Why the U.S. Must Prioritize the 4 GHz Band for 6G

The 4 GHz band offers the most compelling opportunity for U.S. leadership in 6G, striking a balance between favorable propagation characteristics and growing international interest, with few legacy barriers to overcome. Elevating this band as a national priority would provide the clarity and momentum needed to drive early investment, spark ecosystem development, and shape the global trajectory of 6G. With the right policy focus, 4 GHz can serve as a launchpad for rapid innovation and deployment, sidestepping many of the challenges that will slow progress in other midband spectrum. For example, while the lower 3 GHz band remains strategically important, it will require much deeper coordination and harmonization before it is ready to support the demands of next-generation networks.

4 GHz Is the Right Band to Lead the World into 6G

The 4.4–4.94 GHz band offers a timely and strategic opportunity for the United States to lead the world into the 6G era. With growing international alignment, a clean regulatory starting point, and federal operations that are concentrated within the United States Department of Defense (“DoD”) and technically well-understood, this band presents a uniquely solvable spectrum opportunity. Unlike other midband bands encumbered by multiple agencies and legacy commercial uses, 4 GHz involves well-defined DoD radar and tactical systems—creating a clear path for developing coexistence frameworks and enabling phased, full-power commercial access. Prioritizing this band gives the U.S. a practical and actionable route to accelerate 6G development, shape global standards, and unlock the next generation of wireless services.

In contrast, the 3 GHz band—while central to existing 5G deployments—presents a far more complex and fragmented landscape in the U.S. than in other countries. It is subdivided into multiple sub-bands with incompatible service rules, legacy commercial licenses, and dense DoD operations that are unlikely to be resolved for nearly a decade. While other nations are aligning around unified midband strategies for 6G, continued U.S. dependence on 3 GHz risks sidelining American leadership in global standards development and delaying commercial readiness. The 4 GHz band offers the United States a clean slate to drive early ecosystem alignment and shape the technical frameworks that will define 6G worldwide.

4 GHz: A Clear and Strategic Choice for 6G

The 4.4–4.94 GHz band stands out as one of the most technically and operationally attractive candidates for 6G development. It combines international momentum, ecosystem readiness, and a policy environment that favors timely action. Unlike other midband spectrum ranges, the 4 GHz band offers a clean, solvable path for enabling high-capacity, full-power commercial access while maintaining national security priorities.

Key Benefits:

Contiguous 500 MHz Block: The band provides a wide, uninterrupted span of midband spectrum—ideal for supporting 100 MHz+ contiguous and non-contiguous channel bandwidths essential for 6G throughput and performance targets.
ITU Recognition and Global Momentum: At the World Radiocommunication Conference 2023 (WRC-23), the International Telecommunication Union (ITU) formally recommended to study 4.4–4.8 GHz as a potential band suitable to provide desired coverage/capacity tradeoff for IMT-2030 (6G) in Region 1 and 3, with strong support from countries including Japan, South Korea, and China. This growing alignment positions 4 GHz as a leading global candidate for 6G and gives the United States a strategic opportunity to drive similar adoption in Region 2 ahead of WRC-27. Moreover, under agenda item 1.1 WRC-23 considered studies on the protection of Aeronautical Mobile Services (AMS) and Maritime Mobile Services (MSS) located in international airspace and waters from mobile broadband sites located within national territories operating within the band 4.8-4.99 GHz. As part of footnote 5.441B of WRC-23, Forty-seven countries support the use of the band for IMT identification in the new edition of Radio Regulations.
Standards Process Alignment and U.S. Leadership Opportunity: Formal 6G standards development is expected to begin in Fall 2025 within 3GPP and ITU-R WP5D, beginning with requirements setting and candidate band evaluations. A unified U.S. focus on the 4 GHz band would:

Steer global standards to prioritize 4 GHz as a primary FR1 band for 6G.
Shape technical specifications such as emission masks, channel bandwidth structure, blocking characteristics, flexible duplexing, coexistence protocols, and dynamic access mechanisms that enable phased federal-commercial sharing.
Ensure that U.S.-developed coexistence technologies become part of the global baseline for 6G deployment.

