How Wi-Fi shares the air
Wi-Fi devices listen before they transmit. If the channel is busy, they wait. This method keeps transmissions from colliding, but it means every device and network on the same channel shares one pool of airtime. A router can show full signal bars and still feel slow because it is constantly waiting its turn.
Neighbouring networks
In flats and terraced streets, dozens of networks may be visible from one room. Two kinds of overlap matter:
- Co-channel: networks on exactly the same channel. They coordinate and share time, which is manageable.
- Adjacent-channel: networks on partly overlapping channels, such as 3 and 6 on 2.4 GHz. They cannot decode each other, so they act as noise. This is usually worse.
That is why the usual advice on 2.4 GHz is to stick to channels 1, 6 or 11 and avoid the ones in between.
Household sources
Microwave ovens heat food with energy at about 2.45 GHz, right inside the Wi-Fi band. The appliance traces back to Percy Spencer at Raytheon in the 1940s. Shielding keeps most of the energy inside, but some leakage is normal, and 2.4 GHz connections near a running oven may stutter. Other sources include older cordless phones, wireless video senders, baby monitors and some USB 3 ports and cables, which can emit noise around 2.4 GHz.
Other radios in the same band
Bluetooth, overseen by the Bluetooth SIG, also uses 2.4 GHz. It hops rapidly between narrow channels and uses adaptive hopping to avoid busy frequencies, an idea with roots in the frequency-hopping patent granted to actress and inventor Hedy Lamarr and composer George Antheil in 1942. Smart-home protocols Zigbee and Thread, both based on IEEE 802.15.4, sit in 2.4 GHz too. Matter, released by the Connectivity Standards Alliance in 2022, runs over Wi-Fi, Thread and Ethernet, so a single smart home can contain several of these radios at once.
Choosing channels
Many routers pick channels automatically, and modern automatic selection is generally sensible. If you choose manually, use a Wi-Fi scanning app to see which channels neighbours occupy, pick the least busy of 1, 6 or 11 on 2.4 GHz, and leave space between Zigbee or Thread channels and your Wi-Fi channel where your hub allows it.
Channel width
Wider channels carry more data but occupy more spectrum, so they meet more neighbours. On 2.4 GHz, 20 MHz is the courteous and usually faster choice in busy areas. On 5 GHz, 80 MHz is a common balance; 160 MHz pays off mainly where the band is quiet. On 6 GHz, wide channels are more often available.
A short checklist
- Move the router away from the kitchen, the TV and stacks of electronics.
- Use 5 or 6 GHz for devices that support them, freeing 2.4 GHz for simple gadgets.
- Prefer cables for fixed devices such as TVs, consoles and desktop computers.
- Restart and update the router; firmware updates often improve channel selection.