Description
NR E-UTRA Dual Connectivity (NE-DC) is a specific dual connectivity (DC) architecture standardized by 3GPP, defined under the umbrella of MR-DC (Multi-RAT Dual Connectivity). In NE-DC, the user equipment (UE) is configured with two distinct cell groups: a Master Cell Group (MCG) and a Secondary Cell Group (SCG). The MCG is provided by a master node (MN) operating the 5G New Radio (NR) radio access technology. The SCG is provided by a secondary node (SN) operating the 4G Evolved Universal Terrestrial Radio Access (E-UTRA or LTE) technology. The master node terminates the control plane connection to the core network, which in this architecture is the 5G Core (5GC). The MN is responsible for the initial access, connection establishment, and mobility management. The secondary node provides additional radio resources for the user plane, enhancing throughput. The UE maintains a single Radio Resource Control (RRC) connection with the master node (NR), while the secondary node is managed via RRC messages that are transported via the master node. The user plane data can be split and aggregated at various points, such as the Packet Data Convergence Protocol (PDCP) layer in the master node (for MCG split bearer) or in the secondary node (for SCG split bearer). This requires tight inter-node coordination via the Xn interface (between gNB and eNB) to manage radio resources, handovers, and bearer management. NE-DC is a foundational element for non-standalone (NSA) 5G deployment option 3, where the 5G NR layer is anchored by the 5GC but leverages existing LTE infrastructure for coverage and capacity.
Purpose & Motivation
NE-DC was introduced to facilitate the smooth introduction of 5G NR services by leveraging the extensive, existing deployment of 4G LTE networks. It solves the problem of limited initial 5G NR coverage by allowing a device to use a 5G NR connection as the primary anchor for control and high-speed data, while simultaneously using a robust LTE connection for additional data capacity and to maintain service continuity at the cell edge. This approach allows mobile network operators to launch 5G services more quickly and cost-effectively, as they can utilize their LTE assets as a complementary layer. Historically, dual connectivity concepts were first introduced in LTE-Advanced (LTE-A) with intra-LTE DC (where both cell groups are LTE). NE-DC extends this principle to multi-RAT scenarios, specifically targeting the 5G migration path. It addresses the limitations of a pure standalone 5G rollout, which would require ubiquitous NR coverage from day one to guarantee service, by providing a practical intermediate step that delivers enhanced user experience through aggregated NR and LTE resources.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (243 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the NE-DC (NR E-UTRA Dual Connectivity) function was introduced as a late drop, which included specific support for Single-Operator Case 1. The release also introduced technical corrections and clarifications for NE-DC operation, such as a correction to the s-Measure parameter and the addition of the P-EUTRA capability to support power coordination between the NR and LTE nodes.
- Add requirement to support EN-DC management TS 28.657CR0006
- Introduction of EN-DC into 36.212 TS 36.212CR0279
- Agreements for MR-DC TS 37.340CR0073
- Introduction of late drop NGEN-DC, NE-DC and NR-DC TS 38.331CR0916
- Introduction of SUO Case 1 for NE-DC as Rel-15 late drop TS 36.212CR0312
- Miscellaneous EN-DC related corrections TS 36.331CR3386
+ 72 more changes
In Release 16, the enhancements for NE-DC included the introduction of mobility procedures like inter-RAT handover from NR to EN-DC and support for Conditional Handover, alongside new measurement capabilities per QoS level (mapped 5QI or QCI) and per S-NSSAI. The release also standardized mandatory full-rate user plane integrity protection for MR-DC and introduced a UE Radio Capability Mapping procedure specific to EN-DC.
- Add measurements related to Secondary Node Addition for E-UTRA-NR Dual Connectivity TS 32.425CR0184
- Support of inter-RAT handover from NR to EN-DC in TS 36.331 TS 36.331CR4232
- Introduce of alternative cell reselection priority for EN-DC TS 36.331CR4229
- Stage2 Introduction of ARPI&SPID for EN-DC TS 37.340CR0173
- Stage 2 CR for Inter-RAT HO between NR to EN-DC in Rel-16 TS 37.340CR0185
- Correction of TS 37.340 on the support of MR-DC for IAB TS 37.340CR0186
+ 62 more changes
In Release 17, the enhancements for NE-DC (NR E-UTRA Dual Connectivity) primarily involved further multi-RAT dual-connectivity improvements and specific capability updates. These included support for higher uplink power limits in inter-band EN-DC, the addition of new EN-DC band combinations within FR1 and including FR2, and updated UE radio frequency implementation capabilities. Furthermore, the release introduced overheating assistance information for operation in the FR2-2 frequency range for (NG)EN-DC scenarios.
