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LightSquared And The FCC – Still Doing Their Best To Destroy GPS

Cross-posted at Free Geography Tools

Back in February, I had a long post about the FCC’s conditional approval of LightSquared’s wireless broadband proposal. This waiver was vigorously opposed by the GPS industry because tests by Garmin showed that it would seriously disrupt GPS in areas where it was implemented. Read the post for a full rundown, but briefly LightSquared’s plan requires high-power transmissions in frequencies immediately adjacent to the GPS band, which drown out the GPS signal entirely. LightSquared dismissed these Garmin results, stating in a comment to my post:

… the Garmin tests that you refer to were not made under appropriate circumstances so the results are not accurate indications of how our network will perform. To get a real examination of the situation, tests must be conducted in the proper band and with the right filters. We’re now engaging in testing supported by the government and being done with the cooperation of many in the GPS community. We believe that this process will produce the most reliable results and will show that our network and GPS can coexist.

The FCC’s conditional waiver required LightSquared to form a study group with the GPS community to measure and analyze the potential effects of their broadband transmissions on GPS, and report back to the FCC by June 15th, 2011. Concurrently, the government’s National Executive Committee for Space-Based PNT (Position Navigation and Timing) asked a governmental interagency committee (National Space-Based PNT Systems Engineering Forum (NPEF)) to do its own separate, independent measurements to analyze LightSquared’s proposal, and also report their results in June of 2011.

Well, both reports are officially in, but enough results leaked out earlier to make their conclusions no surprise – the LightSquared system as originally described would completely disable the GPS system everywhere in the vicinity of a LightSquared transmitter, including applications for aviation, transportation, high-precision surveying, space, and consumer uses. This was the conclusion of both the LightSquared report, and the NPEF report. While the GPS industry and LightSquared were unable to agree on common wording for most of their conclusions, even LightSquared acknowledged that they were completely wrong in their original conclusion that “our network and GPS can coexist”.

End of story, right? Not quite. The original due date for the LightSquared report was June 15th, but they got a two-week extension from the FCC, apparently to give them time to come up with an alternative proposal that they claim fixes all relevant problems. It essentially consists of two major modifications to their original proposal:

1. Cut the maximum power transmission levels by 50%.

2. Not using 10 MHz of bandwidth closest to the GPS bands, and accelerating plans to use an additional 10 MHz further away, originally intended for service expansion in the future. LightSquared claims that 99.5% of GPS receivers would be free of interference from their transmissions.

The GPS community calls this a “Hail Mary” plan, and with good reason:

Cutting the maximum power transmission level by 50% is no cut at all (Source)

The FCC gave LightSquared approval to transmit at a maximum power of 15,850 watts, but LightSquared stated that its maximum operating power would be 1600 watts, 10% of the maximum. Cutting the “maximum power transmission level” drops that number to 8,000 watts, but unless the operating power is also cut by half, that will make no difference for GPS interference. LightSquared is unlikely to cut that power level in half, as that would require them to construct 4x as many transmitters as originally planned, increasing costs substantially.

“Giving up” 10 MHz of bandwidth may still incapacitate all GPS receivers, and definitely incapacitates all high-precision receivers.

As the GPS community’s rebuttal points out, LightSquared’s conclusion that their revised proposal will eliminate interference for 99.5% of current GPS units isn’t supported by the report they submitted to the FCC. Since LightSquared sprang their proposal at the last minute, without consulting with the GPS industry, most of the tests did not incorporate LightSquared’s new operating conditions. But those that did indicated substantial “harmful interference” to about two-thirds of GPS receivers in the general navigation category (meaning automotive receivers). In order for LightSquared to prove that their revised proposal wouldn’t have harmful effects to the vast majority of GPS devices, the tests would have to be repeated using the conditions of their revised proposal.

What’s more, the NPEF report indicates that several aspects of test conditions used in the LightSquared report tests may have resulted in underestimating the negative effects of LightSquared’s transmissions:

  • The broadcast power level for the LightSquared transmitters was actually lower than that planned for operational use. While the interference results were supposedly compensated for this based on simple distance/power calculations, the NPEF report stated that some interference effects could not be adequately compensated for using such a simple compensation.
  • Tests were done using just a single transmitter, but heavily-populated urban areas would require multiple transmitters, each of which could interfere with a GPS receiver. While modeling could be done to simulate these effects, accurate assessment of these effects would require testing with multiple transmitters.
  • Finally, the LightSquared receivers also broadcast in a frequency range adjacent to the GPS band, albeit a different frequency and lower power than their main towers. It’s possible that these receiver units might also interfere with the GPS signal, but since LightSquared still doesn’t have any of these receivers available for testing, it wasn’t possible to assess what harmful interference they might generate.

As an additional “bonus”, this 10 MHz “surrender” by LightSquared is only temporary – they plan to use that frequency space in the future for service expansion, which would once again, by their own admission, disable GPS receivers completely anywhere within the vicinity of a transmitter.

What’s more, LightSquared freely admits that the vast majority of high-precision GPS units, those used for “agriculture, aviation, construction, engineering, surveying, marine navigation and disaster monitoring as well as federal, state and local government uses”, would be rendered unusable even under their revised proposal. Their solution? Make the GPS industry, and users of those high-precision GPS units, pay to fix the problem themselves. Why and how? Simple:

Paint the GPS industry as mooching off the government

LightSquared commissioned a report from the Brattle Group concluding that GPS satellite transmissions from the government-run GPS program amounted to an implicit $18 billion dollar subsidy of the GPS industry, and that the GPS industry should therefore pick up the tab for any equipment modifications required to co-exist with LightSquared. Seriously? Don’t you know anything about the history and rationale behind GPS?

