6G NTN Waveforms: A Comparison of OTFS, AFDM and OCDM in LEO Satellite Channels

2026-02-10

AI Summary

This study addresses the performance degradation of conventional OFDM in sixth-generation (6G) non-terrestrial networks (NTNs) due to the high mobility of low Earth orbit (LEO) satellites. The authors systematically evaluate the bit error rate (BER) performance of three emerging waveforms—Orthogonal Time Frequency Space (OTFS), Affine Frequency Division Multiplexing (AFDM), and Orthogonal Chirp Division Multiplexing (OCDM)—under 3GPP TDL-A/B/C/D channel models, employing a minimum mean square error with sphere decoding (MMSE-SD) equalization algorithm to enhance receiver performance. To the best of the authors’ knowledge, this work presents the first comprehensive comparison of these three waveforms in a 6G NTN context, revealing that both AFDM and OTFS significantly outperform OCDM, with AFDM achieving the best performance under TDL-B and TDL-C channels at high signal-to-noise ratios. The complete simulation framework is made publicly available to support future research on 6G NTN waveform design.

Technology Category

• Application Domains: Mobility, Driving & Flight
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Security and Privacy: Large-scale security measurements

Abstract

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.

Problem

• 6G
• NTN
• LEO satellite
• waveform comparison
• Doppler shift

Innovation

• AFDM
• OTFS
• LEO satellite channels
• beyond-OFDM waveforms
• MMSE-SD equalization