Practical aspects of discrete fourier transform-based frequency division multiplexing for data transmission

Removal of intersymbol interference from time-invariant channels with memory by a Fourier transform technique is reported. The simulated bit error rate performances of Reed-Solomon and trellis coding with differential phase-shift keying modulation (PSK) signals and discrete Fourier transform on a time-invariant partial-response channel are presented. It is shown that the coded and interleaved scheme with long transform outperforms the corresponding uncoded scheme and the coded but non-interleaved scheme for the same channel. Furthermore, it is demonstrated by simulation that a practical trellis-coded differential quaternary phase-shift keying (DQPSK) scheme with short transform length followed by cyclic extension does not degrade the performance and can be used as an alternative method to channel equalisation techniques currently used or proposed on many high-speed modulation systems for time-invariant or slowly varying channels with memory.