Force one client to use 20MHz instead of 40MHz possible?

Extensive testing reveals while other clients have better throughput with 40MHz connection to my 2.4GHz only OpenWrt router, there is just one single client (a dd-wrt bridge router) that fares worse if the wireless network is on 40MHz channel width.

So I have a question - is there any setting to somehow single out this client, then force it to connect with a channel width of 20MHz instead of 40MHz?

(dd-wrt does not seem to have a setting, when in client mode, to use only 20MHz)

Thanks !

See this wiki article on channel width...

However, there are mechanisms in 802.11n to drop 40 MHz to 20 if interference is detected.

Unless you live in a rural area with not a lot of neighbors, 20 MHz should be used.

Unless I missed something, these settings are 'universally' applied, meaning it applies to the entire network and impacts every single client.

But I want the network to be in HT40 in general, but specifically for one client, I want to force HT20.

You know how some clients that are incapable of utilizing double channel width 40MHz like some mobile phones (e.g. my old Xiaomi Mi9 was like this until I messed with it's wpa_supplicant), and they will connect anyway but utilizing only the primary channel? I'd like to see if I can get my Openwrt to instruct a single client to connect only via primary channel.

Cheers for any help.

I got that.

There are drawbacks to using HT40 on 2.4 GHz in the first place...hence the caution above.

Could have an negative impact on your neighbors (with the exception I mentioned), who won't be happy.

I would not encourage you to use HT40 over HT20.

I don't know if you've tried optimizing your 2.4 GHz configs using HT20 (non-overlapping channels 1, 6, or 11...maximum transmit power...DTIM interval...distance optimization...beacon interval...fragmentation and RTS/CTS threshold.

If you want some help with that, SSH in to the router and run -

cat /etc/config/wireless

Redact the passwords in the "option key" sections.

Post the results in preformatted text, by using the icon highlighted in red...

OpenWRT Posting Icons

Otherwise, it may be time for a dual band router.

Thanks for your help. Fact is most of my other clients see a close to 100% increase in speed when 40MHz is active.... I really doubt any type of optimization on a pipe half the size is going to compensate for the loss of channel width.

I am good with the performance figures (i.e. can save $ on latest and greatest dual bands / wifi 6 / 6GHz) except this one bridge router that is broadcom-based i.e. can't run openwrt well (ironically this router IS dual band), and clashes with something when it connects to my Openwrt router on 40Mhz...

Which is fine...unless it's negatively impacting your neighbors.

Sounds like it's time to upgrade your gear.

Good luck.

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I don't really think you can have the AP using 40 Mhz and somehow force one client from AP side to use 20 Mhz. The AP will just advertise it's 40 Mhz capable and the client will happy use 40 Mhz to connect to it if it's 40 Mhz capable.

If you have any other router not used, use it as AP for the client that has to use 20 Mhz...

In some areas 2,4 Ghz band can't really be considered reliable.
If you live in a flat where your neighbours use weird channels like 2,4,7,10, 40 Mhz when that AP already overlaps with 8 other APs there is plain nothing you can do...
During evening when people return from work it becomes a nightmare to do something using the Wi-Fi.
Add some microwave owens with bad shielding interfering with entire 2,4 Ghz band and you get a nice nightmare...
Situation become so bad that it no longer matters if you are friendly or not with your neighbours on the 2,4 Ghz, the damage done by your neighbours is so bad that you can't really make it worst than it already is...

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I ended up tweaking the client, i.e. the dd-wrt router, to only use 20MHz. Worked.

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