The basic trade
A radio wave's frequency describes how many times it oscillates each second. Wi-Fi uses microwave frequencies measured in gigahertz. As frequency rises, two things tend to happen at once: the signal loses more energy passing through solid objects, and the band offers wider stretches of spectrum that can carry more data. That is why the same router can feel fast in the living room and sluggish two walls away.
Heinrich Hertz first demonstrated electromagnetic waves in the late 1880s, and Guglielmo Marconi turned them into practical long-distance communication. Home Wi-Fi is a distant descendant of that work, standardised by the IEEE 802.11 working group from 1997 onwards and certified for compatibility by the Wi-Fi Alliance.
2.4 GHz: the long-reach band
The 2.4 GHz band sits in a slice of spectrum known as the ISM band, set aside internationally for industrial, scientific and medical use. Because no licence is needed, it is shared by Wi-Fi, Bluetooth, Zigbee, many cordless gadgets and even microwave ovens. Its strengths are reach and wall penetration. Its weakness is space: in most regions there is room for only three non-overlapping 20 MHz channels, usually channels 1, 6 and 11.
For smart plugs, sensors and devices at the far end of a garden, 2.4 GHz is often the only band that reliably arrives. Many such devices support nothing else.
5 GHz: the everyday workhorse
The 5 GHz band offers many more channels and supports wider channel widths of 80 MHz or 160 MHz, which is where most of the speed in Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax) comes from. It loses strength faster through walls and floors, so a single router covers a smaller area. Some 5 GHz channels require Dynamic Frequency Selection (DFS): the router must listen for weather and military radar and move away if it detects any, which can cause brief pauses.
6 GHz: the newest band
In April 2020 the US regulator, the FCC, opened 1,200 MHz of 6 GHz spectrum to unlicensed use, and Ofcom opened a lower portion in the UK the same year; European rules followed through ETSI and national regulators. Devices labelled Wi-Fi 6E and Wi-Fi 7 (802.11be) can use it. Because only newer equipment can join, the band is quiet, and wide channels are easy to find. The cost is range: 6 GHz is the most easily stopped by masonry.
| Band | Reach indoors | Crowding | Best for |
|---|---|---|---|
| 2.4 GHz | Longest | High | Sensors, distant rooms |
| 5 GHz | Medium | Moderate | Streaming, laptops, phones |
| 6 GHz | Shortest | Low | Large transfers in the same room |
Generations and names
In 2018 the Wi-Fi Alliance introduced simple generation numbers: Wi-Fi 4 is 802.11n, Wi-Fi 5 is 802.11ac, Wi-Fi 6 is 802.11ax and Wi-Fi 7 is 802.11be. A generation describes techniques such as OFDMA, which lets a router serve several devices in one transmission, rather than a specific band. A connection runs at the level of the oldest participant, so a Wi-Fi 7 router talking to a Wi-Fi 4 laptop behaves like Wi-Fi 4 for that link.
Practical reading
Leave all bands on. Let devices choose, or use band steering. Reserve 2.4 GHz for range and simple devices, and expect the fastest results on 5 or 6 GHz when you are close to the access point.