SkyOctopus: Enabling Low-Latency Mobile Satellite Network through Multiple Anchors¶

Abstract¶

The rapid deployment of low earth orbit (LEO) satellite constellations has drawn attention to the potential of non-terrestrial networks (NTN) in providing global communication services. Telecom operators are attempting to collaborate with satellite network providers to develop mobile satellite networks, which serve as an effective supplement to terrestrial networks. However, current mobile satellite network architectures still employ the single-anchor design of terrestrial mobile networks, leading to severely circuitous routing for users and significantly impacting their service experience. To reduce unnecessary latency caused by circuitous routing and provide users with low-latency global internet services, this paper presents SkyOctopus, an advanced multi-anchor mobile satellite network architecture. SkyOctopus innovatively deploys traffic classifiers on satellites to enable connections between users and multiple anchor points distributed globally. It guarantees optimal anchor point selection for each user’s target server by monitoring multiple end-to-end paths. We build a prototype of SkyOctopus using enhanced Open5GS and UERANSIM, which is driven by actual LEO satellite constellations such as Starlink, Kuiper, and OneWeb. We conduct extensive experiments, and the results demonstrate that, compared to standard 5G NTN and two other existing schemes, SkyOctopus can reduce end-to-end latency by up to 53%.

低地球轨道（LEO）卫星星座的快速部署，已使非地面网络（NTN）在提供全球通信服务方面的潜力备受关注。电信运营商正尝试与卫星网络供应商合作，以发展作为地面网络有效补充的移动卫星网络。然而，当前的移动卫星网络架构仍沿用地面移动网络中的 单锚点（single-anchor）设计，这导致了严重的用户路由迂回（circuitous routing） 问题，并显著影响其服务体验。

为减少路由迂回所带来的不必要时延、并为用户提供低时延的全球互联网服务，本文提出了一种名为SkyOctopus的先进多锚点（multi-anchor）移动卫星网络架构。SkyOctopus创新性地在卫星上部署流量分类器（traffic classifiers），以实现用户与全球分布式多个锚点之间的连接。它通过监测多条端到端路径，来保障为用户的每个目标服务器选择最优的锚点。

我们使用增强的Open5GS和UERANSIM构建了SkyOctopus的原型系统，并以 Starlink、Kuiper 和 OneWeb 等真实低轨卫星星座进行驱动。我们进行了大量的实验，结果表明，与标准的5G NTN及其他两种现有方案相比，SkyOctopus能够将端到端时延最高降低53%

Introduction¶

Nowadays, we are witnessing the rapid development of low earth orbit (LEO) satellite constellations, such as SpaceX’s Starlink [1], Amazon’s Kuiper [2], and OneWeb [3]. These satellite constellations, with their dense satellite distribution and inter-satellite links (ISLs), provide global internet and communication services while complementing terrestrial mobile networks in underserved areas in a cost-effective manner.

Meanwhile, as the developer of 5G, 3GPP has explicitly stated that non-terrestrial networks (NTN) will be an essential component of future 5G-Advanced and 6G networks [4][6]. In practice, it has become a trend for telecom operators and satellite network providers to collaborate to build mobile satellite networks, as exemplified by partnerships such as TMobile with SpaceX [7] and AT&T with AST [8].

To ensure compatibility with existing terrestrial mobile networks, mobile satellite networks largely adopt the design of terrestrial mobile networks, moving only the access network to the satellite [5]. Since the core network remains deployed on the ground and unchanged, each protocol data unit (PDU) session corresponds to a specific anchor point. Given the global random access patterns of users, this single-anchor design poses significant challenges for the user data plane in satellite mobile networks. In such cases, user traffic transmission needs to traverse a fixed ground anchor point, resulting in circuitous routing and increased latency.

如今，我们正见证着低地球轨道（LEO）卫星星座的快速发展，例如SpaceX的Starlink [1]、亚马逊的Kuiper [2]以及OneWeb [3]。这些卫星星座凭借其密集的卫星分布和星间链路（ISLs），在提供全球互联网与通信服务的同时，也以一种经济高效的方式对服务欠缺地区的地面移动网络进行了有效补充。

与此同时，作为5G的制定者，3GPP已明确指出非地面网络（NTN）将成为未来5G-Advanced和6G网络的重要组成部分[4][6]。在实践中，电信运营商与卫星网络供应商合作构建移动卫星网络已成为一种趋势，T-Mobile与SpaceX [7]、AT&T与AST [8]的合作便是例证。

为了确保与现有地面移动网络的兼容性，移动卫星网络在很大程度上沿用了地面移动网络的设计，仅将接入网部分移至卫星上[5]。由于核心网仍部署于地面且保持不变，每个协议数据单元（PDU）会话都对应一个特定的锚点。考虑到用户全球随机接入的模式，这种单锚点设计为卫星移动网络的用户数据平面带来了严峻挑战。在此类情况下，用户流量传输需要经过一个固定的地面锚点，从而导致 路由迂回（circuitous routing） 和时延增加。

A natural solution to this issue is to deploy the anchor point onto the satellite nearest to the base station. By deploying anchor points on satellites and minimizing the distance between mobile network infrastructures, this approach aims to mitigate the long end-to-end latency caused by circuitous routing. However, considering the changes in network topology caused by the high-speed movement of satellites, users would face severe anchor point reselection issue, significantly impacting service continuity and incurring substantial reselection costs. Therefore, this solution is difficult to widely apply in realworld scenarios.

