A novel Haar wavelet‐based vector BPSK–OFDM robust to channel spectral nulls and with reduced cyclic prefix length and PAPR

Abstract

SUMMARYThe performance of OFDM systems may be degraded when intersymbol interference (ISI) channels have spectral nulls. The communication overhead because of the insertion of the cyclic prefix is high when ISI channels have many taps. Recently, the precoded OFDM systems and vector OFDM (VOFDM) systems were proposed to combat these two problems, respectively. This paper proposes a novel vector binary phase‐shift keying (BPSK)–OFDM system based on Haar wavelet transformation. The Haar wavelet transformation performs decomposition over the vector information symbols produced by a BPSK modulator. It shows that half of the information symbols are zero and the rest are or . Then, the vector BPSK–OFDM becomes the precoded OFDM, which inserts one or more zeros between two sets of K consecutive information symbols. This precoding scheme is able to remove the spectral nulls of an ISI channel without knowing the ISI (like conventional precoded OFDM systems), and it has the same cyclic prefix length as VOFDM systems. The proposed OFDM systems show better robustness to the spectral nulls channel, compared with the conventional VOFDM systems. Because of the insertion of (M −K) zeros between two sets of K consecutive information symbols, the conventional precoded OFDM systems have the data rate expanded and signal‐to‐noise power ratio reduced by 10 log 10(M∕K) dB compared with the proposed OFDM systems. Moreover, because half of the information symbols are zeros after Haar wavelet transformation, the proposed OFDM system can further reduce the transmitting peak‐to‐average power ratio. Finally, we compare the proposed OFDM systems with the precoded OFDM and VOFDM systems. Copyright © 2011 John Wiley & Sons, Ltd.