Computation-Free Phase Rotation by Shifted Circular Repetition for DFT-Precoding Scheme to Peak Power Reduction of OFDM Signals

In peak power reduction of orthogonal frequency-division multiplexing (OFDM) signals, discrete Fourier transform spread OFDM (DFT-s-OFDM) has the advantages of data independence, no side information, and no error degradation. A redundant version of DFT-s-OFDM with frequency-domain pulse shaping and phase rotation can further reduce the peak power. The optimal phase rotation, however, needs many complex multiplications in DFT-s-OFDM systems, limiting its practicality in resource-constrained devices like mobile terminals. This work proposes a novel DFT-s-OFDM scheme to achieve close-optimal peak power reduction with minimal computational complexity, comparable to practical DFT-s-OFDM using plain BPSK or QPSK without phase rotation. The proposed scheme outperforms conventional phase-rotated methods, such as $\pi/2$-BPSK or $\pi/4$-QPSK adopted in current systems in both peak power reduction and implementation efficiency.