A method to decode an orthogonal frequency-division multiplex (OFDM) signal data block that includes symbol-data in a data interval, repeated-data in a cyclic-prefix (CP) guard interval, and noise. The signal is often called a CP-OFDM signal. The method includes determining a first data set based on data samples taken during a first time window of a data block. The method also includes determining a second data set based on data samples taken during a second time window of the data block, wherein the second time window is selected so that the second data set includes repeated-data not present in the first data set. The method also includes combining the first data set and the second data set in a manner effective to increase a signal-to-noise ratio of the signal. The combining process increases signal data energy more than noise data energy.