Signal Processing

Low-Complexity Spoofing Mitigation

December 1, 2011By
Figure 3. Null steering toward the spoofer signals.

Most anti-spoofing techniques are computationally complicated or limited to a specific spoofing scenario. A new approach uses a two-antenna array to steer a null toward the direction of the spoofing signals, taking advantage of the spatial filtering and the periodicity of the authentic and spoofing signals. It requires neither antenna-array calibration nor a spoofing detection block, and can be employed as an inline anti-spoofing module at the input of conventional GPS receivers. read more

This article is tagged with , and posted in GNSS, Receiver Design, Signal Processing

Innovation: Digging into GPS Integrity

November 1, 2011By
Inn-opener

Charting the Evolution of Signal-in-Space Performance by Data Mining 400,000,000 Navigation Messages
There are four important requirements of any navigation system: accuracy, availability, continuity, and integrity. In this month’s column we take a look at one particular aspect of GPS integrity: that of the signal in space and find out how trustworthy is the satellite ephemeris and clock information in the broadcast navigation message. read more

This article is tagged with , and posted in From the Magazine, GNSS, Innovation, Signal Processing

Lone Sentinel: Single-Receiver Sensitivity to RF Interference

July 1, 2011By
Tong_open2

Using signal-to-noise measurements from a single commercial-grade L1 GPS receiver, it is possible to detect interference or jamming that is above the thermal noise floor and below a power that causes loss of position. read more

This article is tagged with and posted in GNSS, Signal Processing

Future Wave: L1C Signal Performance and Receiver Design

April 1, 2011By
L1C-3

The new GPS L1C signal will be broadcast by the Block III satellites, with first launches as early as 2014. L1C innovations significantly enhance PNT performance as well as interoperability with other GNSS signals. The authors describe the benefits of its new features and how best to make use of each one. read more

This article is tagged with , , and posted in Receiver Design, Signal Processing

Innovation: Realistic Randomization

March 1, 2011By
Figure 3. Data collection, Gamla Stan (Old Town), Stockholm (route and street view).

New Way to Test GNSS Receivers
In this month’s article, we look at an approach to GNSS receiver testing that uses realistic randomization of signal amplitudes based on histograms of carrier-to-noise-density ratios observed in real-world environments. It can be applied to any simulator scenario, independent of scenario details (position, date, time, motion trajectory, and so on), making it possible to control relevant parameters such as the number of satellites in view and the resulting dilution of precision independent of signal-strength distribution. The method is amenable to standardization and could help the industry to improve the testing methodology for positioning devices — to one that is more meaningfully related to real-world performance and user experience. read more

This article is tagged with , , and posted in GNSS, Innovation, Signal Processing

Innovation: GNSS and the Ionosphere

February 1, 2011By
Figure 4. Photo of red and green auroras observed near Fredericton, New Brunswick, Canada (46 degrees north latitude) early on October 31, 2003. (Courtesy of Richard and Marg Langley.)

What’s in Store for the Next Solar Maximum?
Although the sun can become disturbed at any time, solar activity is correlated with the approximately 11-year cycle of spots on the sun’s surface. We are just coming out of a minimum in the solar cycle and headed for the next maximum, predicted to occur around the middle of 2013. How significantly will GNSS users be affected? In this month’s column, two ionosphere experts tell us what might be in store. read more

This article is tagged with and posted in From the Magazine, Innovation, Signal Processing

GNSS RF Compatibility Assessment: Interference among GPS, Galileo, and Compass

December 1, 2010By
Figure12

A comprehensive methodology combines spectral-separation and code-tracking spectral-sensitivity coefficients to analyze interference among GPS, Galileo, and Compass. The authors propose determining the minimum acceptable degradation of effective carrier-to-noise-density ratio, considering all receiver processing phases, and conclude that each GNSS can provide a sound basis for compatibility with other GNSSs with respect to the special receiver configuration. read more

This article is tagged with and posted in BeiDou/Compass, Galileo, GNSS, Signal Processing

Innovation: Record, Replay, Rewind

October 1, 2010By
opener-copy

Testing GNSS Receivers with Record and Playback Techniques
Is there a way to perform repeatable tests on GNSS receivers using real signals? This month’s column looks at how to use an RF vector signal analyzer to digitize and record live signals, and then play them back to a GNSS receiver with an RF vector signal generator. read more

This article is tagged with , and posted in From the Magazine, Innovation, Signal Processing