Browsing by Author "O'Keefe, Kyle Patrick Gordon"

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    Accuracy Assessment of Ultra-Wideband for a Site Safety Monitoring System
    (2016) Andolfo, Carlo; Sadeghpour, Farnaz; Dann, Markus; Jergeas, George Farage; O'Keefe, Kyle Patrick Gordon
    Construction has one of the highest rates of accidents among all industries worldwide. In Canada, 22% of workplace fatalities are recorded in the construction industry. An analysis conducted in this study showed that one of the main causes of accidents on construction sites is workers’ lack of awareness of proximity of danger. The objective of this study is to develop a Site Safety Monitoring System that helps improve safety on construction sites by providing safety status of workers in real-time. The system is composed of an available UWB Real-Time Locating System that estimates workers’ location on the site, and a Detection Model that detects when workers are in the proximity of danger using the provided location estimations. Laboratory experiments are conducted to measure the accuracy of UWB in tracking workers, and to examine the reliability of the model in detecting unsafe situations.
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    Design and Implementation of an RTK-based Vector Phase Locked loop in a GNSS Software Receiver
    (2017) Shafaati, Ahmad; Lachapelle, Gerard Jules; Lin, Tao; Moureldin, Aboelmagd MA; O'Keefe, Kyle Patrick Gordon; Ghannouchi, Fadhel; Aloi, Dan
    GNSS carrier phase tracking is very demanding and challenging. The focus of this thesis is to develop and test an innovative tracking loop with potentially better performance than existing loops in harsh environments. The proposed Double-Difference VPLL (Vector-based Phase Locked Loop) is assisted with base station observations to estimate carrier phase and carrier Doppler measurements at the rover station using information from a stationary base station. The double differencing operation eliminates or substantially reduces spatially and temporally correlated errors between base and rover receivers, leading to increased robustness. A backup layer operating in parallel that provides reference satellite measurements and enhances receiver sensitivity in also introduced. It is shown that the two tracking loop parts have complementary performance in the sense that the backup layer has a lower tracking jitter at high C/N0 values whereas the VPLL has superior functionality at low C/N0 values. Comprehensive mathematical derivations and analyses are described to quantify operations and advantages. The theoretical models are supported by a number of simulation scenarios. The proposed method is also assessed with GPS L1C/A IF samples obtained through hardware-in-the-loop simulations. The proposed method is compared with two other tracking methods, namely the scalar-based and VFLL assisted PLL loops in terms of tracking sensitivity and the probability of an integer ambiguity fixed solution for carrier phase positioning. It is shown through extensive simulations and real data that this algorithm results in better carrier phase availability in degraded environments.
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    Frequency Agile and Low Power Homodyne Radio Receivers
    (2018-05-29) Hasan, Abul; Helaoui, Mohamed; Belostotski, Leonid; Ghannouchi, Fadhel M.; Sesay, Abu-Bakarr; O'Keefe, Kyle Patrick Gordon; Wu, Ke
    More than 100 billion devices are expected to be connected wirelessly by 2020 as expected from the Internet of Things (IoT) and 5G deployments. Reconfigurability and sustainable power consumption are two of the major concerns to cope up with the expected changes. In the light of the above challenges, two low-power, frequency agile and broadband radio receiver architectures, namely, the six-port receiver (SPR) and the N-path passive mixer (P-M) receiver, have been explored in this thesis. First, a complexity reduced calibration approach for the SPR is developed that would reduce the power consumption of the SPR system. After analyzing the advantages and drawbacks of the SPR and the N-path P-M receiver architectures, a new quadrature phase shift frequency selective (QPS-FS) receiver architecture is proposed that attempts to retain the advantages of both the existing architectures while it tries to eliminate or minimize their drawbacks. The proposed QPS-FS receiver is a frequency selective architecture in which the desired band RF signal at the signal carrier frequency equal to the local oscillator clock frequency is frequency down-converted and quadrature (I/Q) demodulated while the in- and out-of-band blocker and interferer signals are reflected and collected that could be used for energy harvesting purposes. The thesis culminates in the proposal and implementation of a novel broadband, frequency reconfigurable, low power, blockers and system impairments tolerant energy harvesting radio receiver architecture that is frequency selective, concurrently utilizing the in-band RF signal for information decoding and the in- and out-of-band blocker and interferer signals for energy harvesting for increased battery-life or self-sustainable operation of the receiver system.
