Calculating a phase adjustment includes establishing a current phase adjustment for a signal transmitted from a modifying communication device to a feedback communication device. A control signal is received. The control signal comprises windows communicating power indicators that reflect the power of the signal. A previous window communicates power indicators reflecting the power of the signal, and a current window communicates current power indicators reflecting the power of the signal. A previous power trend is estimated from previous power indicators, and a current power trend is estimated from current power indicators. A power trend change is determined from the previous power trend and the current power trend, and a phase increment is determined in accordance with the power trend change. A next phase adjustment is calculated from the current phase adjustment and the phase increment.