LightSquared: High-Precision Receivers Are Collateral Damage

June 21, 2011  - By

Originally, the LightSquared/GPS Technical Working Group’s (TWG) report was due to the FCC on June 15, 2011. LightSquared requested from the FCC, and received, a two-week extension to submit their report. Three days later, LightSquared announced it found a solution to the GPS interference problem. Its new proposed solution is not good news for the high-precision GPS user community. Instead, it’s a threat directed squarely at high-precision GPS users like you and me. Do you recall what I wrote a month ago? It’s ringing true with the latest LightSquared proposal.

“I’m going to keep this simple. You, the high-precision GPS user, are likely going to be considered collateral damage.


The military is going to be accommodated in the name of national security. The aviation industry is going to be accommodated in the name of safety-of-life. The auto navigation industry is going to be accommodated because they are high-profile. The high-precision user is going to be thrown under the bus because we are the most difficult to accommodate (technically) and don’t have a high profile nor are perceived as significant enough to accommodate.”


If you recall, the TWG consists of LightSquared and GPS industry representatives tasked with testing the effect that LightSquared’s proposed system may have on GPS. Four of the five sub-teams were ready to file their final report with the FCC on June 15. LightSquared’s sub-team, according to the Coalition to Save Our GPS webinar on Thursday June 16, was only sub-team not ready to file its report.

Ok, so after the FCC granted LightSquared the two-week extension, I’m thinking we have a two-week hiatus from the LightSquared discussion as LightSquared compiles and prepares their July 1 submission.


Nope, not a chance.

On Monday, a mere three business days after they requested a two-week extension from the FCC,  LightSquared announced they’ve found a solution to the GPS interference problem and issued a statement titled “LightSquared Solution to GPS Issue Will Clear Way for Nationwide 4G Network.”

LightSquared’s solution is to temporarily abandon the upper frequency they originally planned to roll out (1550-1555 MHz) and rollout its service using the lower spectrum I refer to as “modified” (1526-1536 MHz) in Figure 1.

It’s important to remember that the lines separating frequency spectrums are not “brick walls.” There is signal “roll off” that results in a gray area between spectrums. That’s the reason the LightSquared upper frequency at 1550-1555 MHz was slamming GPS. Even though it is apparently separated from GPS L1, the sheer power of the LightSquared signal at 1,500 watts significantly bled into the red RNSS zone (1559-1610 MHz) in Figure 1.


                                              Figure 1: FCC Spectrum Dashboard

Using only the lower frequency spectrum (1526-1536 MHz), LightSquared claims that they are “largely free of interference issues with the exception of a limited number of high-precision GPS receivers that are specifically designed to rely on LightSquared’s spectrum.” LightSquared’s CEO said that this solution will accommodate 99.5% of the GPS receivers.

Uh oh, guess who the remaining .5% are? Yes, your high-precision GPS receiver. One half of one percent is about the percentage of high-precision GPS receivers with respect to the total GPS market size in the U.S.

I’m pretty confident that LightSquared isn’t weighting the receivers, so that means a $2 GPS chip inside a mobile phone carries the same weight as your $15,000 RTK receiver. But obviously the impact on our infrastructure and economy differs by orders of magnitude between the two.

Remember last month when I wrote that high-precision GPS receivers might be thrown under the bus and considered collateral damage (LightSquared: It’s Worse than You Think)? The latest LightSquared proposal is what I was referring to. High-precision GPS receivers are the most difficult to accommodate, and LightSquared is thinking that if they tell the FCC (and the world) that they’ve taken care of 99.5% of the GPS receivers in the U.S., the other .5% can deal with it.

It’s not yet clear how LightSquared broadcasting on 10L (1526-1536 MHz) will affect high-precision receivers. We should see some of those details at the end of the month when all reports are filed with the FCC.

But either way, it’s clear that LightSquared broadcasting in the 1526-1536 Mhz spectrum would slam OmniSTAR and Deere & Co. Starfire users as you can see in Figure 1.

