Last month, the official effort to define 6G began with a workshop in Korea, attended by wireless industry stakeholders including service providers, equipment and device vendors, and industry associations. These participants presented their visions and requirements for 6G, and from these discussions, several key developments have emerged to shape the context for its future.
This post focuses on the outlook for 6G spectrum, exploring how different aspects will factor into future spectrum valuations. Understanding these factors is crucial as we look ahead to the evolving demands and opportunities that 6G will bring.
Upper-Middle Band in Focus
There is near-unanimous consensus that the upper-middle band between 7–15 GHz is in the bull’s-eye for future 6G network deployments. Specifically, the range between 7.125–8.4 GHz is the band of interest, which will be under study at the WRC27 for IMT use.
This focus arises as sub-6 GHz spectrum is largely exhausted. However, there are regional variations. For instance, studies are underway to release spectrum in the 3.1 GHz range in the US, and China has allocated the 6.425–7.125 GHz band for mobile applications.
Additionally, the focus on the upper-middle band for 6G spectrum comes at the expense of millimeter wave (mmWave) spectrum, which was opened for 5G mobile applications but failed to gain traction. There is strong consensus that mobile mmWave is still premature, with better, more economical options available in lower parts of the frequency spectrum.
As a result, 6G standards activities will likely focus on the lower part of the so-called FR3 band (7.125–24.25 GHz). The physical layer design will aim to optimize performance for FR3. We expect national regulators to study the availability of spectrum in this range for national assignments.
Drivers for the Upper-Middle Band
Performance in the upper-middle band is relatively comparable to that of mid-band spectrum, unlike mmWave spectrum. The goal is to achieve a coverage footprint from 6G equipment that closely matches the 5G mid-band footprint. Additionally, the industry is advocating for 200 MHz-wide channel allocations reaching up to 400 MHz, which are prohibitive in the lower parts of the wireless spectrum. Thus, the upper-middle band is considered the most reasonable option to balance coverage and capacity.
6G Deployment Model
Mobile technologies, by definition, require ubiquitous coverage across wide areas to enable mobility. However, moving higher in the frequency spectrum limits coverage and significantly increases deployment costs. Operators recognize that 6G deployment may not require ubiquity; instead, they may focus deployments on specific areas, such as cities or parts of cities.
Regulators aiming to define the size of service areas for 6G spectrum licenses can engage the industry on how 6G rollouts could take shape to gain valuable insights. Similarly, regulators need to consider financial and other constraints when defining deployment requirements. This is not entirely new, as mmWave spectrum has been auctioned with varying terms. However, it is crucial to update approaches to these issues to reflect present realities and future expectations.
Factoring Energy Consumption
Coverage and capacity primarily determine spectrum quality. Previously, spectrum asset valuations never considered energy consumption, but future assessments should perhaps factor it in.
6G will implement various technologies to extend coverage as much as possible, aiming to match that of mid-band 5G networks. A key technology will be scaling massive MIMO further, potentially reaching 512 elements or more (e.g. 4k elements!), to enhance beamforming capabilities. However, this, together with channel bandwidth reaching up to 400 MHz, will result in very higher energy consumption. 5G already provides a reference, where energy consumption is significantly higher than 4G (energy per bit arguments are irrelevant here—absolute metrics matter). Certainly, 6G will introduce various technologies to reduce energy consumption, such as selective powering down and switching off transmit and receive chains. Yet, even with these measures, parts or all of the spectrum would remain idle. [Such technologies prompt consideration of spectrum-sharing techniques, which deserve a post of their own.]
Overall, there is a valid argument to factor power consumption into spectrum valuation, as it could significantly impact profitability.
Final Thoughts
A couple of points to address here. First is the low interest in mmWave spectrum—primarily FR2 bands for mobile applications. mmWave spectrum prices have declined, as evidenced by recent transactions. We expect the lack of interest in using mmWave for mobility services to continue depressing mmWave spectrum pricing. While there are potential applications in FWA, it remains a niche use case. Satellites, however, will be able to leverage mmWave bands for various applications, presenting an opportunity for the future.
The second point is that there is currently no interest in unlicensed frequency bands for 6G. This concept was first introduced with LTE and carried forward into 5G, but it failed to gain traction in both public and private networks.