This article addresses the problem of multiple preamble detection in random access systems based on orthogonal time frequency space (OTFS) signaling. This challenge is formulated as a structured sparse recovery problem in the complex domain. To tackle it, the authors propose a new approximate message passing (AMP) algorithm that enforces double sparsity: the sparse selection of preambles and the inherent sparsity of OTFS signals in the delay-Doppler domain. From an algorithmic standpoint, the non-separable complex sparsity constraint necessitates a careful derivation and leads to the design of a novel AMP denoiser. Simulation results demonstrate that the proposed method achieves robust detection performance and delivers significant gains over state-of-the-art techniques.
@article{arxiv.2509.03980,
title = {Approximate Message Passing for Multi-Preamble Detection in OTFS Random Access},
author = {Alessandro Mirri and Vishnu Teja Kunde and Enrico Paolini and Jean-Francois Chamberland},
journal= {arXiv preprint arXiv:2509.03980},
year = {2025}
}