Deborah D. McAdams /
09.21.2012 02:40 PM
McAdams On: Why LightSquared Still Matters
WASHINGTON--Writing off LightSquared would be a mistake. The venture is an object lesson in how spectrum allocation is meaningless without consistent receiver standards, and how one industry strategically avoided them by coopting adjacent spectrum.

LightSquared was savaged into submission last year, as much by a public relations campaign as hard science. Tests were conducted on LightSquared’s proposed wireless broadband network, true enough, but comprehensive details about precisely which global positioning systems were affected and how, did not become a part of the wider discussion. LightSquared was driven into bankruptcy by thousands of boaters, pilots, surveyors and farmers whose GPS equipment may have worked perfectly well under LightSquared’s mitigation plan.

That did not matter, however, because the GPS industry successfully whipped users into a fear frenzy, not as a public service, but as a diversion. LightSquared’s proposed network did not bleed into the GPS band. GPS receivers did not adequately reject LightSquared’s transmissions in the adjacent L-band spectrum. Even as the dust settles around the wreckage and lawmakers bang gavels over the $4 billion scrap heap, receiver standards remain mostly the stuff of lip service.

Republican Rep. Cliff Stearns of Florida brought up the issue during a hearing this morning on the role of the Federal Communications Commission in LightSquared’s flame-out. He pressed the FCC envoys for yes-no answers on the implications of receiver standards, but he did not pursue the obvious question of how to establish and enforce them going forward.

“Do GPS device makers have a duty to design receivers that reject signals in adjacent bands?” Stearns asked Mindel Da La Torre, chief of the FCC International Bureau, who answered in the affirmative.

Turning to Julius Knapp, head of the FCC’s Office of Engineering and Technology, Stearns asked, “If [the GPS industry] does not make changes to its receivers, can you envision anyone being able to operate in the L-band if they don’t do anything?”

“The upper 10 is problematic,” Knapp said, referring to the 10 MHz of spectrum situated right next to the GPS band.

I.e., there is a 10 MHz swath of spectrum covering entire country that’s basically useless because GPS manufacturers were not held to receiver standards. GPS manufacturers argued that they couldn’t have anticipated terrestrial operations in L-band because it was designated for satellite transmissions. However, they had 10 years to bring up the receiver overload issue before the FCC granted LightSquared a conditional waiver for terrestrial operations.

“Despite participating in multiple proceedings and raising other interference issues that were ultimately resolved to the GPS industry’s satisfaction, it did not do so,” Knapp and Da La Torre wrote in their joint testimony. “To be clear, in November 2010, the GPS industry was not complaining about out-of-band emissions or interference caused by handsets, or the power levels authorized for the L-band—they were instead notifying us of their own receivers potentially picking up signals from the neighboring band.”

In other words, the GPS industry knew their receivers were not built to FCC specifications where interference rejection capability was concerned, and did absolutely nothing about it for a decade while their devices saturated the market. Some of those devices were even found to treat “the GPS spectrum and the L-band spectrum as one band,” according to Knapp and Da La Torre’s written testimony. Such dual-band devices constitute illegal spectrum squatting, but with everything from drone flight to in-car navigation depending on GPS systems, the FCC can’t just kick them off the L-band.

Meanwhile, the GPS industry has avoided any sort of commitment to anticipate flexible-use scenarios going forward. With spectrum at such a premium that broadcasters stand to lose 40 percent of their real estate, designing for flexible use should be an imperative. If its not, LightSquared won’t be the only company holding stranded spectrum licenses.

