Terrestrial 5G and Starlink NTN Multi-Connectivity Toward 6G Communications Integration Era: An Empirical Assessment

5G networks have become the leading cellular connectivity standard with significant market penetration and widespread mobile infrastructure deployment. However, connectivity can degrade at cell edges even under optimal deployment conditions and high infrastructure density. This is not admissible in critical mobile applications with high-reliability requirements, e.g., autonomous driving. Integration of terrestrial 5G networks with satellite networks, referred to as multi-connectivity, emerges as an opportunity to improve performance and Key Performance Indicators (KPIs) in vehicular connectivity conditions. Therefore, this paper evaluates, empirically, cellular and satellite connectivity in high-mobility scenarios over 5G and Starlink networks, jointly considering latency and throughput KPIs impacting user experience at the network layer and signal quality at the physical layer. The empirical assessment demonstrates the benefit in terms of performance when applying multi-connectivity techniques, highlighting the strong correlation between signal quality and user equipment location within the terrestrial cell. These findings pave the way for selective packet duplication by predicting when and how multi-connectivity strategies should be employed, thus resulting in several packet duplication strategies.