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LightSquared cans spectrum plans in GPS fix

Tue, 06/21/2011 - 8:05am
Maisie Ramsay, Wireless Week

LightSquared said Monday it would largely abandon its own spectrum assets to address problems with GPS interference, an issue that has threatened to derail the venture-backed company's plans for a wholesale LTE network.

LightSquared plans to use spectrum leased under an existing contract with Inmarsat instead of its own L-band spectrum until it can figure out how to use its own bandwidth without affecting GPS.

The company also said its base stations will transmit their signals at half strength to further minimize interference.

"This is a solution which ensures that tens of millions of GPS users won't be affected by LightSquared's launch," LightSquared CEO Sanjiv Ahuja said.

LightSquared has no definite plans for its own spectrum but may use it for satellite services, which run at lower power than land-based base stations and pose less risk to GPS. Harbinger Capital Partners, the hedge fund backing LightSquared, paid $262.5 million last year for access to the spectrum, formerly owned by SkyTerra.

The Inmarsat spectrum slated to be used by LightSquared runs from 1526 MHz to 1536 MHz and is located further away from bands used by GPS receivers, which run from about 1559 MHz to 1610 MHz, helping to reduce the likelihood that LightSquared's transmitters will knock out GPS service.

LightSquared already planned to use some of Inmarsat's spectrum for its LTE network, since both companies hold slivers of L-band spectrum.

Even with the fixes, however, LightSquared's network is still likely to affect precision GPS systems used by the military, aviation industry and agriculture. Martin Harriman, executive vice president at LightSquared, said the company had not yet determined how to fix GPS interference in precision receivers.

"We've only just begun to look at technical fixes," Harriman said.

The company is working with the FCC, NTIA, government agencies and the commercial GPS industry on possible solutions and is expected to deliver a report on the issue July 1.

Harriman said the decision to use Inmarsat's spectrum would not delay the launch of LightSquared's network, slated for early 2012, because the company had already decided to make its transmitters and devices compatible with Inmarsat's L-band holdings.

"Although it's a change in plans, it's not that impactful. Our base stations and devices were designed to operate in this frequency band anyways," Harriman said.

Some expressed skepticism about the viability of LightSquared's plans, questioning whether the company would succeed in minimizing GPS interference.

Jim Kirkland, a spokesman from the Coalition to Save Our GPS and an outspoken opponent to LightSquared's plans, called the company's proposal "nothing but a 'Hail Mary' move."

"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," Kirkland said in a written response. "The government results submitted to date already prove this, and the study group report will also confirm this. It is time for LightSquared to move to out of the MSS band."

Tests conducted by the National Space-Based PNT Advisory Board showed that LightSquared's network still posed some degree of interference even when running between 1526 MHz and 1536 MHz.

The FCC has said it will not allow LightSquared to begin commercial operations of its LTE network until the company can prove the service won't affect GPS service. It is not clear whether the agency will accept a solution that protects less-sensitive receivers used in smartphones while leaving precision GPS receivers vulnerable to interference.

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