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Crawford, Justin LuveneImpacts of Station Dependent Error Sources on the Implementation of the National Height Modernization Program
Master of Science, The Ohio State University, 2013, Civil Engineering
Accurate, reliable, and up-to-date heights are essential for a wide range of economic activities in many professions, including: surveying, engineering, emergency managers, Earth scientists, and natural resource managers [Veilleux, 2013b]. Historically, accurate orthometric heights have been obtained by tying into the control benchmarks of a vertical datum. Spirit leveling and gravity readings are used to establish, maintain, and update the heights of the benchmarks, which is a costly and time consuming process. Contemporary heights can also be established with the Global Positioning System (GPS) and can be combined with a geoid model for a quick and cost effective method of obtaining the orthometric heights used in a vertical datum. The National Height Modernization Program enables access to accurate, reliable, and consistent heights [Veilleux, 2013b]. This program is being employed by the National Geodetic Survey (NGS), with the goal of implementing a new vertical datum by computing the orthometric heights through the combination of GPS and gravimetric data. The expected result is a high accuracy vertical datum that will establish the orthometric heights with an accuracy that will be sufficient for a multitude of applications in science, engineering, mapping, etc. The accuracy of such a vertical datum is, therefore, dependent on the accuracy of the underlying GPS and geoid models and a better understanding of the error sources associated with the GPS ellipsoidal height and the geoid model may enable orthometric heights to be obtained with a high accuracy. This thesis will assume that an accurate geoid model exists and will focus on any inaccuracies in orthometric heights caused by the GPS-derived height. There are many error sources that may enter into the GPS observable, including: satellite and receiver clock errors, satellite orbit errors, atmospheric delays of the GPS signal caused by the ionosphere and troposphere, receiver bias, environmental multipath, and antenna phase center variation [Grejner-Brzezinska, 2011]. These error sources must be accounted for, if high accuracy heights are to be established through GPS. This thesis principally examines the effects of station dependent error sources, including phase center variations (PCV), far-field multipath reflection, and near-field multipath reflection [Berglund, 2011]. The effects of neglecting the PCVs particular to an antenna with a radome will be examined to see how much height deviation is caused by not properly accounting for how the radome alters signal reception at the antenna. The effects of multipath caused by the following near-field error sources will be examined: GPS signal interference caused by high voltage power lines, multipath reflection from a snow-covered field, the effects of a robin sitting on an antenna, and the effects of a seagull sitting on an antenna that will be modeled through simulation. In addition, an investigation will be conducted to analyze the level of height variation caused by using different antenna models to determine the height of the same point. The results of the near-field multipath experiments show that small changes in the snow depth of an area result in a consistent pattern of multipath, while drastic changes in the snow depth of the surrounding environment will alter the magnitude of the multipath reflection. Data collected around high voltage power lines suggests that major obstructions to a GPS signal could perhaps be avoided through site planning and using only those satellites less likely to be obstructed by the high voltage power lines. The test with the birds sitting on antennas showed that the amount of error a bird causes on GPS-derived heights depends on the size of the bird and that the error will eventually average out when the bird leaves the antenna, but will impact instantaneous height estimation in, for example, real-time kinematic (RTK) GPS applications.

Committee:

Dorota Grejner-Brzezinska (Advisor); Alper Yilmaz (Committee Member); Carolyn Merry (Committee Member)

Subjects:

Civil Engineering; Geographic Information Science

Keywords:

National Height Modernization program;GPS Station Dependent Error Sources;Vertical Datum;Orthometric Heights;Multipath;Near-Field Multipath;Far-Field Multipath;Antenna Phase Center Variation

Shukla, ManishTCP Performance With Multipath Routing in Wireless Ad Hoc Networks
MS, University of Cincinnati, 2003, Engineering : Computer Science
Majority of applications on the Internet today use TCP for reliable communication. TCP has been designed for and fine tuned to wired environments, but recent studies have shown that its performance suffers in wireless network environments, particularly in ad hoc networks because of the presence of multiple wireless hops. Routing has been the most focused area of research in recent years in wireless ad hoc networking area. Many on-demand routing protocols have been proposed to improve robustness in the face of link and route failures and facilitate packet transmission. Using multiple paths to route packets is one of them. We examine the performance of the TCP protocol with multiple paths in mobile ad hoc networks (MANETs). We set up multiple routes between the TCP source and destination either manually or using an on-demand multipath routing protocol, and forward packets on both paths to reduce the load on one single path. Ordinarily one would expect the multiple paths to reduce conflict between TCP data and acknowledgement packets thus giving better overall performance. Our results do incidate that TCP performance with multipath routing shows some improvement for long routes; however, shorter routes may experience slight degradation in performance as compared to single path routing. This observation remains true even when contention-based scheduling is used to schedule packets on different paths, or the multiple routes are chosen such that they have a minimum radio interference among themselves. We conclude that the TCP could gain only limited benefits with multipath routing.

Committee:

Dr. Samir R. Das (Advisor)

Keywords:

TCP over wireless; TCP over AD HOC Networks; multipath routing; TCP performance with multipath; multipath in wireless network

Said, Nezar AliPerformance analysis of multi-carrier code division multiple access system in multipath fading channels
Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

Performance analysis of multi-carrier code division multiple access system in multipath fading channels.

