Browsing by Subject "Time resolutions"

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    Ionospheric total electron content estimation using IONOLAB method
    (IEEE, 2007) Nayir, H.; Arıkan, F.; Erol, C. B.; Arıkan, Orhan
    Ionosphere which is an important atmospheric layer for HF and satellite communications, can be investigated through Total Electron Content (TEC). Global Positioning System provides cost-effective means for TEC estimation. Regularized TEC estimation method (D-TEI) is developed to estimate high resolution, robust TEC values. The method combines measurements of GPS satellites above 10° elevation limit and estimates can be obtained with 30 s time resolution. In this paper, parameters that are used in D-TEI method such as ionospheric height, weighting function, and satellite receiver biases are studied. It is found that TEC estimation results of D-TEI method is almost independent of ionospheric height. Different weighting functions are tried and the weighting function that minimizes non-ionospheric effects is selected. By using satellite and receiver biases in the correct form consistent TEC estimation results are obtained with IGS analysis centers. In this paper, the method is improved to include phase measurements. Taking either pseudorange or phase measurements as input, high resolution, robust TEC estimates are obtained using D-TEI method.
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    Ultra-wideband range estimation: Theoretical limits and practical algorithms
    (IEEE, 2008-09) Güvenç, İ.; Gezici, Sinan; Şahinoğlu, Z.
    The high time resolution of ultra-wideband (UWB) signals enables wireless devices to perform accurate range estimation. In order to realize UWB systems with accurate ranging capabilities, both theoretical limits on range estimation and practical algorithms that approach those limits should be investigated. This paper provides a survey of various UWB ranging algorithms and discusses their performance and complexity tradeoffs. In addition, theoretical limits on range estimation are discussed in terms of Cramer-Rao and Ziv-Zakai lower bounds. Index Terms- Ultra-wideband (UWB), time-of-arrival (TOA) estimation, ranging, Cramer-Rao lower bound (CRLB), Ziv-Zakai lower bound (ZZLB). ©2008 IEEE.