A Further PAPR Reduction for $\pi/2$-BPSK in 5G New Radio

Abstract

In this paper, the problem of further reducing the peak-to-average power ratio (PAPR) of a discrete Fourier transform-spread orthogonal frequency-division multiplexing signal is considered for the transmission of $\pi/2$ -BPSK symbols in the 5G New Radio specifications. In particular, a joint optimization of the constellation-rotation angle and the pulse-shaping vector is conducted. To avoid the exponential complexity required to evaluate the PAPR, a computationally efficient upper bound on the worst-case PAPR is presented and adopted as the objective function. The signal-to-interference-plus-noise ratio (SINR) at the output of a constellation-derotating matched filter is also presented. Then, joint optimizations are conducted through numerical search for various target SINRs. Surprisingly, the optimal rotation angle is close to but not exactly equal to $\pi/2$ . It is shown that the proposed combinations significantly outperform the existing combinations of the rotation angle and the shaping vector when the signal is amplified by a nonlinear PA.