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40MHz Channels?

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  • 1.  40MHz Channels?

    Posted Dec 30, 2020 03:30 PM
    Is there an updated VRD coming for High-Density deployments in classrooms and auditoriums using 802.11ax? There is one dated for 2019 for 802.11ac. Is there a new one coming soon?

    The current VRD recommends staying with 20MHz channels. However, A colleague is suggesting that we consider moving to 40Mhz channels, rely on MU-MIMO and the higher client count support of the new 535s, and therefore reduce our AP footprint in auditoriums, potentially by half. Also, if we stick with 20MHz channels, there is no reason for us to deploy mGig/SmartRate ports as it is unlikely we will push > 1Gb/s through an AP.

    However, I'm inclined to stick with the current VRD's 20MHz channel recommendation, especially since there is no way currently to test the idea at scale, given the pandemic. I'm just not comfortable taking the risk of having our service suffer and having to go back and retrofit our auditoriums.

    Any thoughts along these lines would be appreciated.


    Neil Johnson

  • 2.  RE: 40MHz Channels?

    Posted Dec 31, 2020 06:47 AM
    Hi Neil,

    No idea when an ax VRD is coming. But the benefits from AX are only reached if all clients do AX. As long  many client have an AC chipset and can't do OFDMA therefore i would stick to 20MHz channels for VHD. Also note that many AC/AX chipset drivers still have issues with AX those days. Because in a classroom environment a lot of different devices (possible even BYOD devices) have to be supported i prefer to turn off the HE SSID until clients have better and widely support for ax.

    Also note that the IEEE 802.11ax ratification is planned for februari 2021 at the moment, link.

    Marcel Koedijk | MVP Expert 2020 | ACMP | ACCP | Ekahau ECSE

  • 3.  RE: 40MHz Channels?

    Posted Jan 04, 2021 04:57 AM
    It's not as simple as "let's double the channel width then reduce the number of APs". There is a balance in how many APs you can have in one area, the AP power, used channels, number of clients, type of clients. If you are at the point where you need to go to the AP535 in order to go over 256 associations per radio, you are likely to have an RF design issue anyway.

    Without understanding your environment, it is nearly impossible to get to a proper design. Classrooms for 30 students are not so much a challenge as a lecture hall with 5000 seats all occupied with students using a laptop and mobile device or stadium deployments.

    What is in that VRD still most of it is valid with 802.11ax unless you control all clients and are sure they are 11ax compliant and can benefit from the 11ax features (unfortunately that are two different things). It may make sense to reach out to your local Aruba team or Aruba partner if you work through them.

    Herman Robers
    If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.