On Wednesday, October 13, 2011 we attended a press conference in Washington D.C. Martin Harriman, Executive VP of ecosystem development and satellite business of LightSquared and Dr. Javad Ashjaee of Javad GNSS were on hand to explain the filtering technology they say has solved the compatibility issue between precision GNSS receivers and LightSquared’s 4G LTE signal. Harriman (right) explained: “A majority of precision devices can be fixed by replacing the external antenna, others will require a factory retrofit, but in every case LightSquared has an affordable and efficient fix”
LightSquared has collaborated with several high-tech companies to develop solutions to the GPS interference issue, including Javad GNSS. According to LightSquared, other companies with Light-Squared compatible components that can be integrated into receivers include PCTEL, which has developed compatible chip sets, and Partron America, which has created a filtering component that only costs $6. Harriman stressed that the initial fix was accomplished with off-the-shelf parts, and did not require the invention of new technology. During the meeting, Javad’s antenna-based solution was showcased, and Javad said, “Mass production is limited only by a 4-6 week lead time for component parts.”
Regarding the impact LightSquared has on receiver design, Javad described the challenge as a building block for improved, next-generation designs. He said, “With the U.S. government’s GPS modernization program in effect, many legacy receivers will be obsolete in several years regardless. Our research and development has shown that making receivers compatible with LightSquared today produces higher quality results than before.” Unanswered was what this means for existing receivers, or who will pay for the upgrades. Part of the answer lies in the fact that the LightSquared network will not happen overnight, but will take three years to build out. As an example, Harriman said a market, for example Chicago, will be selected, and only the precise receivers in that region will be affected, not the entire country. Build out is scheduled to begin in the second half of 2012.
In comments about how the situation has arrived at the current point, Javad (left) said, “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. LightSquared is going to provide a better, faster, and cheaper communication channel for RTK and DGPS. LightSquared will be a much better system, and although it might shake up the current scenario—the same way e-mail damaged the facsimile business—it is the law of innovation.”
Regarding the viability of the Javad GNSS solution, Javad (left) said this: “Some claim that technology to filter out LightSquared signals—and at the same time keep the GPS signals intact—does not exist and may not come to existence for many years. While listening to the “filter group delay” questions and comments at the NTIA hearing in August, it became clear to me that some do not understand the innovation I developed two years ago. At ION 2009 I explained that we compensate for GLONASS inter-channel biases with the accuracy of 0.2 millimeters and because we do this, our GLONASS is as good as GPS. The underlying principle of this is that we calibrate for group and carrier delay variations of filters, and filter group delay flatness is not an issue any more. In any event, GPS positioning is much less sensitive to group delay variations, to the point that precision positioning users will not see any significant effect. Our test results confirm this as well.”
LightSquared has explained that the “commercial” side of GPS, comprising 99.5 percent, is safe due to its move to a lower band (1526-1536MHz, 23MHz away from GPS). The plan for the lower band was announced in June—according to its estimates costing LightSquared $100 million—and solved the problem for 99.5 percent of all GPS devices, including consumer devices such as cell phones, tablets, automobile systems and computers. Precise devices, which fall in the 0.5 percent, have not been fully tested. These solutions will undergo extensive NTIA and FCC testing in the coming weeks and months. Harriman added, “The previous round of testing by the FCC on LightSquared’s system was the most extensive in the agency’s history.”
When asked about LightSquared’s plans for using the upper band in the future, Harriman refused to rule it out by saying, “We have come up with a quick, inexpensive solution to allow us to use the lower band, but technology has not yet been invented that will allow us to use the upper band. We hope that a solution for that will be found as well, but expect the technical innovation to take years, not months.”
We asked Harriman about the fact that the LightSquared transmissions will be billions of times stronger than the weak GPS signals. Harriman responded, “We have said since 2003 that we will be using a terrestrial scheme, and the authorization was updated in 2004 to give LightSquared a higher power level, and re-confirmed in 2010. How much notice does the industry need that we’re going to use that spectrum for terrestrial?”
LightSquared sees this as an issue of sovereignty, having purchased their spectrum at auction and being granted the first license to deploy and provide terrestrial service in the L-Band spectrum in November 2004. They’ve invested heavily in the project over the last eight years, and frequently cite that their plans have been public for years, open for collaboration and comment.
This is how we’ve arrived at the retrofit. LightSquared has committed $50 million to the retrofit of government-owned legacy GNSS receivers (in the event Javad’s initial solution proves reliable), but sees the upgrade of all remaining precision GNSS receivers as something beyond their liability, something the precise crowd needs to deal with. The only thing that could force this to happen is a reasonable upgrade path, which LightSquared and Javad say they have now developed.
As a result, testing of the proposed solutions will remain front-and-center in the coming weeks and months. Harriman said, “The precise users absolutely should not pay for the upgrades, the manufacturers should pay.” He used Garmin as an example of a mass recall. After units developed a fire hazard with batteries, Garmin recalled 1.2 million units—760K in the U.S.—within a matter of months.
Javad defended his efforts, stating, “If I fail to deliver, in addition to great embarrassment, I stand to lose along with the rest of the precise community.” Javad has high hopes for using LightSquared to deliver RTK correctors. Of course, there are huge issues to address in turning LightSquared into a giant RTN, but theoretically, it could be done, and many agree that it would be a good thing. Javad added, “The manufacturers should be focusing not only on making receivers LightSquared compatible, but future compatible as well.”
Subsequent to the press conference, and to gain more details, we spoke with Javad, and he said, “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 filters allows LightSquared signals into a GPS receiver. This can block and/or damage the GPS signals and cause the receiver to not function properly.
“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 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.
“We have solved the second problem of “self test” by adding “interference analysis” feature to our GNSS receivers. This feature analyses 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 perform in the field.”
If necessity is truly the mother of invention, and LightSquared and Javad are correct, we’ll end up with stronger GNSS and nationwide broadband that’ll make our early 21st century 56kb dial-up service and current RTK capability look like a horse and buggy. Without a doubt, broadband is something we need, and both sides agree on this. I’ve heard anecdotal reports that 4G makes 3G look like dial-up. When there’s not very many people sharing it, speeds as high as 30Mb/sec have been achieved. And even with a lot of people sharing the bandwidth, speeds of 3-5Mb/sec are common.
From an overall perspective, we’re at a crossroads. The precision GNSS industry has enjoyed 20+ years of uninterrupted performance and developed mounds of technology to utilize it, something too far along to lose. As he has many times in his career, Javad stands alone with his solution and opposition to the rest of the GNSS industry’s position. If he is correct, the precise crowd will benefit. And if LightSquared prevails—looking out for my fellow surveyors—it all comes down to who will pay for the retrofits. But as long as both sides disagree, the debate will continue.