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Occasional Contributor II

EIRP anomaly?

I am trying to manually set the power on the ap-135 to go over 15dBm.  First command shows eirp manually setup to 15dBm, the second shows when I changed it to 18dBm. How is it possible that AP Max, and Reg Max changed on the same hardware in the same reg domain (UK)?

I see that the controller gave me wifi0 and wifi1 but now it shows me just wifi1 value every time I execute the command.

Thanks a lot.

Martin

 

 #show ap debug driver-log ap-name lsmaap11 | include EIRP
169714.134476 wifi0: EIRP (Config: 15.0dBm, Set: 15.0dBm, AP Max: 20.5dBm, Reg Max: 30dBm), Conducted Power Set: 10.5dBm, Gain: 4.5dBm

 

#show ap debug driver-log ap-name lsmaap11 | include EIRP
Mon Feb 11 09:11:50 2013:310    408032.456042 wifi1: EIRP (Config: 18.0dBm, Set: 15.5dBm, AP Max: 15.5dBm, Reg Max: 20dBm), Conducted Power Set: 12.0dBm, Gain: 3.5dBm

Guru Elite

Re: EIRP anomaly?

I would try to do it through the controller, first.

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Occasional Contributor II

Re: EIRP anomaly?

I have set it up on controller and then check the results via cli and that was the output you have seen.

The values on the controller/monitoring  are the same as the output from cli.

I don't understant why it appears to have some sort of cap on 15dBm as the ap135 should do "2.4 GHz: 23 dBm" and reg domain is at least 20 dBm according to the cli output so 20dBm should be doable.

When I try to set less dBm lets say 10dBm, it works so I don't think there is something wrong with my 802.11g RF profile.

 

Thanks

Guru Elite

Re: EIRP anomaly?

The EIRP is also dependent on the channel...


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Occasional Contributor II

Re: EIRP anomaly?

For 802.11a yes, but for 802.11g?

Re: EIRP anomaly?

Remember too that with 11n, it is set by maximum power *per transmit chain* (depending on the MCS rates). I am trying to see if we have a good write up somewhere. In short, the total of the transmit chains cannot exceed the regulatory max. 

I am assuming if you are looking at this for the g-only radio, it might be interesting if you disable HT and any MCS at 8 and over and see if those change. But I know from past experience, in the debug logs you are looking at, they only show *per chain* power levels, and do not include the antenna gain.  If you add in a second chain, it would be adding another ~3dB in the 2.4Ghz, without actually reporting that. 

This is one of those cases where the debug log data expects you to know the subtle nuances of logrithmic power calcuations in a multi-chain MIMO AP heh.

 

EDIT - digging in some old emails, it;'s noted that for a 2x2 AP (105) you should add 3dB to get the EIRP, and for a 3x3 AP (135) you should add 4.8dB. The rudimentary foruma for MIMO power combining is: 

10*log(num of active branches)

 

So you have the max EIRP set to 18dB, the controller puts the radio power at 12dB, you get the secret 10*log(2) @ 3dB MIMO power combining @ 2.4, and then the 3.5dBi antenna gain

 

I'm sure there is some fuzzy math somewhere in that the power combinging gain is variable depending on the radio power, but it's gets you in the ballpark and explains the missing ~3dB from the equation.

Hope that helps. 

 

 

Jerrod Howard
Sr. Techical Marketing Engineer
Guru Elite

Re: EIRP anomaly?

What he said...


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Occasional Contributor II

Re: EIRP anomaly?

Great stuff Jerrod!

I really like the forum:smileyvery-happy:

 

Have a good weekend.

Martin

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