2.4Ghz 40Mhz 802.11n wifi and Apple Macbook

Hello everyone,

I am running a TP Link TL-WR1043N which (as TP Link says is a) 802.11n
router working on 2.4Ghz (no support for 5Ghz). I am running it with
flashed OpenWRT.

While using option to pick 40Mhz, I see my Mac only gets 20Mhz to use and
speed is always 130Mbps. There's no other SSID nearby and I am sitting next
to router for testing.

This brings me to question - Has anyone successfully used 40Mhz with 2.4Ghz
on 802.11n standard with Apple Macbook? I wonder if it's limitation on the
chipset or something else.


Everything that I've seen/experienced says that Apple devices won't use 40mhz channels with 2.4 due to the overlapping bands/lack of good separation between channels.

However, I'm not sure if this specifically applies to just the Airport APs like the Extreme, or to the laptops as well, as I use AE's at home, and the Unifi APs I do have in service all have 20mhz channels only set on them to avoid issues.

Shoot me if i'm wrong, but doesn't a mac prefer MIMO in order to work

40MHz on 2.4 is note widely supported, and for good reason - it sucks up the entire unlicensed 2.4GHz band (if you include the 802.12 mask).

On 5GHz, 20/40 are supported, and 80/160 in current and future versions of 802.11ac.

It'd be nice if IEEE would start supporting smaller channel sizes and a sync method in the 802.11 specifications. make the default channel size 5 MHz and it auto increases as necessary. 20 meg Internet could get by just fine on interference free 5 MHz. Have a 1588-like sync mechanism sent from the ISP for residential (or your controller for public\business use) to have them transit in sync as well to reduce interference.

You still get a nice performance boost with 802.11b/g/n in 2.4 range even at 20mhz, but if you go to 40mhz, you'll be splattering all over the entire 2.4 band.

This is why all of the pre-N performance enhancements for G were troublemakers if you had multiple wireless networks in the same area. You turn it on, and one of two things happen - you either wreck performance of everyone else on that band, or everyone else wrecks your performance.

So assuming you live in a decent sized house/lot, should you really care
about squatting all over the entire band? I mean sure I can see my
neighbors wifi signals, but they are too weak for me to connect with them.
So wouldn't mine be just as weak at their location, so why should I care
about using the entire band? Aren't I really only using 2/3 of the band by
going to 40Mhz, leaving an entire 20Mhz wide channel free for my neighbors
AP to switch over to?

I see substantial improvements in going from 20 to 40 Mhz from smartphone's
that have 1X1 fixed antennas which is every smartphone. Going from 20 Mhz
with a max theoretical of 72.2Mbps to 40 Mhz with a max theoretical of
150Mbps is a big difference. Especially when you typically only get half of
the max theoretical speed.

*DING* There's your problem. It doesn't matter if you can link and pass traffic. If **ANY** other signal is detected in the extended channel, the AP is *REQUIRED* to cease operation @ 40MHz. This is why it is nearly impossible (outside a shielded lab) to get 40Mhz mode in the 2.4GHz band. SOMETHING is going to step on it -- neighbors, bluetooth, cordless phone, leaky microwave oven, baby monitor, RC toy, ...

Is this one of those requirements that gets ignored? I have seen plenty of 40Mhz SSIDs polluting spectrum in areas with lots of overlapping APs.

Steve Mikulasik

It's not supposed to be. But what is (originally) submitted for testing and what you get off the shelf are very likely to be different. And then there are vendors that don't bother to be certified.

For reference: my WRT54G-V6 (non-n, doesn't do 40MHz) has a certificate, but doesn't carry the logo -- it was also made well after the 2006 certified date. The Ubee DDW3611 hanging on the wall has a logo, but no certificate (the 3610 has one, from 2010.)