I am surprised no one here has mentioned this. This could potentially have a huge impact on all of us, as well as the rest of the world. Apparently in our Presidents' zeal to deliver on his promise of 4G to all citizens he coerced the FCC into granting bandwidth to this firm called "lightsourced". To "make it happen" FCC did away with the required six months for study and public input and automatically granted the bandwidth request in a two week time period. To make a long story short what it does is gives them permission to build over 40,000 land based antennas for communications. Doesn't sound like that bad of thing, BUT, the bandwidth is directly adjacent to GPS satellite bandwidth. And at 50,000 times the power you can pretty much imagine which technology loses. The military, GPS manufacturers and suppliers, and users groups are fighting this vigorously so it would be nice to believe that this just can't happen but we will see. This directive was in direct opposition to the international commission which oversees bandwidth allocation. Lots on the internet if you care to search it.
FCC and their relationship to "lightsourced"
- Thread starter lloyds
- Start date
matt_unique
New member
"Coerced the FCC"? Sounds serious 
I did a search and did not find anything for "lightsourced". Do you have a link handy? I would be very surprised if any actions were taken that would affect GPS signals as they are so highly integrated.
I did a search and did not find anything for "lightsourced". Do you have a link handy? I would be very surprised if any actions were taken that would affect GPS signals as they are so highly integrated.
Bill Uffelman
New member
LightSquared
http://www.wfsb.com/technology/27448640/detail.html
Bill Uffelman
In Carson City NV through June
http://www.wfsb.com/technology/27448640/detail.html
Bill Uffelman
In Carson City NV through June
Thanks Bill for correcting that. There is quite a bit more to the story but it takes some digging to find it. The administration was in a big hurry to get this thing going and almost got away with it. Now due to pressure on them, the government has put together a committee of users which is now up to about 34 folks. They will meet once a month and issue a report on their progress. I think they have released the first one, which details the committee and its' functions. I think it is supposed to be finished in june or july. That is the FCC standard as I understand it but the government got in a hurry for this one and tried to shortcut it and got caught. I know it sounds impossible that something like this could actually happen but we came incredibly close this time. I have no idea who blew the whistle, maybe another competitor but we are lucky someone was watching.
Panbo, a marine electronics blog, broke the news on Mar 14.
Link. http://www.panbo.com/archives/2011/03/the_lightsquared_problem_time_to_join_save_our_gps.html
Also, our own Brat, Tim, wrote about it on his blog.
Link. http://www.navagear.com/2011/03/15/house-subcommittee-told-fcc-action-poses-a-threat-to-gps/
Link. http://www.panbo.com/archives/2011/03/the_lightsquared_problem_time_to_join_save_our_gps.html
Also, our own Brat, Tim, wrote about it on his blog.
Link. http://www.navagear.com/2011/03/15/house-subcommittee-told-fcc-action-poses-a-threat-to-gps/
There is much hype and fear about this and it is a real concern generally but a little ahead of itself.
"as part of the waiver granted allowing LightSquared to operate a hybrid network in the L-Band -- that LightSquared must work with the satellite industry to study the issue and provide a solution if there is a problem. The first report from the 34-member group arrived on March 1, the second is due April 15, and the final report is due June 15."
They seem to be tasked with solving any problems and I really have a hard time believing that all of our GPS gear is just going to be blurred out for this system. GPS is a bit more established in our countries daily personal and business affairs than that. I am ignoring the hype and waiting to be proved right.
"as part of the waiver granted allowing LightSquared to operate a hybrid network in the L-Band -- that LightSquared must work with the satellite industry to study the issue and provide a solution if there is a problem. The first report from the 34-member group arrived on March 1, the second is due April 15, and the final report is due June 15."
They seem to be tasked with solving any problems and I really have a hard time believing that all of our GPS gear is just going to be blurred out for this system. GPS is a bit more established in our countries daily personal and business affairs than that. I am ignoring the hype and waiting to be proved right.
