## 1 Introduction
In LEO satellite communication networks, the link propagation delay is relatively short. Applying TSN technology to LEO satellite communication networks can build low-latency, low-jitter communication networks, providing an efficient, reliable, and real-time solution for satellite communication, which helps to improve the overall performance and service quality of satellite communication systems [5]. The Cyclic Queuing and Forwarding (CQF) mechanism is primarily used for traffic control and packet scheduling in network switches or routers [10]. It is considered a key technology for achieving bounded latency transmission in TSN. Its core purpose is to ensure fairness among different traffic flows and efficient forwarding, and it is considered a key technology for achieving bounded latency transmission in TSN. The authors in [11] achieved CQF by injecting timing plans that map time-sensitive flows to underlying resources in both time and space. The DetNet working group extended CQF to Cyclic Scheduled Queuing and Forwarding (CSQF) to support deterministic long-distance transmission. The authors in [12] constructed a large-scale deterministic IP network on actual systems and testbeds of CENI. In [13], the authors addressed the joint routing and scheduling issues of CSQF. In [14], the developers created an agent to support remote cyclic scheduling on profinet and IP protocols. The length of the port queues significantly impacts the network transmission performance based on the CQF mechanism and should be configured flexibly based on the specific network environment, service requirements, Quality of Service (QoS) needs, and the capabilities of network devices. How to reasonably choose the length of the queues is an issue that urgently needs to be addressed [15]. This paper presents a Particle Swarm Optimization-based queue scheduling and optimization mechanism (PSO-QSO) for large-scale low-Earth-orbit (LEO) satellite communication networks with the following innovative contributions:  
1. This paper proposes a novel scheduling and optimization mechanism specifically tailored for large-scale LEO satellite communication networks, capable of effectively managing time-sensitive service loads;
2. This paper incorporates the PSO algorithm to optimize the lengths and numbers of the queues within the output ports of each satellite node, obtaining the optimal queue configurations for handling time-sensitive traffic;  
Figure 2: ISL between satellite A and B. 3. Through simulation validation, this paper demonstrates that this mechanism can provide the high-quality and efficient transmission of time-sensitive service traffic in large-scale LEO satellite communication networks. The remainder of this article is organized as follows: Section 2 introduces the queue model of LEO satellites and the impact of CQF queue lengths on transmission performance and describes the principles of the proposed queue optimization mechanism. Section 3 presents the analysis and summary of the simulation results. In Section 4, the advantages of the proposed mechanism and the possible future research directions are discussed. This article is concluded in Section 5.