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Posted by: Deborah McAdams
Wed, 09-26-2012 03:49 PM Report Comment
Really? No one can parse the word "opinion?"
Posted by: Anonymous
Fri, 09-21-2012 05:28 PM Report Comment
Is that upper 10 MHz really useless, or could it be used for other low power satellite signals, similar to GPS? That's what was originally supposed to be there. IIRC, the ruckus started when the FCC wanted to re-designate that satellite-only spectrum for high power terrestrial use by LightSquared. It's kinda like telling the monks to soundproof their monastery, because the zoning commission wants to OK rock concerts next door. That kind of receiver interference rejection is easier said than done, especially at these extremely low powers.
Posted by: Anonymous
Fri, 09-21-2012 05:28 PM Report Comment
I vehemently disagree with "there is a 10 MHz swath of spectrum covering entire country that’s basically useless because GPS manufacturers were not held to receiver standards." If standards for GPS receivers had been written 20 years ago, they would not have contemplated a terrestrial cellular network on the adjacent spectrum. The adjacent spectrum is allocated as primarily satellite communications. This means that weak signals would be near weak signals, and the GPS would work just fine if LightSquared stayed a satellite service. TV and Radio broadcasters know the "near-far" problem quite well, and have relied on an allocations rubric to place their stations and enjoy protected service areas, and tolerate near-far receiver problems usually outside the protected service area of a station. Receiver manufacturers design to the transmission/allocation rubric, knowing what the adjacencies are allocated for. LightSquared's proposal represented a sea change in the use of the adjacent spectrum. Have Charlie Rhodes give you a tutorial on the ins and outs of receiver design and allocations. Fundamentally, licensees deserve a degree of regulatory certainty that major changes in allocations will not obsolete incumbent services.
Posted by: Anonymous
Sat, 09-22-2012 05:33 AM Report Comment
Complete and utter nonsense. The adjacent 10 MHz band is still useful to any application that would be transmitting a signal from space, presenting a reasonable D/U ratio to navigation devices. Then all existing GPS receivers would easily reject the out of band signal. It was LightSquared attempt to place extremely high powered TERRESTRIAL transmitters with the resulting rediculously high D/U ratios that were swamping the front ends of most consumer GPS receivers in the tests. Had LightSquared stuck with a satellite based service, instead of trying to sneak in a terrestrial network disguised as a 'gap filler,' there would have been smooth sailing for LightSquared.
Posted by: Anonymous
Sat, 09-22-2012 06:55 PM Report Comment
1. As this piece points out, the GPS manufacturers were aware of--and indeed had participated in the regulatory process associated with--enabling terrestrial use of the band. Since 2003. As the FCC testimony details, despite numerous waypoints in the proceedings on MSS ATC, they never raised the issue of overload until late 2010, then tried to assert that the waiver then in consideration, later granted, to LightSquared somehow effectively created the company out of nowhere. If the overload problem existed--and indisputably it does for some receivers--the GPS manufacturers were in the best--indeed the only--position to know it did, given that they alone design and build their receivers. Since they are not held to receiver standards, they often chose to build them with poor band rejection since it's cheaper to do so. One can only conclude that they calculated that killing LightSquared with a trumped up PR and political assault, effectively turning the use of at least 10, perhaps as 40 MHz of highly valuable spectrum to guard band for themselves, was cheaper and easier than responsibly designing their products. 2. No modern cellphones failed the most stringent of tests conducted in the TWG process. Why do these devices not suffer overload? Their manufacturers are collocating several radios in a single device and must skillfully employ inexpensive filters in order to reject OOBE while optimizing performance. They succeed. This suggests that other GPS devices could be similarly filtered and perform as well. One often reads of fire-extinguisher sized filters which allegedly would be required. Last time I looked at my iPhone, it seemed quite a bit smaller. 3. Granted, some high-precision and aeronautical devices--less than .5% of overall GPS devices-- cannot so easily be filtered. As the article notes, this is because they use not only the GPS band, but the L- band licensed to LightSquared for both satellite and terrestrial use as well. That is, they achieve higher precision mainly by arrogating for their own use not only the GPS spectrum for which they paid zero, but also the adjacent spectrum in which Lightsquared has invested $Billions on the basis of a wide-open licensing process which took over 10 years. The monks in the monastery knew well that the music venue was coming very early in the development of their order. They might have alerted the zoning folks about their concerns or used a few more bricks in their walls, Had they done a bit of both--or were they to do so now--the concert venue could likely shift its planned location a few doors further away, in combination with the use of additional real estate across the street. And both land uses could coexist. Simply asserting that, as monks who arrived first, they have the moral high ground and a veto on land use in the whole neighborhood won't do--not in a highly-important town with natural space constraints and a rapidly growing population with diverse needs.
Posted by: Anonymous
Mon, 09-24-2012 03:49 AM Report Comment
It isn't merely that the monks got there first. When they built the monastery, the whole neighborhood was zoned for extremely quiet uses. They were OK with the LightSquared Chamber Orchestra. It wasn't until later in the process that LightSquared went all Woodstock on them. Agreed, the right solution would have been for LightSquared to do some land deals and move the rock concerts a few doors or a few blocks away. Alas, they chose instead to fight the laws of physics, and went broke doing it.
Posted by: Anonymous
Wed, 09-26-2012 03:46 PM Report Comment
I guess this is the best we can expect when journalists and politicians attempt to make conclusions in the real world of technical absolutes.
Posted by: Anonymous
Thu, 09-27-2012 06:56 PM Report Comment
If journalists and politicians expended the time and effort it would take to gain an adequate understanding of the technology here, they wouldn't have enough time and energy left to be journalists and politicians. So, they have to come up with ways of coping with insufficient understanding. Mostly they get by, sometimes they blow it.

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