Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

noahsark1126 · 2013-04-07 15:30:21

I recently acquired an Asus N56U router, which is supposedly capable of 300 mbps wireless-N. I'm using the 5 GHz band with the channel width set to 40 MHz.

I also have a 300 mbps wireless card:

$ lspci -nnk | grep -A 3 Network
02:00.0 Network controller [0280]: Intel Corporation Centrino Advanced-N 6235 [8086:088e] (rev 24)
        Subsystem: Intel Corporation Centrino Advanced-N 6235 AGN [8086:4060]
        Kernel driver in use: iwlwifi

When connected, the card does report 40 MHz channel width, but the actual bitrate corresponds to a 20 MHz channel:

$ iw dev wlan0 info
Interface wlan0
        ifindex 2
        wdev 0x1
        addr c4:85:08:11:29:7a
        type managed
        wiphy 0
        channel 36 (5180 MHz), width: 40 MHz, center1: 5190 MHz
$ iw dev wlan0 link
Connected to bc:ae:c5:eb:e7:ea (on wlan0)
        SSID: Kaylee
        freq: 5180
        RX: 17226531 bytes (37021 packets)
        TX: 2895710 bytes (14575 packets)
        signal: -34 dBm
        tx bitrate: 144.4 MBit/s MCS 15 short GI

        bss flags:      short-slot-time
        dtim period:    1
        beacon int:     100

From Wikipedia, this is the fastest possible bitrate on a 20 MHz channel. If I could only get to 40 MHz, I would have the full 300 mbps. From the Linux wireless documentation, I expect to see something like this:

$ iw dev wlan0 link
Connected to 68:7f:74:3b:b0:01 (on wlan0)
        SSID: tesla-5g-bcm
        freq: 5745
        RX: 30206 bytes (201 packets)
        TX: 4084 bytes (23 packets)
        signal: -31 dBm
        tx bitrate: 300.0 MBit/s MCS 15 40Mhz short GI

My actual transfer speed (to another computer connected via gigabit ethernet) is roughly 10 MiB/s.

Signal strength is at 100% (I'm literally only a few feet from the router), and there should not be any interference. There is only one other 5 GHz network in my building and it is 60 MHz away on channel 48 (5240 MHz).

Does anyone know how I can enable full 300 mbps speed?

Last edited by noahsark1126 (2013-04-09 19:25:11)

Strike0 · 2013-04-07 19:25:29

The bitrate reported with "iw link" varies depending on the current net-load, as you probably know. Have you tried to make it static?

iw dev wlan0 set bitrates mcs-5 14

noahsark1126 · 2013-04-07 22:48:09

yes, the bitrate does fluctuate, but it is always a 20 MHz bitrate (reading off the wikipedia chart). 144.4 is the highest it goes, even when the load is maxed out.

I tried setting the bitrate manually but it doesn't seem to have any effect...

bwat47 · 2013-04-07 23:33:09

I think this is either a kernel bug or some sort of intentional change in the kernel

I haven't been able to get 300mbps wireless since kernel 3.8, and I've tried kernel 3.8 on multiple distros (I also have intel wireless, centrino 6235). If i downgrade to 3.7 or previous it works fine. I think there was a change in kernel 3.8 that disabled channel bonding on intel wireless. Doesn't matter if I use the 2.4ghz or 5ghz channel. Both work fine with kernels previous to 3.8.

Last edited by bwat47 (2013-04-08 01:17:44)

noahsark1126 · 2013-04-08 02:53:10

I can confirm this. I got full 300 mbps after downgrading to kernel 3.7.

Do you suppose this should be reported as a bug?

bwat47 · 2013-04-08 04:01:09

noahsark1126 wrote:

I can confirm this. I got full 300 mbps after downgrading to kernel 3.7.
Do you suppose this should be reported as a bug?

I guess so, couldn't hurt.

Strike0 · 2013-04-08 19:44:53

This one sounds similar: https://bugzilla.kernel.org/show_bug.cgi?id=54851
Have a look, if you get the same VHT downgrade warning in the log.

Roken · 2013-04-08 21:03:21

If you switch your router to operate in 802.11n 40Mhz exclusively it should work, but personally I found that the speed fluctuated far too much. Gone back to the wire here, now.

bwat47 · 2013-04-08 21:24:59

Roken wrote:

If you switch your router to operate in 802.11n 40Mhz exclusively it should work, but personally I found that the speed fluctuated far too much. Gone back to the wire here, now.

