What is en-gNB?
An en-gNB (E-UTRA-NR gNB) is a 5G NR base station node that provides NR user plane and control plane protocol terminations towards the UE while acting as the secondary node (SN) in an EN-DC (E-UTRA–NR Dual Connectivity) configuration. In EN-DC (the most widely deployed initial 5G configuration), the 4G eNB serves as the master node connected to the EPC, while the en-gNB provides the 5G NR radio capacity as a secondary node — giving users access to 5G speeds while the network anchor remains on 4G.
How Does en-gNB Work?
In EN-DC architecture (3GPP Option 3/3a/3x), the en-gNB connects to the eNB master node via the X2 interface for control and data exchange. User plane data can flow from the EPC’s S-GW either directly to the en-gNB (option 3a) or through the master eNB (option 3). The en-gNB handles NR air interface procedures — beamforming, HARQ, scheduling — for the UE’s secondary cell group (SCG). The en-gNB does not connect directly to the EPC or 5GC; all core network signalling goes through the master eNB. The UE aggregates data from both LTE and NR radio links simultaneously, achieving combined throughput.
Use Cases
5G NSA initial deployments (the most common 5G deployment worldwide in 2019–2024), capacity augmentation using NR spectrum while leveraging existing 4G core, rapid 5G launch without full 5GC deployment, and enhanced mobile broadband (eMBB) throughput through LTE+NR carrier aggregation.
3GPP / Standards Reference
3GPP TS 37.340 (Multi-connectivity — NR and E-UTRA), 3GPP TS 38.401 (NG-RAN architecture description)
Related Terms
Learn More
This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
