A Novel Low-Complexity Precoded OFDM System With Reduced PAPR

• Published in: IEEE transactions on signal processing 2015-03, Vol.63 (6), p.1366-1376
• Main Authors: Wang, Sen-Hung, Li, Chih-Peng, Lee, Kuan-Chou, Su, Hsuan-Jung
• Format: Article
• Language: English
• Subjects: Bit error rate; Computational complexity; Discrete Fourier transforms; Orthogonal frequency division multiplexing (OFDM); Peak to average power ratio; peak-to-average power ratio (PAPR); perfect Gaussian integer sequence; precoding; Transmitters
• ISSN: 1053-587X; 1941-0476
• DOI: 10.1109/TSP.2015.2389751

The computational complexity and peak-to-average power ratio (PAPR) of conventional precoded orthogonal frequency division multiplexing (OFDM) systems can be reduced using a T-OFDM precoded system based on the Walsh-Hadamard matrix. The present paper proposes a novel precoding scheme for further reducing the computational complexity and PAPR of T-OFDM. In the proposed scheme, the precoding matrix is combined with an inverse discrete Fourier transform to construct a new transform matrix at the transmitter. Notably, the transform matrix is both unitary and circulant, with each column being a perfect Gaussian integer sequence containing just four non-zero elements of {±1,±j}. A low-complexity receiver is additionally constructed for the proposed precoding scheme. A closed-form expression is derived for the bit error rate (BER) in T-OFDM and the proposed precoding scheme under frequency-selective fading channels. The simulation results for the BER are shown to be in good agreement with the mathematical derivations. In addition, it is demonstrated that T-OFDM and the proposed scheme have an equivalent BER performance when their precoding matrices are designed in such a way as to obtain full frequency diversity. However, the proposed scheme has a better PAPR performance and a lower computational complexity than T-OFDM.