Unfortunately, my netgear router's firmware does not appear to have a 40mhz only option for either the 2.4ghz of 5ghz bands, so I have not been able to try that to see if that even works. From the wording on the OP's original post though, it appears he might already have his set to 40mhz only and is still experiencing the problem.

noahsark1126 · 2013-04-09 16:45:24

Roken wrote:

If you switch your router to operate in 802.11n 40Mhz exclusively it should work, but personally I found that the speed fluctuated far too much. Gone back to the wire here, now.

I have the router set to N-only and 40 MHz-only. It still does not work.

Strikeo wrote:

This one sounds similar: https://bugzilla.kernel.org/show_bug.cgi?id=54851 Have a look, if you get the same VHT downgrade warning in the log.

That does look similar but I don't have that warning in my logs (it would be in the systemd journal, yeah?).

litemotiv · 2013-04-09 17:23:15

I'm still waiting for brcmsmac to add 40MHz support: https://bbs.archlinux.org/viewtopic.php?id=153275

P.s., if this is an Intel-only thread, please update the title to reflect that.

bwat47 · 2013-04-09 19:07:52

noahsark1126 wrote:

Roken wrote:
If you switch your router to operate in 802.11n 40Mhz exclusively it should work, but personally I found that the speed fluctuated far too much. Gone back to the wire here, now.
I have the router set to N-only and 40 MHz-only. It still does not work.
Strikeo wrote:
This one sounds similar: https://bugzilla.kernel.org/show_bug.cgi?id=54851 Have a look, if you get the same VHT downgrade warning in the log.
That does look similar but I don't have that warning in my logs (it would be in the systemd journal, yeah?).

according to some of the later comments in the bug report the error itself may be irrelevant:

Wait ... 3.8 doesn't have commit 586e01ededf9b713a1512dd658806791a7ca1a50, so
that message is entirely expected ...
So I don't think this is related. Can you check "iw dev" output?

, so I think it looks like the right bug.

Last edited by bwat47 (2013-04-09 19:08:43)

noahsark1126 · 2013-04-09 19:18:56

bwat47 wrote:

according to some of the later comments in the bug report the error itself may be irrelevant

I think you're right. And I'm assuming that was you who commented just a little while ago, so thanks. I'll also add a comment to confirm.

litemotive wrote:

P.s., if this is an Intel-only thread, please update the title to reflect that.

I didn't know when I made the thread but it does now look like this is Intel-only. I will change the title.

Strike0 · 2013-04-09 19:19:29

@noahsark1126: Yes. However, I just saw that the 3.8.6 that rolled into core has the patch mentioned in that bug: https://git.kernel.org/cgit/linux/kerne … b6a6a9746c which suppresses the error message. But from that description it seems to me now that it probably is not addressing this error here.

@litemotiv: not unlikely that this is the same error (mac80211). the difference is that you experienced it with an earlier kernel, where the OP had it working before 3.8 (see above).

I tried here and it does not work either (iwlwifi with ath9k router). Never turned on 40mhz before. I would have of course, if our neighbours did

edit: this cross-posted with #12 and #13

Last edited by Strike0 (2013-04-09 21:10:20)

richard_wiggler · 2014-02-19 21:47:46

I hate to be that guy an resurrect an old thread, but has this still not been solved/fixed?

I'm on kernel 3.12.9 and I am still unable to get my Intel wireless card to use the full 40 MHz band.

noahsark1126 · 2014-02-20 15:33:49

I have had functioning 40 MHz for some time now. You may want to check if the problem is with your router / signal quality / etc.

Arch Linux

#1 2013-04-07 15:30:21

Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#2 2013-04-07 19:25:29

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#3 2013-04-07 22:48:09

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#4 2013-04-07 23:33:09

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#5 2013-04-08 02:53:10

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#6 2013-04-08 04:01:09

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#7 2013-04-08 19:44:53

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#8 2013-04-08 21:03:21

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#9 2013-04-08 21:24:59

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#10 2013-04-09 16:45:24

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#11 2013-04-09 17:23:15

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#12 2013-04-09 19:07:52

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#13 2013-04-09 19:18:56

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#14 2013-04-09 19:19:29

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#15 2014-02-19 21:47:46

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

#16 2014-02-20 15:33:49

Re: Intel wireless: 300 mbps / 40 MHz channel bonding broken on kernel 3.8

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