This site, a Weather RADAR WLAN channel map, is hosted on personal webspace at University of Vienna, Austria. The web server collects statistical data of web visitors as follows:
In case you don't want to visit the website but still get an idea, know that the WLAN channels most frequently used by weather RADARs are 124, 128, and 120.
If you would like to visit the map now, please go ahead.
This map displays the approximate geographic regions in which certain 5 GHz WLAN channels (color-coded areas on the map) will see high activity from weather RADARs. Your WLAN device will likely encounter DFS events on these channels in a location. Move the mouse pointer across the map to update the channel list for the location indicated. Click or tap the map to place a marker and display the data relevant for this location statically. Click or tap the map again to remove the marker.
The RADAR frequencies, ranges, and site positions that form the shapes presented are provided by Eumetnet's OPERA Programme. Thank you for the permission to use your data!
The map layer is based on OpenStreetMap. Features are drawn using OpenLayers. This implementation is a fan project for FunkFeuer Wien wireless community network.
Depending on the exact regulations in your region, WLANs that operate in the 5 GHz band are required to use a technique called Dynamic Frequency Selection (DFS) to avoid interfering with weather (and other) RADARs in the same band. RADAR activity on the current WLAN channel forces WLAN equipment to switch channels (see below for more details). Switching interrupts connectivity, so you should rather steer clear of WLAN channels used by RADARs in a location to avoid the performance hit.
This map suggests which channels to avoid. In general, channels 124, 128, and 120 are most likely to be occupied by RADARs.
The rough idea behind DFS is that WLAN equipment must monitor its channel for RADARs operating on the channel, and stop using this channel if RADAR activity is detected.
More precisely, a WLAN "master" device must perform Channel Availability Checks to establish the absence of RADARs on a channel before this channel (or channels) may become Available and possibly Operating Channel(s). Once in operation, the device monitors the channel(s) via In-Service Monitoring. If a RADAR is detected, the master device instructs all associated "slave" devices to stop using the channel, and stops using the channel itself as well. The channel is then marked unavailable for the duration of 30 minutes, the Non-Occupancy Period. Only after that, it may be checked for availability again.
DFS is defined in ETSI Standard EN 301 893. See § 126.96.36.199.4 in that document for details on the operating procedure sketched above.
Unfortunately, this map cannot guarantee that nominally unoccupied channels will really be free of DFS events. The WLAN device's detection mechanism might erroneously detect a RADAR signature; or perhaps there's an actual (new or temporary) RADAR on this channel that the map doesn't know about.
Similarly, it's not sure that a nominally-occupied channel really causes DFS events in your WLAN device: Again, its detection mechanism might be faulty; the map data could be incorrect; the RADAR's nominal range may not actually cover your location due to topology; the RADAR could be offline for maintenance, ...
Long story short, we hope that this map will still be useful, but its data are quite static — unlike the radio environment.
The current version of the map incorporates data about European weather RADARs from Eumetnet's OPERA database. Switzerland (.ch) and Serbia (.rs) operate RADARs on 10 and 2 GHz, respectively. This 5 GHz-oriented map does not display them. Some countries such as Luxembourg and Malta seemingly don't operate RADARs. For the European sub-continent, the dataset does not include data for Lithuania, Belarus, the Ukraine, Turkey, and countries east of this approximate geographical line. (I don't know the reasons for any of this, I just noticed.)
Data for other continents is missing as well. If you have it and can sort out the licensing, I'm happy to include it. (For instance, I found data for the United States. Can you get me a FoIA or other official permission to use the data?)
This map is as accurate (in the best case) as the data that go into it. For the RADAR data, we rely on Eumetnet's database, where the site locations, nominal ranges, and frequencies of RADARs are listed. Assuming that the locations are OK, our data preparation causes a number of errors:
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The RADAR frequencies, ranges, and site positions are provided by Eumetnet's OPERA Programme and used by written permission for FunkFeuer Wien. Thanks again!
Note: Eumetnet's own RADAR map is available from their website. It shows more operational details about the RADARs. Our map here focuses on converting the RADAR frequencies to approximate WLAN channels and displaying these instead.
This map application is based on example code from OpenLayers. Following OpenLayers' licensing scheme, the application is licensed under the 2-clause BSD License:
BSD 2-Clause License
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