  • It was originally intended for military use, a function it still fulfills today. The incremental cost for consumer/industry use is trivial in comparison to the total costs.
  • After KAL Flight 007 was shot down by the Russians in 1983, President Reagan issued a policy directive that required the low-precision (Selective Availability) GPS signal to be made freely available for civilian use.
  • In 1996, President Clinton issued a policy directive that GPS officially be declared a dual-use (civilian and military system), and in 2000 that Selective Availability be turned off, making moderate to high-precision GPS signals available to everyone.
  • In 2004, President Bush issued an policy directive that no direct user fees be charged for GPS signals.

But now LightSquared, a commercial initiative that played no part in the development of GPS, feels it has the right to imply that the GPS community needs to shoulder the costs of their proposal? Please.

Accuse the GPS industry of being aware of this possibility, and not designing their equipment to be ready.

LightSquared claims that the GPS industry has known for years that terrestrial transmissions in adjacent frequency bands were coming, but did nothing to either fight them, or re-design their equipment to handle interference from these transmissions. Putting it mildly, this is a total crock. As Trimble’s response to these statements makes clear, these terrestrial transmissions were supposed to be “ancillary”, auxiliary low-power transmissions in limited areas where terrain or foliage blocked reception of the primary low-power satellite transmissions; the GPS industry acknowledged that it could live with such limited low-power terrestrial transmissions. The waiver granted by the FCC to LightSquared flipped this around completely, making the terrestrial component the primary one, and jacking up the transmissions power level by orders of magnitude. Unless the GPS industry had Nostradamus on the payroll, and he could have foretold that the FCC would completely reverse its position on broadcast power levels in these bands, it’s ridiculous to imply that the GPS industry knew this was coming.

Claim that fixing the issue is easy and cheap

LightSquared claims that cost of fixing a GPS receiver was trivially low, on the order of 5 cents for a basic filter, but that the GPS industry wasn’t willing to implement this fix. First off, LightSquared’s technical competence to make such statements is highly suspect, in light of their original position that their system would have no detrimental effect on GPS. Secondly, they are unable (or unwilling) to provide a demonstration GPS unit that incorporates these filters, merely relying on a chip manufacturer’s assertion that they could provide such filters; if it’s so easy and cheap, why can’t they prove it? The GPS industry, with far more experience, doesn’t think such a solution is trivial. The NPEF government report goes even further:

… add-on filtering solutions are not viable for a significant fraction of fielded equipment due to considerations such as performance (signal attenuation, increased thermal noise floor, phase and group delay variations with temperature and between frequencies, loss of narrow correlator benefits), cost, size, and weight.

For a new product, many additional degrees of freedom are opened for mitigation techniques… Unfortunately, redesign is not likely to result in the same level of performance provided by current receivers, especially those employing wide RF front-end passbands… High-precision equipment is among the most difficult to protect against the LightSquared emissions since these receivers typically process wideband GPS signals that require a wideband receiver passband and such equipment usually also has severe differential group delay requirements. For these types of receivers, filtering can typically significantly degrade or even destroy the very information required for the most demanding scientific and precision applications.

In its report, the NPEF concludes that the problems with the LightSquared proposal are so serious and intractable that they recommend:

  • The FCC immediately rescind the conditional waiver granted to LightSquared in January 2011, which would effectively put LightSquared’s planned system on hold
  • Six months of more rigorous tests of the possible effects of the LightSquared system on GPS, and make future decisions based on those results
  • The FCC determine whether any broadband system that relies on frequency bands adjacent to GPS could be implemented without interfering with GPS, and adjust their regulations accordingly if the answer is “no”.

In a sane and rational world, the FCC would adopt these recommendations immediately. But in a sane and rational world, they would never have granted LightSquared a waiver in the first place, even a conditional one. They’ve been tasked by the Obama Administration with freeing up frequency space for broadband, and they seem committed to that goal regardless of the facts. They’ve already shown their bias toward LightSquared (and against the GPS community) a number of ways:


A 30-day comment period now runs through the end of July, with a final decision due August 15th. Based on their past history, I would assume that the FCC will extend their conditional waiver, with possibly a requirement for a few more months of testing. And if the results of  testing shows that the main impact is on high-precision GPS receivers, my gut feeling is that they will grant final approval to LightSquared, and dump the responsibility and cost for “fixing” high-precision GPS receivers on the manufacturers and users. LightSquared apparently feels the same way, as they’ve announced that they’re going to start construction of their network right away, even before the final FCC decision is made.

But it’s my hope that other government bodies will step in to stop this process, and I have to believe they will. Since the waiver was granted in January, this issue has gotten more and more attention from affected industries, elected government officials, and the press. An amendment has already been attached by the House Appropriations Committee to a budget bill, prohibiting the FCC from spending any money or resources on the LightSquared proposal until they prove that it won’t interfere with the GPS system. If the FCC actually approves LightSquared’s plan, I think it’s likely that legislation will be passed quickly to override their decision. Apart from the FCC (and possibly the White House), there isn’t a single government agency that thinks this is a good idea. The Save Our GPS coalition has a growing list of GPS-dependent companies, from a wide variety of industries with substantial political influence, joined in opposition to the LightSquared proposal . In particular, I expect that any Senator or Representative from a farm state is a solid vote in opposition to LightSquared, given how important GPS is in modern industrial farmin. The powerful telecom lobby is aslo in full opposition, partially because of the potential for competition, and partially because LightSquared used loopholes and political influence to gain access to wireless bandwidth for far less than what the telecoms had to pay in open auction. LightSquared has very few friends in Washington, and a lot of opponents; ultimately, I’m optimistic that GPS will be saved.

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