基于SSB的NR非地面网络中低轨卫星定位的可达精度与克拉美罗界
Achievable Accuracy and Cramer Rao Bounds for SSB Based LEO Positioning in NR NTN
AI总结：
该研究针对NR NTN中SSB辅助的LEO定位，推导了延迟与多普勒的CRLB，提出物理加权最小二乘估计器，仿真及星链星座分析验证其可达亚米级定位精度。
AI中文摘要：
先进低轨（LEO）卫星网络，如星链移动卫星服务（MSS），将采用5G新无线电（NR）非地面网络（NTN）标准，这使得基于伪距和多普勒测量的机会性接收机定位可利用无处不在的同步信号块（SSB）。本研究通过推导与伪距和多普勒相关的延迟及载波频率观测量的单SSB克拉美罗下界（CRLB），表征基于SSB定位的估计理论极限；这些下界利用完整的SSB时频能量分布获得，并扩展为多历元、多卫星费舍尔信息框架，该框架联合约束固定用户位置、时钟偏差及时钟漂移。每个SSB的贡献根据接收信噪比确定的依赖距离的CRLB加权，因此估计器与下界共享共同噪声模型。仿真中，所得下界与可达性能紧密匹配，且物理加权最小二乘估计器在实际工作信噪比下接近CRLB；利用基于星链的星座，分析地面用户经历的工作信噪比，证明亚米级定位精度。
英文摘要：
Advanced Low Earth Orbit (LEO) satellite networks, such as Starlinks Mobile Satellite Service (MSS), will adopt the 5G New Radio (NR) Non-Terrestrial Network (NTN) standard. This enables the use of ubiquitous Synchronization Signal Blocks (SSBs) for opportunistic receiver positioning based on pseudorange and Doppler measurements. In this work, we characterize the estimation theoretic limits of SSB-based positioning by deriving single SSB Cramer Rao lower bounds (CRLBs) for delay and carrier frequency observables associated with pseudorange and Doppler. These bounds are obtained using the full SSB time-frequency energy distribution and extended into a multi epoch, multi satellite Fisher information framework that jointly bounds stationary user position, clock bias, and clock drift. Each SSB contribution is weighted according to a range dependent CRLB determined by the received SNR, so the estimator and the bound share a common noise model. In simulation, the resulting bound closely matches achievable performance, and a physically weighted least squares estimator approaches the CRLB at realistic operating SNR. Using a Starlink based constellation, we analyze the operating SNR experienced by a ground user and demonstrate sub-meter positioning accuracy.
