An Integrated LEO Communication and PNT System for Beyond 5G NTN

This paper proposes a pragmatic approach to integrate communication (COM) and positioning navigation timing (PNT) services in (beyond) 5G ((B)5G) low Earth orbiting (LEO) satellite nonterrestrial networks (NTN). The goal is to optimize performance and minimize complementary PNT service costs. The current third generation partnership program (3GPP) fifth generation (5G) standard incorporates positioning reference signal (PRS) for enhancing user equipment (UE) positioning accuracy. However, this approach relies on network connectivity and is not suitable for UE standalone PNT service provision. Additionally, PRS exploitation in a NTN satellite constellation shows major issues on top of its know limitations in terrestrial networks (TNs). To address these limitations, we propose a solution inspired by the Chinese multimedia digital broadcasting standard (CMMB) standard, adapted for satellite NTN. This approach involves broadcasting a dedicated direct-sequence spread-spectrum (DS-SS) PNT signal on-top of the primary COM signal. This allows for efficient PNT service provision without compromising the performance of the core COM services. By decoupling PNT and COM services, we can optimize the satellite payload design providing wide area coverage for the PNT signal with reduced interference on the COM narrow beams, thus optimizing overall system performance. The proposed solution offers a promising and cost effective approach to enable accurate and reliable PNT services in satellite NTN, even in challenging environments with limited network connectivity.