Committee:

Jeffrey Dill (Advisor)

Keywords:

multipath fading channels; Multipath Fading Channels; Rayleigh Channels

Li, KuangminEnhanced Distance Measuring Equipment Carrier Phase
Doctor of Philosophy (PhD), Ohio University, 2014, Electrical Engineering (Engineering and Technology)
Next Generation aviation, in short “NextGen,” requires an Alternate Positioning Navigation and Timing (APNT) system to back up the Global Navigation Satellite Systems (GNSS). Distance Measuring Equipment (DME) is a favorable APNT candidate but likely needs to be upgraded to enhanced Distance Measuring Equipment (eDME) to support the stringent NextGen aeronautical navigation requirements. This dissertation proposes, researches, and demonstrates eDME carrier phase, a key enabling technology that can dramatically improve the eDME system performance. eDME carrier phase provides line-of-sight displacement measurements with mm-level accuracy. After introducing the eDME carrier phase concept, this dissertation discusses the required changes for airborne and ground equipment. A novel flight test methodology is presented that allows evaluation of the eDME carrier phase performance without requiring changes to existing equipment. A spectrum-based carrier phase acquisition algorithm is presented next. Combined with several interference-mitigation techniques, this acquisition method demonstrates fault-free acquisition. Furthermore, a phase-locked loop (PLL) is designed for eDME carrier phase. A correction term is first proposed to modify the conventional PLL design to reduce the undesired loop stability and bandwidth changes when the loop noise equivalent bandwidth is close to the Nyquist frequency of the loop. This modified PLL is then further adapted to accommodate eDME’s random pulse timing. The carrier phase tracking results show dm-level errors for 110-km straight and level flights and for various banking maneuvers up to 60 degrees. These errors are further characterized and quantified. eDME carrier phase can be used in combination with the eDME pulse range to significantly improve the accuracy and integrity of the DME system. Several algorithms are introduced and the resulting improvement of the eDME accuracy and integrity performance are illustrated. Finally, DME-Next is proposed as a most feasible eDME architecture that fully utilizes the benefits of eDME carrier phase and demonstrates performance sufficient to meet the most stringent NextGen APNT navigation requirements.

Committee:

Wouter Pelgrum, Dr. (Advisor); Frank van Graas, Dr. (Committee Member); Maarten Uijt de Haag, Dr. (Committee Member); Sanjeev Gunawardena, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering

Keywords:

Avionics; PBN; APNT; Distance Measuring Equipment; enhanced DME; Carrier phase; Allan deviation; NDFT; PLL; Precise velocity; Carrier smoothed pulse range; Pulse-range-minus-carrier; Pulse noise multipath algorithm

Kapadia, SharvariCramer Rao Lower Bound and Maximum Likelihood Estimation for Multipath Propagation of GPS Signals
MS, University of Cincinnati, 2013, Engineering and Applied Science: Electrical Engineering
Multipath propagation refers to a phenomenon wherein a radio signal winds up taking two or more paths because the signal is reflected off buildings or other obstructions near the receiver, resulting in one or more secondary propagation paths. In a GPS receiver, multipath effect can cause a stationary receiver's output to indicate as if it were randomly jumping about or creeping. The presence of multipath generally causes errors in the phase or delay measurements, thereby degrading the navigation accuracy. The main attention of this thesis is on computation of Cramer Rao Lower Bound that expresses a lower bound on the variance of estimated signal parameters. Cramer Rao Bound is computed for amplitude, phase and time delay signal parameters by taking the diagonal components of the Fisher Information Matrix, which is a 66 matrix for a 2-path multipath model. The Fisher Information Matrix entries are computed by taking the expected value of the product of the partial derivatives of log-likelihood function with respect to the signal parameters. The next part of the thesis is estimation of the signal parameters from distorted received signal of the same 2-path model using Maximum Likelihood estimation theory. The values of estimated parameter variance computed from estimated signal parameters, are compared with the Cramer Rao Lower bound.

Committee:

H. Howard Fan, Ph.D. (Committee Chair); Eric T. Vinande, Ph.D. (Committee Member); Xuefu Zhou, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Cramer Rao bound;GPS signals;Multipath Propagation;Maximum Likelihood Estimation;Parameter Estimation;;

Pike, Cameron M.Multipath signal detection using the bispectrum
Master of Science (MS), Ohio University, 1990, Electrical Engineering & Computer Science (Engineering and Technology)
In this thesis we evaluate a new transient signal detector using bispectral analysis of the received data record. No a priori knowledge of the signal statistics is needed. In addition, we present new theoretical results prescribing upper limits to its performance. Also, results of computer simulations comparing this new approach to more conventional detectors are presented and evaluated.

