Sixth generation (6G) physical layer (PHY) is evolving beyond the legacy orthogonal frequency division multiplexing (OFDM)-based waveforms. In this paper, we compare the bit error rate (BER) performance of three beyond-OFDM waveforms, namely, orthogonal time-frequency-space (OTFS) modulation, affine frequency division multiplexing (AFDM), and orthogonal chirp division multiplexing (OCDM), which are particularly suitable for the highly mobile non-terrestrial network (NTN) vertical of 6G. In order to characterize the effect of mobility and Doppler shift in low Earth orbit (LEO) satellites, we performed BER comparisons over four different NTN tapped-delay-line (TDL) models, TDL-A, TDL-B, TDL-C, and TDL-D, as specified in the 3rd generation partnership project (3GPP) technical report TR 38.811. After channel equalization, a minimum mean squared error with successive detection (MMSE-SD) algorithm was used to enhance the BER performance. It was found that AFDM and OTFS consistently outperformed OCDM across all TDL models, while AFDM performed better than OTFS in TDL-B and TDL-C, in the high signal-to-noise ratio (SNR) regime. The complete simulation framework is made available as an open-source code for quick validation and further development.

翻译：第六代（6G）物理层（PHY）正朝着超越传统基于正交频分复用（OFDM）的波形演进。本文比较了三种超OFDM波形——正交时频空间（OTFS）调制、仿射频分复用（AFDM）和正交啁啾分复用（OCDM）——在比特误码率（BER）方面的性能，这些波形特别适用于6G中高移动性的非地面网络（NTN）垂直场景。为表征低地球轨道（LEO）卫星中移动性和多普勒频移的影响，我们基于第三代合作伙伴计划（3GPP）技术报告TR 38.811定义的四种不同NTN抽头延迟线（TDL）模型（TDL-A、TDL-B、TDL-C和TDL-D）进行了BER性能比较。在信道均衡后，采用基于连续检测的最小均方误差（MMSE-SD）算法以提升BER性能。研究发现，在所有TDL模型中，AFDM和OTFS始终优于OCDM；而在高信噪比（SNR）条件下，AFDM在TDL-B和TDL-C模型中的表现优于OTFS。完整的仿真框架已作为开源代码发布，以供快速验证和进一步开发。