Receiver Design for LEO Satellite Based Asynchronous Massive Access

Low earth orbit (LEO) satellite communication systems offer significant advantages, including extensive coverage, low latency, and reduced deployment costs, making them particularly suitable for massive access scenarios. However, they also face a number of challenges, such as high user mobility, frequent handovers, and large variations in delay. In this paper, we address the problem of massive asynchronous access in LEO satellite communications by proposing a novel receiver design based on the generalized approximate message passing (GAMP) and bilinear generalized approximate message passing (BiG-AMP) algorithm. Our scheme emphasizes multi-path largescale asynchronous access with unknown delays at the receiver, enabling the simultaneous estimation of user activity and channel state information. The receiver architecture is divided into two modules: equivalent channel estimation (ECE) and delay and channel decomposition (DCD). Simulation results demonstrate that the proposed receiver significantly enhances detection performance and channel estimation accuracy under the constraints of massive connectivity and asynchronous transmissions.