Lightsquared and GPS

Nov 2011 | No Comment

“Retrofitting the existing receivers can be a win-win situation”

Javad Ashjaee

President and Chief Executive Officer,
Javad GNSS

LightSquared is a gem! I am not only talking about its nationwide high-speed 4G capabilities and that it will be a boost to our lagging IT industry which has fallen behind 18 other nations. I am focusing on how it can beautifully complement high precision applications of GPS. It is a gem for GPS high precision users and for RTK.
In our GPS receivers we have 6 different communication systems to transmit/receiver RTK messages: 1) UHF, 2)Wi-Fi, 3)LAN, 4)GSM/ GPRS, 5)Spread Spectrum, and 6) L-Band. None of them can conveniently provide a good, reliable and cost-effective RTK communication channel. I say LightSquared is a gem because of what it can do for GPS RTK applications.
Unfortunately, in the past several months so much misinformation has been published about this subject that many have been convinced that LightSquared and GPS cannot exist together. Every single GPS-related magazine is full of editorials and commentaries against LightSquared without giving substance and reason for what they write. There were even attacks on LightSquared executives for their political contributions and how they made their initial money! The root of the problem is us, the GPS manufacturers. We designed our receivers without paying reasonable attention to other systems that may come close to the GPS bands. The problem manifests itself in two ways: 1) Most GPS receivers do not have proper protective filters in the antenna section, and 2) The receivers don’t have a means to indicate if there is any interference in the area of operation.
The first problem of inadequate filter causes our GPS receivers to “invite” LightSquared signals to arrive to our GPS receiver. This can block and/or damage the GPS signals and cause the receiver to not function properly. We solved the first problem by adding a set of Ceramic and SAW filters in the signal entry to our GNSS receivers. The filters were all existing off-the-shelf components. The filter system works fine and does not impose any noticeable negative effect on the quality of GNSS signals and solution results. In particular in has no noticeable effect on the multipath mitigation capabilities of receivers that need intact and undisturbed GNSS signals. The cost of the additional filters is negligible.
The second problem is inadequate test and warning features inside GPS receivers. Most receivers do not give any information regarding the existence of interferences. It is exactly for the lack of such test features that caused NTIA to go through a solid month of hard work to test receivers using external means. Such external means include very expensive test equipment and sophisticated test plans which can only be carried out by highly experienced people. Interferences are not only from LightSquared. Even harmonics of a radio station signal can cause interference. GNSS receiver should have a means to alarm the user of the existing interferences in its area. It is impossible to assemble NTIA-like test setups in every area that users need to use their GNSS receivers and perform such tests ahead of each daily job. We also have solved the second problem of “self test” by adding “interference analysis” feature to our GNSS receivers. This feature analyzes the effect of interferences in a much better way than NTIA test procedures specify and it does it in a much shorter time: It does it in 30 seconds, rather than 30 days, and it does it by a click of a button which any novice user can do easily in the field.
There has been a lot of discussion about what should be done with existing receivers in the field. I have the following points:
1. All existing receivers will be obsolete when new GPS satellites are launched. New GPS satellites will transmit “modernized signals” which, unlike P1 and P2 codes that we currently use, are not encrypted. Currently two of these modernized GPS satellites are on orbit and others will follow soon. It may take until 2020 before the constellation fully consists of all new satellites, but as soon as a few more are launched, users who have GPS receivers that receive the new signals will be able to benefit and have a competitive advantage in the marketplace.
2. All receivers that we currently ship are LightSquared compatible or are eligible for free retrofit. We have also offered to retrofit our existing receivers with cost of $300 to $800 depending on the model. Also, if customers chose to purchase these options, our receivers can track the new modernized GPS and GLONASS signals, as well as Galileo.
3. We have offered to retrofit receivers of other manufacturers to be LightSquared compatible.
4. We also offer a better plan for the qualified existing units in the field. Instead of retrofitting the existing units to be LightSquared compatible and later buy an expensive new receiver, we offer attractive financial incentives to upgrade receivers to not only be LightSquared compatible, but also track new modernized GPS signals as well.
In summary, retrofitting the existing receivers can be win-win situations for all sides. Owners of existing GPS units may need to pay a little, but they will get a lot more in return; and they will not be stumbling blocks on the way of progress and innovations.
There have been rumors that LightSquared signals affect military receivers. If this is true our military has a disaster in its hands. If military units cannot tolerate the LightSquared signals which 1) are far from the GPS band and, 2) are not coming from sophisticated jammers, how can they operate in a hostile theatre of operation? Were there not any anti-jam requirements in RFP of military GPS receivers? Has there been any anti-jam test performed on military receivers? Is LightSquared the first test? The irony is that the filters that we have designed can tolerate LightSquared signals and track encrypted P-codes, but our military receivers cannot tolerate LightSquared while military receivers have access to un-encrypted P-codes which are up to 1,000 times stronger than the encrypted versions that we track.

