UNII Bands
UNII (Unlicensed National Information Infrastructure) bands refer to sub-bands within the 5 GHz frequency range allocated for unlicensed wireless communication. Regulated by the FCC under Part 15, these bands are essential for Wi-Fi systems, particularly those operating under 802.11a/n/ac/ax.
Scope and Band Structure
The 5 GHz spectrum is subdivided into UNII bands, each with distinct regulatory constraints. This classification is important for Wi-Fi device certification and deployment.
| Band | Details |
|---|---|
| UNII-1 |
Frequency Range: 5150–5250 MHz Typical Channels: 36, 40, 44, 48 Usage Notes: Indoor use only |
| UNII-2A |
Frequency Range: 5250–5350 MHz Typical Channels: 52, 56, 60, 64 Usage Notes: DFS required, indoor use |
| UNII-2C |
Frequency Range: 5470–5725 MHz Typical Channels: 100–144 Usage Notes: DFS required, indoor/outdoor permitted |
| UNII-3 |
Frequency Range: 5725–5850 MHz Typical Channels: 149–165 Usage Notes: Outdoor use permitted, no DFS |
| UNII-4 |
Frequency Range: 5850–5895 MHz Typical Channels: n/a Usage Notes: Reserved for ITS/V2X, under FCC review |
| Band | Frequency Range (MHz) | Typical Channels | Usage Notes |
|---|---|---|---|
| UNII-1 | 5150–5250 | 36, 40, 44, 48 | Indoor use only |
| UNII-2A | 5250–5350 | 52, 56, 60, 64 | DFS required, indoor use |
| UNII-2C | 5470–5725 | 100–144 | DFS required, indoor/outdoor permitted |
| UNII-3 | 5725–5850 | 149–165 | Outdoor use permitted, no DFS |
| UNII-4 | 5850–5895 | n/a | Reserved for ITS/V2X, under FCC review |
Note on Extended 5 GHz Channels
In addition to the standardized UNII 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 UNII-1 to UNII-4 allocations defined under FCC Part 15
are typically reserved for registered commercial use, such as Fixed Wireless Access (FWA), under FCC Part 101 or coordination-based frameworks
are not approved for general Wi-Fi operation
While adjacent to UNII-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 UNII-2A and UNII-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 UNII Expansion
In addition to the traditional UNII 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).