Abstract :
[en] Global Navigation Satellite Systems (GNSS) have long served as the backbone of positioning services. However, GNSS signals are highly susceptible to interference, spoofing, and blockage, which poses significant challenges for applications that require robust and reliable positioning. Recent advances in fifth-generation (5G) wireless technologies, New Radio (NR), have opened promising pathways to deliver integrated communication and positioning services. Using the existing 5G framework to embed positioning functionalities can potentially mitigate the vulnerabilities inherent in GNSS, facilitating GNSS-independent positioning solutions.
One of the challenges in a position, navigation and timing (PNT) system is the management of the interference from several transmissions; to address the inherent challenge of interference management in dense satellite constellations, this thesis first develops a comprehensive statistical interference model tailored explicitly for non-terrestrial networks (NTN) scenarios involving multiple satellites. Through Monte Carlo simulations, realistic satellite deployments resembling commercial low-earth orbit (LEO) constellations are assessed, resulting in the formulation of a Generalised Extreme Value (GEV) distribution model for interference. This statistical characterisation reveals the interference bounds crucial for an accurate link budget analysis.
Building upon these insights, two novel payload architectures for joint communication and positioning (JCAP) in 5G-NTN are proposed and evaluated: a shared beam architecture, integrating direct-sequence spread spectrum (DSSS) for navigation signals with cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM) for data, and an independent beam architecture, employing separate beams for navigation and communication services. A trade-off analysis between positioning accuracy and spectral efficiency is conducted, quantifying performance analytically via a Pareto frontier. The simulation results demonstrate that precise, metre-level positioning can be maintained consistently while minimising the impact on the loss of data throughput.
The research then introduces an advanced hybrid receiver design explicitly tailored for the integrated DSSS and OFDM signals. Utilising an extended Kalman filter (EKF), the receiver effectively estimates the Doppler shifts, providing resilient observables even in the presence of strong interference. The performance evaluations demonstrate that the proposed receiver structure maintains robust tracking capabilities under challenging signal-to-interference conditions, significantly improving overall system reliability and service continuity.
The comprehensive simulation results validate the viability and practical benefits of integrating the communication and positioning functionalities within 5G-NTN. These findings highlight that existing satellite deployments, supplemented with minimal modifications, can deliver reliable positioning services without relying on external GNSS infrastructures. This approach not only preserves backward compatibility with conventional 5G NTN terminals, but also establishes a solid foundation for the future convergence of communication, positioning, and sensing capabilities envisioned for sixth-generation (6G) wireless networks. Ultimately, this work significantly advances the feasibility of navigation services in NTN deployments without external GNSS support, paving the way for resilient and integrated next-generation wireless services.
