Adaptive power management methods and systems for a first station and a second station in a wireless network. Each station operating in the power-saving (PS) mode adaptively determines a “listen interval” (LI) according to residual power state, quality-of-service requirements, or other considerations. The LI is composed of a “normal beacon interval” (NBI) followed by the combination of “beacon-window-only beacon intervals” (BBIs) and “sleep beacon intervals” (SBIs). The LI value is one or a prime number which is larger than two, and the positions of the NBI and BBIs in an LI form a cyclic difference set. Each station broadcasts a beacon frame comprising at least information about “the remaining number of BIs (RBI)” within a beacon window. Once the first station correctly receives the beacon frame from the second station, the first station predicts the awake/sleep schedule of the second station, and transmits data frames to the second station at the NBI of the second station.