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Wi-Fi channels and frequency bands: Why Wi-Fi is slow

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tagsglossar, netzwerk, wlan

2 min read

Wi-Fi channels and frequency bands: Why Wi-Fi is slow

In short: Wi-Fi transmits on 2.4, 5 or 6 GHz in channels; crowded channels, walls and many neighbouring networks slow it down, and the right choice of band and channel often brings a lot.

In more detail: All devices share the air. The more networks transmit on the same channel, the more they have to send in turns, and speed falls. Routers often choose channels automatically but not always well.

In Depth

The frequency bands

  • 2.4 GHz: long range, penetrates walls well but slow and crowded (neighbours, Bluetooth, microwave, baby monitors). Only 3 non-overlapping channels in Europe (1, 6, 11 or 1, 5, 9, 13).
  • 5 GHz: faster, many channels, less interference, but shorter range and weaker through walls.
  • 6 GHz (Wi-Fi 6E/7): lots of free spectrum, highest speed, but even shorter range; only newer devices. The channel width (20/40/80/160 MHz) determines the peak rate: wider is faster but more prone to interference.

Standards

Wi-Fi 4 (802.11n), Wi-Fi 5 (ac), Wi-Fi 6 (ax), Wi-Fi 6E, Wi-Fi 7 (be). Newer standards distribute the air more efficiently (OFDMA, MU-MIMO) and are especially better with many devices. Router and device must both support the standard; speed follows the weaker one.

Optimising

  1. With a Wi-Fi analysis app (WiFi Analyzer, NetSpot, Fritz!Box channel overview) see which channels are occupied.
  2. In the router choose a free channel or use the automatic mode, enable the 5 GHz band for laptops, phones, TVs.
  3. Location: router elevated and central, not in a cupboard, not behind metal or an aquarium.
  4. Mesh system or additional access points (connected by cable) instead of many repeaters.
  5. Fixed devices (PC, console, TV) via LAN cable.
  6. Update firmware, switch off unused radio standards (old b/g).

Do not forget security

Use WPA3 (or at least WPA2-AES) with a long password, switched-off WPS, current router firmware, a guest Wi-Fi for visitors and IoT. An open Wi-Fi allows eavesdropping and can make you liable for misuse. Raising transmit power rarely solves range problems because devices cannot send back louder.

See also: Wi-Fi security, Wi-Fi repeater, Powerline, Reading a speed test