Space-Time Rate-Splitting Multiple Access for Multibeam LEO Satellite Networks

2025-10-20

AI Summary

To address the performance degradation of conventional Rate-Splitting Multiple Access (RSMA) in multi-beam LEO satellite systems—caused by channel state information (CSI) uncertainty and dynamic traffic loads—this paper proposes a Spatio-Temporal RSMA (ST-RSMA) framework. Its core innovation lies in the first integration of spatio-temporal coding into the transmission of the common stream in RSMA, thereby overcoming the limitation of single-beamforming and enabling full diversity gain for all users under arbitrary channel conditions and load variations. We further develop a WMMSE-based joint optimization algorithm to concurrently design power allocation for common/private streams and beamforming vectors for private streams. Simulation results demonstrate that ST-RSMA significantly outperforms conventional RSMA and other multiple access schemes in terms of minimum user rate, robustness against CSI errors, and scalability. This work establishes a new paradigm for high-dynamic LEO satellite communications, offering both theoretical rigor and practical viability.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Multiagent Systems: Agent Communication

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Personalized, context-aware and across-device search

Abstract

This paper proposes a novel space-time rate-splitting multiple access (ST-RSMA) framework for multibeam low Earth orbit (LEO) satellite communications (SATCOM) systems, where space-time coding is integrated into the common stream transmission. This design enables full diversity gain in the common stream transmission for all users, regardless of the uncertainty of the channel state information (CSI) and network load conditions, thereby overcoming the performance limitations of conventional RSMA that employs a single beamforming vector for all users. To further enhance performance, we develop a weighted minimum mean square error (WMMSE)-based algorithm tailored to ST-RSMA that jointly optimizes the power allocation for the common stream and the power/beamforming vectors for private streams, aiming to maximize the minimum user rate. Numerical results show that ST-RSMA significantly outperforms conventional RSMA and other multiple access techniques, offering a robust and scalable solution for LEO SATCOM.

Problem

• Achieving full diversity gain in multibeam LEO satellite networks
• Overcoming performance limitations of conventional rate-splitting multiple access
• Maximizing minimum user rate under uncertain channel conditions

Innovation

• Integrates space-time coding into common stream transmission
• Uses WMMSE algorithm to optimize power and beamforming
• Enables full diversity gain regardless of CSI uncertainty