Wireless Access

Occasional Contributor II

SISO, MIMO and EIRP on ArubaOS 6.5.X.X



I'm looking for answers about a particolar solution.

We upgraded our platform system from ArubaOS to and we are using Aruba AP204 (external antennas where ant0 is not a stick omni but a different type of antenna).

We find a riduction of received power. Is it possible that the new firmware considered both antennas as co-polarized instead and cross-polarized.Is there a document? If it's the case is it possible that we have lost 3db? Or it is true only for IAP?

After I would ask, we are working on 802.11g too. Is it possible a difference of power between Ant0 and Ant1?

Last question: are there documents by Aruba where it explains how an AP 2x2, 3x3 works in SISO, SU-MIMO, MU-MIMO modes?

I hope of having explain very clariful

Regards for your helpful


Re: SISO, MIMO and EIRP on ArubaOS 6.5.X.X

In between the versions you mention, some changes were implemented, fixing the way our software calculates EIRP levels and applies regulatory limits. In some cases that has indeed resulted in up to a couple of dB reduction in the transmitted EIRP. In many cases that can be resolved by simply increasing the configured power levels (APs rarely operate at max power), but if the AP is already configured for max regulatory power, you may notice a small reduction.

This applies to both AOS and Instant code.

When provisioning the APs with antenna details you should now have the ability to specify co or cross polarization. That may actually allow you to gain 3dB back (all antennas used to be assumed as co-pol).

The transmit power levels for ant0 and ant1 cannot be controlled independently, and they're identical (within calibration accuracy).

Note that regardless of 11a/b/g/n/ac, all chains and antennas are used.

Your last question is very generic, and it may be better to look for some generic articles or books on Wi-Fi radio techniques.

Occasional Contributor II

Re: SISO, MIMO and EIRP on ArubaOS 6.5.X.X

Firstly, thank you for your answer Onno.


About power and polarization subjects you have deleted my doubts.


I have some difficult to understand how radio chains work with antenna on the different mode as 802.11g, 802.11n and 802.11ac.

You mean every protocols, all radio chain and antenna are used. Don't you?

I try to explain my situation in order to give a full view

Inside my suite we have some APs with an extenal antenna that is not the default omni stick. For simplicity I call it "plus antenna".

It's been running a SSID on 802.11g and no high throughput enabled, where the plus antenna is connected to Ant0 of the APs as best internal pratice.


So I suppose the Aruba AP model 204 is working on SISO mode. Is it correct? Does Radio 1 (2.4) work with only Ant0? Or both antennas? If both antennas are used how AP works in this situation? Can I manage it?


If it is an Aruba 304 with 3 antenna, do you know how it behaves?


Thank you for your availability




Search Airheads
Showing results for 
Search instead for 
Did you mean: