FRITZ!Box 3370 Service - Knowledge Base

FRITZ!Box 3370 Service

FRITZ!Box reports "Wireless LAN transmission quality increased by reduced channel bandwidth"

Computers, smartphones, or other wireless devices display a low speed for the Wi-Fi connection to the FRITZ!Box's 2.4 GHz frequency band displayed. The following message is displayed in the event log of the FRITZ!Box:

  • "Wireless LAN transmission quality increased by reduced channel bandwidth (2.4 GHz)"


  • The FRITZ!Box recognizes when the Wi-Fi channels it uses in the 2.4 GHz frequency band are in heavy use by other Wi-Fi networks. To ensure stable Wi-Fi connections, it automatically reduces the channel bandwidth from 40 MHz to 20 MHz. This FRITZ!Box behavior is conform to wireless coexistence.

Although wireless devices then display a lower data rate, the user data rate is increased because there is less interference and the Wi-Fi connection is no longer affected by constant retransmissions.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 Finding the ideal location for the FRITZ!Box

  1. If possible, place the FRITZ!Box in a centrally located room. The FRITZ!Box has omnidirectional antennas. The wireless signal is therefore emitted spherically in all directions.
  2. Do not place the FRITZ!Box directly in the corner of a room.
  3. Place the FRITZ!Box so that it is as unobstructed as possible, i.e. not directly in back of or under an obstacle such as pieces of furniture or a heater.
  4. Place the FRITZ!Box as high in the room as possible, for example on a shelf.
  5. Place the FRITZ!Box so that there are as few obstacles as possible between it and the wireless devices. Even small objects in the immediate vicinity of your FRITZ!Box can greatly reduce the range of the wireless signal. Metallic objects or objects containing water, such as radiators, refrigerators, or even houseplants, significantly reduce the quality of the wireless signal.
  6. Place the FRITZ!Box away from other radio transmitters, such as microwaves, wireless speakers, or Bluetooth devices.

2 Selecting the best Wi-Fi channel

In the factory settings, the FRITZ!Box automatically checks the Wi-Fi environment and selects the Wi-Fi channel settings. However, with some disturbances it cannot determine the best Wi-Fi channel for all wireless devices. Therefore, select the Wi-Fi channel in the FRITZ!Box that is least affected by interference in the Wi-Fi environment:

  1. Click "Wireless" ("WLAN") in the FRITZ!Box user interface.
  2. Click "Radio Channel" in the "Wireless" ("WLAN") menu.
  3. Use the diagram "Use of the Wireless LAN Channels" to determine which channel in the lower frequency range is least affected by other Wi-Fi networks and interference.
  4. Enable the option "Adjust radio channel settings" in the "Radio Channel Settings" section.
  5. From the drop-down list "Radio channel", select the Wi-Fi channel that was the least affected.
  6. Click "Apply" to save the settings.
  7. If the issue with your wireless connection still occurs, repeat steps 3 - 6 with a wireless channel in the middle and then with one in the higher frequency range. Then, use the wireless channel with the least interference.

    Important:The diagram of the Wi-Fi environment only reflects the current situation! The allocation of the frequency band can change significantly over the course of the day because many Wi-Fi networks are turned on when in use. Therefore, check several times to see which Wi-Fi channels are least affected by interference.

Now the FRITZ!Box automatically selects the best Wi-Fi channel settings. If the message "Wireless LAN transmission quality increased by reduced channel bandwidth (2.4 GHz)" is still displayed in the event log of the FRITZ!Box, this is because all of the Wi-Fi channels in the 2.4 GHz frequency band are in heavy use by adjacent Wi-Fi networks.