Slow wifi on Airport Extreme Extended Network

Question

My network is Time Warner Cable (NYC) wideband cable modem to first generation Time Capsule 80211.n (Speed of wifi is great)
Then I extend the network on the same floor wirelessly using an 80211.n Airport Extreme access point. (The speed of the wifi is still great)
When I extend the network a second time to downstairs - using an 80211.n Airport Extreme access point the speed slows down.
The wireless network remains fast upstairs at the two access points, but internet access at the downstairs access point is very very slow.
- I have all three boxes updated to the latest firmware 7.6
- I have cycled the power so the cable modem is on first and then the time capsule and then the other two Airport Extreme access points
- I have returned the devices to the factory settings and reconfigured from scratch
- I have set up the Time Capsule to only make an 80211.n network
- I have used the default channel settings and also tried individual channels to avoid any interverence. It seems like it makes no difference
- I'm connecting iPads and Mac laptops to the network
QUESTIONS:
- Why is the internet speed plumeting only on the downstairs aiprort extreme?
- The downstairs access point was configured wirelessly and is seen by the upstairs access point. It puts out a full signal, but might it be too far from the original access point to put out fast internet?
- The airport extremes are first generation. They do have 80211.n but might upgrading them speed up the internet access?

Answer 1

- Why is the internet speed plumeting only on the downstairs aiprort extreme?
Think of the 802.11n extended wireless network as a wheel, with the base station being extended at the hub and each of the extending base stations as spokes on that same wheel.
With the extending AirPort Extreme (downstairs) farther from the hub than the other extending AirPort Extreme, you can expect lower bandwidth to be available as the signal quality of the extended Extreme will be much weaker at the location of the downstairs Extreme.
- The downstairs access point was configured wirelessly and is seen by the upstairs access point. It puts out a full signal, but might it be too far from the original access point to put out fast internet?
Correct. However, you may still find that by just making small adjustments to where this extending base station is located, that you may get better bandwidth performance. You can do this by taking SNR measurements with a Mac laptop if you have one available by using the OS X System Profiler utility.
SNR (in dB) = Signal (in dBm) - Noise (in dBm)
ref: Click on the Apple icon on the menu bar > About This Mac > More Info... > Contents > Network > AirPort > Interfaces > en1 > Current Network Information > Find your wireless network > Signal / Noise
While your still in the System Profiler, note the value for Transmit Rate.
These values should be negative numbers. For example, mine currently read: -67 dBm / -95 dBm, with a transmit rate of 27 (Mbps). Plugging in these numbers yield: SNR = -67 - (-95) = 28. My Mac Mini is about four rooms away from my AEBS with about five walls between them. As you can see, the signal is still quite useable ... but the bandwidth is minimal, especially for streaming.
SNR Guideline
40dB+ SNR = Excellent signal
25dB to 40dB SNR = Very good signal
15dB to 25dB SNR = Low signal
10dB to 15dB SNR = Very low signal
5dB to 10dB SNR = No signal
You will want to place the downstairs extending Extreme at a location where the SNR is 25+dB.
- The airport extremes are first generation. They do have 80211.n but might upgrading them speed up the internet access?
Upgrading to the latest generation of AirPort will not affect the Internet speed provided by your ISP. However, the latest generation models do offer better WAN-to-LAN throughput over the earlier generations so theortically, if you use an Internet speed testing program, you should see better results between the test site and your computers.