With the DFS method (Dynamic Frequency Selection) as required for 5 GHz WLANs, an unused frequency is automatically selected, for example, to avoid interference from radar systems or to distribute WLAN devices as evenly as possible over the entire frequency band. Occasionally, however, signals from weather radar stations cannot be identified reliably.
For this reason the European Commission is extending the demands of standards ETSI EN 301 893 V1.3.1 and ETSI EN 310 893 V1.4.1 to additionally avoid the use of three channels (120, 124 and 128) in subband 2 of the 5 GHz band. These are not to be used for automatic channel selection. Methods for detecting weather radar signatures are currently under development.