Efficient OFDM transmission without cyclic prefix over frequency-selective channels

We introduce a computationally efficient OFDM transmission technique that does not require a cyclic prefix and thus provides high spectral efficiency. The intersymbol interference (ISI) due to time dispersion of the channel is combated by ISI cancellation. We show that the inversion of the channel matrix for interchannel interference (ICI) cancellation can be done by the "operator perturbation technique" (OPT) much more efficiently than by conventional equation solvers. We supplement the OPT by blind techniques and hence reduce the error floor to zero for frequency-selective channels. The expense for a 2 Mbit/s transmission is about 500 MFlops. The technique can also deal with time-varying channels in a straightforward way.