The Wi-Fi spectrum, explained end to end

Wi-Fi is not one radio technology. It is a family of radios sharing four very different pieces of spectrum, each with its own physics, its own regulatory baggage and its own failure modes. Choosing the wrong band for a job is the single most common cause of a disappointing wireless network.

Prefer to click than to read? The interactive spectrum explorer covers the same ground band by band.

The four bands at a glance

2.4 GHz — the band you cannot switch off

2.4 GHz spans roughly 2.400 to 2.4835 GHz. In practice you get three non-overlapping 20 MHz channels: 1, 6 and 11. That is the whole story. Anyone running channel 3 or 9 is not being clever, they are creating adjacent-channel interference for two neighbours at once.

It shares the band with microwave ovens, Bluetooth, Zigbee, wireless cameras, cordless phones, video senders and every cheap unlicensed transmitter ever built. Its saving grace is propagation: 2.4 GHz travels further and penetrates walls better than anything else Wi-Fi uses.

Design rule: treat 2.4 GHz as an IoT and coverage-of-last-resort band. Turn the radio off on a substantial fraction of your access points — in a dense deployment, often two APs in three. Never use 40 MHz channels here.

5 GHz — where real work happens

5 GHz gives you the UNII sub-bands: UNII-1 (5.150–5.250), UNII-2A (5.250–5.350), UNII-2C (5.470–5.725) and UNII-3 (5.725–5.850). UNII-2A and 2C are DFS channels — Dynamic Frequency Selection — shared with radar.

DFS is not optional and it is not cosmetic. An AP on a DFS channel must listen for radar before transmitting (a 60-second channel availability check, up to 10 minutes on weather-radar channels 120–128) and must vacate within 10 seconds of detecting a radar pattern. When that happens, every client on the AP is dropped onto another channel.

Whether to use DFS is a genuine judgement call:

• Use DFS in dense offices, campuses and stadiums far from airports and coastlines. You roughly triple your available channels, and the capacity gain outweighs occasional radar events.
• Avoid DFS near airports, military installations, coastal weather radar, and in any environment where a ten-second outage is a safety or revenue problem — operating theatres, trading floors, live broadcast.
• Always exclude channels 120–128 unless you have measured them for weeks. They are weather-radar channels and cause the most disruptive false positives.

6 GHz — Wi-Fi 6E and Wi-Fi 7 territory

The 6 GHz band roughly doubles or triples the spectrum available to Wi-Fi, depending on your regulatory domain. The United States opened 5.925–7.125 GHz (1200 MHz, 59 twenty-megahertz channels). The EU, UK and much of the world opened only the lower portion, 5.925–6.425 GHz (500 MHz, 24 channels) — the so-called lower 6 GHz. Do not design a global standard on US channel counts.

Three things make 6 GHz different in kind, not just degree:

1. No legacy. Only 802.11ax and later devices are permitted. There is no protection overhead for 802.11b, no 20-year-old client dragging the cell down. This is the first genuinely clean band Wi-Fi has ever had.
2. Power classes. Indoor Low Power (LPI) operates at reduced EIRP with no coordination but is restricted to indoor use and cannot be used with external antennas. Standard Power requires an AFC — Automated Frequency Coordination — lookup, where the AP reports its location to a database and is told which channels it may use at what power, protecting incumbent fixed microwave links.
3. Propagation. Free-space path loss is a few dB worse than 5 GHz and wall attenuation is materially higher. Expect roughly 20 to 30 percent less coverage per AP at 6 GHz than at 5 GHz. A design that was AP-limited at 5 GHz will have holes at 6 GHz.

Discovery matters. 6 GHz clients do not scan 59 channels hunting for beacons. They rely on Reduced Neighbor Reports in 2.4/5 GHz beacons, FILS discovery frames and Unsolicited Broadcast Probe Responses. If your 6 GHz SSID is invisible to clients, the discovery mechanism is nearly always the cause, not the radio.

60 GHz — the specialist

802.11ad and 802.11ay operate around 60 GHz with channels 2.16 GHz wide. Oxygen absorption is severe and a human body is an effective wall. It is genuinely useful for fixed point-to-point links, wireless docking, room-scale AR/VR and short-range backhaul. It is not a general-purpose access technology and you should be suspicious of anyone selling it as one.

What about CBRS and private 5G?

CBRS in the US (3.55–3.70 GHz) and equivalent shared-spectrum schemes elsewhere are not Wi-Fi, but they are increasingly on the same shortlist. CBRS uses a three-tier model policed by a Spectrum Access System: incumbents first, Priority Access Licences second, General Authorized Access third.

Choose CBRS or private cellular over Wi-Fi when you need deterministic handover across a large outdoor area, SIM-based identity, or coverage of a port, mine or campus where AP density would be absurd. Choose Wi-Fi when device support, cost per square metre and client diversity matter — which is most of the time.

Practical band plan for a corporate site

• 6 GHz: primary band for laptops and modern phones. 80 MHz channels; 160 MHz only in genuinely low-density areas.
• 5 GHz: main coverage band. 40 MHz channels in dense areas, 80 MHz where the channel budget allows.
• 2.4 GHz: 20 MHz only, enabled on a minority of APs, dedicated to IoT and legacy.

Then verify it. A band plan on a slide is a hypothesis; a validation survey is the experiment.