WiFi: going from good to great is very hard


So i have a moderately complex home network. 5 access points lurk around, hard wired to each other. 3 of them speak 2.4+5, and 2 of them speak only 2.4GHz.

Saturday one of them came up for replacement. And since it covers a small area and is the main north-south gateway for my house, I chose to go for a device that has more RAM/CPU, and more average WiFi capabilities. And thus the rabbit hole of rebalancing occurs.

For those who don't know, the 5-GHz band has some limitations. First, in most regulatory domains (countries usually), there is a requirement that some of the frequencies do 'DFS' which is designed to detect weather radar systems (in case you are near an airport). I'm not, but I'm not allowed to disable DFS. Also, each channel as a different peak power allowed, as well as a different width. You can read about WiFi channels for you country here, and i've reproduced the first few columns below.

So as you can see, you want to use channel 42, 50, 155 from a width standpoint. Channel 155 allows 30dBm of power whereas 42 only allows 17, and 50 allows 24. But, that DFS column, you really want to avoid this if you can. It  turns out that false positives happen here, and, when they do, your router switches to another frequency and drops power.

So you now have a choice. Either not use the VHT80 mode and skip the DFS channels. Or use the VHT80 mode and have overlap (interference). Or use VHT80 and DFS and hope they don't move. Well, I tried that latter, and now my WiFi analyzer is telling me (as is my log file) that weather radar was detected. Boo. It only looks like a lot of channels. Basically there are only 2 non-DFS blocks, and only one of these is high power. And, each uses the whole block if you use VHT80.

Since I'm seeing false positives on the DFS detection, my 3rd 5GHz band is jumping ship and moving (and jumping on top of one of the other 2 non DFS bands which i've used the whole width on). [side note, you can see what your router wants to do by running 'iw reg get' on it).

The 2.4GHz band I managed more simply. There are only 3 non-overlapping channels (1,6,11) for 2.4GHz. I have 5 AP (plus 1 that is there for my alarm system I guess, plus 3 from my neighbours that broadcast @ high power). This gives 9 things vieing for the 2.4GHz 3 channel. So i've tuned my power down, directed the antenna a bit, and well, not a lot uses the 2.4GHz band for clients, just some of the devices like thermostats, older chromecasts, etc, so I don't care too much.

So, anyone care to comment on how they solved this dilemma? Is ignorance bliss and I should just ignore? I can kind of see now why the hackers disable DFS and power limitations, but that would be wrong.

ChannelFreqFreq-RangeBandwidthUSACanada
3651805170-519020YesIndoors
3851905170-521040YesIndoors
4052005190-521020YesIndoors
4252105170-525080YesIndoors
4452205210-523020YesIndoors
4652305210-525040YesIndoors
4852405230-525020YesIndoors
5052505170-5330160DFSDFS
5252605250-527020DFSDFS
5452705250-529040DFSDFS
5652805270-529020DFSDFS
5852905250-533080DFSDFS
6053005290-531020DFSDFS
6253105290-533040DFSDFS
6453205310-533020DFSDFS
10255105490-553040DFSDFS
10455205510-553020DFSDFS
10655305490-557080DFSDFS
10855405530-555020DFSDFS
11055505530-557040DFSDFS
11255605550-557020DFSDFS
11455705490-5650160DFSNo
11655805570-559020DFSDFS
11855905570-561040DFSNo
12056005590-561020DFSNo
12256105570-565080DFSNo
12456205610-563020DFSNo
12656305610-565040DFSNo
12856405630-565020DFSNo
13256605650-567020DFSDFS
13456705650-569040DFSDFS
13656805670-569020DFSDFS
13856905650-573080DFSDFS
14057005690-571020DFSDFS
14257105690-573040DFSDFS
14457205710-573020DFSDFS
14957455735-575520YesYes
15157555735-577540YesYes
15357655755-577520YesYes
15557755735-581580YesYes
15757855775-579520YesYes
15957955775-581540YesYes
16158055795-581520YesYes
16558255815-583520YesYes

 

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