URLLC Challenges in NTN: An Analysis of O-RAN Split-Function Architectures

This paper presents a comprehensive analysis of different functional splits (FS) in an Open RAN-based Unmanned Aerial Vehicle (UAV) Non-Terrestrial Networks (NTN) architecture for Ultra-Reliable Low-Latency Communication (URLLC). We systematically analyse and compare the effectiveness of different FSs, focusing on their impact on UAV computational complex- ity and overall network latency and reliability for URLLC users. Through extensive simulations, we assess the trade-offs between computational complexity, front-haul bandwidth requirements, and network reliability for various FS options, with a particular focus on URLLC traffic. Our results demonstrate that FS-7.2x outperforms other configurations, achieving superior latency performance and enhanced reliability by efficiently balancing onboard processing and front-haul bandwidth utilisation. These findings provide critical insights for network designers in optimising O-RAN configurations for UAV-based NTN, ensuring robust and low-latency communication for next-generation wireless applications.