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Senator Reports Questionable Contact to Ethics Committee
Grassley says he was contacted about softening his LightSquared investigation.
Compiled by staff
Published: Jan 24, 2012
Senator Chuck Grassley, R-Iowa, has notified the Senate Ethics Committee regarding questionable contacts by LightSquared concerning Grassley's interest in the project. Since last April, Grassley has been reviewing why the Federal Communications Commission rushed approval of the LightSquared project without adequately exploring what turned out to be widespread concerns of interference with the Global Positioning System devices widely used by the military, first responders, aviation, precision agriculture, and consumer navigation.
According to a news release from Grassley's office, LightSquared made a questionable contact that intimated benefits for Grassley if he softened his inquiry of government approval of the project. Grassley has written Philip Falcone of Harbinger Capital Partners, expressing concern that two separate incidents implied a desire to have Grassley "pull punches" in his investigation.
The second contact was from someone who intimated that he represented LightSquared in a call to Grassley's staff. The individual, Todd Ruelle, hinted that if LightSquared were allowed to proceed, Grassley's home state of Iowa could get a "call center." Grassley's office advised Ruelle not to contact the office further. Grassley said he won't be a part of that.
Last week, LightSquared called on the National Telecommunications and Information Administration to objectively re-evaluate initial rounds of testing and also to evaluate mitigation proposals the company has proposed. LightSquared is charging that the process used to test GPS devices by Air Force Space Command on behalf of the Space-Based Positioning, Navigation, and Timing Executive Committee was rigged by manufacturers of GPS receivers and government end users to produce bogus results.
Jeff Carlisle, LightSquared's Executive Vice President, Regulatory Affairs and Public Policy; and Geoff Stearn, LightSquared's Vice President for Spectrum Development; charge the testing was shrouded in secrecy; the testing protocol deliberately focused on obsolete and niche market devices that were least able to withstand potential interference; and the testing standard does not reflect reality.
The company has called on the Federal Communications Commission and the NTIA to conduct the second round of tests on high-precision devices at an independent laboratory to ensure objectivity and transparency. LightSquared has agreed to meet every technical guideline requested by the Federal Aviation Administration, FCC and NTIA and will continue to work in collaboration with the federal government to resolve the GPS interference issues.
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Tagged: precision agriculture
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LightSquared, or any competitor using near frequency strong terrestrial transmission, will produce an off-band signal that will be received by the GPS receiver because of the bandwidth of the GPS receiver "patch" antenna. This is called "quality factor" or "Q" and is a measure of center frequency divided by 3db bandwidth. Unfortunately, GPS uses a high frequency, and Q diminishes with frequency (why radios and TVs all use a lower frequency IF stage, to get better transmitter station selectivity, and do not count on the antenna or RF stage for much help there).
GPS receivers can use a DSP computer to, and we will use the analogy of a noise canceling headset, make an interference signal "anti-noise" to add into the desired signal with noise, to remove the noise from the desired signal. Unfortunately, the signal must also be heard in the signal plus noise coming from the antenna to the DSP computer input.
Design assumption: the filter between the patch antenna and the first LNA RF amplifier inside the GPS antenna must reduce the interference signal amplitude down to equal to or lesser than the desired GPS signal before the DSP computer can be effective at eliminating the noise.
If you have zero loss at the GPS bandpass, how much LightSquared signal attenuation do you need over the entire noise spectrum bandpass? Let's do a "back of the envelope" engineering guesstimate:
You need to reduce the power spectral density of the noise to or below the power spectral density of the signal. Power spectral density is measured in watts per square foot.
Watts (the undesired is stronger, goes proportionally):
db = 10 log Pi/Pr
How much does LightSquared transmit - don't know, keeps changing.
How much is the effective radiated power of a GPS satellite - there is a spec for that.
db = 10 log 15,750/300
db = 17.2
Square Feet (the undesired is closer, goes inverse square proportionally):
db = 10 log Rr**2/Ri**2
How far away is LightSquared - assume 1000 feet
How far away is a GPS satellite - assume 11,000 miles x 5,280 feet per mile
Surface of a sphere is 4 x Pi x radius squared
The 4 and the Pi factor out
db = 10 log (11,000 x 5,280)**2 / 1,000,000
db = 95.3
Attenuation required = 17.2 + 95.3 = 112.5db
If you have zero loss at the GPS bandpass, how much LightSquared signal attenuation do you need over the entire noise spectrum bandpass? Let's do this another way, using "the other side of the envelope" engineering numbers, but where do we get those:
Power level and orbital lifetime limit
http://gpsinformation.net/main/gpspower.htm
Which limits have been exceeded on the majority of satellites
http://www.glonass-center.ru/en/GPS/
Which is why it is not working well
http://www.raimprediction.net/ac90-100/summaries.php?id=npa_nobaro
But we knew well in advance that GPS was cratering
http://www.gpsworld.com/gnss-system/block-iif-follow-or-failure-7265
GPS is supposed to be at around -130dBm on the ground, might want to expect less.