Not so fast, say GNSS engineers. What about GLONASS, Galileo, and Compass?

Russia’s GLONASS satellites are increasingly being used by high-precision receivers. In fact, it’s safe to say that all major manufacturers sell GPS/GLONASS receivers, which is an expensive option on most receivers. However, it’s relatively easy to justify the additional expense due to the productivity gains from the additional GLONASS satellites. Generally speaking, more satellites equals less down-time.

The problem is that the U.S. government has no vested interest in protecting the GLONASS spectrum.

The FAA doesn’t care about it. The U.S. military doesn’t care about it. The first-responders don’t care about it. Although GLONASS is starting to show up in consumer GPS chips, it’s not being used in those markets like it is in the high-precision markets such as surveying, engineering, construction, agriculture, GIS, and various machine control applications. Therefore, no GLONASS testing was performed at the Maryland test site (simulator not configured to output GLONASS) and little or no testing was done using GLONASS at the New Mexico or Las Vegas sites unless individual companies took it on themselves.

Some say that GLONASS will get hammered by LightSquared mobile phones.

To this point, most of the talk has been about GPS interference from LightSquared transmitters in the 1525-1559 MHz spectrum. We also need to be aware of LightSquared mobile phones, of which they intend to field 250 million — 100 million by the end of 2012. While LightSquared has control over the filtering on their transmitters, it have no control over the filtering used in mobile phones designed to use their system.

I’ve heard there is some mention of LightSquared mobile phones in the reports that are to be filed with the FCC, but not made public yet. However, no LightSquared mobile phones exist today so it’s only possible to simulate them in a lab environment using a lot of design assumptions.

The uplink frequency used by LightSquared mobile phones (to talk to the nearest tower) is in the range 1626.5-1660.5 MHz. That frequency is getting close to the top end of GPS and really close to GLONASS L1 which has a range of ~1598-1605.4MHz.

According to one RF engineer I’ve spoken to, “We already know that Iridium (1616-1626.5 Mhz) and Inmarsat cannot co-exist in the upper band and seeing that the LightSquared handset transmit frequency is in that same spectrum, I think GLONASS in the U.S. is toast.”

The future of GNSS receivers is definitely trending towards integrating GPS, GLONASS, Galileo, Compass, etc. signal
s. A section of the NPEF report (mentioned above) succinctly describes the interference issue with GNSS receivers.

Another approach examined involves limiting the LightSquared transmissions to the lower 5 or 10 MHz channel of their planned deployment. However, while this approach would protect a limited number of GPS applications other applications would still be susceptible to interference. Using this approach it may be possible to protect classes of GPS receivers, primarily those with greater receiver selectivity. However, some classes of GPS receivers would still not be protected under this mitigation technique. Receivers having wider RF front-end characteristics, such as those used for scientific and commercial uses requiring high-precision measurements, and some receivers capable of receiving multiple signals from different GNSS systems (e.g., GLONASS) would remain susceptible. Additionally, the use of only the lower LightSquared channel would provide only a temporary solution to the existing interference problems as 4G LTE levels of service may not be possible. Thus, even if allowed, the FCC’s objectives and service conditions on the LightSquared license would not be met.

Finally and on a slightly different note, the future GPS L1C signal and L1 signals proposed by Galileo and Compass are a wider band than the current GPS L1 CA, which means they are likely more subject to interference from the LightSquared system.


FCC Chairman Julius Genachowski: “As I have stated previously to Congress, the commission will not permit LightSquared to begin commercial service without first resolving the commission’s concerns about potential widespread harmful interference to GPS devices. Under no circumstances would I put at risk our nation’s national defense or public safety.”

The FCC has stated on numerous occasions that LightSquared won’t be allowed to begin commercial service until GPS interference issues are resolved, but what does that really mean?

Chairman Genachowski has also stated that “It should come as no surprise to anyone involved in the LightSquared matter that the company was planning for some time to deploy a major terrestrial network in the spectrum”. He’s implying that all parties involved should have prepared for this moment, and if the GPS industry didn’t, it should bear some of the burden. This is bad news indeed.

