As frequencies open up en route to 6G, possible frameworks to best utilise spectrum are becoming increasingly important discussion topics among stakeholders. A few of those key discussions took place at the first annual 6G Symposium.
CBRS as a Basis for 6G Spectrum Sharing?
From the get-go, on a panel entitled “Spectrum Sharing in 6G Systems,” the Citizens Broadband Radio Service (CBRS) in the U.S. served as key reference point. With Spectrum Access Systems (SAS) having been deployed to manage use of the 3.5GHz band and ensure incumbents, like the U.S. Navy and its radar systems, are not interfered with, the CBRS was seen by panelists as a success story.
“CBRS has been under full commercial deployment since January of this year and we are approaching the 100,000 mark for the number of base stations that have been authorized in the CBRS band. So it is working, and despite all of those deployments, we have not had a single reported case of interference to incumbents,” said Andrew Clegg, the Spectrum Engineering Lead at Google, who suggested we may be “overprotecting” spectrum from parties like the commercial sector as a result.
The panelists readily acknowledged the need to build on the CBRS template. Monisha Ghosh, Federal Communications Commission (FCC) CTO, and Tom Rondeau of the Defense Advanced Research Projects Agency (DARPA) each cautioned against looking too much into the success of CBRS, as the radar systems in question are relatively simple and feature protection requirements projected to change. Meanwhile, the need for a new propagation model was another focal point.
Sheryl Genco, Director of the Institute for Telecommunications Sciences, reported how it’s currently being addressed at the ITS, where they are seeking buy-in from both government and the commercial sector. She also spoke of the potential for real-time spectrum management.
“That’s a really big push for the whole-of-nation approach and, with the [Department of Defense], the Defense Spectrum Organization, and [National Telecommunications and Information Administration], we’re discussing a pre decisional idea about incumbent-informing capability, where federal users provide data when they’re using spectrum and that data would grant access to nearby commercial users when it’s safe and appropriate to do so,” she said.
Masoud Olfat, Senior Director of Technology Development at Federated Wireless, agreed on the need to inform incumbents as a way to improve the existing CBRS framework. Another, in his view, is the use of artificial intelligence (Al) andmachine learning (ML).
“It allows an entity like SAS to kind of have a better and more efficient spectrum allocation so that it doesn’t necessarily require a lot of exchange to do that,” he said. “By employing those Al-ML systems, we can have a much better and more efficient spectrum-usage prediction and that allows us to make the CBRS model more real-time.”
Moving to Terahertz Frequencies
The preceding panel discussion, “Conquering the Spectrum,” was moderated by Josep Jornet, of event co-organiser Northeastern University’s Department of Electrical and Computer Engineering. He spoke of opportunities exploring terahertz frequencies from a technological standpoint.
“We are in the context of 6G, so the first thing that comes to mind is that we’re trying to create faster wireless networks… There are discussions on utilising the THz band for wireless backhaul, maybe to provide infrastructure to rural areas… Maybe the THz band is helpful for inter-satellite communications or even space networks,” he said.
“At these frequencies different materials, different molecules exhibit some unique electromagnetic signatures and actually those can be leveraged to understand our surroundings. For example, as we speak, there are several satellites orbiting the Earth with THz radios up top … They are characterising the atmosphere and also listening to signals from deep space.”
Speaking to 6GWorld in a separate interview, Marco Giordani of the University of Padova discussed the use of THz frequencies in the context of satellite communications. He said even though they aren’t suitable to provide communications to Earth, intra-satellite communications are a very real use case.
“When you are in free space then you can make satellites communicate with each other at free-space optics and THz,” he said. “So a geo-stationary satellite can communicate with [a Low-Earth-Orbit satellite] using THz and this actually is very good, because the bandwidth at THz is huge and you don’t have the propagation issues that you experience when you are in the atmosphere.”
6G Questions Still to Be Answered
In addition to macro applications, Jornet pointed out 6G use cases at the “nanoscale” as well.
“We can potentially make very small antennas utilised for wireless networks and achieve device-to-device communications, but also more transformative applications like enabling communication between nanosensors with physical, chemical, and biological capabilities,” he said.
“It is not science-fiction. This more than 20-30 years of device research that now finally we may be able to connect to the world… In the Internet of Nano Things or the idea that the user, the human is not just a user but actually a part of the network might start to make sense as we move forward.”
Co-panelist Gerhard Schoenthal, COO of Virginia Diodes, relayed several challenges on the manufacturing and testing side. They include indium phosphide as a semiconductor material, which is not completely developed for infrastructure and commercial applications. Another challenge he presented revolves around microelectronic architectures.
“As you move into the THz spectrum, the devices that are in play that have been used and produced today include integrated mmWave, integrated microwave assemblies and chip and wire architecture,” he said. “These are mostly suited for low-volume, high-mix applications.”
Regarding applications from a spectrum-sharing perspective, Rondeau argued there are still a lot of questions that need to be answered as well.
“I think a lot of the talk right now about getting up to higher frequencies, it seems a bit like a land grab versus actually supporting real needs that we can identify,” he said. “I think helping to identify those over the next few years in the SG era will hopefully lead to exactly what we need to share, how much we need to share, in what timelines does that sharing really need to occur.”
Edward Knightly of Rice University’s Department of Electrical and Computer Engineering spoke on the “Conquering the Spectrum” panel. He felt predicting a single “killer” 6G application wouldn’t do the developing technologies justice.
“I think our fallacy is to try to think of one ultra-ridiculously high-speed application and I think the reality, as we’ve seen with the wired internet, has been it’s aggregate,” he said.
“It’s just many, many people watching Netflix that require the high-speed wired infrastructure. I think with wireless it’s the same thing. I don’t think one terabit app is compelling as many, many users, high density, and just wanting
a massive flow of information up and down, and sensing. They want both those capabilities at the same in a small form factor. I think that together is going to be the key driver.”
The first annual 6G Symposium, co-hosted by lnterDigital and the Institute for the Wireless Internet of Things at Northeastern University, took place on October 20-21. Recordings of individual sessions, including those mentioned above, will be available to view at www.6GWorld.com.
With journalism credits spanning several sectors including finance and tech, Ryan joins 6GWorld with wide eyes looking onward. He aims to lend his experience to the site, covering the latest generation of cellular advancements as it unfolds, leading into 6G.