Performance Improvement of OFDM System with the Spectrum-Sidelobe-Suppressed Precoding

In the scenario of dynamic spectrum access application for cognitive radio (CR), the spectrum-sidelobe problem of OFDM (orthogonal frequency division multiplexing) must be considered. A precoding ahead of IDFT (inverse discrete Fourier transformation) is presented to suppress the in-band-out-of-subband (IBOSB) radiation. Its design is based on generalized eigenvalue problem. In order to improve its performance for practical application, one column of the precoding matrix can be inverted to reduce the signal peak-to-average-power-ratio (PAPR) to a lower level. At the receiver, iterative soft detection with interference cancelation is adopted to detect the precoded data and further employs the frequency diversity. Both methods introduce some additional transceiver complexity compared with pure precoding, whereas simulations show that joint design not only provides improved PAPR statistics, but also achieves the markedly gain of Bit-Error-Rate (BER) performance over multipath fading channel.