Committee:

John Tague (Advisor)

Keywords:

Multipath Signal Detection; Bispectrum; Signal Statistics

Tuncay, OrbayWireless Strain Gauge System in a Multipath Environment
Master of Science, The Ohio State University, 2008, Electrical and Computer Engineering

A wireless strain sensing system utilizing passive, wireless, physically small and light weight sensors is desirable for measuring strain in harsh environments such as jet engine compressor and turbine blades. A cluttered and time varying environment results in high loss, blockage, multipath and modulation of the electromagnetic wave. Also, temperature changes affect the sensitivity of the strain measurement. Isolating the information signal from the reverberations in the environment requires time delays in the order of 100s of ns for jet engine environment. Therefore, a wireless strain gauge system that utilizes surface acoustic wave (SAW) strain sensors was studied and tested.

SAW strain sensors are designed to operate at 2.45GHz. Electron beam lithography is used to achieve minimum required feature size at this frequency. The fabrication process is outlined and scanning electron microscope images of some results are given.

A transceiver circuit is designed and constructed. The circuit is tested in free space, in the presence of signal blockage and a time varying channel. Measurements are shown to be in good agreement with predicted data. Sources of errors in the setup are identified to be leakage from transceiver circuit switches and bounce waveforms from the transceiver antenna.

A General Electric J85 jet engine compressor section is analyzed for signal propagation characteristics. Minimum frequency that can propagate through the compressor section is determined to be 5.2GHz. Measurements are done to show that circumferential polarization propagates stronger than radial inside the compressor section. An analytical approximation for the compressor section is generated by modeling compressor section blades as rectangular waveguides. Good agreement on cutoff frequency is achieved for circumferential polarization with the analytical predictions and measurement.

SAW temperature and strain sensors are measured in comparison to traditional gauges. This concept can be generalized to measuring many different physical quantities wirelessly without disturbing the operation of the equipment.

Committee:

Roberto Rojas-Teran (Advisor); Eric Walton K. (Committee Member); Jonathan Young D. (Committee Member)

Subjects:

Electrical Engineering; Engineering; Experiments

Keywords:

wireless strain sensor; surface acoustic wave (SAW); jet engine; multipath; RFID; strain gauge; wireless strain measurement; SAW fabrication; Lithium Niobate

Kalyanaraman, Sai K.High Accuracy GPS Phase Tracking Under Signal Distortion
Doctor of Philosophy (PhD), Ohio University, 2009, Electrical Engineering (Engineering and Technology)
Array signal processing is a viable method to provide protection against interference to the desired GPS (Global Positioning System) signal. Adaptive array processing can also be used to provide GPS multipath mitigation. As reported in the literature (Hatke, 1998), adaptive nulling to suppress interference can cause errors in the carrier phase and code phase measurements. The output of multi-element controlled reception pattern antennae (CRPA) may be subject to sizeable variations in phase patterns that arise from the application of non-trivial time varying adaptive array weights (Moelker, 1998). Part of this phase distortion can be compensated in the carrier phase tracking loop of the baseband GPS receiver processing. Classical approaches implement constrained beam steering mechanisms to control the phase of the array in the look direction. An alternative approach, using unconstrained adaptive array processing with compensation for the subsequent phase distortion of the GPS signal is demonstrated by the use of a software radio with results to support the theory. This unconstrained adaptive array implementation does not require attitude information and obviates the need for an attitude sensor such as an inertial reference unit. In addition to addressing carrier phase distortions due to adaptive array processing, this body of work evaluates the carrier phase distortion resulting from GPS signal multipath. Phase multipath characterization is performed for GPS receiver architectures that use typical baseband receiver processing designs (using coherent and non-coherent code tracking loops). Prior to this effort, scant attention had been given to validating carrier-phase multipath theory against GPS data (Brodin, 1996). A comprehensive phase multipath equation (Braasch & Van Dierendonck, 1999) which captures the true nature of carrier multipath is presented. Validation of this equation is carried out for wide and narrow correlator spacing within coherent and non-coherent code tracking architectures by comparing bench test data to theoretical predictions. In addition, data collected for non-zero multipath phase rates are presented. The impact of GPS receiver architecture on the mitigation of phase-rate multipath will be discussed.

Committee:

Michael Braasch, Ph.D. (Advisor); Maarten Uijt de Haag, Ph.D. (Committee Member); Gary McGraw, Ph.D. (Committee Member); Frank van Graas, Ph.D. (Other); James Rankin, Ph.D. (Committee Member); Daniel Phillips, Ph.D. (Committee Member); William Kaufman, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

GPS; Adaptive Array; MVDR; MV; CRPA; Carrier Phase; Multipath; Code Tracking

EDWARDS, KARLA ROBERTA LISASite-Specific Point Positioning and GPS Code Multipath Parameterization and Prediction
Doctor of Philosophy, The Ohio State University, 2011, Geodetic Science and Surveying

In spite of the fact that many multipath mitigation techniques are currently implemented in GPS hardware and firmware, there remains a post-receiver-processed multipath error which plagues GPS observations stored in the RINEX files. At static Continuously Operating Receiver Station (CORS) sites, this multipath error expresses sidereal periodicity by virtue of the repeated configuration of the GPS satellite relative to the ground-borne GPS antenna and its environment.

In this study, this repeatability was capitalized upon to investigate the multipath signal (its variability inclusive) generated at a highly multipath-prone Suominet CORS site (named SG03). In this regard, the multipath was parameterized using a Fourier Analysis and a Wavelet Analysis technique. The latter was found to capture in excess of 90% of the identified signal, outperforming the Fourier parameterization.

