Beam-Hopping Pattern Design for Grant-Free Random Access in LEO Satellite Communications

TL;DR

This paper presents novel beam-hopping pattern design algorithms for LEO satellite systems that dynamically allocate resources for grant-free random access, improving success probability and handling traffic demand imbalance.

Contribution

It introduces a binary optimization framework and innovative algorithms using bisection and ADMM to optimize beam-hopping patterns for LEO satellite communications.

Findings

Algorithms outperform existing methods in simulations.

Robustness demonstrated under traffic demand imbalance.

Enhanced decoding success probability achieved.

Abstract

Increasing demand for massive device connectivity in underserved regions drives the development of advanced low Earth orbit (LEO) satellite communication systems. Beam-hopping LEO systems without connection establishment provide a promising solution for achieving both demand-aware resource allocation and low access latency. This paper investigates beam-hopping pattern design for the grant-free random access systems to dynamically allocate satellite resources according to traffic demands across serving cells. We formulate a binary optimization problem that aims to maximize the minimum successful transmission probability across cells, given limited satellite beam generation capacity. To solve this problem, we propose novel beam-hopping design algorithms that alternately enhance the collision avoidance rate and decoding success probability within an alternating optimization framework. Specifically, the algorithms employ a bisection method to optimize illumination allocation for each cell based on demand, while using the alternating direction method of multipliers (ADMM) to optimize beam-hopping patterns for maximizing decoding success probability. Furthermore, we enhance the ADMM by replacing the strict binary constraint with two equivalent continuous-valued constraints. Simulation results demonstrate the superiority of the proposed algorithms compared to other beam-hopping methods and verify robustness in managing traffic demand imbalance.