In a much-anticipated webinar hosted by GPS World yesterday, Dr. Javad Ashjaee presented his efforts to address the LightSquared controversy. 270 people registered for the webinar, and 225 sat for the entire 90 minutes. Unfortunately, time ran out before all the pre-submitted questions has been asked, but the organizers promised to submit all the questions to Javad to allow him to answer for future dissemination via GPS World newsletters.
Javad opened his remarks by discussing his passion for GNSS, what he says "keeps his heart beating." He said that as a GNSS engineer, he is not happy with the solution he has created, but emphasized that this is not just about LightSquared, it’s about all interference. He pointed out that we still have to worry about other sources of interference and harmonics, the signals that overlap outside of their assigned band. He illustrated that his gear at least identifies interferences and attempts to ameliorate them. He reiterated his charge that the GPS industry (himself included) has done a poor job by designing gear that looks outside the GPS band. He added, "My solution provides a short-term answer, but at least I’m trying to solve the problem."
Responding to a question from Erik Gakstetter about the prospect of users have to pay twice for a retrofit, Javad provided financial analysis slides that showed that, even if a second round of retrofits is required, the cost per day amounts to less than the cost of a Big Mac. He said, "LightSquared is a not a disaster. A disaster is what happened in Japan earlier this year. There is no need to stop progress."
Responding to another question from Gakstetter about the costs of retrofitting the seven thousand RTN base stations in the U.S., Javad said, "Rather than approaching this from the angle of what is not possible, we should be approaching it from the angle of what is possible." He added, "I’m the only one who has tried to do something."
Much of his presentation was a repeat of what he presented at the PNT Meeting last month, but after that, he went on the offensive by asking the following questions:
• The PNT Letter was drafted by who and based on what research?
• Should we keep shipping faulty receivers to aggravate the retrofit problems even further?
• How much was spent by companies on finding a solution, and how much on efforts to stop LSQ?
• Did they try to find a solution and fail, or they did not try at all?
• Is this not a national emergency if our military GPS receivers are jammed even by LSQ signals?
• Are they using delay tactics so LSQ run out of time & money and investors get cold feet?
• Evaluate damages to the nation and to the GPS community so far, because of such irresponsible acts.
• 150 GPS scientists assembled at Stanford University 3 weeks ago to discuss the LSQ issue. What was the outcome? Did they find any flaw in my presentation to the PNT board?
• Do the people with special interest exaggerate the difficulty of retrofitting or upgrading existing receivers?
• A question for John Deere: Farmers equipment cannot be interrupted for retrofit or upgrade. They always work. (In the slides following this, Javad presented a joke. The first slide showed Deere combines harvesting corn. The second slide showed the same Deere combines harvesting snow, the obvious implication being that farmers do have downtime…in the winter.)
• The PNT Letter was drafted by who and based on what research?
• Should we keep shipping faulty receivers to aggravate the retrofit problems even further?
• How much was spent by companies on finding a solution, and how much on efforts to stop LSQ?
• Did they try to find a solution and fail, or they did not try at all?
• Is this not a national emergency if our military GPS receivers are jammed even by LSQ signals?
• Are they using delay tactics so LSQ run out of time & money and investors get cold feet?
• Evaluate damages to the nation and to the GPS community so far, because of such irresponsible acts.
• 150 GPS scientists assembled at Stanford University 3 weeks ago to discuss the LSQ issue. What was the outcome? Did they find any flaw in my presentation to the PNT board?
• Do the people with special interest exaggerate the difficulty of retrofitting or upgrading existing receivers?
• A question for John Deere: Farmers equipment cannot be interrupted for retrofit or upgrade. They always work. (In the slides following this, Javad presented a joke. The first slide showed Deere combines harvesting corn. The second slide showed the same Deere combines harvesting snow, the obvious implication being that farmers do have downtime…in the winter.)
The most eyebrow-raising moment of the webinar for me was Slide #92, on which Javad announced future plans for RTK service in connection with LightSquared. The slide contained the following innocuous statement: We will give up to 5 years of reduced-price RTK subscription ($10,000 value). Because I didn’t understand what that means, I posted an online question about it. But because they ran out of time for the Q&A portion, immediately after the webinar I inquired to Dr. Ashjaee. Here’s what he said: "Existing RTN operators charge $2,000 to $6,000 per year for RTK networks services. When we have our RTK networks (at the same time that LSQ is deployed) we will charge about $1,000 per year." This has big implications for existing RTN operators.
Here are the questions, most of which were not asked or answered:
• How can LSQ say that GPS receiver designs are “faulty” when they were designed to access GPS corrections broadcast by LSQ satellites in the MSS spectrum?
• What’s the 10L solution for aviation and military?
• Assuming a 10L solution, hundreds of thousands of receivers and/or antennas need to be replaced. Who will pay and what kind of transition period?
• Assuming a 10L solution, what’s the solution for OmniSTAR/Starfire?
• Assuming a 10L solution, is there potential GNSS interference from external LSQ mobile devices?
