6G Symposium Recap: Conquering the Spectrum
If you missed the 6G Symposium, check out our blog for a full overview of Day 1 highlights, a review of Day 2’s keynote speech by National Science Foundation's Dr. Thyaga Nandagopal and fireside chat with NIST Director Dr. Walter G. Copan, and recaps of the Symposium’s most thoughtful panels. Recordings of the sessions will be available soon.
The second day of the Symposium explored some of the challenges facing the true realization of 6G’s potential, namely the limitations of spectrum.
As wireless data traffic grows exponentially, the question remains: how will we support it? This foundational question provided the framework to begin the panel “Conquering the Spectrum” on Day 2 of the 6G Symposium, moderated by Northeastern University Associate Professor Josep Jornet.
The panel offered a timely discussion to address many of the questions raised during Dr. Nandagopal’s keynote, namely “where will 6G fit in the radio spectrum?” Upcoming 3GPP Release 17 is expected to extend 5G up to roughly 71 GHz, but the most existing radio spectrum lies below 95GHz. It is widely understood that the industry must undertake much innovation to develop use cases and technologies that allow radio communications in the Terahertz bands. There was much discussion about the frequency ranges, which are expected to range between 60 GHz all the way to 3 THz, but less has been said about use cases it will enable.
Discussion moderator Jornet offered a few suggestions, including Terabit wireless backhaul, inter-satellite and space networks, or even potentially for sensing applications like non-damaging imaging and high-resolution radar. Overall, he encouraged the panelists to use the session to answer questions about devices, test beds and materials, as well as propagation and channel modeling. The conversation also addressed questions around signal processing, networking, policy, regulation, and standardization.
Gerhard Schoenthal, COO of Virginia Diodes, Inc., outlined the very real challenges of spectrum availability. "Wireless products have to cover wide swatch of spectrum," he said, adding that since materials like iridium phosphide are not as well developed as other semiconductor materials, the products face a materials challenge at higher frequencies.
Signal propagation was also highlighted as a major challenge by Thomas Kurner, professor at TU Braunschweig. "Particularly in indoor environments, small objects play a role in propagation, reflection and scattering," said Kurner. "Even something as simple as wallpaper over a concrete wall can cause multiple reflections at higher frequencies." He went on to say that while these problems currently exist in the millimeter Wave (mmW) bands, they will become more pronounced at the THz levels, therefore further innovation is needed before such solutions reach the mainstream.
Despite these challenges, early 5G mmW deployments are underway, and are achieving high peak data rates greater than 1 GBps. However, coverage is still intermittent for now. The primary challenges with implementing mmW are directionality, blockage, and range. In addition, there will be greater challenges with device power consumption, high network density and an apparent lack of clear use cases for the technology. "In upper mmW bands, like around 140GHz, there are some savings possible, but power may still be prohibitive because these devices pull a lot of wattage," said Sundeep Rangan, Professor at NYU, pointing toward some potential use cases. "At around 140GHz there may be a good use case to use this band for fronthaul and drones/UAVs, or possibly in point-to-point backhaul links, such as line of sight MIMO at ranges of up to around 1.5 kilometers."
Offering another academic perspective was Edward Knightly, Professor at Rice University, who described exciting research around high frequency beam steering. He described that, because different frequencies emit at different angles, his team has seen the potential for beam steering through adjustments to the antenna. He also discussed how new sensing capabilities could be made possible at the THz level, which could enable high resolution millimeter scale radar with a single antenna. There are also security implications of very narrow beams too – narrow beams emitted at different frequencies can thwart eavesdroppers and side-channel attacks, which would unlock new security capabilities.
There are regulatory and policy considerations for spectrum as well. Relative to other technologies, wireless is a highly regulated industry. Policymakers and regulators frequently ask questions like "how much spectrum does 6G need, and how much is available?" Agencies and government institutions will be looking for more concrete numbers than the industry can currently provide. This issue came up earlier this year with concerns regarding potential 5G interference with NOAA's weather forecasting satellites, which are passive users of some of the adjacent spectrum allocated for 5G. "A study is underway about minimizing interference and enabling a win-win sharing of spectrum," said Mike Marcus, former FCC spectrum policy lead. "Weather satellites will be protected," he added, reminding the audience that the ITU rules on passive bands will not change until 2027, at the earliest.
This riveting discussion was underscored by an interesting consensus among panelists. All agreed that, while there is uncertainly today about where exactly the eventual 6G spectrum will be, key stakeholders will work together with a shared vision to enable the exciting new possibilities in these high frequency bands. Knightly concluded by saying, "if you have devices that can give you millimeter-scale resolution sensing of the world around you, the sky's the limit in terms of what's possible."
To recap more of the key take-aways and thought-provoking presentations from the 6G Symposium, please join us for a 6G Symposium Sync Up webinar on Thursday, November 5 at 1:00 p.m. ET, hosted with Fierce Wireless. Symposium organizers Doug Castor from InterDigital and Tommaso Melodia from Northeastern University will join industry experts to digest and make sense of the event’s varying perspectives on the 6G roadmap, the role of AI and Machine Learning in 6G networks, spectrum sharing approaches, public-private research partnerships, and much more.
You may register here.