Fritzbox 4040 uses only 20MHz channel

Installing and Using OpenWrt
1

I have a Fritzbox 4040 with Openwrt 21.02.0 (but the issue also there with 19.07)
Unfortunately the Wifi is pretty slow. I noticed that no matter which channel I use (2.4GHz and 5GHz) I only get a 20MHz channel. I configured 40MHz for 2.4GHz and 80MHz for 5GHz, but it is never used, even if I am right next to the router. I tried it with different smartphone (which all have faster wifi with other routers).
I tried to use the non-ct firmware for ath10k but the result was the same.
Any ideas what could be the problem?

2

I'm using a Fritzbox 4040 myself and 80 MHz channel operation works fine with OpenWrt 21.02 and it also worked previously with 19.07.

Can you tell more about your configuration? How do you check the channel bandwidth?

By the way, you probably shouldn't use 40 MHz in the 2.4 GHz band due to the limited number of non-overlapping channels. Automatic fallback to 20 MHz is expected behavior in the 2.4 GHz band when other APs are detected on neighboring channels. Thus, you should focus on 5 GHz and make sure your devices are actually connected in the right band.

3

Then lets focus on 5GHz for now. Here is my config:

config wifi-device 'radio1'                    
        option type 'mac80211'                               
        option hwmode '11a'                     
        option path 'platform/soc/a800000.wifi'
        option country 'DE'                                  
        option beacon_int '500'                              
        option htmode 'VHT80'                   
        option channel '40'                                  
                                                             
config wifi-iface 'default_radio1'              
        option device 'radio1'       
        option network 'lan'                                 
        option mode 'ap'                        
        option encryption 'psk2+tkip'                        
        option key 'my_password'
        option wpa_disable_eapol_key_retries '1'
        option ssid 'my_ssid'             
        option disassoc_low_ack '0'

I check the channel bandwith in Luci Network --> Wireless and there under "Associated Stations" it is shown under RX-Rate / TX-Rate.

4

Currently, your configuration forces WPA2 with TKIP, which is an outdated encryption standard. Unless you have old devices that don't support the more modern CCMP, it is best to not enable TKIP at all (i.e. select "Force CCMP").

This will likely also fix your bandwidth issue, as it looks like 802.11ac devices only support TKIP in a fallback mode.

(There are some other non-standard values in your config like the beacon_int and disassoc_low_ack. In case you only changed those to test if that fixes the bandwidth issue, you may want to revert them to the default values.)

1 Like
5

Thanks a lot! That did indeed fix the issue. I didn't expect crypto settings to have such an impact.
The disassoc_low_ack did help with some Android devices which disconnected constantly when the display was off. And I changed the beacon_int because I have 3 SSIDs in parallel and wanted to reduce the time used on those beacons. But I couldn't really tell if that helped, so maybe I should go back to the default there :slight_smile:

6

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