The Janus Bifrons and the Matryoshka - polimi.it

Before you startEricsson Internal | 2018-02-21
The Janus Bifrons and the Matryoshka Radio Access Network Architecture for 5G
Gino Masini, MBA Principal Researcher, Standardization 3GPP RAN WG3 Chairman
Ericsson AB – Systems and Technologies Stockholm, Sweden
International Conference on the Design of Reliable Communication Networks Politecnico di Milano, 19-22/ 4/ 2021
Ericsson Internal | 2018-02-21
Summary
—Scenarios and requirements for 5G – challenges for architecture —What is NG-RAN? —Stand-Alone and Non-Stand-Alone —The unified User Plane —Split architecture —NG-RAN architecture and some 5G features
Scenarios for 5G
ULTRA RELIABLE VERY LOW LATENCY
VERY HIGH AVAILABILITY
SMART AGRICULTURE
SMART BUILDING REMOTE HEALTH CARE
Cr it ic a l MTC Ul t r a -r e l ia b l e Lo w -La t e n c y Co m m u n ic a t io n s (URLLC)
SMART METER
Requirements from ITU (IMT-2020) Performance Measure Requirement Peak data rate DL: 20 Gbps
UL: 10 Gbps Peak spectral efficiency DL: 30 bps/ Hz
UL: 15 bps/ Hz Bandwidth 100 MHz Control plane latency 20 ms (10 ms encouraged) User plane latency, 1-way URLLC: 1/ 0.5 ms, eMBB: 4 ms Infrequent small packets 10s / 20byte packet Mobility interruption time 0 ms Mobility Up to 500 km/ h TRP spectral efficiency 3x IMT-A requirement User spectral efficiency at 5% percentile
3x IMT-A requirement
Area traffic capacity 10 Mbps/ m2 [ITU] User experienced datarate 100/ 50 Mbps DL/ UL [ITU] Extreme coverage (3GPP) 140/143 dB loss MaxCL
Performance Measure Requirement Connection density 1,000,000 devices/ km2
Coverage (3GPP) 164 dB coupling loss Battery life (3GPP) 10-15 yr Reliability 1-10-5 in 1 ms NW energy efficiency Inspection (Qualitative) UE Energy efficiency Inspection (Qualitative) Inter -system mobility Yes Bandwidth scalability Yes Spectrum flexibility Yes Support of wide range of services
Yes
Source: ITU-R Rep. M.2410-0
Ultra-lean design
User data
Deployment
Machine-type communication
— Support for enhanced mobile broadband (“more of the same, butbetter and faster”) — Support Ultra-Reliable, Low-Latency Communications (URLLC); — A single architecture to accommodate centralized, distributed, and monolithic deployments
— Supporting the deployment of certain functions in the cloud — Fully separate Control Plane from User Plane of a centralized unit, for maximum deployment flexibility — Cooperation and resource sharing with existing LTE networksthanks to Dual Connectivity(DC) — Accommodate different migration strategiesand “paths” from 4G to 5G — Time pressure to release “world class specifications” while accelerating the release process
— 3 release “drops” (“early”, “regular”, and “late drop”) for the same 3GPP Release (Rel-15)
Source: 3GPP TR 38.801 v. 14.0.0
—Maximum flexibility for operators
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: either EPC, the existing LTE core network (NSA within “4G RAN”) or 5GC, the 5G core network (NSA within NG-RAN)
—Dual Connectivity (DC) toward the terminal —A Master Node (MN) and a Secondary Node (SN) concurrently provide radio
resources toward the user, for higher bit rate —The terminal “sees” a Master Cell Group (MCG) and a Secondary Cell Group
(SCG)
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
EN-DC (“Option 3”)
eNB as MN, connected to LTE core network “en-gNB” as SN
— Only 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
NE-DC (“Option 4”)
gNB as MN, connected to 5G core network ng-eNB as SN
MN
UPF
SN
NGEN-DC (“Option 7”)
ng-eNB as MN, connected to 5G core network gNB as SN
MN
UPF
SN
gNB connected to 5G core network (SA operation, “Option 2”)
— “NR-NR DC” is supported (gNBs as MN and SN) ng-eNB connected to 5G core network (“Option 5”)
Migration Considerations (1)
Migration choice and path depends on: —Operator strategy —Business decision on when to deploy the 5G core network
—Introduction 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 —…
Migration Considerations (2)
If initial NR deployments use higher frequencies (e.g. above 6 GHz): —Smaller coverage on NR than on LTE —Opt. 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 coverage
—Opts. 5 (ng-eNB for coverage) and 7 (ng-eNB for coverage, NR as booster) use LTE as basis for coverage
Rel-15 Standardization Timeline
Early Drop – consisted of Option 3 (EN-DC)
Main Drop – included NR SA with the 5G core (Option 2)
Late Drop – included the remaining DC options (Options 4 and 7, and NR-NR DC)
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
gNB CP-UP Split Architecture
gNB-CU may be further 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
The Unified User Plane