Bottom line: The FCC is not looking out for your interests. The National Broadband Plan is heavy on their minds. I can clearly see the FCC thinking “in the interest of the bigger picture, the high-precision GPS user community can deal with it since its only .5% of the total GPS market.”

We need to squash this new proposal by LightSquared in a hurry. It’s a threat directed squarely at the high-precision GPS user community.


LightSquared Consultant claim: in the GPS industry’s “insatiable thirst for precision,” it made poor engineering decisions that made GPS receivers more vulnerable to interference from neighboring bands.

Although it appears the statement is from an independent consulting firm, PRTM consultant Dan Hays is a Harbinger crony so don’t let it fool you into thinking it’s anything but another piece of LightSquared propaganda.

But, let’s visit the subject for a minute to clarify because LightSquared has also claimed that high-precision GPS receivers are somehow at fault because they “are looking in our spectrum”.

Jim Kirkland, VP and General Counsel for Trimble Navigation, said it well when I presented Mr. Hays’ statement during the Coalition to Save Our GPS webinar last Thursday. Mr. Kirkland responded:

“… we’ve engineered our products to use services that are available for payment to LightSquared’s predecessors. That’s a critical point…these precision receivers are designed to receive MSS signals to make the services better and they pay for those services to Skyterra (owned by LightSquared) and Inmarsat (LightSquared vendor). So if that’s a bad design decision that we decided to design our receivers so that our customers could pay money to Skyterra (LightSquared), that’s one of the more absurd things I’ve heard in this whole debate.”


What he’s talking about is that OmniSTAR pays SkyTerra (LightSquared) to lease bandwidth on their satellite to deliver corrections to high-precision GPS users on the ground. Yes, if you pay OmniSTAR for their VBS, HP, or XP service, then a portion of what you pay goes to LightSquared. The irony is as thick as molasses. Furthermore, Deere & Co/Navcom offer a similar service called Starfire in which they lease satellite bandwidth from Inmarsat. LightSquared and Inmarsat are connected. Based on an original agreement signed in December 2007 between LightSquared’s predecessor and Inmarsat, Inmarsat is to receive hundreds of millions of dollars from LightSquared towards “the re-banding and efficient reuse of L-band radio spectrum covering North America.”

Essentially, what LightSquared is doing is selling the GPS industry their satellite-to-earth wireless services (a la OmniSTAR), but they are complaining that the GPS industry has designed GPS receivers to utilize services in which LightSquared gets paid. Is that a “poorly designed GPS receiver”?

I’ve even heard, through the grapevine, that some legislators are regurgitating this nonsense of “poorly designed GPS receivers.” Maybe there’s no ill-intent, but it’s either that or a fair amount of ignorance.

Logically, many of today’s high-precision GPS receivers have OmniSTAR/Starfire capability built into their antennas and RF front-ends to look into the 1525-1559 Mhz spectrum for the OmniSTAR/Starfire signals. They don’t focus on particular frequencies in that band because the frequencies change periodically as OmniSTAR users can attest. Also, even if you have the OmniSTAR/Starfire capability turned off in your receiver, the antenna is still designed to look into that band so there’s no way around it.

Like I mentioned earlier, even if your receiver isn’t designed to utilize OmniSTAR/Starfire, no one knows yet if it might be affected by the LightSquared 5L/10L signal.

Where do we go from here?

There’s a lot more to talk about on this issue. It’s as critical as it’s ever been that you make you concerns known to your state senators and representatives as well as the FCC. Scroll to the bottom of this article for web links and contact information.


Free Webinar – Thursday, June 23. LightSquared: What it means to the GPS Surveying/Mapping User Community

Thursday, June 23, I will conduct a webinar to discuss the LightSquared issue as it relates specifically to the GPS Surveying/Mapping community (high-precision users). Joining me will be Dr. Mike Whitehead, VP of Technology at Hemisphere GPS. He’s a leading GNSS design engineer and can speak clearly about the technical ramifications of LightSquared interference on high-precision GPS receivers. Click here to sign up for the webinar. Sign up even if you can’t attend the live webinar on Thursday because you’ll be sent an email on how to view the archived presentation that you can listen/view at your convenience.


