Sunday, October 03, 2010

Real world numbers: 802.11n 2.4GHz MUCH better than 5GHz

We've been all wireless at home for a while. It's worked better than I'd expected, but I think we have a particularly noisy microwave (too bad ConsumerReports doesn't rate microwave emissions). We also have 5.8GHz phones, though from what I read that's plenty of separation from 5GHz 801.11n.

I've been tweaking our AirPort Extreme location within the usual constraints of phone jack and outlet. The latest location seems pretty decent (corner of our bedroom closet), but I wanted to see how signal/noise "ratio" varied between 802.11n 5GHz, 802.11n 2.4GHz (Apple default) and 802.11n 2.4GHz plus microwave (5GHz is supposed to be out of microwave range).

The result surprised me. First, this discussion thread has some useful references ...
SNR is the signal level (in dBm) minus the noise level (in dBm). For example, a signal level of -53dBm measured near an access point and typical noise level of -90dBm yields a SNR of 37dB, a healthy value for wireless LANs...

SNR Guideline
o 40dB+ SNR = Excellent signal
o 25dB to 40dB SNR = Very good signal
o 15dB to 25dB SNR = Low signal
o 10dB to 15dB SNR = Very low signal
o 5dB to 10dB SNR = No signal...
My inital SNR results across the clients were
  • iMac 5i 802.11n 5GHz: 26
  • iMac G5 802.11g: 30
  • Macbook 802.11n 2.4GHz: 41
  • AirportExpress 802.11n 5GHz: 7
  • Nintendo Wii 802.11g: 40
Not bad, though it's surprising who good the Wii results are. It's in the basement. Oh, right -  the Airport Express results sucked. Even the 5i results weren't great.

So I switched the iMac 5i and the AirportExpress to 801.11n 2.4 GHz. The results were much better: 
  • iMac 5i 802.11n 5GHz: 36
  • iMac G5 802.11g: 30
  • Macbook 802.11n 2.4GHz: 41
  • AirportExpress 802.11n 2.4GHz: 40 (later tests weren't this good however, transcription error?)
  • Nintendo Wii 802.11g: 40
I turned on the microwave and the Airport Express dropped to 20, the iMac to 32 -- but even with the microwave on the 2.4GHz SNR was much, much better than the 5GHz SNR.

With the microwave off it's truly no contest. The 2.4 GHz frequency gives vastly better results in our home than the 5GHz frequency.

Obviously, your results will vary. I think I can see, however, why Apple makes 5GHz a non-obvious option on the Airport Extreme.

[1] AirPort Utility - Advanced:Wireless clients to get S/N by Mac address, DHCP clients to get machine name.
[2] Didn't used to work, but does with my latest base station location.

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