My Setup is a Powerbook g4 Titanium with an Airportcard 811b, an AirportExpress 811g and an ethernet cablemodem. No WEP or such.
My internet access account is broadband cable 6000 Kb/sec up and 600 Kbit/sec down.
I made testseries @ http://perftest.green.ch/. When I access the internet wireless I have an average of about 3700 Kbit/sec down (up 595).
When I wire directly to the modem I have an average of around 5500 Kbit/sec (up 614).
I found this thread here:
Submitted by Macinjosh on May 16, 2008 - 3:04am.
"At a guess, your internet connection is 512Kb/sec (512 Kilobits per second.) However an 802.11 card, even in B mode, is capable of 11Mb/sec (11 Megabits per second.)
Put these two in the same terms:
Internet Connection, Max: 512Kb/sec
802.11b Connection, Max: 11,264Kb/sec
- or -
Internet Connection, Max: .512Mb/sec
802.11b Connection, Max: 11Mb/sec
-- Still with me? All of that to say, a b-capable AirPort card is 22 times faster than your Internet connection is, using the theoretical maximums of both (and yes, I know that's not happening.) If you have a g-capable card, theres even more of a speed difference.
So THAT means, yeah, your AirPort card can pull down the same speed as being wired directly in, _from the Internet."
In my case:
Internet Connection, Max: 6000 Kb/sec
802.11b Connection, Max: 11,264 Kb/sec
- or -
Internet Connection, Max: 5.86 Mb/sec
802.11b Connection, Max: 11 Mb/sec
-- So even when the real life performance of the Airport card is only 50 % of theory, it should be as good as wired access. --
The signalstrength should not be a problem, I tested also directly besides the basestation and it doesn't make a big difference for the download performance. Measured with iStumbler: Signal is between 50 % and 95% depending on the distance to the basestation in my appartment, noise 50 %.
There are no other wireless devices in the appartement. There is only one other network nearby, its closed though it does not give informations except vendor, its Xeros, might be a Xerox wireless network adapter for a printer.
I played with the settings of the AirportExpress. The only thing which helped was changing from 811b/g compability to 811b only, this gave an increase to an average around 4000 Kbit/sec (max is about 4800).
I also tryed with a Lucent silver PC card (out of my PB 5300ce) - didn't make a difference.
The graph shows with the results 1 to 30 and 51 to 60 wireless and in between 31 to 50 wired access. The results are better than I first wrote above (this serie was done in the later evening and around midnight when the connection is generaly better and perhaps my tweaking has hit something).
--But clearly the difference in performance rests unexplained--