- Introduction of further multi-RAT dual-connectivity enhancements TS 36.331CR4774
- Introduction of further multi-RAT dual-connectivity enhancements TS 37.340CR0309
- Introduction of further multi-RAT dual-connectivity enhancements TS 38.331CR2954
- Overheating assistance info for FR2-2 in (NG)EN-DC - RIL E801 TS 36.331CR4820
- Corrections for further MR-DC enhancements TS 36.331CR4867
- Corrections to UE History Information in MR-DC TS 37.340CR0332
+ 50 more changes
In Release 18, the enhancements for NE-DC (NR E-UTRA Dual Connectivity) included the introduction of new DRB and performance measurements, which are optionally calculated per QoS level using mapped 5QI or QCI. The release also added signaling support and new UE capabilities for intra-band non-collocated and intra-band channel spacing configurations, alongside the addition of several new EN-DC combination entries to the supported configuration tables and RF baseline capabilities.
- Adding new DRB measurements in case of Dual Connectivity TS 28.552CR0437
- New performance measurements for NR-NR Dual Connectivity TS 28.552CR0524
- Lower MSD capability for EN-DC TS 36.331CR4991
- Introduction of R18 positioning to MR-DC TS 37.340CR0371
- Signaling support for intra-band non-collocated NR-CA, EN-DC TS 38.331CR4396
- Introduction of new capability for intra-band EN-DC channel spacing [Intra-Band_EN-DC_Channelspacing] TS 38.331CR5013
+ 23 more changes
In Release 19, the NE-DC (EN-DC) function was enhanced with new UE capability signaling for both Release 15 and Release 16 EN-DC combinations within FR1, including specific additions for band n71 configurations. The release also introduced new RF baseline implementation capabilities for Power Class 2 (PC2) EN-DC combos from both Release 18 and new Phase 2 deployments, alongside updates to performance measurement specifications where metrics are now optionally calculated per QoS level, mapped to either 5QI or QCI specifically for EN-DC.
- Introduction of signaling support for intra-band non-collocated EN-DC/NR-CA deployment Phase 2: new receiver type(s) TS 38.331CR5479
- Rel-19 CR TS 28.552 update the use of EN-DC TS 28.552CR0633
- Addition of UE capability for R16 EN-DC combos within FR1 TS 38.508CR0832
- Addition of UE capability for R15 EN-DC combos within FR1 TS 38.508CR0833
- Addition of RF baseline implementation capabilities for new PC2 EN-DC combos within FR1 TS 38.508CR0847
- Addition of physical capabilities for Rel-16 n71 related EN-DC configurations TS 38.508CR0853
+ 6 more changes
Explore further
Broader topics and technologies where NE-DC plays a role.
Defining Specifications
3GPP specifications that define or reference NE-DC, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 28.552 vk10 | 5G Performance Management Measurements | Rel-20 |
| TS 28.657 vj00 | E-UTRAN NRM IRP Requirements | Rel-19 |
| TS 32.425 vj00 | E-UTRAN Performance Measurements | Rel-19 |
| TS 36.212 vj10 | LTE Multiplexing and Channel Coding | Rel-19 |
| TS 36.331 vj00 | LTE RRC Protocol Specification | Rel-19 |
| TS 37.340 vj00 | Multi-Connectivity Operation Overview | Rel-19 |
| TS 37.473 vj00 | W1 Application Protocol (W1AP) Specification | Rel-19 |
| TS 37.571 vj00 | UE Conformance for Positioning | Rel-19 |
| TS 37.717 | 3GPP TR 37.717 | Rel-15 |
| TS 37.718 | 3GPP TR 37.718 | Rel-15 |
| TS 37.719 vj00 | 3GPP TR 37.719: Dual Connectivity Band Combinations | Rel-19 |
| TS 38.133 vj20 | 5G UE Radio Requirements for RRC_IDLE Mobility | Rel-19 |
| TS 38.171 vj10 | 5G A-GNSS UE Positioning Requirements | Rel-19 |
| TS 38.213 vj10 | NR Physical Layer Control Procedures | Rel-19 |
| TS 38.331 vj00 | NR Radio Resource Control (RRC) Protocol Specification | Rel-19 |
| TS 38.508 vj11 | 5G NR UE Radio Transmission & Reception | Rel-19 |
| TS 38.521 vj20 | NR Physical Layer UE Conformance Testing | Rel-19 |
| TS 38.523 vj20 | 5G NR UE Conformance Testing: Idle/Inactive | Rel-19 |
| TR 38.846 vi10 | Technical Report | Rel-18 |