Kumu Networks secured a $5 million U.S. Department of Defense (DoD) award to prototype a 5G Full Duplex Integrated Access Backhaul (IAB) at scale and test it at the Hill Air Force Base in Utah.
The DoD has set up 5G testbeds at multiple military installations, and leading equipment vendors Nokia and Ericsson are among those participating in programs at the Hill Air Force Base.
The military is interested not only for their own operations, but also looking at ways to use finite spectrum more efficiently so that more can be released for commercial users.
Work with the DoD is a two-fold win for Kumu, according to VP of Product Joel Brand. It provides an opportunity to sell to the military, and at the same time helps Kumu fund and speed up development of its self-interference cancellation tech for the commercial industry.
Frequency bands utilized by the DoD sit nearby the 3.5 GHz band widely used in international 5G deployments, as well as the shared CBRS and recently auctioned C-band in the U.S.
IAB is of interest to both the DoD and commercial wireless industry. Verizon, for example, completed proof-of-concept trial with Ericsson in 2020 for mmWave spectrum.
Recently standardized by 3GPP, it’s a concept that provides a way to extend coverage by utilizing spectrum from a cell site for both backhaul and access to surrounding sites, essentially setting up a mesh network.
However, one tradeoff is that by using spectrum for backhaul, the already limited resource is further constrained.
Kumu builds a unique solution for IAB’s compared to others, Brand said, in that it doesn’t waste spectrum resources because it enables a radio to both receive and transmit on the same frequency at the same time.
Local interference – or “noise” a radio transmits so that it can’t receive signals because its internal circuitry is too loud - is a long-time problem that isn’t unique to 5G. Academic researchers and others have been working on it for years and while there are already a number of workarounds, they come with drawbacks, according to Brand.
For example, Time Division radios avoid local interference by taking turns based on time to “talk” or send and “listen” or receive. The other is in Frequency Division, which uses two channels to transmit on one frequency and receive on another.
“None of these systems are very efficient,” Brand told Fierce. “They’re always wasting at least half the spectrum.” That’s by either using two frequencies, as is the case in traditional LTE cellular, or the amount of time in the listen and talk mode.
He thinks it’s going to take many years before all radios - including in mobile phones - can transmit and receive simultaneously.
But Kumu’s technology “has made unbelievable progress” toward alleviating the problem, he said, and is the only vendor with a critical-grade commercial product deployed with Tier 1 carriers at scale.
The tech requires a radio to have two separate antennas pointed in different directions, something Brand categorized as too much to put into a mobile phone at this point.
For IAB though, it makes for a very efficient mesh network, receiving from one side and transmitting to the other, enabling high throughput across many more hops.
“So there’s no wasted frequencies, there’s no wasted time,” Brand said.
Kumu is taking the lead on the IAB prototype deployment as part of the DoD’s Dynamic Spectrum Sharing program, which is targeting dual-use for military and commercial users.
Phase one of the roughly three-year project started earlier this year and involves delivering a lab solution. The second phase entails field deployment and testing, while the final third phase calls for deployment at scale at the entire base.
“Our main goal is in addition to meeting the criteria to succeed in this project is to develop a commercial version of the full Duplex IAB for the frequencies… CBRS, the international market and the C-band in the U.S., in parallel to deployments in the defense space,” Brand said.
It will be about a year before carriers start testing, he added, similar to the timeline for phase one of the DoD project and Kumu is hopeful to see commercial deployments soon after.
Kumu also sold this type of self-interference cancelling technology for operators in the LTE environment (but called full duplex for LTE relays).
IAB has been seen as a way to extend the reach of mmWave networks more cost-effectively where fiber backhaul is non-existent or cost prohibitive. But Brand said it can come into play if carriers want to provide wider coverage with those mid-band frequencies as well, not just mmWave hotspots or high-density areas.
“If that’s the case, then IAB will become very very handy in order to extend coverage in a very cost-effective ways,” Brand said. If there are more small cells those will need backhaul “and in places where wireless backhaul makes sense our technology is the optimal wireless backhaul solution.”