A subscriber station is configured to extend a battery life using a method for envelope tracking power amplification. The subscriber station includes a main processor configured to perform a plurality of functions to operate the subscriber station. The subscriber station also includes a power source configured to provide power to one or more components in the subscriber station and an envelope tracking power amplifier (ET PA) configured to amplify a signal. The ETPA also is configured to estimate and adaptively maintain the envelope and RF signal time alignment during operation of the ET PA.