Change the Transmitter Power Level Parameter of the Existing AP
You can change the radio coverage area of an AP when you modify the transmitter power level parameter.
The transmitter power (mW) setting determines the power level of the radio transmitter.** The default power setting is the highest transmit power allowed in a regulatory domain.** Government regulations define the highest power level for radio devices.
Caution: The transmitter power level setting must conform to the established standards of the country in which the setting is used.
This CLI command under the radio interface changes the transmitted power level to the maximum on an AP:
Access Point (config)# interface dot11radio 0
Access Point (config-if)# power local maximum
Use this command to set the power level to maximum. Then, check how much throughput you have, and move the power level to a lower value until you reach a high throughput rate that stays consistent. You can also start from the lowest possible power level and increase the level until you reach a consistent throughput. This is because in some cases, if you do not boost the signal to the maximum level, the throughput and signal strength can change continuously and not remain consistent