6 GHz in practice: LPI, Standard Power and AFC

6 GHz is the most consequential thing to happen to Wi-Fi since 802.11n. It is also the band where the most designs go wrong, because engineers carry over 5 GHz assumptions that no longer hold.

The power classes

Low Power Indoor (LPI) — the class nearly every enterprise AP uses today. No coordination, no database, no location reporting. In exchange: indoor use only, integrated antennas only, and a reduced EIRP limit (in the US, 30 dBm EIRP with a 5 dBm/MHz PSD limit for an access point). Battery-powered client devices are further restricted.

Standard Power (SP) — full power, indoor or outdoor, external antennas permitted, but only under AFC control. The AP reports its geographic location and antenna height to an AFC system, which checks the incumbent fixed-service microwave links in the area and returns a list of permitted channels and maximum power levels. The AP must re-query at least daily.

Very Low Power (VLP) — a low-power class intended for short-range portable use such as AR/VR tethering and wireless docking. Permitted indoors and outdoors without coordination, at very low EIRP.

What AFC means for a real deployment

If you want 6 GHz outdoors — a courtyard, a loading yard, a stadium bowl — you need Standard Power and therefore AFC. Practically:

• The AP must know where it is, accurately. That is either GPS, or a surveyed coordinate you enter and are accountable for.
• Geolocation uncertainty is a real input to the AFC calculation. Sloppy coordinates give you a bigger exclusion zone and fewer channels.
• Channel availability varies by location. Two APs on opposite ends of a campus can legitimately receive different channel lists.
• If the AFC lookup fails or expires, the AP must fall back to LPI or stop transmitting on the affected channels. Build that into your monitoring.

The coverage penalty

Free-space path loss at 6 GHz is only about 1.5 dB worse than at 5.5 GHz — that part is not the problem. The problems are the lower permitted EIRP under LPI and higher material attenuation. Through plasterboard the difference is small; through concrete, brick, tinted glass and lift shafts it is significant.

Expect a 6 GHz cell to be roughly 20 to 30 percent smaller in area than the 5 GHz cell from the same AP. A design where 5 GHz coverage was already borderline will have visible 6 GHz holes. If 6 GHz is meant to be the primary band, survey to a 6 GHz target — commonly -67 dBm at 6 GHz for a primary cell — not a 5 GHz one.

Why clients cannot see your 6 GHz SSID

This is the most common 6 GHz support ticket, and it is almost never the radio. Scanning 59 channels passively would take an unacceptable amount of time and battery, so 802.11ax defines discovery mechanisms instead:

• Reduced Neighbor Report (RNR) — the 2.4 and 5 GHz beacons of the same AP carry an element pointing at the 6 GHz BSS. This is why a 6 GHz-only SSID with no 2.4/5 GHz counterpart is often invisible.
• FILS discovery frames — lightweight frames sent every 20 ms so a scanning client finds the BSS quickly.
• Unsolicited Broadcast Probe Response (UPR) — the AP volunteers probe responses on the preferred scanning channels.

Preferred Scanning Channels are every 16th channel — 5, 21, 37, 53 and so on. Putting your 6 GHz BSS on a PSC channel dramatically improves discovery time. Many controllers default to PSC-only channel selection for exactly this reason, and you should generally leave that on.

Security is not optional here

6 GHz mandates WPA3. No WPA2 personal, no open networks, no mixed mode. Enterprise deployments must use WPA3-Enterprise, and open guest networks must use OWE (Opportunistic Wireless Encryption). If your guest portal assumes an open BSS, it needs rework before it reaches 6 GHz.

Channel width discipline

The temptation with 1200 MHz of spectrum is 320 MHz channels everywhere. Resist it. A 320 MHz channel raises the noise floor by 12 dB relative to 20 MHz, which costs you range and makes the cell far more sensitive to interference. In an office, 80 MHz is the sensible default at 6 GHz; 160 MHz where density is genuinely low and the client base is modern; 320 MHz for point-to-point and demonstration purposes.