Therefore, investigation of an optimal multipath modeling technique (in this case using a third order one-dimensional Daubechies wavelet) served as a pre-cursor to the main focus of this study, that being to construct an Integrated Point Position and Multipath Prediction (IPPMP) algorithm at a static CORS site. To this end, five different IPPMP algorithms were developed in MATLAB based on three types of prior-information models, namely, the Extended Gauss-Markov Model, the Mixed Linear Model and the Random Effects Model. While it is true that other wavelet-based mitigation schemes (such as the trademarked Wavesmooth technique) exist, the implementation of this study emphasized both the mitigation as well as the inclusion of multipath parameters in the IPPMP schemes developed.

The results of this study suggest that use of an elevation-dependent variance model for the high frequency wavelet parameters (called wavelet details) is insignificant to the position determination. It was confirmed that the use of the Random Effects Model is useful where the prior information is actually bias-prone, this model being more suitable to high precision positioning applications. Inclusion of the multipath parameters in the IPPMP models did indeed improve the position determination capability, but only where the receiver coordinates were sequentially-updated– the influence of the prior coordinate values on the solution was greater than that of the multipath prior information. The solution convergence rate was understandably-higher the more accurate the initial coordinates.

Ultimately, the results of this study suggest that there is value in parameterizing the multipath signal at stationary CORS sites with the intention of minimizing the impact of the multipath on position determination at static locations.

Committee:

Dorota Grejner-Brzezinska, PhD (Advisor); Alper Yilmaz, PhD (Committee Member); Andria Bilich, PhD (Committee Member)

Subjects:

Applied Mathematics; Civil Engineering; Engineering; Mathematics; Meteorology; Remote Sensing; Statistics

Keywords:

GPS; multipath; mitigation; point positioning; wavelet analysis; Fourier analysis; Extended Gauss-Markov Model; Mixed Linear Model; Random Effects Model; CORS; prior information models; least squares adjustment

Yang, ZhenghongJoint time frequency analysis of Global Positioning System (GPS) multipath signals
Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

Joint time frequency analysis of Global Positioning System (GPS) multipath signals.

Committee:

Voula Georgopoulos (Advisor)

Keywords:

Global Positioning System; multipath signals; joint time-frequency analysis

Dickman, JeffSingle Platform Relative Positioning for Sensor Stabilization
Doctor of Philosophy (PhD), Ohio University, 2008, Electrical Engineering (Engineering and Technology)

Intelligence, Surveillance, and Reconnaissance (ISR) sensors such as radio detecting and ranging, laser detecting and ranging, electro-optic / infra-red, and other remote sensing activities are becoming increasingly dependent on their position and orientation in time and space. The higher dynamics of flight and the increased sensor requirements have led to the need for sensor stabilization by direct motion measurement. A stabilization system based on the Global Positioning System (GPS) can provide good performance, but high frequency ISR sensor pointing applications have led to the need for additional measurement bandwidth, accuracy, and robustness. Two significant issues will be addressed in this dissertation to improve the stabilization system robustness and accuracy at the mm level: GPS Carrier Phase measurement noise using inertial measurements and carrier phase multipath. Higher bandwidth requirements (i.e., hundreds of Hz) will be addressed with the incorporation of a high-rate inertial measurement unit. All concepts developed in this dissertation will be illustrated using real sensor data from either static aircraft tests on the tarmac or dynamic flight tests.

The work to be described in this document will expand the state-of-the-art in the area of navigation sensor noise reduction while preserving high measurement bandwidth. Coupling GPS and inertial measurements has demonstrated the required improvements in similar applications, but an approach was sought which was tailored for the stabilization application. This dissertation will examine both optimal and non-optimal coupling of navigation sensors to form optimized high-accuracy single-platform relative position measurements with the intent to coherently stabilize ISR sensors.

This dissertation also examines GPS carrier phase multipath as an error contributor in the ground calibration of the ISR sensor antenna baseline. Several indicators will be examined as a means to exclude satellites from the calibration data. Also, the narrowlane measurement combination technique will be used as a means to mitigate the remaining carrier phase multipath in the baseline solution.

The contributions of this work include a framework for the single-platform stabilization problem, sensor integration and alignment techniques for single-platform baseline stabilization, an inertial synthesized baseline technique for smoothing noise in the GPS measurements, multipath considerations pertaining to the ground-calibration of sensors, and a demonstration of the utility of the narrow-lane linear combination for dual frequency GPS noise and multipath reduction.

