A Simplified 256-APSK Soft Demapping Method and Implementation

High-order amplitude phase shift keying (APSK) presents significant challenges in both hardware and software implementations for demapping due to its characteristics such as a large number of constellation points, high computational complexity, and pronounced nonlinear property. In this paper, a low complexity soft demapping method is proposed, where APSK modulation is equivalently decomposed into independent PSK and ASK modulations, and then the computational process of the Max-Log-Map algorithm is simplified in accordance with their respective distributions, resulting in an efficient yet low complexi-ty demapping algorithm. Simulation results indicate that for 256-APSK, the proposed method achieves identical performance to traditional demapping algorithms, with significantly reduced computational complexity.