U-NII Bands
U-NII (Unlicensed National Information Infrastructure) bands refer to sub-bands within the 5 GHz and 6 GHz frequency ranges allocated for unlicensed wireless communication in the United States. Regulated by the Federal Communications Commission (FCC) under 47 CFR Part 15, Subpart E, these bands form the regulatory basis for Wi-Fi technologies, including IEEE 802.11a, 802.11n, 802.11ac, 802.11ax (Wi-Fi 6/6E), and 802.11be (Wi-Fi 7).
Scope and Band Structure
The 5 GHz spectrum is subdivided into U-NII bands under FCC Part 15 (Subpart E), each with distinct regulatory constraints. This classification is important for Wi-Fi device certification and deployment in the United States.
| Band | Details |
|---|---|
| U-NII-1 |
Frequency Range: 5150–5250 MHz Typical Channels: 36, 40, 44, 48 Usage Notes: Indoor use only |
| U-NII-2A |
Frequency Range: 5250–5350 MHz Typical Channels: 52, 56, 60, 64 Usage Notes: DFS required |
| U-NII-2B |
Frequency Range: 5350–5470 MHz Typical Channels: n/a Usage Notes: Not available for unlicensed Wi-Fi under FCC Part 15 |
| U-NII-2C |
Frequency Range: 5470–5725 MHz Typical Channels: 100–144 Usage Notes: DFS required, indoor/outdoor permitted |
| U-NII-3 |
Frequency Range: 5725–5850 MHz Typical Channels: 149–165 Usage Notes: Outdoor use permitted, no DFS |
| U-NII-4 |
Frequency Range: 5850–5925 MHz Typical Channels: n/a Usage Notes: Not permitted for unlicensed Wi-Fi under FCC Part 15 (allocated to ITS in the U.S.) |
| Band | Frequency Range (MHz) | Typical Channels | Usage Notes |
|---|---|---|---|
| U-NII-1 | 5150–5250 | 36, 40, 44, 48 | Indoor use only |
| U-NII-2A | 5250–5350 | 52, 56, 60, 64 | DFS required |
| U-NII-2B | 5350–5470 | n/a | Not available for unlicensed Wi-Fi under FCC Part 15 |
| U-NII-2C | 5470–5725 | 100–144 | DFS required, indoor/outdoor permitted |
| U-NII-3 | 5725–5850 | 149–165 | Outdoor use permitted, no DFS |
| U-NII-4 | 5850–5925 | n/a | Not permitted for unlicensed Wi-Fi under FCC Part 15 (allocated to ITS in the U.S.) |
Note on Extended 5 GHz Channels
In addition to the standardized U-NII bands, some frequency planning tools (including ours) display extended 5 GHz channels such as 169 (5845 MHz) and 173 (5865 MHz). These channels:
lie outside the official U-NII-1 to U-NII-4 allocations defined under FCC Part 15
are used under licensed or coordination-based frameworks (e.g. FCC Part 101), including applications such as Fixed Wireless Access (FWA)
are not approved for general unlicensed Wi-Fi operation
While adjacent to U-NII-4 in frequency, these extended channels are governed by separate regulatory provisions and must not be confused with unlicensed Wi-Fi channels operating under FCC Part 15.
Regulatory Use and Constraints
DFS (Dynamic Frequency Selection) is mandatory in U-NII-2A and U-NII-2C to protect weather and military radar systems.
Transmit power and antenna gain limits vary by band and device class (e.g., low-power indoor, standard power).
Devices must comply with FCC §15.407 requirements, including:
Automatic channel selection
DFS behavior (where applicable)
Band-specific power and usage restrictions
Indoor/outdoor use must be enforced via firmware and hardware design.
International Variations
Many other regions follow similar sub-band structures but may differ in:
Channel numbering and availability
DFS enforcement
Transmit power and modulation constraints
Devices must be regionally configured to meet local regulatory requirements.
6 GHz U-NII Expansion
In addition to the traditional U-NII bands, the FCC has allocated the 6 GHz band (5.925–7.125 GHz) for unlicensed use:
Very Low Power (VLP) operation in U-NII-6 and U-NII-8 was approved in March 2025
Automated Frequency Coordination (AFC) is required for standard-power outdoor devices. AFC systems dynamically allocate frequencies based on geolocation and spectrum databases to prevent interference with licensed incumbents (e.g., fixed microwave links).