Analysis of Combining Communication and Navigation Signals for Emerging LEO Constellations

Current trends in the space industry are shifting from Medium Earth Orbit (MEO) to Low Earth Orbit (LEO) constellations due to cost efficient launching capabilities and COTS-based HW-resources. Several LEO systems currently offer a wide range of services, ranging from Broadband connectivity (e.g., Iridium, OneWeb, and Starlink) to the Internet of Things (IoT) applications (e.g., Hiber, Myriota, etc.). With the LEO constellation becoming popular, the scientific community is also exploring ways to maximize the use of LEO constellations in satellite-based positioning. A comprehensive study on all major aspects of LEO-PNT can be found in (Eissfeller et al., 2024). The classic GNSS Systems like GPS (US), GLONASS (Russia), GALILEO (Europe), NAVIC (India), and QZSS (Japan), currently in operation, completely rely on MEO and/or GEO orbits. All public satellite-based navigation systems work from MEO and GEO, with huge signal attenuation due to path loss compared to the LEO. Since the past few years some LEO-PNT systems are already under development, such as the Pulsar system from XONA (XONA, 2023), and public LEO constellations are under development, like the European Union’s IRIS2 (Infrastructure for Resilience, Interconnectivity and Security by Satellite), which foresees secure communication but also PNT services in future (Ries, 2023). When looking at the PNT receiver complexity, a LEO constellation for PNT could be equipped with a navigation payload generating GNSS signals transmitted placed in existing GNSS bands like in L-band and the PNT receivers would in the best case only need to change the digital signal processing and the software part. An analysis for the theoretical possibilities of placing new powerful signals in the L1 band is given in (Sharma et al., 2024). This paper provides a first analysis for incorporating communication and navigation signals into one signal or band for the downlink from a LEO constellation.