Squared coverage at the Esri Survey Summit (July 7-12, San Diego, CA)

Esri has coordinated comprehensive coverage of the LightSquared issue at this years Survey Summit. Remember, this year the Survey Summit is combined with the ACSM (American Congress on Surveying and Mapping) annual conference so the turnout should be very good.

On Friday, July 8th @ 2pm at the Survey Summit, I’ll be giving a 60 minute presentation entitled “GPS/GNSS Technology Update” focused on covering the latest developments in GPS/GNSS. I will cover the latest LightSquared news as well as other recent GPS/GNSS technology developments.

On Saturday, July 9th @ 3:30p and 4:00p respectively, Jeffrey Carlisle from LightSquared and Peter Large from Trimble Navigation will give 30 minute presentations on the GPS/LightSquared interference issue.

On Sunday, July 10th @ 8:00a-10:00a there will be a GPS/LightSquared discussion panel consisting of myself, Peter Large, Jeff Carlisle, Curt Sumner (ACSM), John Matonich (NSPS), and Dr. Javad Ashjaee. The panel discussion will be moderated by Joe Paiva. This will be the first panel discussion in the industry focused on the high-precision GPS/LightSquared interference issue.

Following the discussion panel, at 10:30am-Noon,  there will be a strategy session designed to plan actions that surveyors (high-precision users) can take to avoid becoming collateral damage.


Take Action Now
The Coalition to Save Our GPS has posted guidance on its website as to how to submit your comments. They are:
Voice your concerns directly to Congressional Representatives
To voice your concerns about GPS interference, you can send letters, emails, faxes, call or visit your Congressional representatives’ office in person to explain how you use GPS as a local business and what the impacts of interference would be to the local economy.
Contact Your Local Senator
Ask your Senator to support and co-sign the letter from Senators Roberts (R-KS), Nelson (D-NE) and nearly a third of the U.S. Senate: explain how you use GPS in your state and what impact interference or any compromise of the GPS service would have on you and the local economy.
Write Your Representative
The Washngton Wire reported this week that “A bipartisan group of 66 House members asked the FCC Tuesday to protect global positioning systems from interference from wireless broadband start-up LightSquared…”
Please include: “Coalition to Save Our GPS and FCC File No. SAT-MOD-20101118-00239” in your correspondence.
Send your comments directly to the Federal Communications Commission (FCC)
Email the FCC:
For your ready reference, below are the actions the Coalition is seeking from the FCC:
  1. The FCC must make clear, and the NTIA must ensure, that LightSquared’s license modification is contingent on the outcome of the mandated study unequivocally demonstrating that there is no interference to GPS. The study must be comprehensive, objective, and based on correct assumptions about existing GPS uses rather than theoretical possibilities. Given the substantial pre-existing investment in GPS systems and infrastructure, and the critical nature of GPS applications, the results of studies must conclusively demonstrate that there is no risk of interference. If there is conflicting evidence, doubts must be resolved against the LightSquared terrestrial system. The views of LightSquared, as an interested party, are entitled to no special weight in this process.
  2. The FCC should make clear that LightSquared and its investors are proceeding at their own risk in advance of the FCC’s assessment of the working group’s analysis. While this is the FCC’s established policy, the Commission’s International Bureau failed to make this explicit in its order.
  3. Resolution of interference has to be the obligation of LightSquared, not the extensive GPS user community of millions of citizens. LightSquared must bear the costs of preventing interference emanating from their devices, and if there is no way to prevent interference, it should not be permitted to operate. GPS users or providers should not have to bear any of the consequences of LightSquared’s actions.
  4. This is a matter of critical national interest. There must be a reasonable opportunity for public comment of at least 45 days on the report produced by the working group and further FCC actions on the LightSquared modification order should take place with the approval of a majority of the commissioners, not at the bureau level.
Thanks, and see you next time.
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