Monday, November 21, 2011

GPS versus LightSquared

           GPS              versus        logo
Most of you should be aware by now there exists controversy between the company known as LightSquared and the present users of the Global Positioning System (GPS) system. LightSquared is a company planning to provide a nationwide 4G-LTE open wireless super high speed broadband network for access to the Internet. The service will fill the gaps in present wireless (WIFI) coverage utilizing Inmarsat satellites built by Boeing as well as 40,000 dedicated ground stations.

The United States now ranks 18th among the countries in making internet connections available to its citizens.  LightSquared is aiming its services to improve the current situation and is currently before the Federal Communications Commissions (FCC) in an effort to approve its use of the frequencies that are close to the frequencies presently used by the GPS receivers.

Opposition to LightSquared plans have risen from the fact that their signals (more than a billion times stronger than the GPS and GLONSS signals) will interfere with the reception of GPS signals by some of the present receivers in use today. The opposition has taken the form of political concerns issued by members of congress as well as testimony and letters to the Federal Communications Commission (FCC) suggesting a denial.

Although most GPS related magazines have supported this denial a paper by JAVAD GNSS will provide a counter point to some of the arguments for denial.

The kinds of GPS receivers most likely to be affected are those used by surveyors for high accuracy measurements that use the Real Time Kinematic (RTK) technique which will result in an accuracy of plus or minus one centimeter.

When the authorities made the decision to accept the lowest powered GPS signals to be utilized, consideration should have been given to the possibility of the ramifications of this decision.  The very low power of the GPS signals makes them vulnerable to interference as well as being easily jammed. When the latest version of the Block III satellites are launched beginning in 2014, the signal strength will be increased by a factor of three.

However, as the signals to be used in LightSquared's service are more than a billion times stronger than the GPS signals, the increased power of the Block III satellites will have little effect.

As a result of recognizing the benefits that LightSquared will offer users of the internet, I have taken the position that LightSquared's efforts should be supported even though some of the present GPS receivers will have to be modified. This modification will cost owners of the affected units as little as $8 to as much as $8,000.  The higher cost is in those units used for high accuracy receivers.

It appears that LightSquared's signals will also affect the Russian Glonass system. but not as seriously. On the other hand, the impact on Galileo will be worse. So far, I have not read if they will affect China's Compass satellite navigation system or not.

The Federal Communications Commission has a difficult decision to make. As far as I know, there is no time line to let us know when the decision will be made.  The most recent technical report to the FCC confirms LightSquared signals interfere with GPS signals.   For a really interesting source of information on this issue, both pro and con, read the Forbes Magazine article as well as the comments to the story that was posted on December 21, 2011. The story will appear in the January 12, 2012 issue of Forbes Magazine.  Stay tuned:
See: LightSquared: GPS Community Has No Legal Gripe
Latest LightSquared comments from Aviation International News Alerts
...updated  Sunday, January 1, 2012