Superimposed-Pilot OTFS Under Fractional Doppler: Modular End-to-End Learning

TL;DR

This paper introduces a modular deep learning framework for OTFS transceivers that enhances performance in high-mobility scenarios by jointly optimizing signal processing modules, including channel estimation and detection.

Contribution

It proposes a flexible, physics-informed end-to-end neural network architecture for OTFS that integrates multiple modules and explicitly models fractional Doppler effects.

Findings

Significant performance improvements in NMSE and detection reliability.

Robustness under both integer and fractional Doppler conditions.

Enhanced adaptability to various communication configurations.

Abstract

Orthogonal time frequency space (OTFS) modulation has emerged as a promising candidate to overcome the performance degradation of orthogonal frequency division multiplexing (OFDM), which are commonly encountered in high-mobility wireless communication scenarios. However, conventional OTFS transceivers rely on multiple separately designed signal-processing modules, whose isolated optimization often limits global optimal performance. To overcome limitations, this paper proposes a modular deep learning (DL) based end-to-end OTFS transceiver framework that consists of trainable and interchangeable neural network (NN) modules, including constellation mapping/demapping, superimposed pilot placement, inverse Zak (IZak)/Zak transforms, and a U-Net-enhanced NN tailored for joint channel estimation and detection (JCED), while explicitly accounting for the impact of the cyclic prefix. This physics-informed modular architecture provides flexibility for integration with conventional OTFS systems and adaptability to different communication configurations. Simulations demonstrate that the proposed design significantly outperforms baseline methods in terms of both normalized mean squared error (NMSE) and detection reliability, maintaining robustness under integer and fractional Doppler conditions. The results highlight the potential of DL-based end-to-end optimization to enable practical and high-performance OTFS transceivers for next-generation high-mobility networks.