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Channel Utilization

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  • 1.  Channel Utilization

    Posted Nov 04, 2020 06:37 PM
      |   view attached
    I wanted to reach out to others in the community to see if they were experiencing similar issues in a high-density dorm area.  When looking at the controller > dashboard > access points we can see poor quality with the channel utilization above 90% on the 2.4 band. 

    We have some students using only 2.4ghz old laptops/devices that do seem to get a poor experience. Students using 5ghz are ok no complaints. 

    We have lower the tx power (max 9 and min 3) for 2.4 and enable mode aware arm on the g profile only. However, we still see the channel utilization high even with 0 clients. We did a survey with Ekahau and did notice some HP wireless printers that operate in channels 1, 6, or 11. However, we cannot tell the students to just buy printers that support dual bands lol anyways the dorm is a 7 story building with 455 access points. I understand there will be interference in the 2.4 because we only have 3 channels available to play with and spread them around. 

    Anyone experiencing high channel utilization with zero clients connected to an AP?

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    Nils Lau
    Nova Southeastern University
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  • 2.  RE: Channel Utilization

    MVP EXPERT
    Posted Nov 05, 2020 05:58 AM
    Hi Nils,

    The first thing a see in you image is that you only use channel 1 and 11, with a two channel plan you will have a lot of co-channel interference. The 2.4GHz radio you will also have very less options to create a channel plan without co-channel interference. For a very high density environment  you have to create very small cellsizes, with minumum power settings and the use of directional antenne's. (max. 9dBm could be quite high).

    The high channel utilization is properly happen because 802.11 management and control frames eats all of your available airtime. The 2.4Ghz available spectrum is really small and most of the times totally occupied. Without the use of very low tx-power, very small cellsizes and directional antennas (and high costs) it will not solve the bad experience in an high density environment. The best solutions is that the clients are 5GHz capable, because the 5GHz band have lots more spectrum, channels and less non-wifi interference sources.

    I don't known your environment so a lot will "it depends". But hopefully your Ekahau Site Survey Engineer is Certified by Ekahau or CWNP and knowns wat the best works in your environment.



  • 3.  RE: Channel Utilization

    Posted Nov 05, 2020 09:40 AM
    Yes, I understand. We do have a 3 channel plan but still is a crowded space. I will try to disable basic rates in a test lab to see I can lower the coverage cell in addition to lowering the power levels. At this time is set up max 6 for the 2.4. 

    We are not Ekahau certified yet we are learning as we go. 

    Thank you
    Nils.

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    Nils Lau
    Nova Southeastern University
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  • 4.  RE: Channel Utilization

    MVP EXPERT
    Posted Nov 05, 2020 01:55 PM
    Hi Nils,

    No problem, we are all here to help you. For urgent matters please open an Aruba TAC case or contact your local Aruba partner, you have an high density environment that needs the right knowledge of RF. I could recommend the 4-days Ekahau Design course, i did,  its around 3000 dollar but give you knowledge about how RF works and how to use Ekahau and read it properly. It could be difficult to get rid of RF issues through the community as there can be many dependencies in your environment, but give it a try.

    Could you show use a picture of your ekahau measurement?
    • Go to "project" > Coverage requirement > set it at Aruba VHD design and make it default.
    • Go to the right up corner and click on the "signal strength quickbar" set your SSID and set it to 2.4Gghz only.
    • Set the spectrum monitor to 2,4Ghz only and show any SSID.
    • Share a screenshot from the "radios" as well the "channels" tap.
    • Look if the high channel utilization is visible in Ekahau (sidekick must be connected)
    • Look if how many channel overlap is find in the on tap "quickbar".


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    marcel koedijk
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  • 5.  RE: Channel Utilization

    MVP EXPERT
    Posted Nov 05, 2020 02:10 PM
    See also this (older) document, but give you a good idea.
    https://community.arubanetworks.com/browse/articles/blogviewer?BlogKey=91531e76-b857-4664-985a-3de7adf19b73

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    marcel koedijk
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