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Forum Discussion
donawalt
Aug 19, 2024Mentor
5 GHz DFS channels - have you tried them?
On the 970 Router, there is now an option to default the 5 GHz channel to one of 4 DFS channels - 48, 52, 56, 60, and 64. DFS stands for Dynamic Frequency Selection. I had to read what a dis channel was, here is a concise definition if you have not heard of it...
The 5Ghz Wi-Fi found around your home and anywhere else modern Wi-Fi hardware is deployed uses a portion of the radio spectrum that is part of a much bigger communication band known as the "C Band."
The C Band is a significant swath of the microwave radio frequency band ranging from 4Ghz up to 8Ghz. Various different portions of that range are used for all manner of things including satellite communication, military and civilian radar, weather radar, cellular communication, and more.
Among the wide variety of things in the C Band, the most common thing that overlaps with the same 5Ghz range used by Wi-Fi devices is weather radar. In theory, this is a win-win for everybody involved. Consumers can use part of the C Band for their home Wi-Fi when the airwaves are clear and the portion of the C Band is handed back over when more important services are needed. In practice, it's not exactly a free lunch situation for consumers and real-world deployment of DFS can either be a boon or a hassle.
The biggest negatives I read about are router startup/reboot can take 1-10 minutes longer! This is because DFS is required to run a check, called a Channel Availability Check, before using the specific channels in that range.
During this check period the 5Ghz network for the access point running the check is not available and it will either fall back, if possible, to the 2.4GHz network or, simply remain unavailable until the check is complete.
If the airspace is clear and the particular channel passes the Channel Availability Check, after the 1-10 minutes Wi-Fi the access point will be available for us. Every single time your router and access points are restarted you'll have X minutes of downtime while the check is run.
To comply with DFS rules, whenever your router or access points detect anything that appears to be interference from a higher-priority source on the portion of the DFS-allocated spectrum a rapid sequence of events unfolds.
The router blocks quickly dumps all clients on that channel, stops use of the channel, broadcasts new information for the local clients to guide them to the new channel, and traffic resumes. Further, the router complies with a Non-Occupancy Period (NOP) of at least 30 minutes (though most consumer routers will often leave the channel unused for longer, potentially until the next day).
When the Non-Occupancy Period has passed, the router will repeat the Channel Availability Check, albeit in a shortened form, before potentially switching to the new channel. Just like with the original longer boot-time scan, the router will be inaccessible to wireless clients on the 5Ghz band during this time.
The tiniest bit of traffic on the restricted frequencies will lead to your router immediately dumping it. There's no back and forth, no confirmation if the traffic is actually a weather radar or such, the DFS system immediately defers to the other traffic and switches.
The good news is that you probably have no neighbors or other 5GHz networks interfering with your network, iff you are in a congested area. The key question is, how frequently does the router have to dump access on the DFS channel due to a higher priority government network, weather, airport, using it?
Does anyone have any experience trying it on an Orbi or other router? Was it worth it or too much pain due to devices being dropped off a lot?
Changed it but don't really think it'll make a difference. Reason why is it was already using the DFS channels. It broadcasts from channel 36-64. so even if I change it in the settings, it still using those channels because its 160hz wide.
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I've used it on my devices but not specifically set it through the wireless settings. Anytime you're using the 160hz wide channels, it uses dfs.
I'll try and remember tonight to set it on my orbi and see how it impacts it.