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LightSquared proposes spectrum change to allay GPS concerns

o John Cox
24.06.2011 kl 14:42 | Network World (US)

LightSquared announced it will change its spectrum use and lower the power of its LTE radios, to allay concerns that the wholesale wireless network will interfere with GPS radios. But it may not be enough to satisfy the company's critics.


LightSquared Solutions has announced a change in its spectrum use, one that will fix potential interference with the U.S. Global Positioning System (GPS) which use some of the same frequencies.

The company says to allay interference concerns it will use a lower-frequency chunk of its 10MHz block of spectrum, further away from the GPS frequencies, and lower the maximum authorized power of its base stations by more than 50%. Just cutting the power levels could force the company to shoulder additional capital and real estate costs to deploy more base stations to cover the same area.

BACKGROUND: Lawmakers want to block LightSquared approval

It may not be enough for critics in a range of industries and the halls of the U.S. Congress. One industry group, formed to block LightSquared's proposed network in the Mobile Satellite Service (MSS) band, has already denounced the changes.

"This latest gambit by LightSquared borders on the bizarre," says Jim Kirkland, vice president and general counsel of Trimble, a founding member of the Coalition to Save Our GPS, in a statement from the coalition.

"LightSquared's supposed solution is nothing but a 'Hail Mary' move," according to the statement. "Confining its operation to the lower MSS band still interferes with many critical GPS receivers in addition to the precision receivers that even LightSquared concedes will be affected. The government results submitted to date already prove this, and the [pending] study group report will also confirm this. It is time for LightSquared to move out of the MSS band."

Coincidentally, the coalition this week released a report that analyzed the disruption and costs to the U.S. economy if the LightSquared network of 40,000 base stations interfered with the burgeoning use of GPS technology. The network "threatens direct economic costs of up to $96 billion to U.S. commercial GPS users and manufacturers," the report says.

"The downstream industries that rely on professional and high-precision GPS technology for their own business operations would face serious disruption to their operations should interference occur, and U.S. leadership and innovation would suffer," according to the report.

The issue of possible interference has been simmering for months. In a press release issued this week, before the coalition's economic report, LightSquared acknowledged, "Early test results indicated that one of LightSquared's 10MHz blocks of frequencies poses interference to many GPS receivers. This block happens to be the specific set of frequencies that LightSquared planned to use for the initial launch of its nationwide wireless broadband network."

The company concluded that a lower-frequency chunk of that same spectrum band was further away from the chunk used by GPS and "did not create such an interference risk," with one exception: a "limited number" of GPS receivers specifically designed to use it. This lower block was one that LightSquared planned to make use of two to three years from now.

The company apparently pushed through a deal with satellite company Inmarsat, which currently controls that alternative spectrum, to let LightSquared use that block much sooner than originally planned.

In addition, the company will modify its FCC license to reduce the maximum power of the base stations. Reducing the power reduces the range signals will carry, which in theory minimizes possible interference with GPS radios.

The company says it will "work closely" with both the FCC and the National Telecommunications and Information Administration, part of the U.S. Department of Commerce, and other agencies and groups to "explore mitigation possibilities and operational alternatives."

Whether that will be enough to stem the rising tide of opposition remains to be seen.

Three days after LightSquared's announcement, Rep. Thomas Petri, R-Wis., chairman of the House Subcommittee on Aviation, spoke Thursday at a hearing on LightSquared's network. He argued that the FCC "shouldn't approve service that disrupts or burdens global positioning system devices in the aviation industry," according to The Wall Street Journal.

"In aviation there's no room for error," Petri said. He added, according to the Journal, that it is important the FCC "does not approve plans that would introduce unacceptable risk into the aviation system or leave aviation GPS users with new, costly burdens."

LightSquared's original plan is to create a nationwide LTE network that would be opened to existing and new service providers, which could then offer a range of 4G services without having to buy spectrum and build the physical network themselves.

John Cox covers wireless networking and mobile computing for Network World.



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