FRITZ!Box 6590 Cable Service - Knowledge Base
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Status message "5-GHz band cannot be used for [...] min. because of check for higher-priority users (e.g. RADAR) on the selected channel (frequency [...] GHz)"
The 5 GHz frequency band is not only used by wireless devices, it is also used by radar systems (for example air traffic control, the military, or weather service). To ensure that such radar systems are not subject to interference, the government granted them primary user status. Wireless devices that use a wireless channel from 52 to 140 must therefore detect primary users and use Dynamic Frequency Selection (DFS) to automatically avoid them.
Scanning for primary users
If the FRITZ!Box is using one of these channels, according to regulatory requirements, it must wait up to 10 minutes before allowing the 5 GHz frequency band to be used. The status message "5-GHz band cannot be used for [...] min. because of check for higher-priority users (e.g. RADAR) on the selected channel (frequency [...] GHz)" is displayed in the event log of the FRITZ!Box. The FRITZ!Box may not allow wireless devices to use the 5 GHz frequency band until the wait time has elapsed. The wait time always begins when the 5 GHz frequency band is enabled (for example after restarting the FRITZ!Box) or after the wireless settings are changed. If you change the wireless settings during the wait time, the timer is reset. Wireless connections are automatically reestablished once the wait time has elapsed. The scan for primary users is then continued; however, this does not have any negative effects on the 5 GHz frequency band.
Recognizing primary users
If the FRITZ!Box detects a radar system, it must automatically switch to a different channel, even if the channel is fixed. The status message "RADAR was detected on channel [...]; channel switched automatically because of higher-privileged user" is then displayed in the event log of the FRITZ!Box.
Avoiding the wait time with Zero Wait DFS
Starting with FRITZ!OS 7, the FRITZ!Box can avoid the wait time by first occupying a channel between 36 and 48. Since this range is not used by radar systems, it does not have to wait. The FRITZ!Box then switches to a higher channel once the wait time valid for channels 52 to 140 has elapsed.
Note:If you enable the option "Allow wireless channels with 160-MHz channel bandwidth (5-GHz frequency band)" in the FRITZ!Box, you cannot avoid the wait time due to the wider channel bandwidth. The option is not enabled in the factory settings.