International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / This paper summarize range error caused by instability of transmission characteristics and change of signal frequency and amplitude. On the basis of transmission system's modulation-demodulation combined characteristic, amplitude-frequency characteristics even symmetry, phase-frequency characteristics odd symmetry, phase orthogonality of demodulator, author analyses influence of factors on range accuracy. And formulas of phase of ranging tone are derived. Using these formulas, the many factors having influence on drift range error may be calculated, and range accuracy can be improved. Above conclusion has been testfied and applied in TT&C system for years.

Geometric errors may compromise the quality of radiation therapy treatments. Optimization methods that account for errors can reduce their effects. The first paper of this thesis introduces minimax optimization to account for systematic range and setup errors in intensity-modulated proton therapy. The minimax method optimizes the worst case outcome of the errors within a given set. It is applied to three patient cases and shown to yield improved target coverage robustness and healthy structure sparing compared to conventional methods using margins, uniform beam doses, and density override. Information about the uncertainties enables the optimization to counterbalance the effects of errors. In the second paper, random setup errors of uncertain distribution---in addition to the systematic range and setup errors---are considered in a framework that enables scaling between expected value and minimax optimization. Experiments on a phantom show that the best and mean case tradeoffs between target coverage and critical structure sparing are similar between the methods of the framework, but that the worst case tradeoff improves with conservativeness. Minimax optimization only considers the worst case errors. When the planning criteria cannot be fulfilled for all errors, this may have an adverse effect on the plan quality. The third paper introduces a method for such cases that modifies the set of considered errors to maximize the probability of satisfying the planning criteria. For two cases treated with intensity-modulated photon and proton therapy, the method increased the number of satisfied criteria substantially. Grasping for a little less sometimes yields better plans. In the fourth paper, the theory for multicriteria optimization is extended to incorporate minimax optimization. Minimax optimization is shown to better exploit spatial information than objective-wise worst case optimization, which has previously been used for robust multicriteria optimization. The fifth and sixth papers introduce methods for improving treatment plans: one for deliverable Pareto surface navigation, which improves upon the Pareto set representations of previous methods; and one that minimizes healthy structure doses while constraining the doses of all structures not to deteriorate compared to a reference plan, thereby improving upon plans that have been reached with too weak planning goals. / <p>QC 20130516</p>

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Multipath remains a dominant error source in Global Positioning System (GPS) applications that require high accuracy. With the use of differential techniques it is possible to remove many of the common-mode error sources, but the error effects of multipath have proven much more difficult to mitigate. The research aim of this work is to enhance the understanding of multipath propagation and its effects in GPS terrestrial applications, through the modelling of signal propagation behaviour and the resultant error effects. Multipath propagation occurs when environmental features cause combinations of reflected and/or diffracted replica signals to arrive at the receiving antenna. These signals, in combination with the original line-of-sight (LOS) signal, can cause distortion of the receiver correlation function and ultimately the discrimination function and hence errors in range estimation. To date, a completely satisfactory mitigation strategy has yet to be developed. In the search for such a mitigation strategy, it is imperative that a comprehensive understanding of the multipath propagation environment and the resultant error effects exists. The work presented here, provides a comprehensive understanding through the use of new modelling and simulation techniques specific to GPS multipath. This dissertation unites the existing theory of radio frequency propagation for the GPS L1 signal into a coherent treatment of GPS propagation in the terrestrial environment. To further enhance the understanding of the multipath propagation environment and the resultant error effects, this dissertation also describes the design and development of a new parabolic equation (PE) based propagation model for analysis of GPS multipath propagation behaviour. The propagation model improves on previous PE-based models by incorporating terrain features, including boundary impedance properties, backscatter and time-domain decomposition of the field into a multipath impulse response. The results provide visualisation as well as the defining parameters necessary to fully describe the multipath propagation behaviour. These resultant parameters provide the input for a correlation and discrimination model for visualisation and the generation of resultant receiver error measurements. Results for a variety of propagation environments are presented and the technique is shown to provide a deterministic methodology against real GPS data. The unique and novel combined modelling of multipath propagation and reception, presented in this dissertation, provides an effective set of tools that have enhanced the understanding of the behaviour and effect of multipath in GPS applications, and ultimately should aid in providing a solution to the GPS multipath mitigation problem.