Dual Connectivity in 5G: Understanding NR-DC, EN-DC, NGEN-DC, and NE-DC
Understanding Dual Connectivity in 5G: An Overview of NR-DC, EN-DC, NGEN-DC, and NE-DC
As 5G networks rapidly gain traction, it’s become crucial to ensure smooth mobility and maintain backward compatibility with 4G LTE. One of the key features making this possible is Dual Connectivity (DC).
Dual Connectivity lets a mobile device (UE – User Equipment) connect to two base stations at once: a Master Node (MN) and a Secondary Node (SN). This setup offers:
Increased data throughput.
Better load management.
Seamless transitions between 4G and 5G.
A gradual shift from LTE EPC to 5G Core (5GC).
The diagram uploaded highlights the main Dual Connectivity Options available in 5G:
NR-DC (New Radio Dual Connectivity)
EN-DC (E-UTRA-NR Dual Connectivity)
NGEN-DC (NG-RAN-E-UTRA-NR Dual Connectivity)
NE-DC (RAN-E-UTRA Dual Connectivity)
Let’s take a closer look at each option and see how they facilitate effective 5G rollouts.
What is Dual Connectivity in 5G?
Dual Connectivity first appeared in 3GPP Release 12 for LTE networks and was later adapted for 5G NR (New Radio).
The Master Node (MN) is in charge of control signaling and handling the UE’s connection to the core network.
The Secondary Node (SN) adds to the connection by supplying extra radio resources.
This dual-node configuration significantly enhances the user experience by leveraging the capacity of multiple networks.
The Four Dual Connectivity Options
Here’s a quick summary of the four DC options:
Name Abbreviation Master Node Secondary Node Core Network New Radio Dual ConnectivityNR-DCgNBgNB5GCE-UTRA-NR Dual Connectivity EN-DC eNBen-gNBEP CNG-RAN-E-UTRA-NR Dual ConnectivityNGEN-DCng-eNBgNB5GCRAN-E-UTRA Dual ConnectivityNE-DCgNBng-eNB5GC
- NR-DC (New Radio Dual Connectivity)
Master: gNB (Next-generation Node B – 5G base station)
Secondary: gNB
Core: 5GC (5G Core)
Key Features
It’s a pure 5G dual connectivity option.
Both the master and secondary nodes are gNBs, meaning devices connect solely to 5G radios.
It relies completely on the 5G Core network for both signaling and data.
Use Case
Perfect for Standalone (SA) 5G deployments where LTE isn’t needed.
Provides ultra-low latency and maximizes 5G capacity.
- EN-DC (E-UTRA-NR Dual Connectivity)
Master: eNB (LTE base station)
Secondary: en-gNB (5G-enabled gNB connected to EPC)
Core: EPC (Evolved Packet Core – LTE core)
Key Features
Here, the LTE eNB acts as the Master Node.
The 5G gNB (en-gNB) functions as the Secondary Node but links back to the EPC, not to the 5GC.
Control traffic is anchored in LTE, while 5G NR boosts user plane data capacity.
Use Case
Commonly used in Non-Standalone (NSA) 5G deployments where LTE anchors signaling, and 5G enhances data throughput.
Helps operators quickly launch 5G without the full transition to 5GC.
- NGEN-DC (NG-RAN-E-UTRA-NR Dual Connectivity)
Master: ng-eNB (Next-generation eNB connected to 5GC)
Secondary: gNB
Core: 5GC
Key Features
The ng-eNB (evolved LTE node) directly connects to the 5G Core (5GC).
The secondary gNB supplements NR connectivity.
It’s a hybrid approach that combines LTE and 5G.
Use Case
Best for networks in the process of moving from EPC to 5GC but still needing LTE coverage.
Offers a smoother experience during the shift from 4G to fully-fledged 5G SA.
- NE-DC (RAN-E-UTRA Dual Connectivity)
Master: gNB
Secondary: ng-eNB
Core: 5GC
Key Features
This is the opposite of NGEN-DC: the gNB is the Master Node here.
The LTE (ng-eNB) plays a supporting role as the Secondary Node.
Both connect to the 5G Core.
Use Case
Handy for operators aiming for 5G-first deployments while keeping LTE fallback options for coverage.
Ensures a seamless user experience as LTE continues to coexist with 5GC.
Comparing the Dual Connectivity Options
Option Master Node Secondary Node Core Deployment ScenarioNR-DCgNBgNB5GCPure 5G Standalone (SA)EN-DC eN Ben-gNBE PCNSA 5G with LTE anchorNGEN-DCng-eNBgNB5GCLTE-first with 5GC migrationNE-DCgNBng-eNB5GC5G-first with LTE fallback
Why Dual Connectivity Matters
Dual Connectivity is crucial in the 5G evolution for several reasons:
It allows for a smooth transition from LTE to 5G without disrupting the user experience.
It offers higher data throughput by combining resources from LTE and NR.
Provides flexibility for operators to select their deployment strategies based on existing spectrum and infrastructure.
Ensures reliability and resilience, allowing devices to maintain connections across two nodes.
Real-World Deployment Examples
EN-DC in early rollouts:
Widely used in initial 5G NSA launches by operators like Verizon, AT&T, and Vodafone.
Enabled the use of existing LTE EPC while incorporating NR capacity.
NR-DC in established 5G markets:
Currently rolling out in places like South Korea, Japan, and parts of Europe.
This ensures ultra-low latency for applications requiring real-time responses like autonomous vehicles and industrial automation.
NE-DC and NGEN-DC during transitions:
Often favored by operators modernizing their networks to 5GC while ensuring LTE service continuity.
Strategic Implications for Telecom Operators
Operators with limited 5G spectrum generally start with EN-DC (NSA), leaning on LTE.
As they advance towards 5GC, NGEN-DC and NE-DC are vital for maintaining a balance between LTE legacy and 5G future.
NR-DC epitomizes the ultimate goal: a completely standalone 5G setup without any reliance on LTE.
Future of Dual Connectivity
Looking down the road, Dual Connectivity will eventually transition to pure 5G Standalone architectures as LTE is phased out. Until then, DC will remain key for:
Supporting IoT, AR/VR, and URLLC (Ultra-Reliable Low Latency Communication) applications.
Facilitating enterprise private 5G networks that need both LTE and 5G.
Ensuring a smooth global transition from 4G LTE to 5G NR.
Conclusion
The four Dual Connectivity options (NR-DC, EN-DC, NGEN-DC, and NE-DC) demonstrate how 5G networks are designed to harmonize legacy LTE with next-gen NR capabilities.
EN-DC supports current NSA rollouts.
NGEN-DC and NE-DC provide hybrid pathways during the transition.
NR-DC illustrates the vision for a pure 5G future.
For those in the telecom industry or enthusiasts, grasping these options is crucial for understanding operator strategies, network designs, and the journey toward a seamless 5G era.