Slow WiFi

March 7, 2006 7:42 AM

Slow WiFi: I have a Linksys WRTP54G Wireless Router plugged into a cable modem. When I connect my laptop to it via an ethernet cable I get downloads of 6mbps, but when I flip to the WiFi connection that drops to ~4mbps. Laptop shows an Excellent Signal Strength and a connection speed of 54Mbps. What gives? Laptop is an IBM T42 running XPSP2.
posted by zeoslap to computers & internet (11 comments total)

Have you tried disabling the encryption/security and seeing if it improves at all? I had a similar issue which seemed to sort itself out after a while, and I have the same network setup that you do.
posted by TeamBilly at 7:44 AM on March 7, 2006

I think one of the steps I tried was disabling security but I'll give it another whirl. I also flipped the preamble to short that improved throughput a little bit but that could have just been a blip.
posted by zeoslap at 8:28 AM on March 7, 2006

I thought it was a given that a wired connection was faster than a wireless connection?
posted by A189Nut at 9:42 AM on March 7, 2006

It is, generally, but 4mbps is pretty low for that router.
posted by Bezbozhnik at 9:59 AM on March 7, 2006

That is pretty weird... encryption would be a good thing to check on. Perhaps you have packet loss/interference... you may be connecting at 54mb (strong signal) but there's some kind of intermittent interference? Do you have 2.4Ghz cordless phones? Try unplugging those, your microwave, and anything else you have in that frequency range.

You might also check that you're in 'pure G' mode, and not mixed-mode. If there's another B-type device in the area, I think it can slow you down. And you might try other channels. Remember that channels 1,6, and 11 are the only ones you should use... they're the only channels that don't interfere with one another. (There's quite a bit of crosstalk/interference between lower channel separations.)

A189Nut: Not in this case. The downstream bandwidth is only 6Mbps, where his 11g connection is 'rated' for 54. (In reality, you can get about 20-25 megabits through 11g.) So the 6 megabit download should be the same speed, whichever way it's being delivered.
posted by Malor at 10:00 AM on March 7, 2006

I'd download one of those wireless network stumblers, and look for other 11g networks in your area -- if there is one with a very strong signal, or a several week ones, you may be getting interference from those stomping your signal. (Seeing if there was a spare channel would be an attempt at fixing it). I forget the name of the program for Windows, but there is an excellent one that is free.

I'd also unplug any cordless phones you have to eliminate them as a culprit, watching for a speed increase when you do (although it's possible that a next-door neighbor's phone could be doing it, too, but that seems a bit unlikely). I doubt it's a microwave -- my microwave immediately makes my wireless bridge essentially unusable (0- 500 bs).

But presumably, both of these would give you less than excellent signal strength. Encryption does seem like a possible culprit, too (I think the manual for my router even states that you won't be getting full bandwidth with encryption on -- it's extra number crunching, and these things don't have powerhouse processors, but 6Mbs is low enough that you'd think it wouldn't really hurt).

If you have eliminated those three, it would seem you're in the realm of odd and esoteric networking issues. That, or the signal strength meter on your card lies.
posted by teece at 10:43 AM on March 7, 2006

Hmm, well it is in G only mode, the phone is a 5GHz one so that shouldn't matter. I'll check the channel I'm using when I get home. I only see one other wireless network, which is the neighbors but that is definitely on a different channel. I will check I'm using 1,6 or 11 though.
posted by zeoslap at 10:49 AM on March 7, 2006

Wired is duplex (Data goes in both directions at the same time) and wifi is simplex (Data only goes in one directions, e.g transmit, stop, receive) so that could explain the difference.
posted by Ferrari328 at 12:24 PM on March 7, 2006

Wired is not necessarily full duplex, it has to be configured that way. Most gear defaults to half-duplex.

Check to see if you have the XP firewall turned on on your wireless adapter?
posted by banshee at 1:59 PM on March 7, 2006

Naw, there's enough overhead to handle both at once on the wireless, Ferrari. 54 megabit half-duplex is way more than fast enough to support a 6 megabit stream, including the return acks. I get 20 megabits or more doing file transfers over my 11g network. (I haven't measured it precisely, but it's pretty fast.)

If his wireless link is working properly (not yet determined), it shouldn't be the bottleneck.

zeo, if none of the above has helped, the next step would be to try a comptuer-to-computer copy... do you have a machine you can run FTP or HTTP on, so you can see how fast you can download locally, running over the wireless?

And what protocol are you currently using for downloads... ie, how can you tell it's slow?

On preview: banshee, on modern stuff, everything defaults to full duplex. That's the difference between switches and hubs. If you're using a hub, it's half-duplex. But hardly anyone uses those anymore... 100mb switches are under fifty bucks. Hell, you can get 16-port GIGABIT switches for under 200 bucks now.

Any recent network card should autodetect link duplex and speed correctly, and probably 95% of the time, it'll end up 100mb, full duplex. The one exception I know is Linux talking to some Cisco network gear, where the autodetect is flaky, and you often have to force the settings manually.
posted by Malor at 2:08 PM on March 7, 2006

Did you get it fixed?
posted by Malor at 12:42 PM on March 8, 2006