Evaluation of integrated framework for terrestrial-LEO 5G networks with new radio dual connectivity

Terrestrial–non-terrestrial (TN–NTN) integration can extend 5G coverage, but maintaining high goodput and low delay is challenging when a 28 GHz terrestrial layer is combined with moving LEO satellites. Existing studies mainly address architectures, analytical models, or handover-based operation, leaving the system-level behaviour of NR Dual Connectivity (NR-DC) with moving satellite secondary nodes insufficiently evaluated. This paper evaluates an integrated terrestrial–LEO 5G network using a customised Simu5G framework with NR-primary master cell group (MCG) operation, dynamic satellite secondary cell group (SCG) selection, PDCP split-bearer forwarding with MCG fallback, and a hybrid TN–NTN channel model. The NR-DC configuration is compared with satellite-only and terrestrial-only baselines under identical topology, traffic, and channel settings. Results show that NR-DC improves downlink delivery: CBR goodput increases by 321.29% and 28.95% over the satellite-only and terrestrial-only baselines, respectively, with corresponding delay reductions of 71.16% and 62.75%. TCP downlink goodput also improves, although delay increases because of heterogeneous path effects. In the uplink, NR-DC outperforms satellite-only operation but remains below terrestrial-only performance, indicating that the benefit depends on traffic direction and transport behaviour.