Aruba Employee
Posts: 10
Registered: ‎07-07-2007

EIRP Values

Here are notes from engineering (specifically related to AP's with external antennas). Many have asked what do we do with the antenna-gain setting when provisioning AP's.


To ensure compliance and proper AP operation, gain should always be provisioned with the correct external antenna gain in the field shown below. The software will use the lesser of the regulatory limit, user fixed setting, or ARM setting. All user and ARM settings are now in EIRP, so that is why it is important to provision this gain correctly (its not just for regulatory reasons anymore!).

The following command can be used to show the current operation of any given AP:

show ap debug driver-log ap-name | include EIRP

This will produce a line similar to the following for each radio (look for the last line of each radio in the reply)
114 2042401.854409 wifi1: EIRP (Config: 21.0dBm, Set: 20.5dBm, AP Max: 20.5dBm, Reg Max: 36dBm), Conducted Power Set: 18.0dBm, Gain: 2.5dBm, TPC Red 16

The relevant info is in the EIRP():
Config : This is the EIRP sent down from the controller (i.e. user fixed config, or ARM setting based config)
Set: This is the current operating EIRP
AP Max : This is the max EIRP the AP is capable of producing based on current user input gain provisioned and AP model output power capability
Reg Max : This is the regulatory maximum EIRP

Besides EIRP, there is the following info
Conducted power set: this is the conducted power output setting
Gain: this is the gain provisioned
TPC red: the tpc (transmit power control) reduction

Note that Conducted power set + Gain = EIRP (Set)

If the AP would be above the regulatory max, the conducted power set will be reduced to keep EIRP (set) within EIRP (Reg Max)
Posts: 485
Registered: ‎04-03-2007

Re: EIRP Values

Thanks, Steve. Isn't it also true that each AP type has its own permitted max conducted power, therefore preventing the AP from getting anywhere close to regulatory maximum allowed EIRP? In your example (an AP-105 or 120 series), the max AP conducted power is 18dBm, so it doesn't matter if ARM chooses 21, 24, 27, or 30 dBm, the EIRP will always end up being the same, true?
Ryan Holland, ACDX #1 ACMX #1
The Ohio State University
Aruba Employee
Posts: 64
Registered: ‎04-07-2007

Re: EIRP Values

This is great info!! I am often trying to find out what an APs power is set to and since the EIRP change I haven't caught up yet.

I would like to know the answer to Ryans post as well. I would hate to try to diagnose a low power setting on an AP only to find out therre was a max setting on the AP that was overriding the config settings.

John W. Turner
Director of Networks & Systems
Brandeis University
Aruba Employee
Posts: 3
Registered: ‎10-30-2007

Re: EIRP Values

Your understanding is correct. Each AP type has two limitations (its max conducted power + antenna gain), regulatory domain constraints for the channel and country of operation...

The maximum that the AP can radiate is therefore bounded by the min of the above two limitations.

ARM internally caps the arm-max-power-level based on max regulatory domain allowed limits, so for certain channels, where the max reg EIRP is 23, ARM will not use higher power levels.

We can extend this to consider AP EIRP limitations as well in future

Posts: 485
Registered: ‎04-03-2007

show ap active

Thank you for the response. I'll end up filing an RFE, but I think it would be most beneficial if the output of 'show ap active' illustrated the true maximum EIRP for the AP based on its model, regulatory domain, and provisioned antenna gain. This would prevent myself, John, and others from unnecessarily troubleshooting power issues.

For example, here's an AP in production:

Active AP Table
Name Group IP Address 11g Clients 11g Ch/EIRP/MaxEIRP 11a Clients 11a Ch/EIRP/MaxEIRP AP Type Flags Uptime
---- ----- ---------- ----------- ------------------- ----------- ------------------- ------- ----- ------
thompson-1-2 tnc3-thompson 0 AP:11/11/33 0 AP:161/18/36 65 7d:4h:13m:2s

My suggestion would change the 3rd number in the "Ch/EIRP/MaxEIRP" columns to be accurate.
Ryan Holland, ACDX #1 ACMX #1
The Ohio State University