BCM4312 & 4322 intermittence description & work-around for Knoppix 7

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After three years of faithful service, the wifi in my Dell 1545 Laptop
began being intermittently troublesome. Left on-line for a few hours
unattended, I would find the wifi not only dead, but whatever it finds
in knoppix-data.img would not allow me to get re-connected. I had to
re-establish persistent store to get on-line again.

I went to Dell's on-line store, gave them my product ID and found there
was a re-furbished wifi for $22 plus tax with free shipping. On this
same site I was able to download an illustrated owner's manual which
spelled-out how I might easily remove and replace the wifi. The $22
replacement arrived in a few days and I was able to do the physical part
of the replacement in mere minutes.

The wifi provided was not an exact replacement, but a slight 'upgrade'
from a/b/g to a/b/g/n. The original and the replacement have different
part numbers, but seem to be operationally interchangeable. The original
was a BCM4312, Dell part nr DW-1397; the replacement a BCM4322, DW-1510.
Both Windows 7 and Knoppix 7 easily found and correctly installed drivers.
The Windows 7 driver installation said, incorrectly, that its install
was 'unsuccessful'.

I was pleased with my diagnosis and my bargain and my successful repair.
For a while, that is. Guess what, the replacement wifi pretty much
matches the original, including my complaint of infrequent intermittence.

So, here's a more complete statement of the intermittence. Very
infrequenly, if I leave my CD-size LiveUSB on-line with no keyboard
activity I may return and find the wifi connection gone, AND the
driver unloaded from the Linux kernel. The connection does not re-
establish itself, even on reboot, without some help.

There are two simple work-arounds that solve my problem for all practical
purposes. First, if I notice a dropped connection, I can get back on-line,
without rebooting, with sudo modprobe b43. Second, I might double-down
by adding, as root, b43 to my /etc/modules file to make sure b43 gets
loaded at boot.

Both the original and the replacement wifis are among those which
the b43/linuxwireless.org folks say work both with b43 and wl drivers.
In Knoppix 6.7.1, with the original wifi I never saw this intermittence
with either driver; however, my experience was mostly with the wl driver,
I only used the b43 driver for a short time before the advent of Knoppix 7.
In Knoppix 7, there is currently only a b43 option. I've seen the
intermittence in both the original and replacement wifis.

In the event of a router failure, things go from bad to worse.
Somehow the default Bit Rate for the 4322 gets set to the default auto
which may in turn deteriorate to 1M instead of 54M in a 'noisy' wifi
neighborhood.

I thought I might simulate conditions that would throw wifi off-line
by interrupting the router, but I find that creates additional problems
not observed earlier. My temporary remedy for this self-imposed problem
is to add 'sudo iwconfig wlan0 rate 54M' to /etc/rc.local. It will
take some detective work to find just where the rate is configured by
Linux and to change the rate definition more directly.

I've not seen the original mode of failure, that is, a failure following
keyboard inactivity, since I added 'b43' to /etc/modules. It may be too
premature to say that's what has been missing in Knoppix 7, but I notice
Ubuntu b43 users add this little wrinkle.

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After two weeks of use, I recommend the following minor adjustments to
Knoppix 7.0.4 to handle infrequent Broadcom BCM-4322 wifi connection
interruptions using a b43 wifi driver.

1. Add 'b43' to /etc/modules; and
2. Add 'sudo iwconfig wlan0 rate 54M' to /etc/rc.local,
assuming wlan0 is the wifi device in question.

These adjustments seem to handle my situation adequately.

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Greetings, Fellow Broadcom b43 wifi users.

I think the new Knoppix 7.0.5 may have a similar problem that 7.0.4 had.

After a period of wifi connection in a crowded internet environment,
and no activity,
I occasionally find my b43 wifi is disconnected, no longer listed on the
wifi icon list and no longer looking to get re-connected. This is always
remedied by a reboot. The problem occurs rarely, and perhaps more
rarely in 7.0.5 than 7.0.4.

Similar complaints exist over may Linux distros with no real solutions
offered that I have found, other than the reboot, that is.

In Knoppix 7.0.4, I thought I might have cured this problem by adding
b43 to /etc/modules. My hope was that this might aid networkmanager to
re-install b43 if ever it is removed from the kernel due to inactivity.

I'd be interested in other b43 users' experiences in 'crowded' internet
environments, and what if any solutions they may have tried if they have
encountered this b43-disconnect phenomenon. Probably any Knoppix 7 b43
has this difficulty to some degree.