A Novel Phase Generation Mechanism for PAPR Reduction in SLM-based OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a widely used digital modulation technique in wireless communication systems. However, its high peak-to-average power ratio (PAPR) may cause nonlinear distortion during transmission. Selective mapping (SLM) is a popular technique to reduce PAPR by generating multiple candidate signals for phase perturbation and selecting the one with the smallest PAPR. However, the traditional SLM technology uses a random phase generation mechanism, lacks systematic design, and has high circuit complexity. Furthermore, generating multiple candidate signals requires inverse fast Fourier transform (IFFT), resulting in increased computational complexity. To address these issues, this paper proposes a system design of a phase generation mechanism using randomly sorted Walsh-Hadamard matrices, and introduces a phase picking mechanism to reduce computational complexity. The simulation results show that the recommended method achieves a similar improved PAPR performance as traditional SLM technology when the selection mechanism is not used. However, when the recommended method incorporates the selection mechanism, it achieves a sub-optimal improved PAPR performance. It is worth noting that this paper considers the number of Inverse Fast Fourier Transform (IFFT) operations, and with the addition of the selection mechanism, the number of operations is significantly reduced by about 35%. This reduction in operations greatly reduces the overall computational complexity. These findings highlight the systematic and efficient nature of the proposed phase generation method in SLM-based OFDM systems, effectively reducing computational complexity while significantly reducing PAPR.