• What is the potential solution for 10H? Will the same type of testing for 10L need to take place for 10H?
• The ‘FIX’ is for a known time specific event, what happens when the ‘FILTER’ fails?
• Isn’t the terrestrial output of Light Squared expected to be much higher than the -10 dBm identified in the tests? Haven’t JAVAD just shown that multipath can be filtered out – not 4G signals?
• Do you believe a filter solution is possible for a 10-hi LightSquared signal broadcast in 1545-1555 MHZ?
• What is involved in upgrading an integrated GNSS receiver with the 10L solution?
• How will federal agencies be compensated for filter upgrades required on hundreds of millions of dollars of existing RTK GNSS GPS systems to allow LightSquared to implement their cell tower system when federal agencies are facing up to 15% or more in across the board budget cuts?
• If no testing of actual equipment/facilities operating at the proposed power levels has occurred, how can Mr. Javad Ashjaee assert that he has "found no GPS signal loss due to a low-10 (10L) signal power of -10 dBm“, taken to mean that there will be no significant interference issues?“
• Have the SAW filters in the proposed solution been tested over temperature? Low-cost L-band SAW filters tend to have high temp coefficients. Results of testing?
• What are the noise figures of your legacy receiver design vs. 10L-modified design?
• Has Javad GNSS participated in the FCC testing?
• Does the proposed 10L solution require group delay calibration? If so, have you tested with an external antenna? Does it require two cables?
• Your zero baseline graphs show that there is a 4-5cm bias on GPS P1 code measurements, whether calibration is on or off, and you indicated that this bias was determined by long term averaging. What is the standard deviation? Same question for GLONASS P1, where the bias is 7 cm with calibration on and 60 cm with it off.
• What is the degradation in rcvr sys. noise figure of ‘LS compatible’ rcvr as compared to similar ‘unmodified’ rcvr? SAW filters by their nature are sensitive to group delay variations with changing temperature, also possibly with aging and vibration. While it is possible to apply corrections to compensate for static GD variations, it may be another matter to comp. for GDs that are dynamically changing. Does the ‘LS compatible’ rcvr account for this? Are ‘dynamic’ corrections done today?
• If the MSS services are moved to the upper band, does the 10L solution cause any attenuation?
• How can LSQ say that GPS receiver designs are “faulty” when they were designed to access GPS corrections broadcast by LSQ satellites in the MSS spectrum?
• What’s the 10L solution for aviation and military?
• Assuming a 10L solution, hundreds of thousands of receivers and/or antennas need to be replaced. Who will pay and what kind of transition period?
• Assuming a 10L solution, what’s the solution for OmniSTAR/Starfire?
• Assuming a 10L solution, is there potential GNSS interference from external LSQ mobile devices?
• What is the potential solution for 10H? Will the same type of testing for 10L need to take place for 10H?
• The ‘FIX’ is for a known time specific event, what happens when the ‘FILTER’ fails?
• Isn’t the terrestrial output of Light Squared expected to be much higher than the -10 dBm identified in the tests? Haven’t JAVAD just shown that multipath can be filtered out – not 4G signals?
• Do you believe a filter solution is possible for a 10-hi LightSquared signal broadcast in 1545-1555 MHZ?
• What is involved in upgrading an integrated GNSS receiver with the 10L solution?
• How will federal agencies be compensated for filter upgrades required on hundreds of millions of dollars of existing RTK GNSS GPS systems to allow LightSquared to implement their cell tower system when federal agencies are facing up to 15% or more in across the board budget cuts?
• If no testing of actual equipment/facilities operating at the proposed power levels has occurred, how can Mr. Javad Ashjaee assert that he has "found no GPS signal loss due to a low-10 (10L) signal power of -10 dBm“, taken to mean that there will be no significant interference issues?“
• Have the SAW filters in the proposed solution been tested over temperature? Low-cost L-band SAW filters tend to have high temp coefficients. Results of testing?
• What are the noise figures of your legacy receiver design vs. 10L-modified design?
• Has Javad GNSS participated in the FCC testing?
• Does the proposed 10L solution require group delay calibration? If so, have you tested with an external antenna? Does it require two cables?
• Your zero baseline graphs show that there is a 4-5cm bias on GPS P1 code measurements, whether calibration is on or off, and you indicated that this bias was determined by long term averaging. What is the standard deviation? Same question for GLONASS P1, where the bias is 7 cm with calibration on and 60 cm with it off.
• What is the degradation in rcvr sys. noise figure of ‘LS compatible’ rcvr as compared to similar ‘unmodified’ rcvr? SAW filters by their nature are sensitive to group delay variations with changing temperature, also possibly with aging and vibration. While it is possible to apply corrections to compensate for static GD variations, it may be another matter to comp. for GDs that are dynamically changing. Does the ‘LS compatible’ rcvr account for this? Are ‘dynamic’ corrections done today?
• If the MSS services are moved to the upper band, does the 10L solution cause any attenuation?
You can view a 7.76Mb PDF of Javad’s
134-slide presentation HERE.
134-slide presentation HERE.