September 28, 2011 By Colin Wood
Others have tried and failed, but with a go-ahead pending from the FCC, one wireless broadband company is a step away from transforming the wireless industry. Backed by billionaire hedge fund manager Philip Falcone, Virginia-based LightSquared has signed a 15-year contract with Sprint Nextel and is ready to begin a cooperative eight-year network build-out that would provide terrestrial and satellite-based 4G-long term evolution (LTE) Internet service to 260 million Americans by the end of 2015.
But the contender has a powerful opponent. LightSquared operates in a band of radio frequency adjacent to GPS, raising fears that the new 4G service could interfere with GPS-based location systems used for public safety, aircraft navigation and other crucial tasks. Indeed, last year, LightSquared’s initial transmissions interfered with GPS receivers — prompting the company to cut both signal strength and the size of its operable spectrum in order to create a buffer between its 4G service and GPS signals.
Additional testing has not yet been done, but analysts predict the changes may eliminate the interference with standard GPS receivers. However, LightSquared still needs to eliminate interference with high-precision receivers, which improve the accuracy of hurricane and earthquake monitoring, as well as farming, construction and surveying equipment. These high-precision GPS receivers account for roughly .5 percent of GPS receivers used nationally.
The GPS industry is up in arms. It wants the FCC to move LightSquared elsewhere on the frequency spectrum in the name of public safety. LightSquared contends that the problems can be solved without relocating its signal. The Federal Aviation Administration (FAA) sided firmly with the GPS industry, issuing a report in July stating that 794 human fatalities would occur from 2014 to 2023 due to “LightSquared impacts to GPS,” and would cost taxpayers $72 billion in GPS retrofitting costs. LightSquared maintains that the GPS interference problems stem from a lack of foresight by GPS device manufacturers and noted that LightSquared is also concerned about the public safety ramifications. Will GPS and LightSquared find common ground?
Organizing the Band
Allowing LightSquared to build a full-fledged network in its current spectrum band — known as the Mobile Satellite Service or MSS band — doesn’t make any sense, contends Jim Kirkland, founding member of the Coalition to Save Our GPS. LightSquared’s current chunk of spectrum is a legacy of the company’s initial business plan to create a land-based network to fill gaps in satellite network coverage, Kirkland said, explaining that, “[In] spectrum planning and management, you put similar uses next to each other.”
In early September, the House Committee on Science, Space and Technology heard testimony from Scott Pace, director of the Space Policy Institute at George Washington University. Pace, who has been involved with GPS issues for more than 20 years, proposed that the FCC, Obama administration and Congress deny LightSquared operation in its current state and withdraw its license to operate in the MSS band.
Allowing LightSquared to operate without searching for alternate solutions, Pace said, violates the traditional organization of wireless spectrum and creates interference issues.
Pace proposed one solution — allowing LightSquared’s satellites to operate in their current spectrum location adjacent to GPS, but moving the company’s terrestrial service elsewhere on the spectrum. Space on the wireless spectrum may be hard to come by, he said, but jeopardizing a utility as important as GPS is not an option. “When it comes to spectrum efficiency, GPS is arguably the most efficient use of spectrum the world has ever seen,” Pace said. “Almost a billion people are currently benefiting from the 20 MHz GPS signal that is available today.”
As with any feud, the story of LightSquared’s open wireless broadband network and GPS changes dramatically depending on who’s telling it. In 2002, LightSquared and GPS industry representatives were on the same page when they drafted an agreement restricting any part of LightSquared’s signal from entering GPS frequencies. In the intervening years, several revisions were made to LightSquared’s plan through the FCC; some industry rules changed and now both parties are living with the reality that being a good neighbor is easier said than done. Determining who is in the wrong and what will happen next is a complex matter that will affect how much of the country connects to the Internet.
To help make sense of things is Alex Wyglinski, an assistant professor at Worcester Polytechnic Institute, who specializes in wireless spectrum and signal processing issues. “It’s kind of scary that they’re trying to do this so close to the GPS band,” he said. “The problem is, there’s not enough spectrum out there.”
Across the United States, 200 million cell phones are stuffed into purses, jammed into pockets and clipped to belts — and more are added every day. LightSquared simply is attempting to meet that connectivity demand, Wyglinski said. “The problem in modern society is that frequency is getting really crowded.”
Wireless signals aren’t well defined like cars driving down lanes on a highway, so every wireless signal automatically interferes with every other signal to some degree. But GPS is particularly vulnerable.
“GPS signals are ridiculously weak,” Wyglinski said. “The satellites are something like 20,000 kilometers up in space. When it reaches Earth, it’s an extremely weak signal. The signal from GPS is actually weaker than the thermal agitation of the electrons in the metal of the receiver.”
The only reason GPS works is because there are complex signal processing algorithms that distill the GPS signal from competing noise and interference within its frequency band. If GPS signals whisper, LightSquared signals scream — and that noisy neighbor could interrupt these quiet conversations.
LightSquared mitigated interference with standard GPS receivers by moving slightly away from GPS on the spectrum band and lowering signal strength. But this creates new problems for the company, Wyglinski said. Reduced signal power means weaker, spottier service for LightSquared customers, and creating a buffer zone — known as a guard band — means there is prime spectrum real estate that’s going unused. “It doesn’t make much business sense,” he said. “LightSquared is really stuck between a rock and a hard place.”
Another problem is the interference with high-precision receivers. If LightSquared can solve that issue, the GPS industry might be appeased. Jeff Carlisle, the company’s vice president of regulatory affairs, said LightSquared has been very cooperative, and now it’s the GPS industry’s turn to carry the onus.
Interference with high-precision receivers isn’t the company’s fault, Carlisle contends. “The GPS industry council asked us to limit our out-of-band emissions, so we did. We spent $9 million developing a filter that did that.”
What the GPS industry didn’t tell LightSquared, Carlisle said, was that high-precision receivers only work properly by reading signals outside the GPS band. In late August, the Information Technology & Innovation Foundation, an IT policy think tank, filed comments with the FCC supporting LightSquared’s claim that the commercial GPS industry is responsible for interference problems between GPS devices and LightSquared’s network. The foundation alleged that the manufacturers of high-precision GPS devices ignored government warnings and guidelines when they built their receivers, deliberately building devices that listen into the satellite L-band spectrum, which is where LightSquared wants to operate.
“The GPS people like to pretend this is something that started a couple of months ago, but they’ve known about this for 10 years,” Carlisle said.
LightSquared isn’t alone in its fight against the GPS industry. Many public interest groups and
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