Beamforming methods and systems are described in which differential channel estimation can be computed based on measured power at receiver. Simultaneous activation of antennas in separate pairs can be used to determine relative phases of antennas with respect to a reference antenna based on the power measurements. In turn, the beam forming signals can be weighted in accordance with the relative phases to adapt the signals to a multipath environment. Existing power measurement capabilities of conventional receivers can be employed to achieve approximate channel estimates.