Committee:

Chris G. Bartone, PhD (Advisor)

Subjects:

Electrical Engineering; Engineering

Keywords:

GPS; INS; multipath; sensor stabilization; high accuracy relative positioning; navigation; carrier phase;

Katragadda, MaheshDesign and Simulation of a Planar Crossed-Dipole Global Navigation Satellite System (GNSS) Antenna in the L1 Frequency Band
Master of Science (MS), Ohio University, 2012, Electrical Engineering (Engineering and Technology)
The purpose of this research was to design and investigate the performance of a planar cross-dipole Global Navigation Satellite System (GNSS) receiver antenna to operate in GNSS L1 frequency band with multipath mitigation performance. First, a crossed-half-wavelength dipole antenna was designed to resonate centered at 1.6 GHz, and then various configurations were investigated and simulated. In an attempt to improve the antenna’s multipath mitigation performance, these various configurations included the addition of concentric rings in various numbers and sizes with the inclusion of cavity banking. Roger’s dual copper clad RO3010¿¿ material was used as a substrate for the design. The simulated cavity backing consisted of a thin block of Styrofoam¿¿ and Cumming’s RGDS-124 (microwave absorbing material) placed between the substrate and the ground plane (finite and infinite), simulated to increase the antenna performance. The prototype crossed-dipole antenna configurations were tuned and optimized based on the simulated results obtained from the Agilent’s Advanced Design System Momentum 2009U1 software. The S-parameters and radiation pattern results obtained from these simulations were compared and analyzed in MATLAB¿¿. The simulated antenna prototype performance is expected to meet the performance requirements for L1 GNSS receiver antenna.

Committee:

Chris Bartone, PhD (Committee Chair); Sanjeev Gunawardena, PhD (Committee Member); Simbo Odunaiya, PhD (Committee Member); David Ingram, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Multipath Mitigation; VSWR 2:1; ADS Momentum; GNSS L1 Frequency Band Antenna; Printed Dipole; Concentric Rings; 1.6 GHz; S-parameters

Mamidisetty, Kranthi KumarContour Guided Dissemination In Regular Multihop Networked Systems
Doctor of Philosophy, University of Akron, 2012, Computer Engineering

The problem of exploiting all the available shortest paths between a source and destination to improve Quality of Service (QoS) is deceptively simple. From prior work it is known that even when multiple shortest paths are available, a straightforward approach to using such paths will result in nodes along one of the paths handling more entities than the nodes along the other shortest paths. This phenomenon, called Loading, limits the QoS and warrants the design of new methods to better utilize the available paths. A contour was defined as the union of all the shortest paths between a source and a destination. It was also shown that contours have an interesting structure that depended on the number of neighbors of each node and the relative location of the source and the destination. This structure characterized the number of corner nodes, the length of the shortest paths, the number of shortest paths, the depth of the expansion region, and depth of the contraction region in graph theoretic terms. The structural characterization of contours was important both for precisely characterizing loading and for designing effective methods to exploit the paths available in the contours. However, several questions remained open.

This dissertation presents a new graph theoretic characterization of the structure of contours in regular mesh connected topologies when each node has three neighbors. This is a particularly interesting structure because it appears to be robust while making efficient use of the available resources. The results show that the structure of contours are severely affected by the relative location of the source and destination. This means that a small change in the location of either the source or the destination can dramatically change the structure of the contours and hence affect the QoS that can be achieved. The results here show that for over two-thirds of the source-destination pairs that are possible, the contours will have a pendant node, i.e., a node that is connected to only one neighbor - and this node is the bottleneck node that limits performance.

For a new application, it is possible to use different kinds of connectivity between the nodes - for example, nodes can have four neighbors, eight neighbors, six neighbors or three neighbors. Each choice has a cost associated with it and the choice critically affect the QoS. This dissertation presents empirical results that offer new insights into the Cost Vs. QoS tradeoffs in the design of mesh connected systems. These results show that the best throughput can be achieved when each node has six neighbors and the best latency is achieved when each node has eight neighbors. This dissertation also presents two applications that demonstrate how the structure of the neighborhoods and the structure of contours can be exploited to improve performance. The first application is in the domain of data aggregation - it is shown that the structure of neighborhoods help to identify cluster heads. The second application demonstrates how the structure of contours can be exploited to improve QoS in a Network-on-Chip that is central to the design of next-generation processors.

The third focus for this dissertation is to understand how to weaken the regularity assumption that was central to the graph theoretic characterizations. Given a system that does not have a regular topology, the discovery of contours is not a significant challenge because simple extensions of the classical shortest path algorithms will discover contours. However, it is difficult to characterize the structure of contours. In the absence of such a characterization, one needs to use a stochastic technique to improve QoS. It is shown that classical machine learning algorithms can effectively exploit the contours to improve QoS. It is first shown empirically that critical parameters that control the performance of the machine learning algorithm, namely the learning rate and feedback interval, depend on the topology. Next it is shown that when multiple contours overlap, the machine learning algorithm effectively spreads entities to improve QoS. Finally, empirical results also show that the machine learning algorithm exploits non-shortest paths to achieve the best possible QoS.

Committee:

Shivakumar Sastry, Dr (Advisor); Nathan Ida, Dr (Committee Member); Hamid Bahrami, Dr (Committee Member); Ali Dhinojwala, Dr (Committee Member); Dane Quinn, Dr (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Multipath Routing; Regular Mesh Topologies; Message Dissemination; Machine Learning

Bartone, Chris GregoryRanging airport pseudolite for local area augmentation using the global positioning system
Doctor of Philosophy (PhD), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)

The Local Area Augmentation System (LAAS) is being developed to support precision approach and landing operations in and about the local area surrounding an airport. The LAAS Program is currently under development by the Federal Aviation Administration (FAA) with Minimum Aviation System Performance Standards for the LAAS being developed by RTCA, Incorporated. The LAAS uses differential Global Positioning System (DGPS) and includes one or more airport pseudolites (APL) to increase the availability for certain installations.

