Getting to L5, A More Modern Signal


Through L5-Direct, oneNav makes it possible to access the L5-band with zero dependence on the weaker, more vulnerable L1.


About seven years ago, Paul McBurney decided it was time  to make an L5-only receiver. It was clear the signal was superior to L1, with less noise, less error and more resiliency to jamming attacks. But back then, to get to the L5 band, you had to go through L1.

McBurney left his job at Apple and started assembling a team to help him change that. oneNav was soon born, and over the years that team, which includes VP of Strategy and Ecosystems Development Greg Turetzky, has worked to create a solution that bypasses L1 entirely.

The IP core that makes it all possible is ready and available today, Turetzky said, and the solution applies to just about every market.

Here, Turetzky tells us more about the technology and why this is such a significant advancement for the industry.

TURETZKY: Paul saw that L1 was a giant pain point for phone hardware teams that had to use dual frequency receivers to get to the modernized L5 signal. And he saw from a navigation perspective that once you’re tracking L5 signals, you don’t want to use L1 at all. L5 has a lot of benefits over L1, so he thought this would revolutionize the mobile phone industry again. So, at first, we mostly focused on mobile phones and consumer handhelds.

TURETZKY: Once we got the team together, we started pitching. People were interested, but the challenge was the only way to prove the IP core we developed for the solution worked was to build a test chip, which is a very expensive proposition. Instead, we demoed the technology with an off-the-shelf FPGA. It took us two years to do that, and we showed it around to all the usual suspects. They said yeah, that’s cool, but nobody is asking for it and we could do it ourselves if we wanted to.

The other problem was somebody has to make the silicon to go into the product, so we ran into a roadblock with OEMs wanting the solution, but silicon makers not interested in adding the capability. That was the first phase of the company. Next, we started pitching the technology to the consumer smartwatch market and IoT.

In the IoT business, we had a different set of silicon providers, smaller companies making lower power solutions. Most of them looked at this and said we don’t know how to do that. They didn’t know how to build a chip. It became clear we needed to build our own test chip, so we raised the money to do that. We worked with silicon implementation teams to create the physical design that included an RF only L5 chain so we could demonstrate the size and power reduction in the RF. The only thing we didn’t do was build an antenna.


TURETZKY: With the test chip, we found we could go beyond handsets and OEM commercial products. There’s also a great market for this technology in automotive because the problems associated with L1 aren’t problems with L5. Most people are building dual frequency receivers even in automative to acquire L1 and then turn it over to L5. But if L1 gets jammed you lose your L5. With our solution, you acquire them independently. The fact they are not dependent on each other increases reliability.

There are multi frequency markets where the IP core is valuable but they still need that centimeter level accuracy, like drones and autonomous vehicles. Now, they rely on L1 and if they get L5 great, it will make life better. But they should think about it the other way. L5 is the signal they really want first and nothing should be in the way of them getting it. And if they can get another signal for dual frequency, that’s a great add on.

The feedback from the defense side is L1 dependency is a nightmare and it’s worse with the conflicts going on. They love the L5 solution. We’re hearing the same from the cellular infrastructure world, which has experienced jamming problems on L1. There’s also talk about GNSS co-existing with the LEO comms satellites rather than cellular. A lot of the frequency bands allocated around L1 are harder to integrate with an existing receiver than L5. So, having a direct L5 receiver with no reliance on L1 has started to get more attention over the last few months.

TURETZKY: The L5-Direct method is going to change everything. We’ve had this standard on L1 for decades, but now we have better technology and don’t need to keep the old technology built 40, 50 years ago. You don’t have analog or 2G in cell phones anymore because you don’t need it.

TURETZKY: We understand that CPNT means other systems not just GNSS, but everyone wants GNSS to be included and be as robust as can be. If you look at L1 versus L5, you’re talking about 15 db of interference protection because you have longer codes with shorter code lengths. Could you jam L5? Yes, but it would take more power to do it and the radius you could jam would be less. With this solution, we’re trying to make sure the GPS portion of your system is as robust and reliable as it can possibly be.

TURETZKY: I like to think of an IP core as a democratization of this capability. You don’t have to get it from a current GPS supplier. You can build it directly or engage a third-party chip manufacturer to build the chip you want. The hard engineering is done; the only thing left is implementation. The core enables anyone to have that level of performance without buying it from existing players. We’ve brought this technology out in a way that anyone can access it, whether you’re in phones, IoT, automotive or defense.

We’ve solved the technical problems; all you need is somebody who builds silicon. You can be in control of your own silicon if you want a bigger CPU, this type of memory, etc. You can do that with an IP core. You can’t do that with somebody else’s chip. It really can disrupt the supply chain that today is a small number of large companies that control the entire market.

It’s important to note that even though we’re not in the chip business, our test chip could be a production chip. Somebody could decide to take it and be in business in three months. There’s a real benefit in this solution because we’ve already done a lot of the legwork.

TURETZKY: The user improvement is pretty clear in terms of accuracy and availability. L1 works just fine in open sky with a great antenna and no jamming. But if you go into an urban canyon or experience interference or have an antenna that isn’t so great, the degradation of the solution is massive. With an L5-Direct receiver, that degradation is much smaller. The problem becomes smaller so maybe you decide you don’t need to fix it, maybe it’s good enough for the application. GNSS can be made significantly better than it is today, which changes the whole ball game for system architects.

And without L1, the digital core is smaller and your RF section is smaller. You have lower power and better performance. We can acquire L5 directly, so you don’t need L1.

I can’t think of a single market that would say, “oh, I really want to keep my L1 for acquisition.” They want L5 to be independent. There is now a really good technical answer to that. You’re not losing anything by letting go of L1. You’re making your solution more reliable, more robust and lower power.


Read the interview in Inside GNSS


About oneNav

oneNav is enabling AI-powered next generation GNSS silicon. Based in California, oneNav is developing L5-direct™ GNSS receiver technology for smartphones, wearables, drones, tracking devices, and more and has built a large L5-band patent portfolio. oneNav’s team comprises top GNSS experts from Qualcomm, Apple, Intel, SnapTrack, SiRF, Trimble and eRide. With extensive experience in GNSS system architecture, multipath mitigation, signal processing, ASIC design and AI/machine learning, oneNav engineers have designed and built billions of GNSS receivers on the market today and have collectively filed over 300 career GNSS patents. World-class VC investors include Google Ventures, Norwest Venture Partners, and IQT.

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