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Adjusting Min/Max EIRP

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  • 1.  Adjusting Min/Max EIRP

    Posted Sep 28, 2022 05:54 PM
    Hi All,

    In our ArubaOS 8.7, dual controller, single virtual Mobility master, high-density environment, we use RF Management profiles to keep the power levels from getting too high.  We have profiles for both 2.4 and 5GHz radio and they are located in Configuration -> System -> profiles -> RF management.

    I then assign these RF management profiles to AP groups.  For example in the building the tech office is in, it's two-story with a hallway sandwiched between two rows of classrooms.  there's an AP in each classroom so I keep the power levels pretty low.  The profile EIRP min and Max is set to:

    5GHz = Min 3db, Max 12db
    2.4GHz = Min 3db, Max 6db

    we have four SSID.  Employee and Student are A only, Guest and BYOD are both A and G.

    I wanted to do some testing to see if I could lower 2.4GHz G band even lower.  I created a profile for the 2.4GHz radio and set the Min and Max to 3db.  But then I went to verify I noticed the radios may not be doing this.

    If I do a "sh ap active," it looks like the APs are still at 9db, or 7db, or 5db, even though I assigned this profile to it.  Actually, the AP-325 are 9db, the AP-225 are 7db, and the ap-205 are 5db.

    here's the output for the AP-325 in my office:
    Radio 0 Band Ch/EIRP/MaxEIRP/Clients    Radio 1 Band Ch/EIRP/MaxEIRP/Cli
    AP:5GHz-VHT:48/12.0/27.0/1                     AP:2.4GHz-HT:6/9.0/26.7/0

    Can someone help me understand what I'm seeing?


  • 2.  RE: Adjusting Min/Max EIRP

    Posted Sep 28, 2022 05:59 PM

    OES,

    I believe what you're seeing is EIRP, which includes antenna gain (usu ~5dBi).

    Thanks,

    Brad

     






  • 3.  RE: Adjusting Min/Max EIRP

    EMPLOYEE
    Posted Sep 29, 2022 05:22 AM
    The previous poster is correct.  Due to internal antenna gain, the minimum you can lower some access points is 5 to 7.  In any event, the best link quality matches the transmit power of clients and access points.  Asymetric transmit power between clients and access points can lead to low performance especially with bandwidth and delay sensitive applications.  For good uniform roaming, to start you might want to set the lowest transmit power to 12 or 15 and match the maximum transmit power to that (12, 12 or 15,15 for example).  You can then increase the power and observe the command below.

    For the controller side, you can check to see if the TX and RX are matched by executing:
    show ap debug client-table ap-name <name of ap> and look at the tx_rate and rx_rate of stationary clients.  The TX and RX won't always match exactly, but it should not differ by hundreds.  That will allow you to understand if you are in the ballpark.

    For an individual Windows device, you can execute "netsh wlan show interfaces" on the commandline to observe the transmit/receive rate of clients.  Again, you are not looking for perfect parity between transmit and receive; you are looking to get the highest transmit and receive for what you get with the least administrative overhead.  Things like congestion could decrease your numbers, so there is no perfect number.

    If you have Airwave, you can also look at the goodput numbers over time in your environment after you make a transmit power change to observe if overall things are better or worse.

    Good luck.


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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.

    HPE Design and Deploy Guides: https://community.arubanetworks.com/support/migrated-knowledge-base?attachments=&communitykey=dcc83c62-1a3a-4dd8-94dc-92968ea6fff1&pageindex=0&pagesize=12&search=&sort=most_recent&viewtype=card
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  • 4.  RE: Adjusting Min/Max EIRP

    Posted Sep 29, 2022 12:10 PM
    Thanks cjoseph I appreciate your posts.

    So what I'm taking out of that is, no need to set the minimum transmit power.  Once I find the optimal power value, just set min and max to that amount.

    To find the optimal power value, try EIRP values to get the best relatively equal TX and RX rate.  Then use the lowest of those values.  For example, if the best TX and RX rates I can get for my clients is around TX 216 RX 216, then use the lowest EIRP where I still get those rates.

    Two things:

    1. My Windows client is showing rates of 173.3 and 173.3 with a signal strength of 86% in the same room as the AP.  Does that tell you anything?

    2. What about 2.4GHz?  I can do this for the above 5GHz radio, but I would imagine want to just use the minimum for 2.4GHz.  I'm showing out of 1600 clients connected right now, only 80 of them are 2.4GHz.  would it be in my best interest to try to reduce the amount of 2.4GHz band?


  • 5.  RE: Adjusting Min/Max EIRP

    EMPLOYEE
    Posted Sep 29, 2022 12:50 PM
    @OESTech - This is my opinion:
    1.  You may or may not get better signal strength/performance based on the multipath or other physical structures that you might not be able to control.  173.3/173.3 with 86% is a good number in the same room.  Compare with other clients on that AP in the same room.  It is even better that it is symetric.
    2.  Since the majority of your clients are on 5ghz, I would focus on those.  Since there is less client density on the 2.4ghz band, if you just provide good coverage and the RF Utilization on those bands are not 70% and above, you should be fine.  If desired, you can go back and tune the 2.4ghz, but you shouldn't need to, since there are fewer channels, your coverage should be good and performance should be okay 


    ------------------------------
    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.

    HPE Design and Deploy Guides: https://community.arubanetworks.com/support/migrated-knowledge-base?attachments=&communitykey=dcc83c62-1a3a-4dd8-94dc-92968ea6fff1&pageindex=0&pagesize=12&search=&sort=most_recent&viewtype=card
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