The Pentagon and Department of Transportation have a written the Federal Communications Commission a letter insisting that they're more than a bit worried about a new satellite-based wholesale broadband service: LightSquared wireless.

"The new LightSquared business plan and the new FCC rules significantly expand the terrestrial transmission," the letter warns, "increasing the potential for interference to GPS receivers." Furthermore, the Department of Defense and DOT "were not sufficiently included in the development of the LightSquared input from federal stakeholders," the agencies claim.

The missive comes not long after everyone was breaking out the champagne over LightSquared. In late January, the FCC granted the company permission to offer wholesale broadband via its satellite and base station networks to a wide variety of mobile broadband partners. The move opens the prospect of new, innovative 4G services across the country, especially under-served areas. In fact, the company has just announced a partnership with Open Range Communications to roll out 4G LTE to rural regions.

But now this. "LightSquared will not be permitted to move forward with service under the waiver until potential interference issues are addressed," the FCC's Robert Kenny told Ars on Thursday. "The process followed in addressing those issues will include the ongoing input of our federal partners, the GPS community and industry."

So what's the problem?

Boys in the L-Band

LightSquared is a mobile satellite service (MSS) provider with two space vessels that cover North America. It operates in the 1.5-1.6GHz zone, part of what the FCC calls the L-Band. In November of 2010 the company applied to the Commission for more expansive rules that would allow it greater leeway to transmit satellite broadband signals to its "Ancillary Terrestrial Component" (ATC). In Earthspeak that means its ground level mobile stations.

LightSquared would thus reuse its space frequencies to offer wholesale broadband via ground transmitters. When the company applied for this regulatory largesse, it tried to convince the FCC that the proposal would pass the agency's "integrated service" rule—providing both MSS and ATC. Satellite mobile providers often honor the provision by offering "dual mode" handsets that can access either the satellite or land station signal.

The FCC decided that LightSquared's proposal didn't really pass the integrated service rule to the letter—the vendors who bought LightSquared broadband would provide earth mobile Internet, but LightSquared wouldn't. But the agency gave the satellite venture a waiver anyway, since its would "improve the ability of small, rural wireless providers to utilize ubiquitous MSS spectrum and the MSS/ATC device marketplace."

A billion more times

You can see how this proposal would be attractive to the FCC—more broadband providers rolling 4G service out to the countryside. The Commission appears to have liked this concept from the get-go. But LightSquared's L Band frequencies will also broadcast close to the Global Positioning System (GPS) bands, and the agency's authorization has provoked considerable concern, even alarm, among commercial GPS users. So much that some have formed an organization called The Coalition to Save Our GPS.

LightSquared's intended radio signals would be "one billion or more times more powerful than GPS signals as received on earth," the group claims, "potentially causing severe interference and rendering useless millions of GPS receivers—including those used by US Federal and Local Government agencies, first responders, airlines, agriculture, and everyday consumers in their cars and on hand-held devices."

If the modification is approved, "widespread, severe GPS jamming will occur," insists the Garmin International GPS maker on the basis of its experimental tests. In the company's tryouts, "two common state-of-the-art Garmin GPS receivers experienced significant jamming within a radius of several miles from a simulated LightSquared transmitter."

The Save Our GPS Coalition is backed by Caterpillar, Deere Company, and UPS. It also protests the way the waiver was issued. "The usual FCC process is to conduct extensive testing followed by approvals," the group's literature says. "For LightSquared, the process was approve first, then test."

Working groups

Not exactly. The FCC's LightSquared Order made it very clear that the Commission understood that interference could be an issue. The agency thus proposed a "working group" to map out and address the problem. It told LightSquared to convene the group, send regular reports to the FCC and the National Telecommunications and Information Administration, and submit a final report on the interference question by June 15 of this year.

"The process will be complete once the Commission, after consultation with NTIA, sends a letter to LightSquared stating that the process is complete," the Order concludes. "Addressing the interference concerns regarding GPS must be completed to the Commission's satisfaction before LightSquared commences offering commercial service pursuant to this waiver on its L-band MSS frequencies."

So in that sense, the FCC's latest announcement doesn't depart from the agency's original proposal. "This is something that we’ll be looking at closely as part of our comprehensive review and efforts to identify problems and come up with solutions," the Commission's Rob Kenny adds.

But the Pentagon and one of its biggest vendors, Lockheed Martin, complain that they weren't given sufficient notice about the LightSquared application. Lockheed goes so far as to ask the FCC to vacate its Order and pretty much start over again.

The DoD and DoT don't go quite that far, but the agencies "strongly advise that a comprehensive study of all the potential interference to GPS is needed... An exchange of all pertinent technical and operational information is also crucial to ensure the effectiveness of interference mitigation solutions."

(update) LightSquared sent us the following statement after we went to press:

“LightSquared’s new satellite-4G LTE network will build on our record of service and commitment to public safety, providing a huge benefit to defense, first responders and public safety officials by providing an affordable, reliable and ultra-portable satellite link in the event of natural disasters or unexpected crises when the terrestrial network is lost."

“We are sensitive to concerns about potential interference which is why we have fully committed ourselves to a comprehensive process that will ensure our network can coexist with GPS devices and agreed to only launch commercial operations when this process is completed to the FCC’s satisfaction. As part of this effort we are cooperating with federal agencies, the GPS community and GPS engineers in a transparent and technically accurate testing program to address issues relating to GPS receivers. We are also providing equipment and personnel to the U.S. Air Force’s Space Command, NASA and other federal agencies to help them begin their own testing processes.”