6G Spectrum Discussions So Far...

There is no shortage of 6G spectrum related discussions so here is a post from us. Here are the main points we get asked:

Q: How much spectrum would be needed for 6G?

A: Well, we don't know that for sure right now. It would depend on how much spectrum is made available in a particular band, which applications become popular and what devices are used and what their data requirements are. In short, it's too early to say.

Q: Will 6G use Terahertz (THz) spectrum or will it use Millimetre wave (mmWave) frequency as well?

A: There is a common misconception that 5G uses only mmWave frequencies for operation. In fact, 5G can be deployed in many different frequencies like low-band (sub-1 GHz) for coverage, mid-band (1 - 6 GHz) for capacity and high-band (24 GHz +) for very high throughput. The same will be true for 6G. In fact, 6G could be deployed in existing bands used for 2G, 3G, 4G & 5G. 

The picture above clearly highlights that 6G will need to be deployed in multiple bands to provide optimal user experience, regardless of whichever application is being used. With regards to the terminology, instead of THz, sub-THz makes much more sense to be used.

ATIS whitepaper on "Terminology for Frequency Ranges" explains the different names used for different bands nicely.

The recently released ITU Recommendation ITU-R M.2160-0, "Framework and overall objectives of the future development of IMT for 2030 and beyond" nicely explains this point:

No single frequency range satisfies all the criteria required to deploy IMT systems and the same is expected to apply for IMT-2030. There are differences in the deployments and timings of mobile data growth in different countries. Multiple frequency ranges would be needed to meet the capacity and coverage requirements of IMT systems and to serve the emerging services and applications. It is envisaged that IMT-2030, similar to the previous IMT systems, would be used in a variety of deployments. Research and development into enhanced coexistence and spectrum sharing approaches (including technical aspects) will continue.

New generations of IMT may expect new spectrum for increasing data rates, capacity, new applications and to provide for new capabilities. IMT-2030 is envisaged to utilize a wide range of frequency bands ranging from sub-1 GHz up to frequency bands above 100 GHz. Low bands will continue to be crucial to enable nationwide coverage, in particular addressing the digital divide and expanding deep indoor coverage. Mid bands provide a balance between wide area coverage and capacity.

The development of IMT for 2030 and beyond is expected to enable new use cases and applications with high data rate and low latency, which will benefit from large contiguous bandwidths of tens of GHz. This suggests the need to consider spectrum in higher frequency ranges above 92 GHz as a complement to the use of lower frequency bands.

A series of propagation measurement activities are being carried out in frequencies above 100 GHz under several different environments (such as outdoor urban and indoor office). ITU-R is developing a Report on the technical feasibility of IMT technologies in bands above 92 GHz, including coverage, link budget, mobility, impact of bandwidth and needed capabilities to support new use cases of IMT.

Further studies on the enabling antenna and semiconductor technologies, material technologies including reconfigurable intelligent surfaces, MIMO and beamforming technologies are needed to overcome major challenges of operating in bands above 92 GHz such as limited transmission power, the obstructed propagation environment due to high propagation losses and blockage.

Given the large bandwidth and high attenuation characteristics of bands above 92 GHz, some typical use cases include indoor/outdoor hot spots, integrated sensing and communication, sidelink, flexible wireless backhaul and fronthaul, etc.

The radio wave propagation assessment, measurements and technology development done so far indicate that utilizing the bands above 92 GHz could be feasible for some IMT deployment scenarios and could be considered for the development of IMT-2030.

Q: Has the 6GHz spectrum, originally destined for Wi-Fi, now been given to IMT for mobile communications?

A: That's a misunderstanding. 6GHz is a large band with 1200 MHz bandwidth. It spans from 5925 - 7125 MHz. The lower 6 GHz band (5925 to 6425 MHz) is generally reserved for Wi-Fi around the world, with some exceptions. Of the upper 6 GHz band (6425 to 7125 MHz), the band 6.425-7.125 GHz (or 6425 to 7125 MHz) was identified for IMT in Region 1 and 7.025-7.125 GHz (or 7025 - 7125 MHz) in Region 3. A footnote clarified that "The IMT recognize that the frequency bands are also used for Wireless Access System including Radio Local Area Networks." RLAN in ITU-R terminology means Wi-Fi.

Q: What decisions regarding 6G frequencies were taken at WRC-23?

A: Here is a summary from recent 5G Americas white paper, "The Evolution of 5G Spectrum":

International Telecommunications Union World Radio Conference (ITU WRC 2023), several proposals have been adopted across various regional groups to recommend for either identification or inclusion in a future agenda item that identifies a spectrum pipeline for the next generation of wireless technology. In particular, the following bands were identified for IMT:

  • 3.3 – 3.4 GHz. Identified for IMT in Region 1 and are across Africa and Asia Pacific
  • 3.6 – 3.8 GHz. The band 3.6-3.7 GHz was identified for IMT in Region 2
  • 6.425 -7.125 GHz. The band 6.425-7.125 GHz was identified for IMT in Region 1 and 7.025-7.125 in Region 3
    • Brazil, Mexico Cambodia, Laos, and the Maldives have also identified the 6.425-7.125 GHz band for IMT in Indonesia, Thailand, Vietnam, China, Philippines, Bangladesh, Myanmar, and Sri Lanka in Region 3 indicated their intent to join in 2027, making the band suitable for 6G/IMT-2030. The IMT recognize that the frequency bands are also used for Wireless Access System including Radio Local Area Networks.
  • 10 - 10.5 GHz. IMT identification in Region 2. The maximum EIRP of the base station is limited to 30 dB (W/100 MHz) to protect radio location and Earth Exploration Satellite Services, which may restrict the deployment to hotspots only.

The following bands were identified for study for IMT under WRC-27 Agenda Item 1.7:

  • 4.4 – 4.8 GHz, or parts thereof, in Regions 1 and 3
  • 7.125 -8.4 GHz, or part thereof, in Regions 2 and 3
  • 7.125 – 7.25 GHz and 7.75 – 8.4 GHz, or portion, in Region 1
  • 14.8-15.35 GHz

On an individual country level, and as indicated previously, China has already announced its support for IMT identifications in the 6.425 GHz to 7.125 GHz band. In the U.S., Chairwoman Rosenworcel has identified the 7-15 GHz range for studies for the next generation wireless technology. NTIA published a U.S. national spectrum strategy on November 13, 2023 (https://www.ntia.gov/sites/default/files/publications/national_spectrum_strategy_final.pdf) which included identifying spectrum for key stakeholders. To date, the U.S. has only included the 3.1-3.3 GHz and 12.7-13.25 GHz bands for study.

Q: Why can't we keep things simple and use 7-20 GHz centimetre wave (cmWave) band for 6G worldwide?

A: The cmWave band is already in use by other incumbents worldwide. These services/bands are not aligned so you will find different countries using different bands for different services. It is very difficult, if not impossible, to reach an agreement for the whole band. It is quite likely that the regulators in each country would decide and allocate spectrum based on availability which may give rise to many different 3GPP bands for 6G. We will have to wait and see after WRC-2027.

As we move towards 2030, we will see many of these assumptions and understanding change, depending on new research and results. Right now it looks as if most of the 6G deployments will happen in bands below 30 GHz.

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