针对此问题，一种自然的解决方案是将锚点部署到距离基站最近的卫星上。通过在卫星上部署锚点并最小化移动网络基础设施间的距离，该方法旨在缓解由路由迂回所造成的长端到端时延。然而，考虑到卫星高速移动所带来的网络拓扑变化，用户将面临严峻的锚点重选问题，这会严重影响服务连续性并产生巨大的重选开销。因此，该方案难以在现实场景中广泛应用。

In this paper, we present SkyOctopus, an advanced multianchor mobile satellite network architecture. SkyOctopus supports the simultaneous existence of multiple anchor points within a single PDU session by using traffic classifiers deployed on satellites. It also employs a fine-grained selection strategy, which uses location-based criteria for the initial selection of anchor points and updates anchor point choices based on network conditions through continuous monitoring. Additionally, based on the correspondence between base stations and traffic classifiers, and parallelized signaling transmission, we design a new PDU session establishment process for SkyOctopus. Users can quickly establish PDU sessions without concern for the number of anchor points.

We construct a prototype of SkyOctopus using enhanced Open5GS [9] and UERANSIM [10], driven by real LEO satellite ephemerides, including Starlink, Kuiper and OneWeb. Based on this prototype, we conducted extensive experiments, and the results indicate that SkyOctopus significantly reduces end-to-end latency by up to 53% compared to the other three schemes and reduces session establishment time by 86%.

在本文中，我们提出了 SkyOctopus，一种先进的多锚点移动卫星网络架构。SkyOctopus通过在卫星上部署流量分类器，支持在单个PDU会话中同时存在多个锚点。它还采用了一种细粒度的选择策略，该策略利用基于位置的标准进行锚点的初始选择，并通过持续监测根据网络状况更新锚点选择。此外，基于基站与流量分类器的对应关系以及并行化的信令传输，我们为SkyOctopus设计了一种新的PDU会话建立流程。用户可以快速建立PDU会话，而无需关心锚点的数量

我们使用增强的 Open5GS [9]和 UERANSIM [10]，并由包括Starlink、Kuiper和OneWeb在内的真实LEO卫星星历驱动，构建了SkyOctopus的原型系统。基于该原型，我们进行了大量的实验，结果表明，与其他三种方案相比，SkyOctopus将端到端时延最高降低了53%，并将会话建立时间减少了86%

Contributions of this paper can be summarized as follows:

• We for the first time expose the issue of high end-to-end latency caused by circuitous routing in emerging mobile satellite networks, which is essentially due to the design of single-anchor PDU session.

• We propose SkyOctopus, an advanced mobile satellite network architecture that achieves low-latency global internet services through multiple anchor points and fine-grained anchor point selection strategy.

• We construct a prototype of SkyOctopus and conduct comprehensive experiments to demonstrate its effectiveness in reducing end-to-end latency and its efficiency in terms of session establishment time.

The rest of this paper is structured as follows. Section II introduces the background of the problem and our motivation. Section III presents an overview of the proposed SkyOctopus architecture. Section IV provides detailed explanations of the three aspects of SkyOctopus. We conduct extensive experiments and analyze the results in section V. Section VI presents a review of related work in the field. Section VII discusses additional considerations and issues related to our work. Finally, Section VIII briefly concludes this work.

本文的贡献可总结如下：

我们首次揭示了在新兴移动卫星网络中，由路由迂回所导致的高端到端时延问题，其本质源于单锚点PDU会话的设计
我们提出了SkyOctopus，一种通过多锚点和细粒度锚点选择策略来实现低时延全球互联网服务的先进移动卫星网络架构
我们构建了SkyOctopus的原型系统，并进行了全面的实验，以证明其在降低端到端时延方面的有效性以及在会话建立时间上的高效性

本文的其余部分结构如下。第二节介绍问题的背景与我们的动机。第三节概述所提出的SkyOctopus架构。第四节详细阐述SkyOctopus的三个方面。我们在第五节中进行了大量的实验并分析了结果。第六节回顾了该领域的相关工作。第七节讨论了与我们工作相关的额外考量和问题。最后，第八节简要总结了本项工作。