Title: Direct-to-Cell: A First Look into Starlink's Direct Satellite-to-Device Radio Access Network through Crowdsourced Measurements Show Chinese title

Title: 直连手机：通过众包测量初步了解星链的卫星到设备无线接入网络

Abstract: Low Earth Orbit (LEO) satellite mega-constellations have recently emerged as a viable access solution for broadband services in underserved areas. In 2024, Direct Satellite-to-Device (DS2D) communications, which enable unmodified smartphones to connect directly to spaceborne base stations, entered large-scale beta testing, with Starlink globally leading deployments. This paper presents the first measurement study of commercial DS2D services. Using crowdsourced mobile network data collected in the U.S. between October 2024 and April 2025, our research derives evidence-based insights into the capabilities, limitations, and prospective evolution of DS2D technologies providing Supplemental Coverage from Space (SCS) services to expand existing mobile network connectivity. We observe a strong correlation between the number of satellites deployed and the expanding extension of observed measurements, concentrated in accessible but poorly covered areas by terrestrial networks, such as national parks and large low-density counties. The data reveal stable physical-layer value measurement throughout the observation period, with a lower median RSRP (24-dB difference) and a higher RSRQ (3 dB difference) compared to terrestrial networks, reflecting the SMS-only usage of the DS2D network during this period. Based on SINR measurements, we estimate the expected performance of the announced DS2D mobile data service to be around 4 Mbps per beam in outdoor conditions. We also discuss strategies to expand this capacity up to 24 Mbps in the future, depending on key regulatory decisions regarding satellite licenses, spectrum availability, and allowable radiated power levels. Show Chinese abstract

Abstract: 低地球轨道（LEO）卫星 mega 星座最近成为欠发达地区宽带服务的一种可行接入方案。 到 2024 年， 直接卫星到设备（DS2D）通信技术允许未经修改的智能手机直接连接到天基基站，并进入了大规模测试阶段，其中星链在全球部署方面处于领先地位。 本文首次研究了商业 DS2D 服务的测量情况。 利用 2024 年 10 月至 2025 年 4 月在美国收集的众包移动网络数据，我们的研究基于证据得出了关于提供从太空补充覆盖（SCS）服务的 DS2D 技术的能力、限制和潜在演进的洞见。 我们观察到部署的卫星数量与观测测量值扩展之间存在很强的相关性，这些测量值集中在地面网络可访问但覆盖较差的区域，例如国家公园和人口稀疏的大县。 数据显示在整个观测期间物理层值测量稳定，与地面网络相比，接收信号参考功率（RSRP）中位数较低（相差 24 分贝），接收信号质量（RSRQ）较高（相差 3 分贝），这反映了此期间 DS2D 网络仅用于短信服务。 根据信噪比（SINR）测量结果，我们估计宣布的 DS2D 移动数据服务在户外条件下的预期性能约为每束波束 4 Mbps。 我们还讨论了未来根据卫星许可证、频谱可用性和允许辐射功率水平等关键监管决策，将容量扩展至 24 Mbps 的策略。