Product and Software: This article applies to all Aruba APs and ArubaOS 3.0 and later.
The radio driver of each AP is set with a country code before the radios are turned on. Unfortunately, the code that limits the power and channels is buried in the driver, which makes it difficult to display information about the actual transmit power of an AP.
In ArubaOS 2.5.x, Aruba had power levels specified from 0 to 4. These levels did not provide much granularity and power level 0 was really low. This was not accurate, but it was simple.
In ArubaOS 3.x, Aruba implemented a new feature to set the power in dBm and with finer granularity. The power values in the CLI/WebUI are now the desired EIRP in dBm. This power setting is expected to be the transmitted power over the air (EIRP) and depends on things like antenna gain and cables loss.
The drawback of this setting is that APs do not calculate the regulatory power limits in the user interface, but the driver still clips the transmitted power to stay within regulation limits. Regulation rules are complex, and they sometimes limit the actual tx power (out of the radio) and sometimes EIRP (out of the antenna), which makes it a very difficult thing to show in the GUI.
In short, the GUI setting is the requested EIRP. Due to regulations, the actual AP tx power is done automatically in the driver of the APs.
To view a "hidden" report from the AP radio driver that lists the actual power settings, issue the following command:
#show ap debug driver-log ap-name ap-test | include Tx
14 0.12933 wifi0: Tx Power 0dBm, Actual EIRP 4dBm, Max EIRP 5dBm, TPC Red 1
33 0.52933 wifi1: Tx Power 11dBm, Actual EIRP 12dBm, Max EIRP 27dBm, TPC Red 15