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View Full Version : [all variants] b43 Bit Rate - Strange Findings



kevdog
January 5th, 2009, 05:03 PM
I used to run ndiswrapper and theoretically achieve a rate control of 54 Mb/sec. At least this setting was specified in the iwconfig statement and I could set the card similar to
sudo iwconfig wlan0 rate 54M

I switched back to the b43 driver beginning in Ibex since I could no longer get the ndiswrapper solution to work with my bcm4306 rev 03 card with WPA2. I noticed by default the bit rate is set at 2 Mb/sec. This can be manually changed to 11 Mb/sec and still successfully run. If I change to 54 Mb/sec however, the card no longer functions.

This is quite disappointing to me. I'm not sure if it makes any practical difference however, but nonetheless I'm disappointed.

Reading through http://linuxwireless.org, I see that other open source drivers such as ath5k, ath9k are also by default set at a rate control or 2Mb/sec, and the documentation states 11 Mb/sec can be set safely for operation. I think this is really disappointing for 2 reasons:
1. Why limit the default setting to 2 Mb/sec?
2. Why can't the card function at a rate control of 54 Mb/sec?


For others not aware of this, you can check your card statistics with
iwconfig

and change your rate control with

sudo iwconfig <interface> rate xxx (where I am using 11M or 54M)

kevdog
January 6th, 2009, 03:03 PM
Going to try to bump my own thread

Ayuthia
January 6th, 2009, 03:35 PM
As far as I know, I thought that the rate auto-adjusts to the speed it needs. My laptop was sitting idle at 1Mb but as soon as I ran an update, it jumped to 54Mb. This is on my 4311 rev 01 card using 2.6.28 on Gentoo. It also was able to set at 54Mb.

I did also try this on my other laptop and I set it to 54Mb and it had no problems. It is on a 4306 rev 03 also using a nubuntu 8.10 live USB.

Is it possible that the issue is on the current kernel update? I will try to test it out later today if I can get my laptop back from my child...

kevdog
January 6th, 2009, 10:49 PM
Is there a way to test the bit rate -- mine was idling at 2 Mb/sec. I didn't see what it became when downloading a package.

Are you just checking the results of iwconfig?

Ayuthia
January 7th, 2009, 12:22 AM
Is there a way to test the bit rate -- mine was idling at 2 Mb/sec. I didn't see what it became when downloading a package.

Are you just checking the results of iwconfig?

That is all that I am doing. You might try using iperf to test the network speed if you have two computers. Does it look like you are topping out at 2 Mb/sec? I am curious (more hoping than curious) if your chipset is not registering the Mb info correctly.

kevdog
January 7th, 2009, 01:29 AM
You stated your changes -- can you post examples and tell me what you are specifically doing when it changes?

Ayuthia
January 7th, 2009, 02:09 AM
I first started out with the iwconfig command:

sudo iwconfig
Password:
lo no wireless extensions.

eth0 no wireless extensions.

wmaster0 no wireless extensions.

wlan0 IEEE 802.11bg ESSID:"linksys"
Mode:Managed Frequency:2.437 GHz Access Point: 44:55:66:77:88:99
Bit Rate=1 Mb/s Tx-Power=27 dBm
Retry min limit:7 RTS thr:off Fragment thr=2352 B
Encryption key:off
Power Management:off
Link Quality=90/100 Signal level:-40 dBm Noise level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

Then I ran sudo emerge --sync (the package manager update--gentoo's version of sudo aptitude update) and then ran iwconfig while it was updating:

sudo iwconfig
lo no wireless extensions.

eth0 no wireless extensions.

wmaster0 no wireless extensions.

wlan0 IEEE 802.11bg ESSID:"linksys"
Mode:Managed Frequency:2.437 GHz Access Point: 44:55:66:77:88:99
Bit Rate=54 Mb/s Tx-Power=27 dBm
Retry min limit:7 RTS thr:off Fragment thr=2352 B
Encryption key:off
Power Management:off
Link Quality=90/100 Signal level:-40 dBm Noise level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0


I just tested the adjusting of rates again (but when the wireless was idle) and found the following:

sudo iwconfig rate 54M
sudo iwconfig
lo no wireless extensions.

eth0 no wireless extensions.

wmaster0 no wireless extensions.

wlan0 IEEE 802.11bg ESSID:"linksys"
Mode:Managed Frequency:2.437 GHz Access Point: 44:55:66:77:88:99
Bit Rate=1 Mb/s Tx-Power=27 dBm
Retry min limit:7 RTS thr:off Fragment thr=2352 B
Encryption key:off
Power Management:off
Link Quality=90/100 Signal level:-40 dBm Noise level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
Apparently, the system does not seem to care about the rate or else I am not doing it properly. However, as soon as I do anything (even a ping), it just right back to 54 Mb/sec.

kevdog
January 7th, 2009, 04:19 AM
Ok, I guess I was totally wrong on this one. I saw my bit rate jump anywhere from 1 mb/sec to 48 mb/sec. The funny part in addition was that I also saw the link quality go over 100 also (as high as 121).

Interesting to say the least.