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Contributor

adjacent channel interference--ACI happening

Hi In one environment where many APs join to one WLC, adjacent channel interference--ACI happening is due to very closeness of two AP in RF or physical distance or both? Thank you

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Rising star

Re: adjacent channel interference--ACI happening

Couple of things

In 5GHz ACI is normally avoided by physical separation of APs of atleast 1-2m due to free space path loss.

In 2.4GHz as there are only 3 non overlapping channels if you have AP on channel 1 and another on channel 2 you will have ACI if either can be heard below -85dBM

 

Nice post about ACI here: http://www.revolutionwifi.net/revolutionwifi/2014/08/80211ac-adjacent-channel-interference.html

and here: https://www.metageek.com/training/resources/adjacent-channel-congestion.html

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Contributor

Re: adjacent channel interference--ACI happening

Thank you for your reply. I think there is a best distance between any two AP in each model. If the AP is 3502, what is best distance? 

omz Rising star
Rising star

Re: adjacent channel interference--ACI happening

Hi

I think .. distance between APs would be proportional to power i.e high power more distance.. low power less distance. 

It would depend on cell size.

 

To determine the cell radius given that the inter-access point separation and the percentage of overlap are known, we proceed as follows:

where:O = the desired overlap percentage divided by 100 is expressed in radians d = the inter-access point distance in feet

R = the cell radius in feet

We substitute either 15 (for 802.11a) or 10 (for 802.11bg) as the percentage of overlap O, and 45.9 feet for the inter-access point distance d. Solving for R as an approximate root of the function shown above, we determine that the cell radii should be equal to 30.88 feet for a 15% cell-to-cell overlap using 802.11a and 33.4 feet for a 20% cell-to-cell overlap using 802.11bg3.

https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Mobility/WiFiLBS-DG/wifich5.html#wp1051949

Contributor

Re: adjacent channel interference--ACI happening

Do we have a general idea how far the two AP 3602 should be? Maybe i should start another topic. Thank you

VIP Advocate

Re: adjacent channel interference--ACI happening

Open space, walls between? How many clients? Voice enabled Wi-Fi?
Those are just a few questions that have an influence on how close/far the APs should be placed.
Also a 2802 AP is generally way faster, thanks to 802.11ac and the brand new 911x will be even faster (once the clients are 802.11ax capable). In my case I have replaced two 3502 with a single 2802 in certain fairly high density locations (class rooms) without any user complaints.
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Contributor

Re: adjacent channel interference--ACI happening

Thanks for your reply. I think the simpler way to do that is to measure the signal strength and let overlap 20%, and then decide the distance of two APs. please see the attached picture. 

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