This dissertation addresses the addition of a differentially corrected, ranging APL into a LAAS. Prior to this work, no ranging APL has been integrated into a prototype LAAS and demonstrated in a real-time flight environment showing that an increase in LAAS availability is feasible.

The APL requirements resulted in a prototype APL transmitting and receiving subsystem with a coarse-acquisition (C/A) code format that could be operated at any frequency within the L1 ± 10.0 MHz band.

To investigate the major APL error the developmental approach was performed in two phases. Phase I implemented an APL operating at a center frequency off-L1 and concentrated on multipath limiting. The Phase II on-L1 APL architecture implemented a unique pulsing, automatic gain control (AGC) and GPS Blanker technique in the common reception path to maximize APL signal tracking and minimize electromagnetic interference to DGPS.

To minimize ground multipath for the APL geometry, which is more severe than for GPS, a multipath limiting antenna (MLA) was designed, fabricated, and tested within a 4-month period. The implementation of this MLA concept was a first for APL applications and also contributed to the successful multipath limiting of ground multipath at the DGPS LAAS Ground Station. This effort successfully demonstrated that ground multipath can be limited (with low variance and no long-term bias) for the APL geometry and that suitable precision approach performance can be achieved.

For this effort a total of 11 flight tests with three test aircraft (Piper Saratoga, FAA Boeing 727, and Ohio University DC-3) and 14 distinct laboratory tests were conducted to produce the APL Subsystem Architecture, data, and system performance documented in this document.

Committee:

Frank van Graas (Advisor)

Keywords:

LAAS; APL; airport pseudolite; global positioning system; automatic gain control; multipath limiting antenna; local area augmentation system

Aloi, Daniel NicholasDevelopment and verification of a mathematical model to investigate the effects of earth-surface-based multipath reflections at a differential global positioning system ground reference site
Doctor of Philosophy (PhD), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

This dissertation investigates errors on the pseudorange observable due to earth-surface induced multipath reflections. This research is important to Differential Global Positioning System (DGPS) users since multipath at the ground reference site is the major source of error. The theory used to develop this model is described. The model is then verified with real GPS data for various surfaces. The verification procedure was designed such that it could test the model's ability to predict the amplitude, phase, and phase-rate-of-change for multipath reflections from various media. Furthermore, the model was subjected to various antenna polarizations. This research provides a database of measured multipath errors from various surfaces that may be encountered at a DGPS ground reference site.

Committee:

Frank van Graas (Advisor)

Keywords:

earth-surface multipath reflections; positioning system; pseudorange observable

Dickman, JeffreyMultipath limiting antenna design considerations for ground based pseudolite ranging sources
Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

The next generation of advanced aircraft landing system will utilize the Global Positioning System (GPS). The availabilityof GPS is augmented by the use of pseudolites "pseudo satellites." Pseudolites transmit a GPS-like signal that can be used as a ranging source in place of or in addition to ranging sources from a satellite. The Local Area Augmentation System (LAAS) is being used to further augment GPS for precision approaches and landings by using a concept known as Differential GPS (DGPS). One major error source in DGPS is due to transmitted signal reflections (multipath) off nearby obstacles. Efficient antenna design can be used to mitigate multipath by severely attenuating signals from negative elevation angles.

The research contained in this document was conducted in order to optimize the current wideband airport pseudolite (WBAPL) multipath limiting antenna (MLA) for pseudolite transmission in the LAAS. To that end, three phases of study were conducted. The first stage modeled the ground-to-air link between the WBAPL transmitting MLA and the reception antenna during approaches with an attempt to define optimal WBAPL antenna locations. The second stage was conducted to characterize the basic pattern requirements of the WBAPL transmitting MLA and sought to project a hypothetical coverage volume given a preliminary pseudolite antenna pattern. The third stage was performed to attain some level of validation for the new WBAPL MLA transmitting antenna pattern measured by an external contractor through the independent synthesis of a similar antenna radiation pattern.

Committee:

Chris Bartone (Advisor)

Keywords:

Aircraft Landing System; Global Positioning System; Multipath Limiting Antenna; Pseudolite; Local Area Augmentation System; Differential GPS

Kelly, Joseph MichaelFading multipath bias errors in global positioning system receiver tracking loops
Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)

Fading multipath bias errors in global positioning system receiver tracking loops.

