55,692 research outputs found
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A Testbed for Developing and Evaluating GNSS Signal Authentication Techniques
An experimental testbed has been created for developing
and evaluating Global Navigation Satellite System (GNSS)
signal authentication techniques. The testbed advances the state
of the art in GNSS signal authentication by subjecting candidate
techniques to the strongest publicly-acknowledged GNSS spoofing
attacks. The testbed consists of a real-time phase-coherent GNSS
signal simulator that acts as spoofer, a real-time softwaredefined
GNSS receiver that plays the role of defender, and
post-processing versions of both the spoofer and defender. Two
recently-proposed authentication techniques are analytically and
experimentally evaluated: (1) a defense based on anomalous
received power in a GNSS band, and (2) a cryptographic
defense against estimation-and-replay-type spoofing attacks. The
evaluation reveals weaknesses in both techniques; nonetheless,
both significantly complicate a successful GNSS spoofing attackAerospace Engineering and Engineering Mechanic
Recommended from our members
Considerations for Future IGS Receivers
Future IGS receivers are considered against the backdrop of GNSS signal modernization
and the IGS’s goal of further improving the accuracy of its products. The purpose of this paper is to
provide IGS members with a guide to making decisions about GNSS receivers. Modernized GNSS signals
are analyzed with a view toward IGS applications. A schedule for minimum IGS receiver requirements
is proposed. Features of idealized conceptual receivers are discussed. The prospects for standard commercial
receivers and for software-defined GNSS receivers are examined. Recommendations are given
for how the IGS should proceed in order to maximally benefit from the transformation in GNSS that
will occur over the next decade.Aerospace Engineering and Engineering Mechanic
Characterizing Power Consumption of Dual-Frequency GNSS of a Smartphone
Location service is one of the most widely used features on a smartphone.
More and more apps are built based on location services. As such, demand for
accurate positioning is ever higher. Mobile brand Xiaomi has introduced Mi 8,
the world's first smartphone equipped with a dual-frequency GNSS chipset which
is claimed to provide up to decimeter-level positioning accuracy. Such
unprecedentedly high location accuracy brought excitement to industry and
academia for navigation research and development of emerging apps. On the other
hand, there is a significant knowledge gap on the energy efficiency of
smartphones equipped with a dual-frequency GNSS chipset. In this paper, we
bridge this knowledge gap by performing an empirical study on power consumption
of a dual-frequency GNSS phone. To the best our knowledge, this is the first
experimental study that characterizes the power consumption of a smartphone
equipped with a dual-frequency GNSS chipset and compares the energy efficiency
with a single-frequency GNSS phone. We demonstrate that a smartphone with a
dual-frequency GNSS chipset consumes 37% more power on average outdoors, and
28% more power indoors, in comparison with a singe-frequency GNSS phone.Comment: Published in IEEE Global Communications Conference (GLOBECOM
SNR degradation in GNSS-R measurements under the effects of radio-frequency interference
©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Radio-frequency interference (RFI) is a serious threat for systems working with low power signals such as those coming from the global navigation satellite systems (GNSS). The spectral separation coefficient (SSC) is the standard figure of merit to evaluate the signal-to-noise ratio (SNR) degradation due to the RFI. However, an in-depth assessment in the field of GNSS-Reflectometry (GNSS-R) has not been performed yet, and particularly, about which is the influence of the RFI on the so-called delay-Doppler map (DDM). This paper develops a model that evaluates the contribution of intra-/inter-GNSS and external RFI effects to the degradation of the SNR in the DDM for both conventional and interferometric GNSS-R techniques. Moreover, a generalized SSC is defined to account for the effects of nonstationary RFI signals. The results show that highly directive antennas are necessary to avoid interference from other GNSS satellites, whereas mitigation techniques are essential to keep GNSS-R instruments working under external RFI degradation.Peer ReviewedPostprint (author's final draft
Tightly Coupled GNSS and Vision Navigation for Unmanned Air Vehicle Applications
This paper explores the unique benefits that can be obtained from a tight integration of a GNSS sensor and a forward-looking vision sensor. The motivation of this research is the belief that both GNSS and vision will be integral features of future UAV avionics architectures, GNSS for basic aircraft navigation and vision for obstacle-aircraft collision avoidance. The paper will show that utilising basic single-antenna GNSS measurements and observables, along with aircraft information derived from optical flow techniques creates unique synergies. Results of the accuracy of attitude estimates will be presented, based a comprehensive Matlab® Simulink® model which re-creates an optical flow stream based on the flight of an aircraft. This paper establishes the viability of this novel integrated GNSS/Vision approach for use as the complete UAV sensor package, or as a backup sensor for an inertial navigation system
Detecting Targets above the Earth's Surface Using GNSS-R Delay Doppler Maps: Results from TDS-1
: Global Navigation Satellite System (GNSS) reflected signals can be used to remotely sense
the Earth’s surface, known as GNSS reflectometry (GNSS-R). The GNSS-R technique has been applied
to numerous areas, such as the retrieval of wind speed, and the detection of Earth surface objects.
This work proposes a new application of GNSS-R, namely to detect objects above the Earth’s surface,
such as low Earth orbit (LEO) satellites. To discuss its feasibility, 14 delay Doppler maps (DDMs) are
first presented which contain unusually bright reflected signals as delays shorter than the specular
reflection point over the Earth’s surface. Then, seven possible causes of these anomalies are analysed,
reaching the conclusion that the anomalies are likely due to the signals being reflected from objects
above the Earth’s surface. Next, the positions of the objects are calculated using the delay and
Doppler information, and an appropriate geometry assumption. After that, suspect satellite objects
are searched in the satellite database from Union of Concerned Scientists (UCS). Finally, three objects
have been found to match the delay and Doppler conditions. In the absence of other reasons for these
anomalies, GNSS-R could potentially be used to detect some objects above the Earth’s surface.Peer ReviewedPostprint (published version
Retrieving Precipitable Water Vapor From Shipborne Multi‐GNSS Observations
©2019. American Geophysical UnionPrecipitable water vapor (PWV) is an important parameter for climate research and a crucial factor to achieve high accuracy in satellite geodesy and satellite altimetry. Currently Global Navigation Satellite System (GNSS) PWV retrieval using static Precise Point Positioning is limited to ground stations. We demonstrated the PWV retrieval using kinematic Precise Point Positioning method with shipborne GNSS observations during a 20‐day experiment in 2016 in Fram Strait, the region of the Arctic Ocean between Greenland and Svalbard. The shipborne GNSS PWV shows an agreement of ~1.1 mm with numerical weather model data and radiosonde observations, and a root‐mean‐square of ~1.7 mm compared to Satellite with ARgos and ALtiKa PWV. An improvement of 10% is demonstrated with the multi‐GNSS compared to the Global Positioning System solution. The PWV retrieval was conducted under different sea state from calm water up to gale. Such shipborne GNSS PWV has the promising potential to improve numerical weather forecasts and satellite altimetry
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