Precoding Design for PAPR Reduction in Mixed-Numerology MU-MIMO OFDM Systems

Abstract

Orthogonal frequency division multiplexing (OFDM) is widely adopted in modern wireless systems for high spectral efficiency, yet its high peak-to-average power ratio (PAPR) limits power amplifier efficiency. Mixed-numerology transmission, which enables flexible subcarrier spacing for diverse services, further aggravates the PAPR problem. Although PAPR-aware precoding has been investigated in single-numerology multi-user multiple-input multiple-output (MU-MIMO) OFDM systems, the PAPR suppression in mixed-numerology MU-MIMO OFDM systems has not been thoroughly addressed. In this letter, we propose a low-complexity precoding method to jointly suppress per-antenna PAPR, inter-numerology interference (INI), and multi-user interference (MUI) in mixed-numerology MU-MIMO OFDM systems. By decomposing the complex precoding design problem into low-dimensional subproblems, we develop an efficient algorithm with closed-form or semi-closed-form updates. Simulation results demonstrate that the proposed algorithm effectively reduces transmit power while satisfying per-antenna PAPR, INI, and MUI constraints, highlighting its application potential for MU-MIMO data-channel transmission with available channel state information (CSI).