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  The American Surveyor     

Three Possible Scenarios for Broadband versus GPS Print E-mail
Written by Gavin Schrock, LS   
Monday, 14 March 2011

By now you have probably read a lot about the ongoing Broadband-vs-GPS controversy (as some call it) – could this spell certain disaster for GPS? Or will this be as much of a non-event as Y2K? The only thing for certain is that no one, absolutely no one, knows for certain what will happen (at all levels) when the broadband provider in question throws the switch. There are a number of possible scenarios ranging from substantial interfernce, to minimal interference, to no effect at all. Substantial interference would prompt the FCC to act to mitigate or halt the signals. It is perhaps the potential for very low interference may not warrant a big enough hammer for the FCC to yield and ironically might prove to be the most troubling for GPS end users. We should examine some of these scenarios, but first a little background.

The root of this current panic (or concern) is the January 2011 FCC Order DA 11-133 authorizing the communications giant Lightsquared to operate a new set of services and transmissions directly within the L-band in which GPS signals reside. Just on the surface this sounds rather scary, and especially when some concerned parties start throwing around hyper-charged statements like “the new signals are one billion times the power of a GPS signal as received on the ground”. Depending on how one computed the comparison, that might be true but a bit off target.

There is a fine line between hype or sheer panic, and measured concern (pardon the pun).  On the one hand even the layman has experienced signals bleeding over where they were not intended – remember CB radios causing interference on your TV? On the other hand some have noted that the proposed signals are farther from the GPS signals than the width of say, the consumer FM band – does 84.5FM interfere with 105.6FM down the dial? None of this provides solace to those who are increasingly dependent on GPS for their livelihood, public safety, trade or commerce. The GPS signal is in many ways a dim light bulb in space compared to some other types of signals; the very thought of something powerful anywhere near it is frightening to say the least and absolutely worthy of concern and examination.

Demonizing the FCC or the broadband provider in question is not the answer. The FCC is trying to juggle the demands of the public for ever increasing wireless internet services within the limitations of the crowded radio spectrum, and Lightsquared, the communications giant granted the FCC order is simply doing business. While many find the terms of the FCC order unacceptable; allowing Lightsquared to build out their multi $B infrastructure ahead of a comprehensive study of the hazards, the order does spell out the requirement that Lightsquared work directly with the GPS community on evaluation of hazards before said infrastructure will be allowed to offer full services. To this end, a broad coalition has been formed, standing vigilant over the whole process – saveourgps.org. Among the numerous requests for review submitted to the FCC is one by the ACSM. The US GPS Industry council, leading the charge among the concerned parties has paired with Lightsquared in a working group to study the potential hazards and filing monthly reports to the FCC; the final report due June 15th, 2011. The process is transparent and inclusive, but what is unclear is what the course of action might be depending on the levels of interference the study might predict, or more importantly what happens if the levels of interference are higher than predicted once the switch is thrown?

What if there are high levels of interference? If GPS were to experience substantial outages, denials of service, or dramatic errors then it is fully expected that the FCC would simply stop the new broadband services and send Lightsquared back to the drawing board. The FAA, Commerce Department, DoD, DHS, and many other filed letter of concern with the FCC. It is beyond credulity that anyone would allow GPS, a critical element of our national infrastructure, to be compromised to that degree. The FCC order is conditional – the FCC can revoke the authorization.

What if the effect were more moderate, or localized?
This might not result in the revocation of the authorization, but may place more conditions on operations; filtering, redesign of some elements, conditions on placement of transmission facilities. The FCC would have to stop short of revocation, chiefly because Lightsquared had been allowed to sink billions into the infrastructure and would more likely be expected to fix, rather than dismantle. Just how firm the orders would be could depend on how much of the consumer market was affected, and just how loudly they would be willing to whine about it.

What about “just-enough-interference-to-irritate-end-users”? People love their wireless internet, bordering on flat out addiction. While folks also love GPS and depend on it a lot, the true value and utility of GPS is unknown to the average consumer. If the interference is very localized, and perhaps only an irritant to a relatively small segment of end users (like surveying or precision agriculture) the FCC and Lightsquared might characterize this as an acceptable loss. Acceptable loss?  Some already view the lofty goal of “broadband for all” as the cause du jour and “what’s wrong with a little collateral damage”. “The needs of the many…blah blah blah…” Some point out that there might even be a net gain for surveyors in the form of improvements in wireless access for RTN type corrections… maybe, but the new broadband services will be aimed at heavily populated areas already served by cellular data. Indeed the new services are designed to be offered wholesale from the provider, so that third parties (like big-box chains) will be able to offer data services via very inexpensive devices they can have built overseas. Ok, maybe our data access will get cheaper, but what if our GPS is sub-par around the transmission towers?

So what would the affected end users be forced to do if there is actual interference? Some supporters of these new services are already spinning notions like “a lot of GPS equipment is old and should be upgraded“, presumably to equipment that would be able to filter out the interference. Great, so we foot the bill? If that were such good thing then one would expect that the very same GPS manufacturers (that are in the coalition to monitor this situation) to be thrilled to sell lots of new “interference hardened” equipment. Or perhaps those same manufacturers are worried that the end users may choose cheaper gear from different globalized manufacturers, or gear tuned to different constellations if forced to upgrade. Ok, spiraling off into paranoid speculation... sorry. Even if there is no actual documented interference the seeds of doubt will have been planted. How many users will mistakenly attribute some instances of substandard GPS performance to these new signals… after all there are still folks who  think the military is blocking their signals when their car GPS puts them on the wrong side of the intersection…

Again, no one knows for sure what will happen when the switch gets thrown; our best view into the likely outcomes will come in June when the final joint report. Hopefully, this is just a lot of hype and there will be no measurable interference, but in the event that there is, however little that might be, it can only be good thing for the voices of surveyors and our industry to remain strong within the already broad coalition of concerned parties.

Note: Cartoon drawn by Gavin Schrock

 
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