Existing 5G Ecosystem via 3GPP Band n79: The 4.4–4.94 GHz range is already part of 3GPP Band n79 (4.4-5.0 GHz), deployed across parts of Asia for 5G. This means that foundational technologies, chipsets, and radio components are commercially available today, enabling a faster path to product development and global interoperability. This ecosystem maturity positions the U.S. to act quickly while standards evolve.
Clean Regulatory Starting Point: In contrast to the encumbered and fragmented licensing regimes in AMBIT, C-Band, and CBRS, the 4 GHz band has no legacy commercial licenses. It offers a flexible foundation for developing modern licensing models that align with emerging 6G use cases, including dynamic and hybrid access.
No Legacy 5G Deployments to Manage: Unlike other midband spectrum already in commercial use, the 4 GHz band has not been widely deployed for 5G in Region 2. This enables a clean launch for 6G, free from the complexities of legacy coexistence, device refarming, or spectrum migration. As a result, the US operators can deploy 6G using purpose-built architectures, streamlined core network functionality, and lower total cost of ownership.
Centralized and Solvable Federal Use: The band is primarily used by the Department of Defense, in contrast to bands like 2.7–2.9 GHz, which involve multiple federal agencies. DoD use of radar and tactical systems is well-understood and technically tractable, allowing the development of purpose-built coexistence strategies that support phased commercial entry without requiring wholesale relocation.*
Suitable for coverage/capacity tradeoff: The propagation characteristics of the band are generally similar to the C-Band, and the contiguous 500 MHz of available spectrum, combined with the small number of incumbents in United States provides a desired tradeoff between the coverage of capacity of 6G deployments.
Simplified Primary/Incumbent structure simplifying sharing/coexistence with commercial use: Compared to 3.1-3.45 GHz and CBRS bands, the simplified structure of incumbents in the band (fixed Line of Sight (LOS) and transportable-fixed point-to-point microwave systems, drone vehicle control and telemetry systems in 4.4-4.5 GHz, DoD training exercises, air-to-ground operations for command and control, telemetry and video, law enforcement, drug interdiction missions and nuclear emergency response activities in 4.5-4.8 GHz, and military tests and law enforcement, and drug interdiction in 4.8-4.94 GHz) enables development of simplified sharing and coexistence of federal and commercial use in the band, as compared to dynamic incumbent structure in CBRS and EMBSS bands

The 3 GHz Band: Fragmented, Complex, and Not Yet Ready for 6G

The 3 GHz band—from 3.1 to 4.2 GHz—is divided into several sub-bands, each with distinct service rules, protection requirements, and commercial viability. This regulatory fragmentation limits the ability to scale a unified, high-performance 6G framework across the band.

3.1–3.45 GHz (or EMBRSS band partially overlapping with 3GPP Bands n77 and n78): This portion remains reserved for exclusive Department of Defense (DoD) operations, supporting a dense concentration of radar and airborne systems. Although once considered a candidate for reallocation or shared access, recent legislation has sidelined any near-term commercial use. Future access will depend on the development of next-generation spectrum sharing technologies—a complex R&D effort expected to take at least a decade.
3.45–3.55 GHz (AMBIT – subset of 3GPP Bands n77 and n78): Licensed for full-power commercial use through Auction 110, this sub-band supports traditional 5G deployments within 3GPP Bands n77 and n78. However, it remains subject to coordination zones (Cooperative Planning Areas, or CPAs, and Periodic Use Areas, or PUAs) to protect ongoing federal operations, limiting deployment flexibility and complicating seamless, nationwide service rollout. Licenses in the AMBIT band were issued in 10 MHz blocks on Partial Economic Area (PEA) basis.
3.55–3.7 GHz (CBRS – 3GPP Band n48): Operates under a three-tiered shared access model, coordinated by certified Spectrum Access Systems (SAS). Auction 105 licensed Priority Access Licenses (PALs) within this band. Licenses in the CBRS band were issued in 10 MHz blocks on a county-by-county basis. While innovative, CBRS is currently constrained by band-specific transmit power limits and out-of-band emission (OOBE) restrictions that differ from adjacent 3 GHz sub-bands. An important first step toward harmonization is now underway through the FCC’s Notice of Proposed Rulemaking (NPRM), which proposes aligning technical rules—including power and emission limits—more closely with those in AMBIT and C-Band.
3.7–3.98 GHz (C-Band – a subset of 3GPP Band n77): Fully cleared and licensed through Auction 107, this portion of 3GPP Band n77 supports high-power 5G operations by major U.S. mobile operators. However, it follows a separate licensing and technical framework from both AMBIT and CBRS, leading to interoperability and spectrum management challenges across the broader 3 GHz band. Licenses in the C-Band were issued in 20 MHz blocks on a Partial Economic Area (PEA) basis.

