help debugging 'dropouts'

[gizmomelb]

Hi,

I'm trying to debug some wireless issues we're having - random users report dropping off the network, however when we monitor them we are unable to record any instances of service interruption.

I've been running Wirelessmon v4.0 for the past day on a test machine and whereas the signal strength is low (-65bDm), there has been no occurences of Windows (7) thinking it has been disconnected. However looking in Wirelessmon there have been 18,000+ dropouts (1 dropout occuring every second or so).

looking in the Statistics frame reveals the following:

Transmitted Frame Count: 1410722
multicast frame count: 869930
failed count: 977
retry count: 9708
multiple retry count: 2284
RTS success count: 0
RTS failure count: 0
frame duplicate count: 78
received fragment count: 619517
ACK failure count: 126468719
multicast rec frame count: 593345
FCS error count: 24187229

the wifi adapater is a built in Atheros AR9285 802.11b/g/n
the wifi router is a Linksys WAP54G running stock firmware (and no, we're not going to install any third party firmware on it).

I'm at a loss how to interpret the information given to me re: dropouts, can anyone please help or point me in the direction to do some ready on how to decipher this into useful info please?

thank you.

[David (PassMark)]

What sample rate are you using in WirelessMon?

Some cards don't like a very high sample rate. For what you are doing a 5sec sample should be OK.

A drop out means that the wireless card can no longer detect an access point which was previous detected. So you can never have more drop outs than samples.

If for example you did 1000 samples at 5 sec and had 100 drop outs. Then it would be fair to assume the AP was not available 10% of the time.

Wireless is notoriously unreliable & slow. I would never use it in an office environment. Can be very prone to interference if you are in a built up area as well.

[gizmomelb]

What sample rate are you using in WirelessMon?

the default 3.0 second sample, I'll run it again with a 5.0 second sample.

A drop out means that the wireless card can no longer detect an access point which was previous detected. So you can never have more drop outs than samples.

If for example you did 1000 samples at 5 sec and had 100 drop outs. Then it would be fair to assume the AP was not available 10% of the time.

Thanks for the explanation - it might be advantageous to include that in the HELP section with Wirelessmon

I'm curious though why Wirelessmon is reporting so many dropouts, when the OS doesn't report any disconnection at all - the only reason I was investigating was because of one user who has 2-3 disconnections to the Sales software in the course of a week.

So are there any suggested wireless settings I can look at tweaking on the router etc. please?

Wireless is notoriously unreliable & slow. I would never use it in an office environment. Can be very prone to interference if you are in a built up area as well.

Unfortunately the Sales Team were all upgraded to laptops many months ago, to be more mobile and thus responsive to customers. I've only had the one user 'complain' about dropouts in that time and was digging a little deeper.

[David (PassMark)]

Not sure what the O/S behavior is. Could well be the case the it doesn't report a network disconnect until either the AP wasn't available for a full long period, e.g 30sec, or maybe if the AP has disappeared AND there is some network activity going on. That is to say it might not record a disconnect if the machine is idle. But this is just speculation. I haven't studied the behavior, so don't really know.

Check the interference levels on the channel you are using. Maybe you can move to a less used channel. If you have the option to use 5Ghz instead of 2.4Ghz, have a look at that. 5Ghz tends to have less people on it for the moment.

Maybe you can stick a directional antenna on the router, or move the router to a more central location to shorten the average distance to the laptops or put in a 2nd router on a different channel, or install a repeater.

[gizmomelb]

Thanks, yeah was just discussing it with another IT body here at work and we were discussing replacing all the G wifi routers with N, going to 5GHz might also be a good idea. Thank you your help.