Researchers from the Aerospace Information Research Institute, Chinese Academy of Sciences, have pioneered a combined pseudo-range and Doppler positioning method that leverages signals from constellations like Starlink and Iridium NEXT, without relying on conventional navigation signal designs. The study was published in Satellite Navigation.
Positioning scenario and signal acquisition of Iridium NEXT satellites’ signal in the long baseline positioning scenario. Image Credit: Satellite Navigation.
A groundbreaking navigation technique utilizing opportunistic signals from Low Earth Orbit (LEO) satellites is expanding the boundaries of satellite-based positioning. The team achieved impressive accuracy by employing inexpensive, wide-beam antennas and a specifically engineered time-frequency inversion algorithm: 3.6 m in 2D and 6.2 m in 3D, outperforming Starlink-based positioning methods using parabolic antennas by 35%.
Traditional Global Navigation Satellite Systems (GNSS), such as GPS, often face challenges in urban canyons or under dense foliage due to signal blockage and reflections that degrade accuracy. The researchers are exploring Signals of Opportunity (SOP)—ambient radio emissions not originally intended for navigation, including those from LEO satellites. Among these, Starlink is notable for its extensive coverage and global reach.
However, technical hurdles persist, including unknown signal transmission times, weak signal strength, and imprecise orbital data, all of which hinder accurate positioning. Overcoming these challenges necessitates a novel approach to extract usable navigation information from LEO constellations.
Researchers introduced a joint pseudo-range and Doppler positioning technique using wide-beam antennas to receive LEO satellite SOPs. The core of this method is a signal time-frequency inversion algorithm that reconstructs crucial signal parameters, along with a new accuracy metric called Equivalent Position Dilution of Precision (EPDOP). Real-world experiments combining Starlink Doppler data and Iridium NEXT pseudo-range signals demonstrated strong performance, particularly in long-baseline scenarios, highlighting the method’s global applicability.
To reduce the cost and complexity of existing satellite tracking equipment, the team used low-cost, Low-Noise Block (LNB) wide-beam antennas capable of simultaneously receiving signals from multiple Starlink satellites. The key innovation lies in a signal processing algorithm that estimates transmission time and frequency from the received code phase and Doppler shifts, enabling both pseudo-range and Doppler measurements without requiring precise satellite clock data or real-time ephemeris. To assess the system's performance under real-world errors, the researchers developed the EPDOP metric, tailored for mixed measurement inputs.
Tests showed the method's robustness, achieving 3.6 m 2D and 6.2 m 3D positioning accuracy using Starlink Doppler signals, and up to 24 m (2D) and 41 m (3D) accuracy using Iridium NEXT SOPs over a 40 km baseline. Compared to standalone Doppler positioning techniques, the algorithm reduced positioning errors by over a third and effectively mitigated the impact of orbital inaccuracies present in publicly available Two-Line Element set (TLE) datasets.
This work marks a key step toward accessible, accurate navigation using commercial satellite constellations. By integrating Doppler and pseudo-range measurements and introducing a flexible precision metric, we can now harness Starlink and Iridium NEXT signals for high-precision positioning, even without access to proprietary signal structures. The proposed low-cost architecture opens new possibilities for resilient navigation in GPS-denied environments.
Dr. Ying Xu, Study Lead Author, Aerospace Information Research Institute, Chinese Academy of Sciences
This technique has the potential to support a wide array of applications, ranging from autonomous driving and Unmanned Aerial Vehicle (UAV) navigation in remote areas to emergency response and IoT asset tracking due to its ability to function with low-cost antennas and weak, unstructured signals.
Its resilience to satellite orbital prediction errors and adaptability across different LEO constellations make it a strong contender for next-generation positioning systems. As LEO deployments continue to expand globally, this approach offers a scalable and practical solution for real-time, high-accuracy navigation, promising enhanced capabilities for both civilian infrastructure and defense operations.
Journal Reference:
Xu, Y., et al. (2025) Joint pseudo-range and Doppler positioning method with LEO Satellites‘ signals of opportunity. Satellite Navigation. doi.org/10.1186/s43020-025-00163-y