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    Investigating RTK using Geostationary Satellites and IRNSS
    (2017) Bhandari, Vimalkumar; O'Keefe, Kyle Patrick Gordon; Detchev, Ivan Denislavov; O'Keefe, Kyle Patrick Gordon; El-Sheimy, Naser M; Gao, Yan; Messier, Geoffrey; Macabiau, Christophe
    The IRNSS and SBAS constellations have geostationary satellites in the space segment. Geostationary satellites provide additional observations and are always visible to a given user. However, due to their small line-of-sight velocities, geostationary satellites have two unique challenges: Doppler collision and observability, both of which can affect their use in an RTK solution. The first phase of this research is aimed at understanding Doppler collision. It is a unique phenomenon in GNSS where tracking errors are introduced in the measurements due to cross-correlation between two or more satellites. Doppler collisions affect geostationary satellites for longer durations and the error resembles code multipath. If not mitigated, Doppler collision could have an impact on the ability to use code measurements of geostationary satellites in RTK positioning. This research describes likely conditions for Doppler collision, derives a Doppler collision error envelope for geostationary pseudorange measurements, and then demonstrates the effect using simulated and live signals. The second phase of this research presents the effect of Doppler collision on an RTK solution using geostationary satellites, with emphasis on ambiguity convergence time. Multiple mitigation techniques such as de-weighting of geostationary observations and use of narrow correlator are proposed to reduce the impact of Doppler collision. iii The third phase talks about the observability of a geostationary satellite. The relatively static nature of geostationary satellites leads to poor observability and has a direct impact on the convergence of ambiguities. The poor observability can limit the use of standalone constellations such as IRNSS in an RTK solution. Finally, an investigation is conducted on both hardware-simulated and live data of IRNSS to understand the impact of Doppler collision and observability. Mitigation methods are applied, and the improvement in the code measurement error and the convergence of ambiguities is presented. Overall, this thesis is aimed at addressing some of the key issues arising from the use of geostationary satellites in an RTK solution so that a multi-constellation RTK solution progresses one step closer to the possibility of an all-constellation RTK solution, including IRNSS.
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    Modeling High-Latitude Ionospheric Scintillations for Radio Occultation GPS Receiver Performance Analysis
    (2017) Najmafshar, Maryam; Skone, Susan; Gao, Yang; O'Keefe, Kyle Patrick Gordon; Knudsen, David J.; Datta-Barua, Seebany
    The performance of a radio occultation GPS receiver carrier tracking loop, subjected to ionospheric scintillations, is studied in this thesis. A physics-based simulation of high-latitude ionospheric disturbances for radio occultation signals has been employed to generate a variety of test cases to assess receiver performance. This scintillation simulator is built on an existing tool and is novel in allowing simulation of high-latitude ionospheric perturbations on multiple frequencies for radio occultation signals. Further, an experimental simulation method is developed which extracts scintillation-induced perturbations directly from real observations and applies them to a nominal GPS signal. Simulation results are validated against scintillation perturbations extracted from real radio occultation signals collected during solar maximum. The simulation approach is found to closely represent the real effects of scintillation. Scintillated signals are analyzed for effectiveness of detrending methods and selection of cutoff frequency for filtering scintillation data and capturing scintillation information. It is determined through spectral analysis that a higher cutoff frequency is required for filtering high-latitude scintillation signals. Also, scintillation measurements are dependent on the method applied for detrending. According to the studies conducted in this thesis, receiver tracking performance depends on both scintillation levels and the receiver mode (tracking versus acquisition). The receiver can track strong scintillation signals provided sufficient time to acquire signals pre-scintillations. Signal acquisition and tracking during scintillations, however, is challenging and might fail for severe scintillation conditions. Also, it is found that the presence of amplitude scintillation alone does not cause significant carrier performance degradation unless it is severe enough to reduce signal power below tracking threshold level leading to loss of lock. Strong phase scintillations, on the other hand, result in noticeable tracking loop performance degradation and measurement errors.