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Gunawardena S.,Air Force Institute of Technology | Pany T.,IFEN GmbH
27th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2014 | Year: 2014

During its January 2014 Meeting in San Diego, the Council of the Institute of Navigation approved the formation of a working group to establish a free and open standard for the exchange of GNSS software radio metadata. The goal of this effort is to promote interoperability between GNSS software defined radio (SDR) data collection systems and SDR processors. This paper reports early activities of the working group, including efforts to involve a representative cross section of the navigation community, requirements capture of various interests represented, draft technical details to date, and technical issues facing the committee. Copyright © (2014) by the Institute of Navigation All rights reserved.

Fritsche C.,IFEN GmbH | Klein A.,TU Darmstadt | Gustafsson F.,Linkoping University
IEEE Wireless Communications Letters | Year: 2013

A computational algorithm is presented for the Bayesian Cramer-Rao lower bound (BCRB) in filtering applications with measurement noise from mixture distributions with jump Markov switching structure. Such mixture distributions are common for radio propagation in mixed line- and non-line-of-sight environments. The newly derived BCRB is tighter than earlier more general bounds proposed in literature, and thus gives a more realistic bound on actual estimation performance. The resulting BCRB can be used to compute a lower bound on root mean square error of position estimates in a large class of radio localization applications. We illustrate this on an archetypical tracking application using a nearly constant velocity model and time of arrival observations. © 2012 IEEE.

Yin F.,TU Darmstadt | Fritsche C.,Linkoping University | Fritsche C.,IFEN GmbH | Gustafsson F.,Linkoping University | Zoubir A.M.,TU Darmstadt
IEEE Transactions on Signal Processing | Year: 2013

We consider time-of-arrival based robust geolocation in harsh line-of-sight/non-line-of-sight environments. Herein, we assume the probability density function (PDF) of the measurement error to be completely unknown and develop an iterative algorithm for robust position estimation. The iterative algorithm alternates between a PDF estimation step, which approximates the exact measurement error PDF (albeit unknown) under the current parameter estimate via adaptive kernel density estimation, and a parameter estimation step, which resolves a position estimate from the approximate log-likelihood function via a quasi-Newton method. Unless the convergence condition is satisfied, the resolved position estimate is then used to refine the PDF estimation in the next iteration. We also present the best achievable geolocation accuracy in terms of the Cramér-Rao lower bound. Various simulations have been conducted in both real-world and simulated scenarios. When the number of received range measurements is large, the new proposed position estimator attains the performance of the maximum likelihood estimator (MLE). When the number of range measurements is small, it deviates from the MLE, but still outperforms several salient robust estimators in terms of geolocation accuracy, which comes at the cost of higher computational complexity. © 1991-2012 IEEE.

Ioannides R.T.,European Space Agency | Pany T.,IFEN GmbH | Gibbons G.,Gibbons Media and Research LLC
Proceedings of the IEEE | Year: 2016

Global navigation satellite systems (GNSS) like GPS but also Galileo, GLONASS, and Beidou represent an important infrastructure to our society. They provide position and timing for numerous applications. A GNSS is a rather complex system consisting of around 30 satellites, a number of monitor stations, plus a control center. Billions of GNSS receivers represent the user segment. The receivers and the monitor stations receive a weak satellite radio signal and thus are susceptible to interference like jamming or spoofing. This paper outlines the core operation principles of satellite navigation to describe those kind of interference and to analyze the impacts. Different types of interference attacks result in different effects at the target receiver. The attack schemes are categorized within this paper. Reported incidents are summarized as well as the potential impact of GNSS vulnerability on critical infrastructure. Well known countermeasures at user receiver level or at system level are outlined and discussed for their suitability. The political and socioeconomic context of GNSS vulnerability is described emphasizing the large impact of a potential disruption of the GNSS service. © 2016 IEEE.

A well-known effect of multipath propagation is multipath fading that typically causes periodic signal variations. Such signal variations may become visible in some basic GNSS observables such as the code minus carrier observable, single or double differences or in C/N0 time series. The frequency of these variations-also called fading frequency or multipath phase rate-strongly depends on the multipath environment, i.e. on the actual geometric conditions which can be described by the location of the satellite causing the multipath signal and the reflector location with respect to the receiving antenna. This paper gives a detailed insight on the expected multipath phase rates in different multipath environments. Different geometric conditions are analyzed, from arbitrary reflector positions to the point of dealing with the special case of ground multipath. Fading frequencies are determined by means of an empirical approach using the characteristics of real satellite passes. The approach results in distributions of multipath phase rates which are computed for a multitude of possible reflector locations and from which minimum, mean and maximum multipath phase rates can be derived. © 2010 Springer-Verlag.

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