A subcarrier scrambling method for use in a transmitter with multiple subcarriers, the transmitter being configured to allocate pilot symbols and data symbols for each of a plurality of resource units (RUs). The method includes: applying, for each of the plurality of RUs, a first intra RU sequence to the pilot symbols, to thereby generate a plurality of scrambled pilot symbols; applying, for each of the plurality of RUs, a second intra RU sequence to the data symbols, to thereby generate a plurality of scrambled data symbols; and combining the plurality of scrambled pilot symbols and the plurality of scrambled data symbols to form the plurality of RUs.