Technical Article

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April 18, 2011

Keeping the Spoofs Out

The demand for techniques capable of authenticating the GNSS signals and detecting simulation attacks (spoofing) has increased exponentially in the last years, mainly targeted to financial and safety critical applications.

Associated proposals and developments addressing these issues focused on two different approaches: user segment authentication services that leveraged existing services in order to detect signal spoofing and that integrated signal authentication services into the GNSS system itself.

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By Inside GNSS
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March 14, 2011

Coherent Integration Time Limits

Equation: signal variance for a “ring of scatterers” model

Indoor GNSS propagation environments are characterized by multiple reflected signal paths (multipath) terminating at the receiver. Consequently, the received signal’s amplitude, phase, and perceived angle of arrival attributes vary randomly as the receiver moves. This has created significant interest among receiver designers and manufacturers to develop powerful processing for GNSS handsets such that these can operate effectively in indoor faded environments.

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By Inside GNSS

The Civilian Battlefield

Figures 1 & 2

For the complete story, including figures, graphs, and images, please download the PDF of the article, above.

Growing dependence on GNSS for positioning, navigation, and timing (PNT) has raised a parallel concern about the potential risks of signal interference. The popular press has recently highlighted accounts of car thieves using GPS jammers, solar flares pumping out L-band radiation, and faulty television sets causing havoc to GPS receivers across an entire harbor.

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By Inside GNSS

GNSS Inside Mobile Phones

Figure 1 & Table 1

For the complete story, including figures, graphs, and images, please download the PDF of the article, above.

Recent years have seen GPS receivers built in as a standard feature in many consumer products. A growing number of mobile phones, personal navigation devices, netbooks and tablets are equipped with GPS receiver chips and navigation software that enable consumers to navigate from A to B or find their nearest coffee shop. According to Berg Insight, annual shipments of GPS-equipped mobile phones are estimated to reach 960 million devices in 2014.

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By Inside GNSS
January 21, 2011

Spectrum-Compact Signals

FIGURE 1 (a, b, c) & FIGURE 2

For the complete story, including figures, graphs, and images, please download the PDF of the article, above.

In the early stages of developing space-based radionavigation, the spectrum compactness of ranging signals was not proclaimed among the material priorities. Conventional bi-phase shift keying (BPSK) modulations, although they consume a rather large amount of spectrum, were adopted as the basis for both GPS and GLONASS signals.

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By Inside GNSS
January 9, 2011

A Model-Based Approach

For the complete story, including figures, graphs, and images, please download the PDF of the article, above.

Galileo receiver designers require formal interface specifications for the Galileo signal-in-space (SIS) in order to write unambiguous and accurate specifications for Galileo receivers. To compute their positions, Galileo receivers must be able to retrieve timing and orbital information from the data stream conveyed in Galileo analog signals.

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By Inside GNSS
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