This has been in the view finder since at least mid Feb. It is difficult to see where it will go. Even if Lightsource goes ahead, it will not cause a problem for marine navigation--but airplanes, and inland it can be a possible issue. The question remains if filters on both the recievers and transmitters will be adequate. I don't see a threat to our boating issues curently--but it is something which we need to keep an eye on.
There was also a threat a couple of years ago--broad band via power lines--and that would have caused some serious RF spectrum interference--and was eventually put on the back burner.
There was also a threat a couple of years ago--broad band via power lines--and that would have caused some serious RF spectrum interference--and was eventually put on the back burner.
This pdf of a report from Garmin is quite interesting. It describes some experiments done at Garmin's facility in which they simulated the signals that would be sent by Light Squared's proposed system and measured the effect on two GPS systems - the Garmin Nuvi 265w and the GNS 430W. The former is one of the most common systems used in cars while the latter is one of the most common systems used in aircraft. Garmin picked these units because they have high market share and are representative of other units in the field. In the interest of getting some testing done quickly, they didn't test other units.
The bottom line of their testing is that the car units will be jammed when within 0.6 miles of a Light Squared transmitter when they have open sky to the GPS satellites (best case scenario) and at about 1.8 miles when they are in "urban canyons" (e.g. amongst tall building that block some satellite signals). For the aviation GPS, which has line of sight to both the transmitters on the ground and the GSP satellites, the situation is worse with jamming occurring at a distance of 5.6 miles from the simulated Light Squared transmitter.
As someone with some experience in electronics in these frequencies (I did a lot of spectroscopy using similar types of test equipment), Garmin's testing setup seems reasonable and (as they plainly stated) was done to provide a simulation of the conditions and setup most favorable to Light Squared - e.g. not at the full power Light Squared would be permitted to use and not at the full edge of the spectrum that Light Squared could conceivably use. Given Garmin's testing and the large number of deployed GPS's, I can't see the Light Squared units actually get deployed as projected. My money says that the rug is pulled out on this prior to it becoming a problem.
The bottom line of their testing is that the car units will be jammed when within 0.6 miles of a Light Squared transmitter when they have open sky to the GPS satellites (best case scenario) and at about 1.8 miles when they are in "urban canyons" (e.g. amongst tall building that block some satellite signals). For the aviation GPS, which has line of sight to both the transmitters on the ground and the GSP satellites, the situation is worse with jamming occurring at a distance of 5.6 miles from the simulated Light Squared transmitter.
As someone with some experience in electronics in these frequencies (I did a lot of spectroscopy using similar types of test equipment), Garmin's testing setup seems reasonable and (as they plainly stated) was done to provide a simulation of the conditions and setup most favorable to Light Squared - e.g. not at the full power Light Squared would be permitted to use and not at the full edge of the spectrum that Light Squared could conceivably use. Given Garmin's testing and the large number of deployed GPS's, I can't see the Light Squared units actually get deployed as projected. My money says that the rug is pulled out on this prior to it becoming a problem.
This concern was announced a few weeks ago and the 4G company indicated that it was in their interest to be sure 4G and GPS were compatible, since 3G &/or 4 G is often used with GPS at the same time on the same device. They won't have much market share if their 4G damages GPS performance.
I used Sprint 4G all last week in Seattle w GPS some of the time - no problem. The measured download speed up to 8 MB sec was fantastic
Jim
I used Sprint 4G all last week in Seattle w GPS some of the time - no problem. The measured download speed up to 8 MB sec was fantastic
Jim
Captains Cat
New member
lloyds":1z51pd1i said:
Oh, NO. Please don't. We'll have to watch him read another speech off his teleprompter! Wish he'd turn it around and then we could all read it at the same time!
Charlie
matt_unique
New member
Da Nag":28v043so said:
Thank you Bill.
