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Super Contributor I

Maximum transmit power and transmit power per chain

Hi there,

 

I am checking the IAP-325 datasheet and I see the following:

 

• Maximum (aggregate, conducted total) transmit power
(limited by local regulatory requirements):
--2.4 GHz band: +24 dBm (18 dBm per chain)
--5 GHz band: +24 dBm (18 dBm per chain)

 

This IAP is a 4x4 MIMO, so it has 4 transmit chains. If each one has 18 dBm transmit power, it would have a maximum transmit power of 18+18+18+18 = 72 dBm, which is a huge power and doesn't match that of the datasheet which is 24 dBm. What am I doing wrong?

 

Regards,

Julián

Guru Elite

Re: Maximum transmit power and transmit power per chain

Please see the thread here:  http://community.arubanetworks.com/t5/Wireless-Access/Question-about-AP-s-maximum-EIRP/m-p/59010



Colin Joseph
Aruba Customer Engineering

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

Super Contributor I

Re: Maximum transmit power and transmit power per chain

Not clear :(

I will look for more sources.

 

Regards,

Julián

Guru Elite

Re: Maximum transmit power and transmit power per chain

It is complicated and quite frankly can be further restricted by regulatory requirements.  It is easier to see the maximum power on each channel by running the command "show ap allowed-max-eirp" to see the real number:   http://www.arubanetworks.com/techdocs/Instant_423_WebHelp/InstantWebHelp.htm#CLI_commands/show ap allowed_max_EIRP.htm?Highlight=allowed



Colin Joseph
Aruba Customer Engineering

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

Super Contributor I

Re: Maximum transmit power and transmit power per chain

Yes, I already know that power will be restricted by the regulatory domain where the IAP resides in. Where I am confused is with the relation between the max transmit power and the transmit power per chain, but I didn't know is so complicated.

By the way, thanks for the link with all that information about Instant, I didn't know about it. It's great!

 

Regards,

Julián

Guru Elite

Re: Maximum transmit power and transmit power per chain

The indoor maximum power does not really vary that much between channels.  It is almost not worth understanding the calculations..



Colin Joseph
Aruba Customer Engineering

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

Aruba

Re: Maximum transmit power and transmit power per chain

18dBm is 63mW (10^1.8). You ca sum the linear power numbers (in mW), so in total you have 4x 63 = 252mW. Expressed in dBm that is 24dBm (10*log(252)).

4x corrsponds with +6dB.

 

/Onno
Super Contributor I

Re: Maximum transmit power and transmit power per chain

Hi Onno,

 

Great explanation here and in the other posts! Completely understood.

 

Regards,

Julián

Super Contributor I

Re: Maximum transmit power and transmit power per chain

Hi Onno and Colin,

 

One more doubt about this. When you modify the output power on an AP, for example an Instant AP within the ARM section, do you modify the aggregate transmit power or the per chain transmit power?

Super Contributor I

Re: Maximum transmit power and transmit power per chain

Hi there,

 

Any idea? I guess it is the aggregate transmit power, I would just like to confirm.

 

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