Hallo
I have an Acer Travelmate 5310 with SuSE11.1 and a broadcom 4311 wireless card. Regularly, the contact between laptop and wireless router breaks down temporarily (for a minute or so) and then it recovers. I don’t think it is a router problem since I have other computers working fine with that router all the time. The things I have sensed are:
a. The noise level given by iwconfig wlan0 is too high. The other computers display noise = -127 dBm, while this one lies around -60 or -70. The signal oscillates between -50 and -90. My hypothesis is that the problems arise when the signal is smaller than noise level.
b. The txpower of this laptop is quite high, 27, while the other computers work fine with 24 and even 15. Reducing txpower with e.g.
iwconfig wlan0 txpower 21 does not change noise level and/or signal level significantly.
c. After an interruption, dmesg|grep b43 gives the following message, repeated a lot of times:
b43-phy0: ERROR: PHY transmission error
I interpret this as the driver sensing the bad signal/noise ratio.
Questions:
Why is my noise level so high?
Can it be modified by software? How?
If not… what should I do to reduce noise level?
Thanks,
MNatiello
On 12/14/2009 03:56 AM, mnatiello wrote:
>
> Questions:
> Why is my noise level so high?
Noise is due to interference on the channel. Those noise value of -127
dBm just means that the driver/device is not reporting a noise value,
or it is returning 0 and the output routine is changing that into the
smallest value that is possible,
> Can it be modified by software? How?
No.
> If not… what should I do to reduce noise level?
You might try changing the channel for your AP. In general, to have
minimal interference from other APs, choose 1, 6, or 11 while avoiding
the strongest APs in your neighborhood. The “out-of-the-box” setting
for most APs is channel 6. If yours is one of them, try 1 or 11 to see
if this helps.
There are many sources of 2.4 GHz radiation in a standard environment,
such as microwave ovens, some compact fluorescent light bulbs, etc.
Try to correlate your periods of signal loss with some electrical
activity in your surroundings.
You might try changing the channel for your AP. In general, to have
minimal interference from other APs, choose 1, 6, or 11 while avoiding
the strongest APs in your neighborhood. The “out-of-the-box” setting
for most APs is channel 6. If yours is one of them, try 1 or 11 to see
if this helps.
There are many sources of 2.4 GHz radiation in a standard environment,
such as microwave ovens, some compact fluorescent light bulbs, etc.
Try to correlate your periods of signal loss with some electrical
activity in your surroundings.
Thanks lwfinger.
I doubt that the problem could be just external. I have changed channels in the past, with no observed differences. Regarding external noise sources… I have two other computers in the same network and they don’t sense any interference. I can move around the house the problem-laptop and the others, but the result is always the same. This laptop has a higher noise level than the other two, anywhere in the house. On the other hand, the signal level is more or less similar in all computers, slightly higher when near the router, of course, so it is not an antenna problem as I first believed.
Why is only this computer sensing high interference?
Regards,
M.Natiello
On 12/14/2009 04:06 PM, mnatiello wrote:
> Why is only this computer sensing high interference?
If you mean the noise level for this one is > -127 dBm, I thought I
discussed that.
Perhaps your motherboard has a part that is breaking down. In any
case, this kind of interference is not found in other BCM4311 parts. I
have one that works for days with no interruption in signal.
Hallo lwfinger again,
There is nothing wrong with the motherboard. The problem was that the noise levels were higher than the signal levels, but apparently the noise is somehow originated by the b43 driver.
I replaced the b43 drivers with the broadcom-wl drivers. The card declares now significantly lower noise levels (-96dBm instead of the previous -60 – -70), the incoming signal is still in the same previous values (around -50 to -60) and is similar to the values from other laptops in the house. The connection problems are now gone, the link is never dropped. Hence there is no hardware problem, since now everything works fine.
The bottom line is: If the b43 drivers give large noise values for your broadcom card, try other drivers. I suppose I should
file a bug report on the b43-list.
I use the b43 driver and have no noise. Noise is not created by software, but by electro-magnetic interference. Things like speakers, power supplies, TV’s. 10 tips for improving your wireless network
Hallo
I use the b43 driver and have no noise. Noise is not created by software, but by electro-magnetic interference. Things like speakers, power supplies, TV’s.
It doesn’t really matter now because my problem is solved, but I will comment in case somebody else has a similar problem. Many (most?) people use the b43 without problems. I would like to do that as well, it was in fact my first choice, but I can’t. And I cannot assign the problem to anything other than the driver.
Under the b43 driver iwconfig reports large noise level: -60dBm Concomitantly, when signal level is below noise, the network link is dropped. Putting another laptop beside this one, I could read in it the same signal level but no noise and -most important- the network link is never dropped by this second computer sharing the same physical conditions than the faulty one. This experiment was repeated all over the house, both near and far from the router, with and without TV or microwave on, etc. Always the same result.
Hence, since the second computer is always working and never reporting noise, there is no external noise of such a level that can compromise communication.
Since iwconfig still reports noise and the link fails, then the source of the problem must be internal to the faulty laptop: Either internal noise due to hardware defect or some software failure that either generates noise or acts “as if”, since the facts are that the network link is lost. Changing the driver from b43 to the broadcom-wl this problem dissappeared completely. Iwconfig now declares noise level to be -96, well below signal level. Link is never dropped again.
It is unlikely that it was hardware-generated noise then, since the hardware is quiet now. The only cause left seems to be that the b43 driver somehow originated the noise and subsequent link drop. I honestly believe this but I don’t have a clue about how it happens.
Yours,