Time Domain Zero-Postfix (TZP) AFDM with Two-Stage Iterative MMSE Detection

In this paper, we investigate the design of lowcomplexity, high-performance transmission and detection schemes for the emerging affine frequency division multiplexing (AFDM) waveform to combat doubly selective channels. We first introduce a new time domain zero-postfix (TZP) AFDM transmission frame, which simplifies the time domain input-output (IO) relation for AFDM while preserving the spectral efficiency. Based on this IO relation, we design a novel two-stage detector. The first stage performs a low-complexity time domain linear MMSE initial detection. In the second stage, we develop a cross-domain iterative MMSE detector, which utilizes statistics from the first stage, incorporates discrete affine Fourier transform (DAFT) domain symbol constraints to enhance error performance, and exploits the time domain IO relation for complexity reduction. Simulation results show that the proposed TZP-AFDM and detector significantly outperform existing methods by achieving superior error performances, higher spectral efficiency and lower computational overhead.