标题： 星链Ku波段下行链路的定时特性 显示英文标题

标题： Timing Properties of the Starlink Ku-Band Downlink

摘要： 我们开发了信号捕获和分析技术，以精确提取和表征星链星座Ku波段下行链路传输的帧定时。 这项工作的目的是确定星链帧定时是否具有足够的短期稳定性，以支持基于伪距的偶然定位、导航和时间（PNT）。 第二个目标是确定帧定时是否受控于统一的时间尺度，如GPS时间。 我们的分析揭示了几种以前未知的定时特性，这些特性对PNT有重要的影响。 有利的一面是，所有卫星版本的帧到达时间中存在纳秒级抖动的时期，这表明星链硬件本质上能够满足支持类似GPS的PNT所需的短期稳定性。 但有几个不利的特性，如果不加以解决，将使类似GPS的PNT变得不切实际：(1) v1.0和v1.5星链卫星每秒出现一次突然的帧定时调整，其幅度（高达数百纳秒）和符号似乎不可预测。 类似的不连续性也存在于v2.0-Mini帧定时中，但幅度较小且间隔不规则。 (2) 偶发的15秒高帧抖动周期经常打断正常的低抖动帧到达时间。 (3) 星链帧定时受控于GPS时间，但仅是松散地：通过每隔15秒进行的调整，误差在几毫秒以内；否则会表现出可能超过20 ppm的漂移。 这些不利的特性基本上与精确的PNT不兼容。 幸运的是，它们似乎是软件设计选择的结果，而不是硬件限制。 此外，可以通过第三方提供的校正来补偿它们。 显示英文摘要

摘要： We develop signal capture and analysis techniques for precisely extracting and characterizing the frame timing of the Starlink constellation's Ku-band downlink transmissions. The aim of this work is to determine whether Starlink frame timing has sufficient short-term stability to support pseudorange-based opportunistic positioning, navigation, and timing (PNT). A second goal is to determine whether frame timing is disciplined to a common time scale such as GPS time. Our analysis reveals several timing characteristics not previously known that carry strong implications for PNT. On the favorable side, periods of ns-level jitter in frame arrival times across all satellite versions indicate that Starlink hardware is fundamentally capable of the short-term stability required to support GPS-like PNT. But there are several unfavorable characteristics that, if not addressed, will make GPS-like PNT impractical: (1) The v1.0 and v1.5 Starlink satellites exhibit once-per-second abrupt frame timing adjustments whose magnitude (as large as 100s of ns) and sign appear unpredictable. Similar discontinuities are also present in the v2.0-Mini frame timing, though smaller and irregularly spaced. (2) Episodic 15-s periods of high frame jitter routinely punctuate the nominal low-jitter frame arrival timing. (3) Starlink frame timing is disciplined to GPS time, but only loosely: to within a few ms by adjustments occurring every 15 s; otherwise exhibiting drift that can exceed 20 ppm. These unfavorable characteristics are essentially incompatible with accurate PNT. Fortunately, they appear to be a consequence of software design choices, not hardware limitations. Moreover, they could be compensated with third-party-provided corrections.