[time-nuts] LightSquared testing
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Sun May 15 09:53:04 UTC 2011
Testing of new wireless network could cause GPS outages
ED ANDRIESKI / AP
By Karoun Demirjian, Steve Kanigher
Sat, May 14, 2011 (9:09 p.m.)
A warning for night drivers: If your GPS navigator gives out on you this week, don’t despair. What you’re experiencing is only a test of the emerging broadband system.
Starting Monday, broadband developr LightSquared will start testing its planned 4G speed wireless network in the Las Vegas area. The test will run after midnight for several hours for 10 days, and if it works, Las Vegas could become one of the first U.S. cities to get on a super-high speed Internet grid that’s independent of any particular service provider.
But if it fails, government agencies warn that it could compromise or even black out the GPS systems in the area, rendering temporarily useless everything from your car’s navigator to the systems that allow airplanes to come in for a safe landing.
LightSquared’s plans have caused some consternation in Washington, D.C., since January, when the company received conditional authorization from the Federal Communications Commission to build a system of tens of thousands of ground transmitters from which to run this broadband network.
The problem is one of bandwidth. The frequency LightSquared plans to send ground-based wireless signals through directly bumps up against the one satellites use to transmit the much weaker Global Positioning System, or GPS, signals — and lab tests have shown there’s a pretty good chance that in the vicinity of those transmitters, those signals are going to get crossed.
“There are definitely interference effects,” Tony Russo, director of the National Coordination Office of Space-Based Positioning, Navigation, and Timing told a meeting of the GPS Partnership Council in Los Angeles last week, according to a report in the trade magazine InsideGNSS. “The question is how much and for what kinds of receivers.”
That’s exactly the question that Nevada’s air traffic, emergency services, and military outfits are trying to answer.
Late last week, the Federal Aviation Administration alerted pilots that “the GPS signal may be unreliable or unavailable” within a nearly 300-mile radius of Boulder City, where the test transmitter will be located, from 11 p.m. to 5 a.m. local time daily from Monday to May 27.
Nellis Air Force Base has plans for two military exercises during the period in which the testing is to take place involving air support units that rely on the use of GPS technology.
“Anything that affects operations is of concern,” said Nellis spokesman Charles Ramey. “We rely heavily on GPS to accomplish our mission.”
But Las Vegas public safety personnel are shrugging off suggestions that the test is cause for concern.
“GPS is really nice, but we’ve got a backup,” said Las Vegas Fire & Rescue spokesman Tim Szymanski. “We might be a little bit inconvenienced, but we’re not going to lose anything on the call.”
Fire trucks and police cars are hooked with GPS units to help officers respond to distress calls, but it’s really just an added level of insurance that’s mostly for convenience, officials said.
“All of our officers know how to read a map,” said Metro Police spokesman Bill Cassell. “They know how to look up an address, find that address on a map, and then drive to it ... and we even still know how to triangulate off of mountaintops and give aircraft cardinal bearings to help land search-and-rescue mission flights.”
Potential GPS outages may pose the greatest risk, it seems, to noncommercial pilots.
“The traveling public has nothing to worry about with these tests,” said Chris Dancy, spokesman for the Aircraft Owners and Pilots Association. “But this is something that noncommercial pilots need to be aware of...They’ll need alternative means of communication.”
The difference exists because commercial pilots are able to rely on navigational beacons and other radio communications equipment predating GPS that they use regularly; recreational pilots aren’t usually geared up with as much finely calibrated backup equipment. Thus in February, the association wrote to the FCC in a legal complaint to say the threat LightSquared’s project posed to the general aviation industry was “unconscionable.”
In March, the deputy secretaries of the Departments of Defense and Transportation, which houses the FAA, sent a letter to the FCC’s chairman, demanding he better explain why concerns about the potential for GPS interference hadn’t been addressed.
Lawmakers have jumped into the mix, too.
Last week, Rep. Mike Turner, a Republican from Ohio, inserted a provision into the national defense authorization bill requiring the defense secretary to notify Congress if there’s a potential for widespread interference with GPS, which is critical to several military functions.
In the Senate, Iowa Republican Chuck Grassley also chided the FCC for expediting LightSquared’s application before GPS concerns were resolved.
On April 5, the FCC issued a report that said, among other things, that “responsibility for protecting services rests not only on new entrants but also on incumbent users themselves, who must use receivers that reasonably discriminate against reception of signals outside their allocated spectrum.”
The FCC also stated that projects like LightSquared had been “anticipated in the L-band for at least eight years.”
LightSquared calls its broadband “L band 1,” and it operates on frequencies between 1525 MHz and 1559 MHz. That’s where GPS picks up: It operates from 1559 MHz to 1610 MHz.
Early this year, personal car navigation systems manufacturer Garmin conducted tests showing GPS receivers’ signals started getting jammed at frequencies toward the upper end of that spectrum.
Tests showed that the kind of GPS receiver in a personal vehicle started getting jammed about 3.5 miles from a ground transmitter modeled after LightSquared’s specifications. By the time the receiver was within two-thirds of a mile of the transmitter, it stopped working.
With aviation use, jamming started even earlier: at almost 14 miles away, and the receiver lost the signal completely around 5.6 miles from the transmitter.
LightSquared, which didn’t return calls for comment Saturday, says on its website that it is simply taking steps to fulfill President Barack Obama’s dream of a country where wireless Internet can reach every city, county and farm.
LightSquared, which will operate as a wholesaler, plans on launching the commercial phase of its 40,000-tower plan in the second half of this year. It expects to reach 100 million Americans by the end of 2012 and 92 percent of the country by 2015.
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