Rotated precoder-based OFDM system robust to channel spectral nulls and with reduced PAPR

Recently, the precoded orthogonal frequency division multiplexing (OFDM) was proposed to show robustness to intersymbol interference channels with spectral nulls. However, due to inserting (M-K) zeros between each two sets of K consecutive information symbols, the average transmitting power of the precoded OFDM system reduces by 10 log10 (M/K) dB compared with the conventional OFDM system. Under the same points, inverse fast Fourier transformation (IFFT), the precoded OFDM system has a higher peak-to-average power ratio (PAPR) compared with the conventional OFDM system. This paper proposes a rotated precoder-based OFDM system robust to channel spectral nulls and with reduced PAPR. The rotated precoder makes the N-point IFFT with N/2 zeros padded. Since half of the information symbols for IFFT are zeros, we have the PAPR reduced by 10 log10 2≈3 dB approximately, compared with the conventional precoded OFDM system. We also show that the proposed OFDM system has the same bit error rate (BER) performance as the conventional precoded OFDM system. Both theoretical performance analysis and simulation results are presented to verify the correctness of our theory analysis.