Isn’t it fantastic when you find yourself seated on an aircraft next to a person who knows something about your industry? That’s how I felt on a recent Delta Air Lines flight from Newark to Atlanta (my first stop before heading to visit AeroMobile in London and later #AIX11 in Hamburg).
My seatmate, engineer Tim Cailloux, works as a supervisor at Panasonic (the parent). In addition to chatting about in-flight entertainment (naturally) and in-flight Wi-Fi (he’s a regular Aircell Gogo user), we touched on the controversy surrounding LightSquared’s plans to deploy 40,000 high-power transmitters beginning this year, and what that means for GPS interference.
Since this topic falls squarely outside my regular scope, I asked Tim to write a guest blog to break things down for the average Joe (or Mary) and he graciously obliged.
Lightsquared, a company that’s been around in one form or another for several years, is creating a new 4G wireless network in a novel way. They are using radio frequencies allocated for satellite use to build out a ground-based wireless network that is augmented by satellite coverage. Lightsquared has come under fire from the aviation community for creating the potential for interference with GPS receivers. But, before I talk about Lightsquared, I’m going to talk about XM Radio.
I love XM radio. Their XM-WX in-flight weather data revolutionized aeronautical decision making. And I, along with 20 million others, have satellite radio in my car. XM primarily transmits its radio stations using satellites. But XM doesn’t limit itself to satellites because tall buildings prevent the small antenna on your car from seeing the satellite. To fill in the shadows caused by buildings, XM installed ground-based transmitters. The radio in your car receives both signals and automatically switches between the two of them, depending on which one is stronger. XM has done for years what Lightsquared is attempting.
So, back to Lightsquared. The difference between XM and Lightsquared, and the cause for all the recent commotion, is that Lightsquared’s frequencies are directly adjacent to the frequencies used by GPS. Garmin, and several other companies that rely heavily on GPS, have performed tests that show there’s the potential for a GPS receiver to lose the signal if it gets near a Lightsquared ground transmitter. That’s because the strength of the signal from the ground stations is so much stronger than the signals from satellites.
The real problem here is that, 15 years ago, nobody at the FCC envisioned that someone would use this spectrum to create a nationwide 4G network. At the time, we didn’t even know we were dealing with 1G. (Think Michael Douglass’s phone in Wall Street.) Usage of the spectrum was supposed to be harmonized. Adjacent licensees were supposed to be doing about the same stuff with approximately the same transmitter power.
That’s not the case here. Lightsquared’s “out of character” use of the spectrum is in the worst possible place, located right next to GPS. I’m sure Lightsquared would be much happier if their spectrum was almost anywhere else.
Lightsquared has a June deadline to work with the GPS industry to figure out how they can operate their ground stations without impacting GPS. Lightsquared has pledged $20M to fund the necessary studies to develop appropriate countermeasures to interference. The opposition insists that the FCC prohibit any operation of the network until interference is prevented. Ultimately, I don’t think there will be interference when the system goes live; GPS is a core component of the FAA’s NextGen air traffic control system and is central to our lives in many ways.
When I got first got XM, I grumbled about losing signal in cities. But I still gladly spent $10 per month for service. I don’t know that I would have the same patience for Lightsquared if they caused my GPS to stop working. I really hate getting lost. At least I can listen to XM while waiting for my GPS to finish recalculating.