I love talking about boats here.
jstates":3f0jdgu7 said:
Sprint's 4G network is in a different part of the spectrum than the one that Light Squared is using. The Sprint4G system using spectrum around 2.5GHz. The proposed Light Squared system uses frequencies 1.525-1.559GHz which is immediately adjacent to the GPS spectrum of 1.559-1.610GHz. Light Squared already "owned" this spectrum for use in transmitting signals from satellites to earth (weak signals by the time they get here). What they have requested is to re-purpose this spectrum for land based networks (strong signals). Current GPS systems are designed to filter out signals from other frequencies BUT EVERY filter has varying degrees of efficiency as a function of frequency. I.e. a small fraction of signal from adjacent channels leaks through the filter. When this is a small fraction of a weak signal (e.g. the satellite signals currently in the 1.525-1.559 GHz range), no problem. However when this is a small fraction of a large signal (ground based transmission in the same frequency range) it's a problem. Especially when the GPS itself is listening to a weak signal from satellites transmitting in the designated GPS spectrum.
Light Squared is making the spurious argument that the GPS receivers are "eves dropping" on signals in Light Squared's spectrum so that the GPS users should pay the cost of putting better filters in their system. In practice this would mean that most current GPS receivers would be obsolete. Given the huge investment in current GPS systems, I don't see the Light Squared technology getting off the ground in this frequency range.
Every Mobile phone has been required to contain a location device (gps primarily) for years to provide location for E911 (which is admittedly only partially enabled) and now people think they will just nullify that system and so many other imbedded systems in the country? Really? Filters won't just slide into these devices.
Excellent explanation by Roger about the frequency involved. WIMAX used by Sprint is also a different technology than the LTE (long term evolution) used by leasees of Light squared spectrum. AT&T and Verizon are going to use LTE. Our current GPS receivers may be overwhelmed or jammed on rare occasions if near military ships, or high powered transmitters. I suspect that there is just some spectrum spread in harmonics, rather than intentional jamming.
Many phones do not use or have a GPS chip set, and rely on proximity to cell towers and triangulation to give their position for emergency communications. E911 Phase 2 standards currently only has to give the location by lat and long within 300 meters, & within 6 minutes. GPS accuracy is with in one to thee meters and is almost instantly available, encoded in the signal.
Many phones do not use or have a GPS chip set, and rely on proximity to cell towers and triangulation to give their position for emergency communications. E911 Phase 2 standards currently only has to give the location by lat and long within 300 meters, & within 6 minutes. GPS accuracy is with in one to thee meters and is almost instantly available, encoded in the signal.
There is a huge row going on about this in the press and in Congress with opposition from just about everyone flying airplanes, emergencey services etc etc. and, as Roger said, GPS has probably been "poaching" a little. That said, it is obvious that there would be no simple fix to the millions of GPS fitted devices already in service without a HUGE windfall for the manufacturers and a HUGE bill for the users and taxpayers who will have to replace receivers.
Given the amount of money involved by BIG business on both sides, guess who will lose :roll:
M
Given the amount of money involved by BIG business on both sides, guess who will lose :roll:
M
To be clear, I didn't say that GPS is "poaching" a little, Light Squared is making that claim and I deem it to be spurious (e.g. false). To me this argument is the functional equivalent of saying that someone should build thicker walls when the neighbor suddenly decides to play loud music. Had you moved into a house immediately adjacent to a well-known outdoor concert center, it would be reasonable (IMHO) for the concert center to say you should beef up the sound insulation in your house instead of complaining about the noise. If however, that large concert center simply appeared in an area previously zoned a hospital quiet zone, then it's the concert center's problem.Grumpy":i4artvs4 said:
In the case at hand, Light Squared is wanting to suddenly make a lot of noise in the previously quiet frequency space adjacent to GPS. Since GPS was not designed with filters to deal with this level of noise, it's a problem. My money is not on all of use getting screwed, my money is that Light Squared won't be able to use the spectrum as they had hoped.