March/April 2011

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Road transport and location-based services will comprise a trillion-euro global market for core GNSS products during this decade, according to a European GNSS Agency study. This has inspired a number of efforts—such as the GNSS for INnovative Road Pricing (GINA) project — to develop practical applications using the European Geostationary Navigation Overlay Service (EGNOS) and GNSS.

The GPS community is seething over a January 26 decision by the Federal Communications Commission (FCC) giving a conditional go ahead to a new broadband network with the potential to overwhelm GPS receivers across the country. Dee Ann Divis reports from Washington, D.C.

Multiple satellite constellations and regional and augmentation systems raise new — and commercially strategic — questions for GNSS product designers and system integrators. Is it worth it to add additional signals to new receivers? How do technical differences among systems affect product development? And what about single-die receiver chip designs?

GPS vulnerability is in the news, and for good reason. GNSS receivers are highly susceptible to jamming and spoofing. Historically, signal jamming and efforts to protect against it have been considered a military problem. Today, signal interference threatens millions of GNSS civilian receivers as well. But antenna and receiver design options can mitigate or even eliminate the problem.

In order to capture GNSS signals indoors, receiver designers often use longer coherent integration intervals that supply the additional processing gain these weak signals require. But, in the field, users move their handsets around. And this erases any advantage, due to the spatial decorrelation of the multipath-faded GNSS signals. Here’s how University of Calgary researchers are attempting to solve the problem.

Like questionable genealogies that trace one’s roots back to some royal family or other, the LightSquared arguments beg the question of what its initiative means in the near future.

Tracking the carrier phase of GNSS signals has evolved into a widespread practice for achieving rapid and very accurate positioning. A key to this process is implementing a robust method for determining the number of carrier waves between a GNSS satellite and receiver, including any fractional wavelength, in a given signal transmission — so-called integer ambiguity resolution. Researchers have developed a variety of approaches for calculating the number of integers, but reliable means for testing and accepting the results of such calculations — a crucial factor for ensuring the integrity of such measurements — are not as well developed. This column introduces the principle of integer aperturte estimation and show how it can accomplish this goal.

Does the magnitude of the GNSS receiver clock offset matter?

Northern Hemisphere, Fernanda de Noronha Islands, Toulouse, Perth, Sendai