WiFi Channel Planning for OpenWrt

Non-overlapping channels

The 2.4 GHz band has up to 14 channels spaced 5 MHz apart, but a 20 MHz channel overlaps its neighbours. That is why only channels 1, 6 and 11 are non-overlapping in most regulatory domains. Using any other channel interferes with neighbours on 1, 6 or 11.

The 5 GHz band is much wider, so most channels are non-overlapping at 20 or 40 MHz width. At 80 MHz, four channels combine; at 160 MHz, eight combine.

• 2.4 GHz: use 1, 6 or 11 only.
• 5 GHz 20 MHz: channels 36, 40, 44, 48, 149, 153, 157, 161.
• 5 GHz 80 MHz: blocks at 36, 52, 100, 149 (each spanning four 20 MHz channels).

Channel width trade-offs

Wider channels (40, 80, 160 MHz) offer higher maximum throughput but are more vulnerable to interference. In a congested apartment, a 20 MHz channel that is clear often outperforms a crowded 80 MHz channel.

For 2.4 GHz, stick to 20 MHz. For 5 GHz, start at 80 MHz and test; if throughput is unstable, drop to 40 MHz. Reserve 160 MHz for environments with few nearby access points.

• 2.4 GHz: use 20 MHz; 40 MHz adds interference in most environments.
• 5 GHz: 80 MHz in quiet areas, 40 MHz in busy ones.
• 160 MHz: only when few neighbors use 5 GHz.

DFS channels

Some 5 GHz channels (52-64 and 100-144 in most regions) overlap with weather radar. OpenWrt must perform radar detection (DFS) before using them and must vacate the channel if radar is detected. This causes a 60-second startup delay and occasional channel changes.

For a stable home network, prefer non-DFS channels: 36-48 and 149-165. Use DFS channels only if the non-DFS band is saturated.

Survey the neighborhood

Before choosing a channel, scan to see what nearby access points are using. In LuCI, go to Network → Wireless and click "Scan" next to each radio. The scan results show the SSID, channel, signal strength and channel width of every nearby AP.

For a more detailed picture, use the `iw` command over SSH. It lists every access point the radio can see, including hidden ones, with their signal strengths in dBm.

iw dev wlan0 scan | egrep "SSID|freq:|signal:|channel:"

Scans on the 2.4 GHz radio (wlan0) and filters for the key fields. Use wlan1 for 5 GHz.

Set the channel in LuCI

Go to Network → Wireless, edit the radio, and pick a channel from the dropdown. For 2.4 GHz, choose 1, 6 or 11 based on the scan. For 5 GHz, choose a non-DFS channel with the fewest strong neighbors.

Set the channel width in the same page. Save and apply; the radio will restart and clients will reconnect.

uci set wireless.radio0.channel='11'
uci set wireless.radio0.htmode='HT20'
uci set wireless.radio1.channel='36'
uci set wireless.radio1.htmode='VHT80'
uci commit wireless
wifi

Sets 2.4 GHz (radio0) to channel 11 at 20 MHz and 5 GHz (radio1) to channel 36 at 80 MHz. VHT80 is 802.11ac; on an 802.11ax radio the driver expects HE80. The names radio0/radio1 and the valid htmode values depend on the device.

Auto channel mode

OpenWrt supports channel auto-selection by setting the channel to "auto". The driver picks a channel at boot, but it does not dynamically re-evaluate if the environment changes later.

For most homes, manually selecting a clear channel gives more predictable results. Re-survey every few months, especially if a new neighbor appears or you change your own AP placement.