Self-interference cancellation doubles bandwidth

Article By : Brian Santo

A start-up founded by Sriram Vishwanath has developed a signal cancellation technology, which may become an integral element of just about every communications system moving forward.

Kissing contention goodbye in open bands may not be possible yet, but a self-interference cancellation technology promises to change the wireless game.

Start-up GenXComm spent the last five years developing the technology, which claims to support the use of single-frequency full-duplex communication, or adjacent and overlapping channels, and even reduce all those bandwidth and latency compromises. If it proves out, signal-cancellation technology could become an integral element of just about every communications system moving forward.

The company got its first round of financing—₹10.20 crore ($1.5 million)—from FAM Capital Partners, the UT Horizon Fund (GenXComm grew out of research performed at the University of Texas) and others. It is using the funding to produce prototype chips. Co-founder and president Sriram Vishwanath (pictured above, source: GenXComm) told EDN his company also just got a design win with a “massive” OEM—which he, of course, could not identify.

More than just noise cancellation

The company calls its technology S-Six, an almost-acronym of simultaneous self-interference cancellation. Vishwanath didn’t dive too deeply into the technical details, but provided this overview of what the S-Six does: “We take something at 100W power and drop it all the way down to 100pW. We exploit structure. We learn the structure—we estimate it, learn it and exactly match it to cancel it. It’s a much, much more sophisticated process than traditional noise cancellation.”

The ability to cancel out a signal in this manner leads to the ability to communicate in full duplex mode, essentially doubling the bandwidth. The company has performed a demonstration of communicating from a base station to a user and using the same frequency for backhaul.

But then the technology does more than double the bandwidth. The biggest value proposition of S-Six, the company said, is that spectrum can be used much more efficiently.

Today, Vishwanath said, “If one radio is on band A, the other one has to be on band B far away from it. If they’re even close to each other, they interfere with each other. We can get bands to be right next to each other—in fact overlap each other—and still they will not see interference from one another. We get rid of co-channel, adjacent channel interference. As a result, now you can actually have radios literally not just in the same band, but in adjacent and overlapping bands. You can make maximum use of the spectrum." Imagine how useful that could be in, say, public Wi-Fi networks.

“It scales gracefully as the number of people increases. Today, with Wi-Fi, you keep adding people, the whole system crashes. With our technology that does not happen,” Vishwanath said. The company says it can increase network performance up to 30× for dense environments.

Asked if inclusion of the technology requires any changes in how the Wi-Fi standard is implemented, he said no; “Same Wi-Fi, same protocol, same standard,” he said. The same is true of any communications standard.

Dozens of university research departments are working on the same problem. Vishwanath believes GenXComm has a jump on all of them. He said that while almost everybody else is stuck at 20MHz to 40MHz of bandwidth, GenXComm’s solution can operate across 800MHz of bandwidth, heading toward 1GHz.

“Everyone else has a board or a box, a big fat solution that consumes watts of power,” Vishwanath said. GenXComm’s implementation, meanwhile, is chip-scale and consumes less than 1W.

GenXComm currently works in centimetre-scale wavelengths; the company is confident it will be able to do millimetre-wave spectrum, including many of the bands more recently set aside for 5G wireless communications.

The company’s solution includes some digital hardware and an RF component, plus software for monitoring and management. GenXComm intends to sell the chip and license the IP for the software.

Vishwanath said the company expects several technology demos in the fall, trials of the technology in 2018, and general commercial availability in 2019. Depending on the application, the technology might add a dollar to the total cost of the bill of materials (BOM), he said.

Figure 1: GenXComm Wi-Fi contention chart. (Source: GenXComm)

GenXComm’s signal cancelling technology can enable more robust Wi-Fi. This chart models a dense Wi-Fi environment, for example, a sport stadium. The blue and yellow lines indicate Wi-Fi traffic dropping off as the number of users scales up. The other two lines show performance using the company’s technology.

First published by EDN.