Committee:

Michael Braasch (Advisor)

Keywords:

fading multipath; bias errors; global positioning system; receiver tracking loops

Kalyanaraman, Sai K.A comparative study of advanced multipath mitigating global positioning system receiver architectures
Master of Science (MS), Ohio University, 1999, Electrical Engineering & Computer Science (Engineering and Technology)

A comparative study of advanced multipath mitigating global positioning system receiver architectures

Committee:

Michael Braasch (Advisor)

Keywords:

global positioning system receiver; satellite constellation; multipath parameters

Ellinger, John DavidMulti-Carrier Radar for Target Detection and Communications
Doctor of Philosophy (PhD), Wright State University, 2016, Electrical Engineering
This dissertation considers the optimization of radar performance within the structure imposed by a coded Orthogonal Frequency Division Multiplexing (OFDM) format required to achieve an acceptable communication link. The dual goal of achieving both satisfactory radar and communication performance raises challenges that can be substantively addressed by combining phase coding and modulation techniques to provide the temporal and spectral structure necessary to implement simultaneous radar and communication operations. In particular, the specific techniques, as introduced within this dissertation, of using the Multi-Frequency Complementary Phase Coded (MCPC) sequences, as prescribed by Levanon and Mozeson, for simultaneous radar and wireless communication operations represent a novel contribution and offers a significant improvement in the study, implementation, and performance of dual use radar and communication waveforms and signal processing techniques. Specific contributions of this dissertation include: 1) as will be demonstrated, not all valid MCPC sequences can be used for data transmission, and, therefore, a subset of MCPC sequences are chosen with consideration to radar detection performance, 2) communication operation is improved through the introduction of an algorithm that enables Gray codes to be applied to MCPC sequences, 3) the orthogonality of MCPC sequences is exploited to overcome the effects of multipath fading and intercarrier interference, 4) a new detector type, termed the Beta detector, is developed for both communications operations and radar detection, 5) a radar detection method, termed Polar Signal Detection, is developed that combines the Beta detector with a traditional matched filter detector to achieve superior detection performance as compared to traditional Cell-Averaging Constant False Alarm Rate (CA-CFAR) detectors in multi-target environments, and 6) a novel method of measuring Doppler frequencies is introduced that is superior to the measurement performance of traditional radar systems.

Committee:

Zhiqiang Wu, Ph.D. (Advisor); Fred Garber, Ph.D. (Committee Member); Kefu Xue, Ph.D. (Committee Member); Bin Wang, Ph.D (Committee Member); Chi-Hao Cheng, Ph.D. (Committee Member); Vasu Chakravarthy, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

radar; communications; orthogonal frequency division multiplexing; OFDM; MCPC; multi-carrier; multi-carrier complementary phase codes; MCPC; polar signal detection; intercarrier interference; ICI; fading; multipath fading; beta detector; doppler

Brennan, StephenExploring Alternative Routes Using Multipath TCP
Master of Sciences, Case Western Reserve University, 2017, EECS - Computer and Information Sciences
Multipath TCP (MPTCP) is an extension to TCP which allows hosts to establish connections consisting of multiple TCP “subflows” that travel across different Internet paths. MPTCP it is based on the assumption that at least one communicating host is multi-homed. Meanwhile, the Internet contains considerable path diversity, and research has shown that routes chosen by the Internet’s routing infrastructure are not always the most efficient. Although mechanisms have been proposed which are designed to take advantage of detour routing, none can be applied to unmodified applications. In this thesis, we leverage MPTCP to allow unmodified applications on single-homed devices to use detour routes. We find that this mechanism is capable of significant bandwidth aggregation under appropriate network conditions.

Committee:

Michael Rabinovich (Advisor); Mark Allman (Committee Member); Vincenzo Liberatore (Committee Member)

Subjects:

Computer Science

Keywords:

mptcp; multipath tcp; detour routing; overlay networking; openvpn; netfilter; linux kernel; mptcp path manager

Braasch, Michael S.On the characterization of multipath errors in satellite-based precision approach and landing systems
Doctor of Philosophy (PhD), Ohio University, 1992, Electrical Engineering & Computer Science (Engineering and Technology)

This paper addresses the characterization of multipath errors in satellite- based precision approach and landing systems. Satellite-based navigation systems such as the NAVSTAR Global Positioning System (GPS) are currently being considered for use as precision approach aids. However, before these systems can reach full maturity the issue of multipath must be addressed. Multipath represents the dominant error source for the precision approach application.

The work presented in this dissertation provides insight into the range and behavior of multipath errors in satellite-based precision approach and landing systems. Multipath error has been shown to be a function of multipath strength, delay, phase and phase rate-of-change relative to the direct signal. These parameters have been characterized for the precision approach environment and have been shown to be capable of producing severe multipath error. In the absence of pathological multipath-producing obstacles, collected data reveals the Earth's surface to be the major multipath source.

Committee:

Frank van Graas (Advisor)

Keywords:

multipath errors; satellite-based precision approach; landing systems; NAVSTAR Global Positioning System

Kaur, JasmanRealizing Connectivity with Independent Trees in DAGs - An Empirical Study
MS, University of Cincinnati, 2012, Engineering and Applied Science: Computer Science

Reliability and fault tolerance are an important part of data gathering at a base station (sink) in a wireless sensor network. Due to the uncertain environments of the network it becomes necessary to have robustness and information security integrated into the routing schemes. Multipath routing using independent trees is an eective way to achieve it. In real world applications, every node of the network does not have homogeneous connectivity to the base station. A more practical approach and a recent research area is having heterogeneous node connectivity with independent trees which are not necessarily spanning. A recent algorithm, referred to as DAG Independent Trees that gives vertex independent trees in heterogeneously connected directed acyclic graphs (DAGs) is discussed.

