Spread-Pilot-Aided Channel Estimation for Zak-OTFS-Based Multi-Satellite Cooperative Transmission

Abstract

Multi-satellite cooperative transmission (MSCT) is a promising paradigm to enhance transmission performance in Low Earth Orbit constellations. Benefiting from the robustness against doubly-selective channels, orthogonal time frequency space (OTFS) modulation is suitable for such high-mobile MSCT scenarios. However, conventional OTFS-based channel estimation (CE) schemes require guard intervals and iterative processing, resulting in stringent spectral efficiency and excessive computational complexity. To address these challenges, this paper proposes a guard-free and non-iterative spread-pilot CE framework for Zak-OTFS-based MSCT systems. Specifically, we design a Zak-OTFS-based spread pilot to suppress the pilot-data interference, enabling a superimposed pilot and data transmission scheme without guard intervals. Furthermore, leveraging the delay-Doppler domain characterization distinction among different satellite channels, we propose an aggregate non-iterative multi-satellite CE algorithm based on the cross-ambiguity. The simulation results demonstrate the effectiveness of the proposed scheme compared to the typical CE baselines.