Hi Giovanni, great content, thanks! For the beamforming note on the minute 34:00 in the video, you say that beamforming is not permitted, that’s why we’re lowering the Tx power to compansate.. However, what happened to “MIMO Gain” we all calculate with 10 log (#tx chains) ? And the MIMO gain is very easy to observe in the field.. With the same client listening to the air and all variables fixed, you’ll hear 3 dbm stronger signal if you jump to 4x4 AP from 2x2 AP and another 3db stronger signal if you jump to 8x8 from 4x4
Thanks Oguzhan! My understanding is that your spatial degrees of freedom are being used to focus power only when # antennas > # streams, and thus (in theory) you should reduce your power by 10 * log10 (# antennas / # streams). But I am not 100% sure this is what regulations mandate right now. Some relevant info can be found here on slide 113: transition.fcc.gov/oet/ea/presentations/files/oct07/Oct_07-Basics_of_Unlicensed_Trans-JD.pdf
@@giovannigeraci2874 Thanks Giovanni, I'll check that! Just a real world example: Aruba 515 has 2x2 2.4Ghz radio and 4x4 5Ghz radio. So, when it comes to output power, 2.4Ghz radio aggregate conducted power is 21dbm (per chain power is 18dbm) so, 21-18=3dbm is the MIMO gain of this radio, because this is a 2x2:2 radio, that means you have 3db MIMO gain with 2 streams. On the 5Ghz band, MIMO gain is 6dbm because 5Ghz radio is 4x4:4. So, the per-chain power is still 18dbm but total conducted is 24dbm (18+6dbm MIMO gain). Note: These are conducted powers. For the EIRP, we need to add antenna gains. So the power calculation is per chain (stream) output power + MIMO gain + antenna gain = EIRP You can check the details here: www.arubanetworks.com/assets/ds/DS_AP510Series.pdf The MIMO gain is a very generic calculation we all do when we calculate EIRP with MIMO APs. Sometimes we increase AP model to get that MIMO gain (extra 3db or 6db) However, we we hear your comment about MIMO Gain is not permitted so you should lower your Tx power to compansate the gain here, that means our whole calculations are completely incorrect so far :) That's why I wanted to clarify what happened to our beloved MIMO gain :)
@@oguzhaneren thanks for these real-world examples. Two additional things to notice are that (i) if an AP does not normally operate at maximum allowed power, then there might be no need to reduce the power when adding beamforming; and (ii) there should be no limitation in doing uplink beamforming, which could also be helpful in case of limited STA power.
@@giovannigeraci2874 Exactly. That’s what I thought. Probably beamforming is not permitted if you want to go beyond what’s allowed in terms of max RF power (EIRP). If you’re not exceeding that, then it’s allowed. Thanks a lot for the explanation and thanks for the GREAT content you provide in your videos. Keep them coming! :)
Hi Giovanni, great content, thanks! For the beamforming note on the minute 34:00 in the video, you say that beamforming is not permitted, that’s why we’re lowering the Tx power to compansate.. However, what happened to “MIMO Gain” we all calculate with 10 log (#tx chains) ?
And the MIMO gain is very easy to observe in the field.. With the same client listening to the air and all variables fixed, you’ll hear 3 dbm stronger signal if you jump to 4x4 AP from 2x2 AP and another 3db stronger signal if you jump to 8x8 from 4x4
Thanks Oguzhan! My understanding is that your spatial degrees of freedom are being used to focus power only when # antennas > # streams, and thus (in theory) you should reduce your power by 10 * log10 (# antennas / # streams). But I am not 100% sure this is what regulations mandate right now. Some relevant info can be found here on slide 113: transition.fcc.gov/oet/ea/presentations/files/oct07/Oct_07-Basics_of_Unlicensed_Trans-JD.pdf
@@giovannigeraci2874 Thanks Giovanni, I'll check that!
Just a real world example: Aruba 515 has 2x2 2.4Ghz radio and 4x4 5Ghz radio.
So, when it comes to output power, 2.4Ghz radio aggregate conducted power is 21dbm (per chain power is 18dbm) so, 21-18=3dbm is the MIMO gain of this radio, because this is a 2x2:2 radio, that means you have 3db MIMO gain with 2 streams.
On the 5Ghz band, MIMO gain is 6dbm because 5Ghz radio is 4x4:4. So, the per-chain power is still 18dbm but total conducted is 24dbm (18+6dbm MIMO gain).
Note: These are conducted powers. For the EIRP, we need to add antenna gains. So the power calculation is per chain (stream) output power + MIMO gain + antenna gain = EIRP
You can check the details here: www.arubanetworks.com/assets/ds/DS_AP510Series.pdf
The MIMO gain is a very generic calculation we all do when we calculate EIRP with MIMO APs.
Sometimes we increase AP model to get that MIMO gain (extra 3db or 6db)
However, we we hear your comment about MIMO Gain is not permitted so you should lower your Tx power to compansate the gain here, that means our whole calculations are completely incorrect so far :)
That's why I wanted to clarify what happened to our beloved MIMO gain :)
@@oguzhaneren thanks for these real-world examples. Two additional things to notice are that (i) if an AP does not normally operate at maximum allowed power, then there might be no need to reduce the power when adding beamforming; and (ii) there should be no limitation in doing uplink beamforming, which could also be helpful in case of limited STA power.
@@giovannigeraci2874 Exactly. That’s what I thought. Probably beamforming is not permitted if you want to go beyond what’s allowed in terms of max RF power (EIRP). If you’re not exceeding that, then it’s allowed.
Thanks a lot for the explanation and thanks for the GREAT content you provide in your videos. Keep them coming! :)