“A general GNSS industry view that retro-fitting new filters on all fielded receivers was impractical”

John Pottle

Marketing Director,
Spirent, Positioning and Navigation Group

LightSquared has forced to see GPS device makers what they could not foresee earlier. Has it caught GPS device makers unguarded?

The GNSS community has been operating on the assumption that the band that LightSquared would use, just below the GPS L1 band, would not be occupied by a high power terrestrial signal. In other words, the assumption has been that GPS would not have “noisy neighbours”. The current debate between LightSquared and the GNSS community is whether LightSquared signals in the adjacent band to GNSS L1 are powerful enough to cause operational issues for GPS receivers. The results of the initial testing have been published and are available online. Further testing based on a revised LightSquared signal, with less power directly adjacent to GPS L1, is now underway and results are due to be published later in 2011.

What is the Spirent’s position on LightSquared GPS interference issue?

For many years Spirent has provided test equipment that enables quantification and analysis of GPS system performance. We also supply systems that enable GPS performance to be evaluated in the presence of one or more interference signals. As such, Spirent’s position on LightSquared has been that it’s helpful to assess quantitatively effects of the proposed LightSquared signals on GNSS receiver performance. This is what has been done in the testing conducted under the auspices of the FCC-mandated Technical Working Group.

How can Spirent help in addressing this issue?

Spirent has helped in three ways: provision of test equipment to generate the signals involved (GNSS and LightSquared simulated signals); providing expertise on test methodology; and providing automation scripts to run the hundreds of tests that have been defined by the Technical Working Group.

Do you think that filter in GPS can solve the problem?

There has been a lot of debate over the “right” level of filtering on GPS receivers in future. However, a major consideration is that there are literally millions of GPS receivers already in the field and being used by consumers, businesses and governments for a huge range of applications. At a recent debate on this topic at the Institute of Navigation conference in Portland, Oregon, USA there was a general GNSS industry view that retro-fitting new filters on all fielded receivers was impractical.

Can there be a scenario where GPS and LightSquared network can comfortably coexist?

This is a difficult question to answer until further test data is available. The current testing will report from later this year and this question will be assessed by LightSquared, the GNSS community and the FCC.

House Small Business Committee asks the FCC to halt waiver on LightSquared

House Small Business Committee Chairman Sam Graves (R-MO) along with eight members of the Committee sent a letter to Federal Communications Commission (FCC) Chairman Julius Genachowski requesting that the FCC not proceed with LightSquared’s waiver until federal testing ascertains that there will be no interference with all types GPS devices. The Committee also requested the FCC to report their action plan regarding the proposal to the Committee. LightSquared is proposing to build a ground-based broadband network that could interfere with current GPS technology and impact millions of small businesses. “While LightSquared’s aim to increase broadband to rural areas is a noble goal, we must find a solution without jeopardizing established GPS systems and further burdening small businesses,” said Graves. “Under the current LightSquared proposal, small businesses would be left to foot the bill that will easily cost billions to replace or retrofit their current GPS devices. “Small companies should not be required to spend one dime on account of this plan— and that is why we are calling on the FCC to put a hold on the waiver until all federal tests make clear there will be no interruptions to current GPS systems.”

LightSquared and PCTEL to resolve precision GPS applications

PCTEL has developed an antenna that will allow existing high precision users to retrofit their GPS devices to make them compatible with LightSquared’s network. This antenna provides high precision GPS users with another in a series of solutions to make their equipment LightSquared-compatible. PCTEL’s antenna solutions address applications including public safety, agriculture, construction and aviation. The new antenna will be independently tested with a range of receivers at the world-renowned Alcatel-Lucent Bell Labs in Murray Hill, NJ.These solutions will undergo extensive National Telecommunications and Information Administration (NTIA) and Federal Communications Commission (FCC) testing in the coming weeks.

Javad to discuss GPS receiver filter solutions at PNT meet

The National Aeronautics and Space Administration have announced a meeting of the National Space-Based Positioning, Navigation, and Timing Advisory Board during November 9-10. These meetings are generally open to the public, in accordance with the Government in the Sunshine Act. The meet is expected to have a panel on LightSquared with LS2 Executive VP Martin Harriman and Javad Ashjaee, CEO of JAVAD GNSS to discuss their proposed GPS receiver filter solutions as well as the latest test results.

My Coordinates
His Coordinates
Phil Gabriel, Leocadia I Zak
Intergeo 2011
Mark your calendar
November 2011 TO October 2012

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