In all, each of these sub-bands differs in:

Licensing structure
Transmit power limits
Federal protection criteria
Incumbent presence and access rights
Emission (in-band and out of band emissions) characteristics
Blocking Requirements
Device ecosystem and network deployment models

This regulatory and technical heterogeneity creates a fragmented spectrum environment that is misaligned with the global 6G vision of wideband, harmonized midband allocations that support scalable, high-capacity mobile networks. Without significant reforms, these mismatched rules prevent coherent spectrum planning and inhibit the industry’s ability to leverage the 3 GHz band as a unified 6G platform.

Comparison of EIRP and Emission Limits Across AMBIT, CBRS, and C-Band
This Effective Isotropic Radiated Power (EIRP) and out-of-band emission (OOBE) limits applicable to the AMBIT, CBRS, and C-Band spectrum segments. The current regulatory landscape is highly fragmented, with differing power and emission constraints across adjacent bands. This lack of harmonization restricts the use of wide channel bandwidths that may span sub-bands and creates challenges for equipment interoperability and efficient spectrum utilization. The complexity underscores the need for a more unified framework to support scalable, flexible, and high-performance deployments across the 3 GHz midband spectrum.

Future 6G Use of 3 GHz Depends on Long-Term DoD Decisions

Any credible plan to leverage the 3 GHz band for 6G must include the lower 3.1–3.45 GHz segment—but its future remains highly uncertain. The core question of whether and how the Department of Defense (DoD) will support commercial access is unresolved. DoD has signaled that any potential transition would involve years of technical analysis, coordination, and investment, with no meaningful policy clarity expected before 2033.

Until that process unfolds—and until the broader 3 GHz band is technically harmonized and institutionally aligned—it is premature to build a national 6G strategy around it. The U.S. should instead prioritize readily available spectrum like 4.4–4.95 GHz, which offers a more immediate and achievable path to global leadership in 6G.

Conclusion

To secure global leadership in 6G, the United States must act with strategic clarity and urgency. The 4.4–4.95 GHz band offers a rare combination of technical suitability, international momentum, regulatory flexibility, and manageable federal use—positioning it as the strongest near-term candidate for national 6G development. In contrast, the 3 GHz band remains a fragmented landscape, burdened by unresolved federal access issues and divergent licensing regimes that will take years to harmonize. By prioritizing the 4 GHz band now, the U.S. can lead global standards-setting, accelerate domestic innovation, and establish the spectrum foundation required to usher in the next era of wireless connectivity.

By contrast, the 3 GHz band is already in heavy commercial use—especially in the 3.5 GHz CBRS band, which has become one of the most dynamic and expansive midband ecosystems in the country. There are now over 400,000 active CBSDs (Citizen Broadband Radio Service Devices) and hundreds of commercial operators, ranging from major mobile network operators to rural ISPs, utilities, industrial users, and enterprises. This level of deployment reflects CBRS’s success—but it also means that any future transition to new 6G standards will need to carefully navigate an already-mature ecosystem.

The contrast is clear: while CBRS is thriving and operational, it also brings complexity when evolving toward next-generation technologies. The 4 GHz band, with zero legacy deployments, offers a cleaner slate for 6G innovation.

*The 4.4–4.95 GHz band is used today by DoD and select federal agencies for radar, telemetry, microwave links, and law enforcement operations. These uses are well-defined and primarily centralized within DoD, enabling a clear path toward phased commercial access. The long-term goal should be to gradually clear and repurpose as much of the band as possible to support full-power, unencumbered commercial use as federal systems evolve and transition over time