The problem of realizing the vertex connectivity in independent trees is NP-complete. Therefore, an experimental analysis of the connectivity realized with independent trees given by the algorithm, and vertex connectivity from the nodes to sink is given. The results show that the algorithm nearly satises the condition that all nodes realize at least half the connectivity. A close approximation to the connectivity at more than half the nodes is achieved. In the case, when the algorithm does less than half the connectivity for most of the nodes, an optimization of the algorithm is given. The optimization over all permutations of the sink nodes is presented in the case when it does not fair well.

Committee:

Kenneth Berman, PhD (Committee Chair); Fred Annexstein, PhD (Committee Member); Anca Ralescu, PhD (Committee Member)

Subjects:

Computer Science

Keywords:

Connectivity;Independent trees;DAGs;Multipath Routing;Data gathering;Wireless Sensor Networks;

MADATHIL, DILIP KUTTYA MULTIPATH ROUTING FRAMEWORK FOR UNIFORM RESOURCE UTILIZATION WITH SERVICE DIFFERENTIATION IN WIRELESS SENSOR NETWORKS
MS, University of Cincinnati, 2003, Engineering : Computer Science
Most sensor network applications demand that the network have a long operational lifetime.This requires that energy efficient routing schemes be used while routing sensor data.In traditional routing schemes some nodes are utilized considerably more than the other nodes, which results in these energy constrained nodes becoming bottlenecks, thereby reducing the operational lifetime of the network. In this work we propose a Multipath routing protocol to avoid the creation of these bottleneck nodes. This protocol deterministically distributes the routing load on all nodes in the query region thereby creating a more stable and balanced network where all the nodes are at similar energy levels. Our simulations have shown a significant improvement in the operational lifetime of the sensor network. These networks are expected to find wide applicability and increasing deployment in coming years, as they enable reliable monitoring and analysis of the environment. Users of such a system will expect to get a real time warning when time-critical situations occur in the network and also to be able to retrieve any required information by issuing queries to the network. Our scheme classifies available paths based on their route length, so that time critical queries could be routed through low latency paths. We exploit the knowledge of the nature of queries to determine which path would be most suitable for fulfilling the application specific requirements. The routes assigned to non-critical query traffic are dynamically adapted at run time to balance the excess load generated by the critical queries along minimum delay routes.

Committee:

Dr. Dharma Agrawal (Advisor)

Subjects:

Computer Science

Keywords:

sensor networks; multipath routing; energy efficient; service differentiation; ADHOC wireless

TALESARA, ANKITSIMULATION/ANALYSIS OF MODULATION SCHEMES FOR UWB IN PRESENCE OF MULTIPATH AND MUI
MS, University of Cincinnati, 2003, Engineering : Electrical Engineering
Many wireless technologies exist today to support specific applications. Ultrawideband (UWB) fits into wireless personal area network (WPAN) category Communication over the indoor wireless channel is a technical challenge because it is varies from place to place and signal suffers from heavy multipath propagation. UWB systems operate in the power limited region and not in bandwidth limited region. This fundamental difference has significant impact on the design of modulation and coding techniques. We have compared the performance of two new modulation schemes, namely, time hopping - binary phase shift keying (TH-BPSK) and time hopping - binary phase shift keying - pulse position modulation (TH-BPSK-PPM) with the existing one time hopping - pulse position modulation (TH-PPM) over different channel models. The BER performance was analyzed for these modulation schemes in presence of MUI and multipath interference. Finally, conclusions are drawn and some future research directions are suggested.

Committee:

Dr. James Caffery, Jr. (Advisor)

Keywords:

UWB; ultra wideband; multipath; modulation

Smallcomb, Joseph MichaelSpread spectrum communication over a fading multipath HF channel using transform domain signal processing and a transmitted reference signal
Doctor of Philosophy (PhD), Ohio University, 1992, Electrical Engineering & Computer Science (Engineering and Technology)

This dissertation presents a method of spread-spectrum modulation which we call Transform Domain / Cyclic Code Shift Keying (TD/CCSK). This system uses CCSK modulation in conjunction with a digital receiver which is implemented almost entirely in the transform domain. While the computational load of this approach is relatively high, it is achievable with current microprocessor technology. It is believed that this type of modulation offers a number of significant performance advantages over more conventional spread spectrum systems, especially on multipath and/or fading channels.

The TD/CCSK modulation scheme is introduced and several possible variations of the receiver structure for this system are presented. It is shown that for any channel with a known, time invariant impulse response, the TD/CCSK scheme can achieve a bit error performance of M-ary orthogonal signalling. It is also shown that when the channel impulse response is time varying, the use of a transmitted reference signal may be beneficial. Performance bounds are derived for the transmitted reference system, assuming a perfect reference estimate and an instantaneous reference estimate as the limiting cases of interest. Frequency Domain Interleaving, Tail Clipping, Center Clipping and Time Averaging are also presented, which improve performance of the basic TD/CCSK scheme. Performance bounds with these improvements are derived for the transmitted reference system. We also identify three possible families of CCSK base vectors which result in simulated performance near the theoretical predictions.

Committee:

Jeffrey Dill (Advisor)

Keywords:

Spread spectrum communication; multipath HF channel; transform domain signal processing transmitted reference signal

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