements from the Millstone Hill Incoherent Scatter Radar (ISR), we showed that this enhancement is part of a global phenomenon in the Northern Hemisphere, and is possibly related to the Southern Hemisphere's Weddell Sea Anomaly. We also tested a potential mechanism involving thermospheric winds and geomagnetic field configuration which showed promising results and will require further modeling to confirm (Chapter 3).
The second ionospheric feature was a type of decameter-scale irregularity associated with very low drift velocities. Previous work had established that these irregularities occur throughout the year, during nighttime, and equatorward of both the auroral regions and the plasmapause boundary. An initial analysis suggested that the Temperature Gradient Instability (TGI) was responsible for the growth of such irregularities. We first used our ray-tracing model to distinguish between HF propagation effects and irregularity occurrence in SuperDARN observations. This revealed the irregularities to be widespread within the mid-latitude ionosphere and located in the bottom-side F-region (Chapter 4). A second study using measurements from the Millstone Hill ISR revealed that TGI driven growth was possible but only in the top-side F-region ionosphere. We found that initial growth may occur primarily at larger wavelengths, with subsequent cascade to decameter-scale with coupling throughout the F-region (Chapter 5).
In summary, the research conducted during this PhD program has established a robust method to analyze quiet-time SuperDARN observations. It also furthered our physical understanding of some prominent features of the mid-latitude ionosphere. It leaves behind a flexible ray-tracing model, multiple online tools to browse SuperDARN data, and a thorough and growing Space Science API providing access to multiple datasets, models and visualization tools.Ph. D.
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Parameswaran, Subramanian T. "Software for site specific propagation prediction." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06232009-063433/.
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Nzeribe, F. C. F. "Propagation and interference studies in broadcast frequency bands in Nigeria : The refinement of propagation data in tropical Africa, enabling African Broadcast Network planners to minimise interference and maximise spectral utilisation." Thesis, University of Bradford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381049.
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Motta, Marcelo Jorge de Assis. "Equivalent impedance of rough surface at low grazing angles." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA369420.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1999."September 1999". Thesis advisor(s): R. Janaswamy. Includes bibliographical references (p. 77). Also avaliable online.
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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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Blakaj, Valon, and Gent Gashi. "Implementation of a 3D terrain-dependent Wave Propagation Model in WRAP." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-36774.
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The radio wave propagation prediction is one of the key elements for designing an efficient radio network system. WRAP International has developed a software for spectrum management and radio network planning.This software includes some wave propagation models which are used to predict path loss. Current propagation models in WRAP perform the calculation in a vertical 2D plane, the plane between the transmitter and the receiver. The goal of this thesis is to investigate and implement a 3D wave propagation model, in a way that reflections and diffractions from the sides are taken into account.The implemented 3D wave propagation model should be both fast and accurate. A full 3D model which uses high resolution geographical data may be accurate, but it is inefficient in terms of memory usage and computational time. Based on the fact that in urban areas the strongest path between the receiver and the transmitter exists with no joint between vertical and horizontal diffractions [10], the radio wave propagation can be divided into two parts, the vertical and horizontal part. Calculations along the horizontal and vertical parts are performed independently, and after that, the results are combined. This approach leads to less computational complexity, faster calculation time, less memory usage, and still maintaining a good accuracy.The proposed model is implemented in C++ and speeded up using parallel programming techniques. Using the provided Stockholm high resolution geographical data, simulations are performed and results are compared with real measurements and other wave propagation models. In addition to the path loss calculation, the proposed model can also be used to estimate the channel power delay profile and the delay spread.