Method and apparatus for modulating symbols in an orthogonal frequency division multiplexing system and transmission apparatus using the same

An apparatus for modulating a symbol in a transmitter of an Orthogonal Frequency Division Multiplexing (OFDM) system, the method comprising:

• a Twiddling factor generator for generating a Twiddling factor used for circular-shifting frequency-domain data by a Cyclic Prefix (CP) length, the frequency-domain data undergoing an Inverse Fast Fourier Transform (IFFT);
• a multiplier for multiplying the frequency-domain data by the Twiddling factor;
• an IFFT unit for performing IFFT on the frequency-domain data multiplied by the Twiddling factor;
• and
• a CP inserter for buffering the IFFT-transformed output stream beginning from a forefront thereof by a CP length, and adding the buffered stream to a back of the output stream.