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NR Architecture

Gino Masini3GPP RAN WG3 Chairman

Ericsson

RWS-180009

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Acknowledgments

My heartfelt thanks to:

Gao Yin (ZTE) 3GPP RAN WG3 Vice-Chair

Sasha Sirotkin (Intel) 3GPP RAN WG3 Vice-Chair

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TSG RANRadio Access Network

RAN WG1Radio Layer 1 spec

RAN WG2Radio Layer 2 spec

Radio Layer 3 RR spec

RAN WG3lub spec, lur spec, lu spec

UTRAN O&M requirements

RAN WG4Radio Performance

Protocol aspects

RAN WG5Mobile Terminal

Conformance Testing

RAN WG6GSM EDGE

Radio Access Network

TSG SAService & Systems Aspects

SA WG1Services

SA WG2Architecture

SA WG3Security

SA WG4Codec

SA WG5Telecom Management

SA WG6Mission-critical applications

TSG CTCore Network & Terminals

CT WG1MM/CC/SM (lu)

CT WG3Interworking with external

networks

CT WG4MAP/GTP/BCH/SS

CT WG6Smart Card Application Aspects

Project Coordination Group (PCG)

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Summary

What is NG-RAN?

Stand-Alone (SA) and Non-Stand-Alone (NSA)

gNB split architecture

The unified User Plane

gNB CP-UP split architecture

Conclusions

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What is NG-RAN?

The New RAN (Radio Access Network) for 5G

Provides both NR and E-UTRA (“LTE”) radio access

An NG-RAN node is either

gNB – (“5G base station”, providing NR access) or

ng-eNB (“enhanced 4G base station”, providing E-UTRA access)

NG-RAN nodes are connected:

To the 5G core network – NG interface

To one another – Xn interface

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The NG-RAN

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Deployment Options (1)

Both Stand-Alone (SA) and Non-Stand-Alone (NSA) deployments are possible

Maximum flexibility for operators

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Deployment Options (2)

Stand-Alone (SA): gNB connects to the 5G Core Network (5GC)Non-Stand-Alone (NSA): tight interoperation between gNBs and ng-eNBs

Connected to the same core network: eitherEPC, the existing LTE core network (NSA within “4G RAN”) or5GC, the 5G core network (NSA within NG-RAN)

Dual Connectivity (DC) toward the terminalA Master Node (MN) and a Secondary Node (SN) concurrently provide radio resources toward the user, for higher bit rateThe terminal “sees” a Master Cell Group (MCG) and a Secondary Cell Group (SCG)

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Architecture “Options”

Combinations of various alternatives for Master Node (MN), Secondary Node (SN), and core network types

(numbering is for reference only)

Different migration paths are possible according to operator strategy

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Option 3 (“EN-DC”)

eNB as MN, connected to LTE core network

“en-gNB” as SNOnly a subset of 5G radio functionality is needed for this use

MeNB

S-GW

en-gNB

S1

-U

X2-U

S1-U

MeNB

MME

en-gNB

S1

-MM

E

X2-C

Control Plane User Plane

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Option 4 (“NE-DC”)

gNB as MN, connected to 5G core network

ng-eNB as SN

MN

UPF

SN

NG

-U

Xn-U

NG-U

MN

AMF

SN

NG

-C

Xn-C

Control Plane User Plane

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Option 7 (“NGEN-DC”)

ng-eNB as MN, connected to 5G core network

gNB as SN

MN

UPF

SN

NG

-U

Xn-U

NG-U

MN

AMF

SN

NG

-C

Xn-C

Control Plane User Plane

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Other Available Options

Option 2: gNB connected to 5G core network (SA operation)

“NR-NR DC” is supported (gNBs as MN and SN)

Option 5: ng-eNB connected to 5G core network

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Migration Considerations (1)

Migration choice and path depends on:Operator strategy

Business decision on when to deploy the 5G core networkIntroduction of new distinctive 5G features (e.g. slicing)

Availability of new frequencies for NR

Existing network density

Increase of end-user traffic

Availability of terminals with the right feature set / bands

…

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Migration Considerations (2)

If initial NR deployments use higher frequencies (e.g. above 6 GHz):

Smaller coverage on NR than on LTEOpt. 3 uses LTE for coverage and NR for higher capacity in busy areas, leveraging existing investments

When 5G core network is deployed:Opts. 2 (SA) and 4 (NR for coverage, LTE as booster) use NR as basis for coverageOpts. 5 (ng-eNB for coverage) and 7 (ng-eNB for coverage, NR as booster) use LTE as basis for coverage

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gNB Split Architecture

gNB may be split into a central unit (gNB-CU) and one or more distributed units (gNB-DUs)

More deployment flexibility

Better support for e.g. low latency services

One gNB-CU may connect to multiple gNB-DUs

One gNB-DU may support one or more cells

5GC

NG NG

Xn-C

NG-RAN

gNB

gNB-DU gNB-DU

gNB-CU

gNB

F1 F1

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The Unified User Plane

The same user plane protocol is used for:

Xn-U (between NG-RAN nodes connected to 5GC)

X2-U between an eNB and an en-gNB for Option 3

F1-U (between gNB-CU and gNB-DU)

A single user plane instance may run all the way from the gNB-DU to another NG-RAN node

One “hop”, no intermediate terminations

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gNB CP-UP Split Architecture

gNB-CU may be split into its control plane and user plane parts (gNB-CU-CP and gNB-CU-UP)

More deployment flexibility

One gNB-CU-CP may connect to a single gNB-CU-UP

One gNB-DU may support one or more cells

E1

gNB-DU

gNB-CU-CP

F1-C F1-U

gNB

gNB-CU-UP

gNB-DU

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Conclusions

NR tightly interoperates with existing LTE networks

The NG-RAN interfaces and protocols specified by 3GPP facilitate the evolution of 4G to 5G and help the uptake of the 5G core network

Upcoming enhancements address new requirements beyond mobile broadband

e.g. automated driving, industrial automation, e-health services, etc.