The Commerce Spectrum Management Advisory Committee (CSMAC) finalised a draft report sharing recommendations on the next steps for developing 6G in the United States. CSMAC answers to the Department of Commerce’s National Telecommunications and Information Administration (NTIA).

The subcommittee found that carriers are currently focused on deploying 5G and moving on to 5G-Advanced – which, according to the report, should take “a few years.” On the other hand, RAN and device vendors are aggressively defining 6G technology elements and spectrum for 6G.

“Given the early stage of its development, the state of 6G is currently enduring a clash between visionary ideas and practical realism,” the report reads.

“Equipment providers and researchers are driving the development of 6G visionary ideas on the evolution of legacy as well as newly defined use cases until service providers complement the process by providing operational and business requirements for their choice of use cases commensurate with their business objectives and plans.”

Also, the subcommittee highlighted that carriers and network infrastructure vendors see open networks and Open RAN as key for 6G.

The subcommittee conducted around 40 interviews with federal agencies, service providers, equipment manufacturers, academia, and other non-profit organisations to write the report. CSMAC presented the draft in its latest meeting on September 21. The final version is scheduled for December 2023.

Use Cases

The report highlights that one of the 6G tasks will be to fulfil the 5G promises by “properly addressing” usage scenarios and applications that have not been widely developed and deployed yet.

According to CSMAC, challenges include making the business case and achieving the expected return on investment, the need for convergence of vision and the path forward, the risk of fragmentation, and regional divergence.

“There are always tradeoffs between economies of scale, economies of specialisation, and economies of scope as well as between open architectures and diverse specialised systems,” the document reads. “These tradeoffs are expected to impact both the business case and the market for 6G.”

The most important indicators to keep track of would be the ones that assess use case viability and eventual adoption by users – including R&D investment by both public and private sources, technology readiness level progression, convergence, low barriers to entry, and demonstrated societal and economic impact.

Spectrum

If terahertz and millimetre waves were the initial focus for terrestrial communications, the subcommittee says that the industry is shifting to mid-bands, extending them up to around 15 GHz. “Interest in the sub-terahertz spectrum is limited to research areas for mostly short-range communications and have a longer associated timeframe for commercial use,” the report reads.

CSMAC considered various frequency ranges for potential 6G use, including terrestrial and non-terrestrial services:

• Low-band: This range is generally congested, but under-utilised bands, particularly in large geographic areas with relatively few users, could be pieced together via carrier aggregation and multi-radio connectivity for increased coverage.

• Mid-band: Of widespread interest for supporting terrestrial 6G applications and use cases. Most, if not all, of IMT spectrum proposals under consideration in ITU-R Regions for study toward WRC-27 are in mid-bands.

• Millimetre wave is a valuable spectrum for enabling “information showers” via wireless local and personal area networks for home, office, transportation centre, and city hotspot access. Portions of these bands remain critical for satellite communications, including support for 6G.

• Sub-THz and THz: These bands are suited for fixed wireless and backhaul, high bandwidth applications if feasible, and passive services.

Recommendations

The CSMAC 6G subcommittee made several recommendations – both general and focused on the impacts to government users.

Recommendations to Help Prepare for Impact to Government Users

• NTIA should work with the FCC and federal agencies to develop more spectrum-sharing friendly plans and designs across government and commercial systems.
  • NTIA should engage early with federal incumbents with assignments in bands of particular interest for 6G, including mid-bands and above 95 GHz, to understand the type and degree of use and ability to share.
  • NTIA should work with FCC to leverage more data-driven, automated, and dynamic methods into its plans, such as the incumbent informing capability vision and use of schedulers.

• NTIA should work with the FCC, federal agencies, the White House, and Congress to consider acquisition reform and incentives for federal agencies and commercial industry to use spectrum as efficiently and effectively as possible to increase spectrum sharing and/or facilitate relocation, as appropriate.

General Recommendations to NTIA

• NTIA should work with federal agencies to identify if and when commercial 6G services would benefit their missions, characterise any expected differentiated requirements (such as related to standards, security, and technical performance criteria) in alignment with the ITU-R timeline, and coordinate with industry to address federal agencies requirements.
• NTIA should work with federal agencies to update the spectrum compendium more frequently, adding more detailed and granular data, such as location and time of use, describing federal spectrum uses and extending its compendium above 7.125 GHz to at least the terahertz range.
• NTIA should adopt a “toolbox” approach to spectrum sharing to best match sharing approaches to specific conditions by customising sharing techniques to the frequency band and range of incumbent systems (including commercial incumbents) and consider the requirements of commercial services in the process of devising and implementing new sharing methods. Also, less management may be required in the sub-THz or Terahertz ranges where propagation, including building losses, is helpful in enabling sharing.
• NTIA should collaborate with the FCC to facilitate innovation in the THz spectrum for 6G on an exploratory basis (waivers, possible additional unlicensed spectrum), considering that operations tend to be localised based on the propagation characteristics of this range.

Featured image by the US Department of Commerce