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I just upgraded my broadband connection to 64mbps. When I connect my MacBook Pro laptop directly to the router, reveals my downstream speed to be around 61mbps, which seems reasonable.

But when I try the same thing over my Wi-Fi network, through my AirPort Express 802.11n router, my downstream slows down significantly to 21mbps. Now, this is still quite fast, but its not what I'm paying for.

Note that I also have an Apple Time Capsule on the same network, and it's configured to extend the network. I would hope that this would not result in a 50% reduction in speed.

What could the problem be here? My Wi-Fi connection reports that it is at full strength.

edit: By request, here is the info provided on the wifi connection:

PHY Mode: 802.11n
BSSID: 90:27:e4:5e:32:53
Channel: 2 (2.4 GHz)
Security: WPA2 Personal
RSSI: -64
Transmit Rate: 117
MCS Index: 14
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Press the ⎇-key and click on your airport symbol in the menu bar. What does it say? – trurl Jul 8 '11 at 22:37
Good idea, info added to my question. – sanity Jul 8 '11 at 22:47

You didn't say if you're running in 2.4GHz or 5GHz, and if 5GHz, whether you've wisely left it set to the default of using wide channels.

If you're running your AirPort Express in 2.4GHz, it will only use normal (narrow) 20MHz-wide channels so that it leaves room in the band for Bluetooth and other uses. So your maximum signaling rate is 130 or 144mbps depending on the guard interval in use.

The rule of thumb for overhead inherent in all 802.11 networks is that even in ideal conditions, your TCP throughput will only be about 50-60% of your 802.11 signaling rate. So it's possible under ideal conditions (completely clean channel, nothing else using your network, and your client is within a few meters of the AP) for your wireless link to match your broadband link.

If you have a Time Capsule on the same network, and it's configured to wirelessly extend the network, and your client happens to be joining the Time Capsule rather than the Express, and it's joining in 2.4GHz (because you have one of the old one-band-at-a-time Time Capsules from 2008, or the client happened to select 2.4GHz when it joined your simultaneous dual-band Time Capsule from 2009 or later), then yes, that will cut your bandwidth in half in the best case, and possibly by much more.

If you hold down option when clicking the AirPort menu extra, you'll be able to see the BSSID (the wireless MAC address) of actual AP you're connecting to, so you can determine which device you're really connecting to. You'll also be able to see what signaling rate you're getting, and what channel you're on.

For best results:

  1. Switch your network to 5GHz and use wide (40MHz) channels if you aren't already. Note that iPhones, iPod Touches, and PowerPC Macs can't do 5GHz with their built-in Wi-Fi radios. Even the iPhone 4 which does 802.11n doesn't do 5GHz. iPads (both 1 and 2) can do 802.11n in 5GHz. iPads don't take advantage of the fastest 802.11n modes, but it's better than 802.11a/g.
  2. Run an Ethernet cable between your Express and your Time Capsule. Use wired Ethernet for stationary devices. Save your wireless bandwidth for your mobile/portable devices.
  3. If you don't have a wired Ethernet backhaul between your APs, when you want the best Internet bandwidth, make sure you're associated to the upstream AP.
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Ah, thanks, great answer. However, it sounds like the cure is worse than the disease - unless I run ethernet cables around my house :-/ The other option is to downgrade my cable internet plan. Seems like wifi technology has failed to keep-up with broadband speeds. – sanity Jul 8 '11 at 23:23
@sanity Actually Wi-Fi has kept well ahead of broadband speeds, but you have to make the jump to 5GHz and wide channels. It would also help if you upgraded from 2007-era 2x2 802.11n (the stuff advertised as 300mbps because of its wide channel speed, but only does 144 mbps in narrow channels) to 2010-era 3x3 802.11n (which can do 450 mbps in wide channels, and 216 mbps in narrow channels). The nice thing about upgrading to a current AirPort Extreme (not Express) and Time Capsule is that not only do you get 3x3, but you get simultaneous dual-band so you don't leave your iPhones behind. – Spiff Jul 9 '11 at 1:24

Using a repeater will decrease your data rate by 50%. That and the overall overhead on wlan networks (wpa encryption will cut another 20-30%) results in a real data rate which isn't capable to sustain 64 MBit/s.

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My speed went back up to where it should be when I unplugged my cordless phone base that is on 2.4 .

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