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arXiv · 2608.10270

Achievable Accuracy and Cramer Rao Bounds for SSB Based LEO Positioning in NR NTN

Rainer Bachl·Tingting Lei·Muhammad Nabeel
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Abstract

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.

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Rainer Bachl, Tingting Lei, Muhammad Nabeel. 2026-08-10. Achievable Accuracy and Cramer Rao Bounds for SSB Based LEO Positioning in NR NTN. https://arxiv.org/abs/2608.10270

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