What is UNII-8?
UNII-8 is the highest of the four sub-bands that make up the 6 GHz Wi-Fi band. It covers 6.875 to 7.125 GHz, a 250 MHz block with 20 MHz channels 185 to 233. Its top edge, 7.125 GHz, is the upper limit of 6 GHz Wi-Fi in the US. UNII stands for Unlicensed National Information Infrastructure, the FCC's name for these bands. Wi-Fi 6E and Wi-Fi 7 devices use it.
The four 6 GHz sub-bands
| Sub-band | Frequency range | 20 MHz channels | US access point rules (FCC) |
|---|---|---|---|
| UNII-5 | 5.925 to 6.425 GHz | 1 to 93 | Low-power indoor, or standard power with AFC |
| UNII-6 | 6.425 to 6.525 GHz | 97 to 113 | Low-power indoor; no standard power |
| UNII-7 | 6.525 to 6.875 GHz | 117 to 181 | Low-power indoor, or standard power with AFC |
| UNII-8 | 6.875 to 7.125 GHz | 185 to 233 | Low-power indoor; no standard power |
Together the four sub-bands span 1,200 MHz, with 59 channels at 20 MHz. 6 GHz channel numbers start over at 1 and go up by 4. A channel's center frequency is 5.950 GHz plus 5 MHz times the channel number, so channel 233 is centered at 7.115 GHz. Channel 185 is centered exactly on the 6.875 GHz line between UNII-7 and UNII-8 and is listed here with UNII-8.
US rules for UNII-8
In the United States (FCC), standard-power operation isn't allowed in UNII-8, so AFC (Automated Frequency Coordination) doesn't apply here. Access points use it as low-power indoor (LPI) devices: indoor-only units at limited power that can't be weatherproof or battery powered. The FCC kept standard power out because this sub-band carries mobile licensed services, such as TV broadcast links, that a location database can't protect.
There's no DFS in UNII-8 either. DFS is a 5 GHz rule.
Using UNII-8 in practice
UNII-8 channels suit indoor networks, since US rules keep them at low power. The 6 GHz channel grid doesn't line up exactly with the sub-band edges, so some 80 and 160 MHz channels straddle UNII-7 and UNII-8. The Wi-Fi Alliance's preferred scanning channels (PSCs) in this sub-band are 197, 213 and 229. Many countries outside the US, including the European Union, opened only the 6 GHz spectrum below 6.425 GHz, so UNII-8 channels may not be available there.
For the CompTIA A+ exam
Core 1 (220-1201) objective 2.2 lists 6 GHz among the Wi-Fi frequencies and covers channel regulations. UNII-8 isn't named in the objectives. Know that the 6 GHz band is split into sub-bands with different rules, and that 6 GHz needs a Wi-Fi 6E or Wi-Fi 7 device.