Methods and arrangements for wireless communications are described. Embodiments include transformations, code, state machines or other logic to receive from a transmitter a signal representing a known sequence of symbols. The signal may be transmitted over a plurality of sub channels. The embodiments may also include determining channel responses at the sub channels and determining a reception of the known sequence. The determining may include treating the channel responses at the sub channels in a differential manner to cancel out channel phase responses and obtain channel amplitudes. In some embodiments, the cancelling may be performed by multiplying frequency domain values representing reception of a sub channel by the complex conjugate of frequency domain values of a neighboring sub channel. Many embodiments may also include calculating a carrier to interference and noise ratio (CINR) of the signal. In several embodiments, the signal may represent the preamble of a wireless frame.