D-Link USB adaptor going too fast for signal strength

[joemck2004]

I have a D-Link AirPlus G DWL-G122 USB WiFi adaptor connecting to a Linksys WRT54G router. The signal strength is almost always low or very low on Windows XP's bar meter (around -80 dB in NetStumbler).

When it first connects, the speed is around 5.5-18 Mbit and everything works fine. Often within minutes, the speed has climbed to 36-54 Mbit, and no packets ever get through. The only way to get it to work again is to disconnect from the network and reconnect. Quite irritating, especially when I'm trying to do large unattended transfers.

I currently have the router's transmit rate set to 11 Mbit, and right now I'm looking at a dead connection sitting at 54 Mbit. It seems that this adaptor won't obey the speeds set by the router.

Is there any way to get this adaptor to behave? I'd like to limit its connection speed or make it connect as an 802.11b, but I can't find options to do this.
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Details: I'm running Windows XP Home. The adaptor is revision B and I'm using the latest driver. I have the Wireless Zero Configuration service off because it kept trying to connect to neighbors' encrypted networks. I'm using the utility program that came with the adaptor to configure it.

 

[G0AOZ]

Address the very low signal strength issue before anything else. Why is it so low? Long distance between PC and router? Lots of walls, floors, buildings in between? Duff aerial on the router?

You should also check out the channel number(s) that your neighbour and any other networks within range are using. Choose a channel to use which is furthest away from them (all) if possible. That will reduce your chances of being affected by adjacent channel interference.

ROGER - G0AOZ.

 

[joemck2004]

Thanks for the reply. The low signal strength is due to distance. By moving the antenna around, I can usually get good to very good signal strength.

I'm using channel 2, and there's another network on channel 1. However, there seems to be some weird interference here. When I use any channel above about 3, my NetStumbler graph looks like a comb:

I don't know what could be causing this, but the signal drops momentarilly every few seconds. When I'm lucky (as in the screenshot), it comes back up very quickly. Other times, it drops out entirely each time, resulting in the utility reporting even 50% or better strength, yet it's unable to connect. Other times, the adaptor remains connected to the signal, but it stays at the low level and never comes back up again, and no traffic can get through.

The signal strength is usually better on channels around 8, but the intermittent inteference makes it perform worse than on 2.

Also, even when the signal strength is better, the speed still sometimes climbs too high and it stops working. It only seems to work at all reliably when the signal strength is high enough to actually transfer data at 54 Mbit.

Why is it that the connection still flies up to 54, even when I've set the router's network-wide rate to 11?

 

[G0AOZ]

I don't have Netstumbler setup here at the moment, but I'd have expected those very small gaps between the bars as it regularly samples the revelant wanted signal. The variations are a different matter. There's no calibration scale shown on the vertical of your graph, so difficult to determine by how much the signal is varying. You did initially mention -80dB, which is extremely low indeed, and if you're still anywhere near this figure, then I'd say signal strength is the main issue.

You said "The low signal strength is due to distance.". Tell us what distance you're talking about here, and how many walls, floors, objects etc., the signal is having to go through. If there are people moving about, even to the side of the signal, this can cause it to vary.

The signal strength indicators are usually merely just indicators - they're not generally very accurate. However, for a half decent solid connection, one often needs to see 55 to 60% or better, and it needs to remain at that level, not wander up and down very much.

Interference can come from many sources. You have indicated a neighbour uses Ch.1. Look specifically to see if there are any others in use. Some cordless phones can generate interference for WiFi networks, as they often use 2.4GHz band as well. Baby alarms/monitors, microwave ovens, airport radar(!), etc, etc. Keep mains power cords and other cabling away from the router and the antenna.

Is your PC a laptop? Can you temporarily move it to within a couple of feet of the router? Signal strength should now zoom up and data transfers should run smoothly and continuously.

I have no idea why setting the router to run at 11Mbps still results in an occasional transfer rate of 54. I assume you've saved and rebooted the router after making such changes...

ROGER - G0AOZ.