Dual 5 GHz, interference, and guidelines to consider

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I came across this blog post where the author argues that the retry percentage is "so dramatic [...] that in the vast majority of enterprise wireless network scenarios (again, the stuff that I care about) the WiFi will be better if the second AP radio is DISABLED than if the second AP radio is set to the same 5 GHz band as the first AP radio".

http://www.sniffwifi.com/2015/03/two-radios-are-better-than-one-unless.html?m=1

The access point in question was a Xirrus 620 and not an AP250, but I'm still curious what your thoughts are on his findings. Also: How would one configure the second 5 GHz radio? Are there any guidelines to consider? Best practices, etc.
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oc

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Posted 2 years ago

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Roberto Minotti, Employee

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Jan Boje

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after reading both, the big quistion is who shoud I belive in.

I would really like to belive in Keith Mcintyre. But It would be nice if someone have some experience with AP250 with bort radio set to 5 GHZ

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Roberto Minotti, Employee

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Hi Jan,

I have several installation with dual 5Ghz. One of my recent is performing quite good. Please, speak with your local SE in order to be more confident with AP250 and dual radio.

Ciao
Roberto
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Ho Ka Lok

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We used AP230 for a few years with Dual Band 2.4G+5G. Our new office deployed AP250 and enabled Dual Band 5G+5G. We found that 5G retry percentage drop from 4-5% max to 2-3% max. However, under our 12x AP250 deployment, in order to support legacy laptop and smartphone, we deploy 2.4G+5G on 3 of 12 AP250.
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Carsten Buchenau, Champ

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Out of interest:
  • Did you fix the 5GHz channels or kept them on auto?
  • If fixed manually, did you take care to not have neighbouring channels on one AP, or you didn't bother?
  • Did you fix the power output or kept it on auto?
  • If auto, did you limit the max power output inside the radio profile?
  • Which channel width did you enable?
  • And did you enable DFS, or are you working with legacy, non-DFS channels only?
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Ho Ka Lok

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- We use Auto for Power and Channel, but we'll have Channel Auto Selection every morning before working hour, say 30mins earlier. Channel Width is 40MHz, no DFS
- We set the Max Transmit Power to 20 dBm, Radio Range 300M

Originally all 12x AP250 are Dual-5G Channel, but seems user still have legacy smartphone(new LG phone bought in 2016! ) and laptop, so I choose some APs that have the lowest Auto Power Transmit, i.e. 3 out of 12 APs spread evenly to the area, changed to 2.4G+5G and covered most of the office area by 2.4G. Coverage mainly checked by Maps->RSSI and user experience on corner area

However, as it's a new office, the interference condition maybe different. Only user practice 
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Carsten Buchenau, Champ

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Thanks a lot for the details!

I am surprised you get away with 40MHz wide channels and no DFS... unless the legislation in your area is different then here (only 36, 40, 44 and 48 are no-DFS).

Would be interesting to see how often your radios are really transmitting with the full 40MHz width, or if they almost only fall back to their base channel, 20MHz...

Anyway, good to see your feedback from the field!
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Ho Ka Lok

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You're welcome! I got much help here when I first touch AeroHive 2 years ago.

No DFS mainly for compatibility problem as even some mid-range android smartphone, old iOS device, old laptop and some projector devices not working very well on DFS, and most likely very slow on detecting wifi network. This is the setting we choose 2 years ago when working with AP230. For AP250 on new office, we're still fine tuning and gathering feedback from users too.
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Metka Dragos

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Just to add to what Roberto was saying.
The blog that you read was written some time ago and it references OLDER Xirrus gear. It is true that it was not performing that well at the time. Since that time, other vendors, not  only Aerohive, have developed much better multi-5 GHz solutions. Aerohive ha developed a special antenna array with the polarization diversity to deal with the interference problem. We have an additional set of antennas that change the polarization based on the frequency that is selected and based on the client response. Please reach out to your sales rep to possibly get an unit to evaluate.