Low-complexity FFT structures for OFDM transceivers

Orthogonal frequency-division multiplexing is a multiple-access technique with modulation and demodulation implemented by an inverse discrete Fourier transform (DFT) and a DFT, respectively. In a downlink (uplink) environment, an individual receiver (transmitter) may only use a small number of subchannels at any given time, in which case it does not make sense to require full DFT demodulation (inverse DFT modulation). Several existing low-complexity techniques for computing a partial DFT or inverse DFT with power-of-two size are examined. Low-complexity fast Fourier transform structures for full, few input, and few output nonpower-of-two transforms are derived.