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LightSquared offers new network changes for GPS fix

Tue, 12/13/2011 - 2:47pm
Maisie Ramsay, Wireless Week

LightSquared is again modifying the deployment plan for its hybrid satellite-terrestrial LTE network to address problems with GPS interference.

The venture-backed company told the FCC in a letter filed Monday that it was changing its plan to increase the power of its signal over the course of the next five years.

“LightSquared is taking these steps to show that as the Commission's process continues, we are doing everything we can to address concerns raised by the GPS community," LightSquared regulatory affairs chief Jeff Carlisle said in the letter.

The original proposal called for LightSquared to increase its maximum power of the ground from -30 dbm to -27 dbm after Jan. 1, 2015. Under the new plan, LightSquared would postpone that increase until the beginning of 2016.

The first proposal also called for another increase to -24 dbm after the start of 2017. LightSquared has scrapped that plan and now says it won't dial-up its power of its ground transmissions beyond -27 dbm.

Lowering the power of its transmitters could force LightSquared to deploy more base stations to ensure coverage.

LightSquared also wants the FCC to remove deadlines for the deployment of land-based LTE service on its lower 10 MHz downlink channel and its entire uplink band. The company will instead operate its ground network on its upper 10 MHz downlink channel.

The changes to LightSquared's deployment plan come amid the company's increasing efforts to convince the FCC that it has addressed its network's impact on GPS receivers. Tests of LightSquared's first build-out plan showed the service caused widespread blackouts to GPS service, forcing the company to abandon the proposal in favor of spectrum located further away from GPS bands. The company says it has also developed filters and receivers that make GPS devices compatible with its network.

However, a report leaked to the media last week indicated LightSquared's optimism may have been unwarranted.

The report showed that 75 percent of GPS devices in recent government tests conducted by ExCom were affected by LightSquared's signal. LightSquared says the report showed only selective results. Its analysis found that just 14 of the 92 devices tested suffered a 1 DB change in the noise floor, the government's threshold for interference.

LightSquared said the report was purposely leaked to damage its chances of getting FCC approval and has demanded the Department of Defense and Department of Transportation investigate the leak.

The DOD said in a statement that it is "still in the process of reviewing the test results, so it would be premature to report on the results prior to completion and interagency coordination of that review."

The committee in charge of the testing is scheduled to meet this week to discuss the test results. The government's review of the results and its subsequent report will take "several weeks" before it is submitted to the NTIA, the DOD said.

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