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LightSquared Plan Would Devastate U.S. GPS System

A year ago, LightSquared LLC (LS) applied for and received approval from the Federal Communications Commission (FCC) for an unprecedented use of LS’s mobile satellite system (MSS) spectrum. If approved, the plan would cause the end of the GPS system in the U.S.

LS has proposed to use its spectrum – centered at 1552.5 megahertz and 1528.7 megahertz, adjacent to the GPS L1 spectrum – to transmit signals to a proposed 40,000 terrestrial towers to be built throughout the United States.

According to GPS system engineers and users, this new system will completely overpower the GPS network in the United States, both by interfering with the L1 signal and by drowning out all GPS signals in the vicinity of its towers, which will transmit 1,500 watts each. In view of the company’s plan to blanket the U.S. with these towers, virtually no GPS signal could survive in the United States once the system is activated.

An important aspect of the peaceful co-existence of users within the MSS spectrum is the sparing use of ancillary terrestrial components (ATCs). These are transmitting towers that fill in signals where satellite signals are blocked. The existence and use of ATC’s is regulated by the FCC, who requires that the towers be an ancillary (“of secondary importance”) component of a satellite communication system.

LightSquared proposed, and the FCC agreed, that this requirement be waived just for them, so they could build 40,000 towers, each transmitting at 1,500 watts, to be used by its lessees SOLELY AS A TERRESTRIAL SYSTEM without any satellite component.

The combination of a transmitting frequency a billion times stronger than that used by existing companies, the unprecedented number and concentration of transmitting towers, the fast-track approval of the scheme by the FCC, and the perceived participation of the Obama administration stunned the GPS users community, which reacted quickly and decisively, and continues to do so.

According to the publication GPS World, in cooperation with Hemisphere GPS, a test of the proposed towers revealed that, “wide-band (20+MHz - typical of L1/L2 receivers) began feeling the effects of LS within 1,800 meters of the tower and jammed within 1,600 meters. Medium-band (12MHz) L1 receivers began feeling the effects of LS within 1,200 meters of the tower and jammed within 1,000 meters.”

This system is being developed to bring high speed wireless to most of the country, which is a goal of the Obama administration and the FCC. But the process involved in implementing the plan is extremely suspect, not least because the GPS and GNSS user communities only found out about its details on Friday, November 19, 2010, when the Federal Communications Commission (FCC) issued a public comment notice regarding an order and waiver it had approved for LightSquared LLC, authorizing the company’s proposed expanded use of its spectrum, and a waiver regarding its construction and use of a dense terrestrial transmitting network.

Comments were due by December 2, 2010 – less than two weeks fom the date the notice was issued, which included the four-day Thanksgiving holiday.

Those who knew of the company in previous years had assumed – wrongly – that the company was following the usage guidelines followed by other users of MSS, and that the FCC was looking out for their interest and the public interest.

The FCC received many objections, which included objections to the brevity of the comment period, and well-informed explanations by users such as the Department of Defense, maritime, aviation, geophysical and others that the strong signals adjacent to other bands, and the strong signals from the towers, would interfere with and even completely block GPS signals.

The response on January 26, 2011 by Mindel De La Torre, chief of the FCC International Bureau, was that since the industry had responded so quickly, the comment period was obviously long enough. She stated that the motion to deny was denied, and that “LightSquared may commence offering commercial service on its MSS L-band frequencies under the authority granted herein only upon the completion of the process for addressing interference concerns relating to GPS, as set forth in paragraphs 41-43 of this Order.”

These paragraphs ordered the establishment of a working group to “to fully study the potential for overload interference to GPS devices and to identify any measures necessary to prevent harmful interference to GPS.”
This process should have taken place as part of the development of the system - not after FCC approval was given.

On March 10, a group of representatives from industries and companies who use GPS announced that they had formed the Coalition to Save Our GPS “to resolve a serious threat to the Global Positioning System (GPS) – a national utility upon which millions of Americans rely every day.”

Their Web site - - provides information on the issue, including regular news releases as the situation develops.

Members are from the agricultural, aviation, car rental, construction, boating, railroad, surveying and mapping, marine, and manufacturing industries, including companies associated with the dredging industry: Hemisphere, Magellan, Leica, OmniSTAR, Trimble, Topcon, Caterpillar and Manitowoc. Associate members run the full spectrum of GPS users, including some municipalities, survey companies and others.

After intense testing at two sites revealed that the LightSquared system was damaging to the GPS network, on November 8, Save Our GPS filed a statement with the FCC, calling on the commission to “promptly rule” that LightSquared can never use the upper mobile satellite spectrum (MSS) band for high powered terrestrial operations. Such use of the upper band “should be taken off the table now,” the filing said.

The filing further noted that there is “overwhelming technical evidence” that if LightSquared is permitted to operate in both its lower and upper MSS bands that those transmissions would create “impermissible interference” with GPS and other satellite signals “well outside of LightSquared’s authorized frequencies,” and said that once tests earlier this year had shown the use of the upper band caused devastating interference to GPS “there has been little further consideration of the overwhelming evidence of problems with upper band operations” even though LightSquared has said it may need to use the upper band as early as 2015.

(LightSquared had proposed to begin by using only its lower band, in response to the objections of the industry.)
The filing stated that, “In the absence of a decision from the Commission relative to the upper MSS band, the GPS industry, (is) in an untenable position” because LightSquared has acknowledged that any solution to the interference in the lower band will require that a substantialnumber of GPS devices be either retrofitted or replaced. At a minimum, this includes a large number of expensive, high precision devices in use in critical economic sectors such as agriculture, aviation, and construction, as well as government uses including national defense, disaster response, and public safety.

The filing added that many commercial high precision devices typically have useful lives in excess of 10 years - a major investment on the part of the users.

The filing said that once users have gone through the disruptive transistion process to accommodate LS’s lower band operations, they could be required to undergo the same, futile testing several years later, if the FCC does not forbid LS’s use of the upper band.

“This suggestion is contrary to any notion of the public interest,” the document stated.

Other points raised in the statement

• The interference potential from the use of the upper band is clear and undisputed, which includes testing results showing that LightSquared’s proposed network would result in the loss of airborne GPS use in large portions of the United States and the “potential to cause GPS failure for hundreds of millions of cell phones.”

• Simultaneous transmission in both its upper and lower MSS bands causes “intermodulation” that, because of the close proximity of the MSS band to the GPS band, cause interfering signals to occur “in the center of the GPS band."

• Use of the upper band will have a particularly severe impact on military uses of GPS, including the military signal designated the “M code,” which was finalized by the military in 2000 and made a matter of public record at the time.

• Future use of the upper MSS band is inconsistent with LightSquared’s proposal for mitigation of lower band interference to high precision GPS receivers.

• LightSquared has “offered no solutions – because none exist – for resolving interference from its proposed operations in the upper 10 MHz. . .it is plain that there simply is no means to address the interference that would be caused by LightSquared’s use of the upper 10 MHz.”

LightSquared came on the scene several years ago when Harbinger Capital Partners acquired a company called SkyTerrain for $280 million, thereby obtaining use of its 1525 to 1559 megahertz sprectrum. Harbinger established LightSquared LLC, continued to lease its bandwidth to other users, then embarked on a fast-tracking of the process to receive FCC approval for a far different plan – a process that involved the apparent participation of individuals at the highest levels of government, including in the Obama administration, and the FCC. The stated purpose is to establish a nationwide high-speed wireless system.

Whether this goal is justified at this time is beside the point, when put in place without exploring the effects of the system on the entire utility.

Judith Powers

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