The evolution of 6th generation (6G) networks increasingly relies on satellite-based Non-Terrestrial Networks (NTNs) to extend broadband connectivity to remote and unserved regions, and to support public safety. In this paper we compare two representative and conceptually different satellite constellation architectures, namely Starlink and IRIS 2. Starlink is a commercial private Internet constellation by SpaceX, based on dense Low Earth Orbit (LEO) satellites. It is primarily designed to deliver high-capacity broadband services for civil applications, with performance targets comparable to those of terrestrial networks. In contrast, IRIS 2 is a planned public initiative to be deployed by the European Union, based on a multi-layer combination of LEO, Medium Earth Orbit (MEO), and Geo-stationary Earth Orbit (GEO) satellites. It is primarily designed to provide a secure, resilient, and sovereign infrastructure for government and critical communications. After describing the main technical characteristics of Starlink and IRIS 2, we run a comprehensive simulation campaign to evaluate the design tradeoffs between the two. Specifically, we evaluate the per-cell and per-user achievable capacity, the impact of satellite mobility and handover, and identify the capability of each architecture to support global and reliable connectivity. We also provide design suggestions for possible future IRIS 2 deployment extensions.

翻译：第六代（6G）网络的发展日益依赖于基于卫星的非地面网络（NTNs），以将宽带连接延伸至偏远和未服务区域，并支持公共安全。本文对比分析了两种具有代表性且架构理念迥异的卫星星座系统——星链（Starlink）与IRIS 2。星链是SpaceX公司运营的商业化私有互联网星座，采用密集的低地球轨道（LEO）卫星部署。该系统主要面向民用领域提供大容量宽带服务，其性能指标可与地面网络相媲美。相比之下，IRIS 2是欧盟规划建设的公共卫星基础设施，采用低地球轨道（LEO）、中地球轨道（MEO）与地球静止轨道（GEO）卫星的多层混合架构。该系统核心目标是为政府及关键通信构建安全、弹性且自主可控的基础设施。在阐述星链与IRIS 2主要技术特征后，我们开展了系统性仿真实验，评估两种架构的设计权衡。具体而言，我们量化分析了单小区与单用户可达容量、卫星移动性与切换带来的影响，并识别了各架构支持全球可靠连接的能力。最后，我们针对IRIS 2未来可能的扩展部署提出了设计建议。