Most of the time no one has to think about how the mobile networks that we all depend on work. But it won’t surprise many to hear that, as is often the case with infrastructure, some pieces are state-of-the-art and others haven’t changed in decades. Eridan is a well-funded startup that aims to replace one of the latter with a fundamentally different hardware approach that could make mobile networks much more efficient.
Everywhere you look, or more likely, right on top of where you look, there are cell phone towers connecting your phone to the Internet at large. You can think of these as being made up of three big pieces: the modem, which exchanges data with the rest of the network; the antenna, which broadcasts the radio signal in sync with dozens or hundreds of nearby devices; and the transceiver, which sits in the middle and converts the digital data from the modem into the actual RF signal that the antenna emits.
Obviously the modem must change with the times and increase the capacity, and it has done so. Similarly, the antenna must change to reflect new and reused segments of spectrum that are used for mobile data. But the transceiver is something like a digital-to-analog converter in that its job hasn’t really changed much: data in, signal out.
Recently, however, we have begun to probe the limits of that middle bit, which is a dinosaur in technological terms.
“The way that transceiver has powered the antenna hasn’t changed in the last 70 years,” said Eridan co-founder Doug Kirkpatrick. “It’s called a linear amplifier, and that device, that circuit architecture approach is literally on the edge of what 5G is today.”
These amps are essentially analog devices, and due to their fundamental nature, the more power you put into them, the less efficient they are. And over the years, the power used has only increased as the number and complexity of signals has grown; 5G transceivers are about half as efficient as 4G, which were half as efficient as 3G; however, due to spectrum limitations and growing demand, we will need many more 5G cells. Even if the difference is only a handful of watts, it adds up very quickly if you plan to cover all populated areas plus highways.
“If you want to get everywhere, it’s like 20 times more radios, and with the efficiency going down as well, you’re talking about consuming 50 percent of the electricity in the US,” Kirkpatrick said. “This dog does not hunt.”
“What we’ve done is something the industry has been looking for maybe 30 years, and something every wireless company has been looking for, spending billions. If you want everyone to have 5G without melting the planet, we are the absolute only way to make this happen,” he continued.
And what exactly has Eridan done? I hinted at my skepticism that a startup with limited means could skip decades of research by some of the richest companies on the planet.
“Well, we cheated,” admitted Kirkpatrick. One of the company’s founders, Earl McCune, who sadly passed away two years ago during the development process, was among those doing research at those big telecommunications companies, where his approach never took off. Not to say he took any trade secrets with him of course, they just found a way to make the theory a reality outside of the corporate structure.
After meeting during a failed recruitment to do a related job for a large company, the founders decided they liked each other enough to pursue the concept independently.
“We did what you would do, we sat down with a bar napkin and a beer,” he recalled, and after filling up the think tanks a bit, “it was one of those epiphanies. Everyone’s eyebrows went up and they said, ‘That’s a crazy idea… but it could work.’ Then literally the first time we turned it on, it was the most perfect signal you’ve ever seen. We said, ‘how the hell are we going to explain this to someone?’ ”
The advance is somewhat simple, like going from vacuum tubes to transistors.
“A linear amplifier is an analog amplifier; as they care about cost and efficiency, they made the best of a bad deal – how dirty [i.e. how noisy] Can you make the signal and still be efficient? This is fundamental to what linear amplifiers do,” he explained. “We are a digital switch: we send an ultra clean signal. We combined a switch-mode architecture with silicon gallium nitride, and it went from 60% efficiency to over 99%. It’s a hundred times smaller and a hundred times cheaper.”
“Earl wrote books on this kind of direct polar architecture; he was an expert in this kind of approach,” Kirkpatrick said. The other co-founder of it, Dubravko Babic, is a materials expert who focuses on gallium nitride, which without going into too much detail is used in combination with silicon to create high-efficiency chip architectures. They first got a $5 million contract from DARPA, thinking it could be used to shrink military radios, but soon realized the technology went far beyond the defense category and took it into telecommunications.
The resulting “miracle” device (which looks like a regular printed circuit board, by the way) is so different from existing infrastructure that they’ve had trouble getting potential companies to understand its qualities. “But just over a year ago, the doubters got everything they needed: We demonstrated it on top of a mast. You can doubt the technology all you want, but when you turn it on a mast, it’s game over,” Kirkpatrick said.
Still, he admitted, the infrastructure market is conservative. These are companies that pay huge sums to build millions of facilities to serve hundreds of millions of people; they tend to choose what they know works even if there is a newcomer who is better. Y more economical. But a pilot test at Fort Hood should show off Eridan’s 5G small cell capabilities, which, assuming all goes well, should lead to commercial deployments around the end of the year.
What probably won them over, beyond the existential threat of linear amplifiers pushing the theoretical limits of the amount of data they can handle, is the greater scalability of Eridan’s technology. It would be enough to make 5G deployments cheaper and better, but what about the next upgrade?
The latest signal protocols coming from mobile data authorities and standards makers involve 8-bit signals driving 256 QAM; We won’t go into the technical details here either, but you can think of it as equivalent to home internet bandwidth. Essentially, the more bits you can fit on a given stretch of signal, the more data you can deliver, although, as is always the case with wireless technology, the greater the risk that this increasingly complex and fragile signal won’t arrive intact.
As you can imagine, going from analog to digital production of that signal has a big effect on the efficiency of a broadcast. “Which do you think propagates farther, a clean signal or a dirty signal?” Kirkpatrick asked, obviously rhetorically. Using GaN allows the system to operate at high voltages, eliminating the need for an amplifier, further improving the signal because amplifiers amplify “the garbage along with the good” into a dirty signal.
Eridan had an experimental 10-bit 1024-QAM released by 3GPP up and running within hours of its release, and has gone on to demonstrate in a lab environment that they can transmit a 16-bit, 64K (ie 65,536)-QAM signal. . (Trust people who like wireless protocols will find that number very impressive.)
The promise of being a major part of the infrastructure to be built for a decade and more has clearly activated the check-writing portions of investors’ brains. After DARPA’s $5 million, Eridan has raised a total of $46 million between today’s B round announcement and a secret round of $8 million. The last round was led by Capricorn Investment Group, Monta Vista Capital and Social Capital.
The money will go toward contracting and manufacturing: “We’re gearing up to make tens or hundreds of millions of these things,” Kirkpatrick said. Although he couldn’t name potential customers, it’s not hard to imagine who would benefit from this hardware. Basically, if you’ve heard them shout about 5G at any point in the last 5 years, they’re probably on the list.
Commercial displays should start appearing early next year after official demos at Ft Hood and elsewhere. You probably won’t notice anything, but then again, that’s the point.