Direct-to-Device Integrated NTN Positioning and Messaging in LEO-PNT

Florin Grec, Riccardo de Gaudenzi, Roberto Prieto Cerdeira, Raul Orus Perez, Pietro Giordano, Miguel Cordero Limon

Peer Reviewed

Abstract:	The future of positioning, navigation, and timing (PNT) services lies in the seamless integration of multiple technologies into a cohesive system-of-systems that enhances PNT resilience, accuracy, and availability. This paper further develops the vision of a low Earth orbit PNT (LEO-PNT) solutions leveraging 5G satellite technology and spectrum to offer alternatives to GNSS in terms of resilience and novel services. The primary objective of this paper is to introduce and assess the feasibility of a potential downlink ranging which can be integrated with a two-way messaging service direct to smartphones. To demonstrate this concept, the European Space Agency (ESA) has launched Celeste In Orbit Demonstrator (IoD) that features a mini constellation aimed at demonstrating the potential of LEO-PNT. The first satellites, currently being integrated and tested, will launch in late 2025, with experimentation phase concluding by late 2027. The messaging capability is primarily intended to support public safety emergencies. Traditionally, emergency communications rely on GNSS for location estimation and terrestrial communication systems for information dissemination, both of which have inherent limitations. GNSS availability is susceptible to jamming and spoofing, while terrestrial networks offer limited coverage and are vulnerable to failure in disaster-stricken areas. This paper describes LEO-PNT new service capabilities for mass-market use cases, together with key system and signal design aspects for enabling an integrated messaging and positioning system with positioning accuracy and bit rate sufficient for emergency services. The paper provides elements in support of the feasibility of an emergency communications and positioning concept leveraging Internet of Things – Non-Terrestrial Networks (IoT-NTN) radio technology defined by 3GPP and S-band Mobile Satellite Services (MSS) spectrum. The proposed standalone User Equipment (UE) positioning exploits the range and possibly Doppler measurements on reference pilot signals in the Narrowband – IoT (NB-IoT) waveform such as the optional Narrowband Positioning Reference Symbols (NPRS) specified by 3GPP in TS 36.211. Preliminary performance evaluations indicate that positioning accuracy can be better than 50 meters are feasible, and compatible with the user needs. By integrating messaging capabilities within the same signal structure, the concept is expected to provide operational flexibility, supporting both coarse accuracy positioning and robust two-way communication in a single wide area beam, and have limited impact on satellite design and cost.
Published in:	Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025) September 8 - 12, 2025 Hilton Baltimore Inner Harbor Baltimore, Maryland
Pages:	3436 - 3449
Cite this article:	Grec, Florin, de Gaudenzi, Riccardo, Cerdeira, Roberto Prieto, Perez, Raul Orus, Giordano, Pietro, Limon, Miguel Cordero, "Direct-to-Device Integrated NTN Positioning and Messaging in LEO-PNT," Proceedings of the 38th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2025), Baltimore, Maryland, September 2025, pp. 3436-3449. https://doi.org/10.33012/2025.20462
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