LightSquared's lower, re-re-revised (they're going to turn it way up later, they admit) power level is -30dBm "near" their tower. Don't expect a definition of "near", and keep in mind that LightSquared keeps changing numbers.
Attenuation required = -30dbm - (-130dbm) = 100db
But what does this mean:
db is a log scale so 10db is a factor of 10, 20db is 100, 30db is 1000, 40db is 10,000, 50db is 100,000...
100db is, everybody get, 10**10 = LightSquared 10,000,000,000 times stronger than GPS, might want to expect stronger
112.5db is, everybody get, 10**11.25 = LightSquared 177,827,941,000 times stronger than GPS, by geometery ratio watts/foot**2
Really really really really big! Somehow, LightSquared accusing the PNT committee of being off by 32 times doesn't seem like much (only 15db)!
You can adjust the number down as LightSquared offers new lower power limits, and up as they increase the power as they c
Posted by Anonymous on January 24 at 11:24 AM
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LightSquared, or any competitor using near frequency strong terrestrial transmission, will produce an off-band signal that will be received by the GPS receiver because of the bandwidth of the GPS receiver "patch" antenna. This is called "quality factor" or "Q" and is a measure of center frequency divided by 3db bandwidth. Unfortunately, GPS uses a high frequency, and Q diminishes with frequency (why radios and TVs all use a lower frequency IF stage, to get better transmitter station selectivity, and do not count on the antenna or RF stage for much help there).
GPS receivers can use a DSP computer to, and we will use the analogy of a noise canceling headset, make an interference signal "anti-noise" to add into the desired signal with noise, to remove the noise from the desired signal. Unfortunately, the signal must also be heard in the signal plus noise coming from the antenna to the DSP computer input.
Design assumption: the filter between the patch antenna and the first LNA RF amplifier inside the GPS antenna must reduce the interference signal amplitude down to equal to or lesser than the desired GPS signal before the DSP computer can be effective at eliminating the noise.
If you have zero loss at the GPS bandpass, how much LightSquared signal attenuation do you need over the entire noise spectrum bandpass? Let's do a "back of the envelope" engineering guesstimate:
You need to reduce the power spectral density of the noise to or below the power spectral density of the signal. Power spectral density is measured in watts per square foot.
Watts (the undesired is stronger, goes proportionally):
db = 10 log Pi/Pr
How much does LightSquared transmit - don't know, keeps changing.
How much is the effective radiated power of a GPS satellite - there is a spec for that.
db = 10 log 15,750/300
db = 17.2
Square Feet (the undesired is closer, goes inverse square proportionally):
db = 10 log Rr**2/Ri**2
How far away is LightSquared - assume 1000 feet
How far away is a GPS satellite - assume 11,000 miles x 5,280 feet per mile
Surface of a sphere is 4 x Pi x radius squared
The 4 and the Pi factor out
db = 10 log (11,000 x 5,280)**2 / 1,000,000
db = 95.3
Attenuation required = 17.2 + 95.3 = 112.5db
If you have zero loss at the GPS bandpass, how much LightSquared signal attenuation do you need over the entire noise spectrum bandpass? Let's do this another way, using "the other side of the envelope" engineering numbers, but where do we get those:
Power level and orbital lifetime limit
http://gpsinformation.net/main/gpspower.htm
Which limits have been exceeded on the majority of satellites
http://www.glonass-center.ru/en/GPS/
Which is why it is not working well
http://www.raimprediction.net/ac90-100/summaries.php?id=npa_nobaro
But we knew well in advance that GPS was cratering
http://www.gpsworld.com/gnss-system/block-iif-follow-or-failure-7265
GPS is supposed to be at around -130dBm on the ground, might want to expect less.
LightSquared's lower, re-re-revised (they're going to turn it way up later, they admit) power level is -30dBm "near" their tower. Don't expect a definition of "near", and keep in mind that LightSquared keeps changing numbers.
Attenuation required = -30dbm - (-130dbm) = 100db
But what does this mean:
db is a log scale so 10db is a factor of 10, 20db is 100, 30db is 1000, 40db is 10,000, 50db is 100,000...
100db is, everybody get, 10**10 = LightSquared 10,000,000,000 times stronger than GPS, might want to expect stronger
112.5db is, everybody get, 10**11.25 = LightSquared 177,827,941,000 times stronger than GPS, by geometery ratio watts/foot**2
Really really really really big! Somehow, LightSquared accusing the PNT committee of being off by 32 times doesn't seem like much (only 15db)!
You can adjust the number down as LightSquared offers new lower power limits, and up as they increase the power as they c
Posted by Anonymous on January 24 at 11:21 AM
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