The same User Plane protocol is used across 3 interfaces: —Xn-U (between NG-RAN nodes connected to 5GC) —X2-U between an eNB and an en-gNB, for EN-DC —F1-U (between gNB-CU and gNB-DU)
A single instance all the way from the gNB-DU to another NG-RAN node
—One “hop”, no intermediate terminations
gNB Split and Other RAN Functions (1)
— gNB-CU and gNB-DU become part of the positioning services architecture — gNB-CU exchanges information with
positioning servers in the core network — gNB-DU hosts Transmission and Reception
Points for positioning-related radio signals and measurements
— 5G Multicast/ Broadcast Services (MBS): gNB-CU as coordinator for multicast transmission across several connected gNB-DUs — No need for external coordination entities
gNB Split and Other RAN Functions (2)
— Integrated Access/Backhaul (IAB): 5G as self-backhaul — IAB node includes a gNB-DU and a Mobile Termination (MT) part — IAB node’s gNB-DU connects to the gNB-CU of a “donor” node via F1, carried over the air
interface (Uu)
Influences of Split Architecture on LTE
— Split architecture has been introduced also in LTE — eNB-CU, eNB-DU, W1 interface — Now possible to “carve out” eNB UP functionality; E1 interface reused toward gNB-CU-UP
(same UP node for LTE and NR)
— Challenges: — Some LTE functions (e.g. NB-IoT, MTC, MBMS, V2X) had no counterpart in Rel-15 NR, hence
no support in W1 (backported from F1) — Protocols between LTE network and terminals optimized for “monolithic” node, not modular
Other Types of Splits
— 8 different options had been studied for standardization — Different sets of logical functions for the two nodes and a different logical interface between
them (“different, incompatible sets of matryoshkas ”) — Option 2was selected, and resulted in current architecture
Source: 3GPP TR 38.801 v. 14.0.0
Low-Layer Split
— Additional “low-layer” split options were further studied — Aim: concentrate low PHY functions in an “RU”, assuming an
“ideal” backhaul to carry I/Q data — (“further opening up the inner matryoshka ”)
— Opt6: all PHY functions in DU — Opt7-1: FFT and Cyclic Prefix removal/ addition in DU;
remaining PHY functions in CU — Opt7-2: FFT, Cyclic Prefix removal/ addition, and resource
mapping/ de-mapping in DU; remaining PHY functions in CU — Opt7-3 (DL only):Encoder is in CU; remaining PHY functions
in DU — 3GPP could not converge on a single option; discussion continues
in other industry alliances — Feasibility and performance strongly depend on fronthaul
performance (which in turn is also tied to radio configuration) Source: 3GPP TR 38.816 v. 15.0.0
3G: UTRAN Architecture (Source: 3GPP TS 25.401 v. 16.0.0)
RNS
RNC
RNS
RNC
Iu Iu
— 5G: NG-RAN Architecture — Towards 6G: …?
Conclusions
NR tightly interoperates with existing LTE networks while capable of stand-alone operation NG-RAN interfaces and protocols specified by 3GPP have facilitated the evolution of 4G to 5G and the uptake of services offered by 5G
Additional flexibility, critical to 5G use cases, thanks to “nodes within a node” architecture
Acknowledgments
Gao Yin (ZTE) 3GPP RAN WG3 Vice-Chair Sasha Sirotkin (Intel) 3GPP RAN WG3 Vice-Chair
References
— Lin X., Lee N. (Editors), 5G and Beyond – Fundamentals and Standards, Springer, 2021. — Sirotkin S. (Editor), 5G Radio Access Network Architecture – The Dark Side of 5G, Wiley, 2021. — ITU-R Report M.2410-0 (11/2017), “Minimum Requirements Related to Technical Performance for IMT-2020
Radio Interface(s): https://www.itu.int/dms_pub/itu -r/opb/rep/R -REP-M.2410-2017-PDF-E.pdf
— 3GPP TR 38.801, “Study on new radio access technology: Radio access architecture and interfaces”, v. 14.0.0: https://www.3gpp.org/ftp/Specs/archive/38_series/38.801/38801-e00.zip
— 3GPP TR 38.874, “Study on Integrated Access and Backhaul”, v. 16.0.0: https://www.3gpp.org/ftp/Specs/archive/38_series/38.874/38874-g00.zip
— 3GPP TR 38.816, “Study on Central Unit (CU) – Distributed Unit (DU) lower layer split for NR”, v. 15.0.0: https://www.3gpp.org/ftp/Specs/archive/38_series/38.816/38816-f00.zip
— 3GPP TS 25.401, “UTRAN overall description”, v. 16.0.0: https://www.3gpp.org/ftp/Specs/archive/25_series/25.401/25401-g00.zip
— 3GPP TS 36.300, “E-UTRA and E-UTRAN; overall description; stage 2”, v. 16.5.0: https://www.3gpp.org/ftp/Specs/archive/36_series/36.300/36300-g50.zip
Summary
Requirements from ITU (IMT-2020)
Diapositiva numero 8
The NG-RAN Architecture
EN-DC (“Option 3”)
NE-DC (“Option 4”)
NGEN-DC (“Option 7”)
Influences of Split Architecture on LTE
Other Types of Splits
Conclusions
Acknowledgments
References

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