ran functional decomposition the options and interfaces… · nodeb iub interface rnc nokia umts...

British Telecommunications plc 2018

RAN Functional Decomposition the options and interfaces…

Andy SuttonPrincipal Network ArchitectArchitecture & StrategyBT Technology 19th November 2018


Contents

• RAN architecture evolution

• RAN functional decomposition

• Access network connectivity

• 5G network deployment

• 5G demo update

• Summary

2


GSM - fully distributed RAN

• GSM BTS is a fully distributed radio base station

• All radio related protocols terminate in the BTS

• Radio interface encryption terminates in the BTS

• Distributed intelligence with centralised BSC

3

BTS Abis interface BSC

Nokia GSM Ultrasite BTS

Core network

NOTE: IP Sec GW used between BTS and BSC with IP Abis implementation


UMTS - many centralised functions

• UMTS is a simple L2 radio base station (known as Node B)

• All radio related protocols terminate in the RNC

• Radio interface encryption terminates in the RNC

• Distributed radio with centralised intelligence

4

NodeB Iub interface RNC

Nokia UMTS Ultrasite BTS

Core network


LTE - distribution wins again…

• LTE eNB is a fully distributed radio base station

• All radio related protocols terminate in the eNB

• Radio interface encryption terminates in the eNB

• X2 interface between adjacent eNBs, no centralised network controller

5

eNB S1 interface EPC

Huawei 3900 eNB (+GSM BTS)

eNB S1 interface SecGW Core network

2600MHz RRU


LTE - RAN options

• LTE eNB is a fully distributed radio base station

• However, this radio (eNB) is made up of two components which can be

geographically separated

• RRU/RRH and BBU - separated by CPRI interface

6

RRU CPRI BBU

Huawei 3900 eNB (+GSM BTS)

RRU CPRI BBU S1 interface

2600MHz RRU

S1 interface


Base station architecture - LTE

7

RRU BBU

RRU

S1 interface

BBU S1 interface

RRU BBU S1 interface

CPRI

CPRI

D-RAN with cabinet RFU

D-RAN with external RRU

C-RAN with centralised BBU

Note: a site may support

one or more base station

architectures for different

radio channels/bands


RAN functional splits - protocol architecture

8

RRC

PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

RRC

PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

Option1

Option2

Option3

Option4

Option5

Option6

Option7

Option8

Relaxed Very lowEnd to end latency

Traffic/capacity related Very highCapacity requirement

Higher layer splits Lower layer splits

S1

CPRI

Reference 3GPP TR 38.801


RAN functional decomposition

9

gNB

RU* DU CU

* RU could be integrated within AAU (mMIMO) or standalone RU (RRU/RRH) with coaxial connections to passive antenna (typically 8T8R)

CPRI

eCPRI

F1

interface

S1 interface (EPC+)

N2/N3 interfaces (NGC)

NR (air)interface


RAN functional decomposition - E1 interface

10

gNB

RU* DU

CU-c

* RU could be integrated within AAU (mMIMO) or standalone RU (RRU/RRH) with coaxial connections to passive antenna (typically 8T8R)

CPRI

eCPRI

F1-cNR (air)

interface

CU-uF1-u

N2

N3

E1

Additional work is on-going on:

• DU-CU split for LTE (W1

interface)

• E2 interface between CU and

RAN Intelligent Controller (RIC)

• A1/O1 interface between RIC

and NMS & Orchestration layer


Base station architecture - 5G - EN-DC (Option 3x)

11

RU CU

RU

S1 interface

DU

RU DU

D-RAN with AAU/RRU

C-RAN with option 2 split

C-RAN with option 7/8 split

and further CU centralisation

DUCPRI

eCPRI

CU S1 interfaceF1CPRI

eCPRI

CU S1 interfaceF1CPRI

eCPRI





Note: In full C-RAN configuration the DU and CU may be co-located or on separate sites



12

RRC

SDAP/PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

RRC

SDAP/PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

Option1

Option2

Option3

Option4

Option5

Option6

Option7

Option8




S1

CPRIeCPRIF1

Reference 3GPP TR 38.801

Note:Service Data Adaptation Protocol (SDAP), has been introduced to the NR userplane to handle flow-based Quality of Service (QoS) framework in RAN, such asmapping between QoS flow and a data radio bearer, and QoS flow ID marking.


Base station architecture - 5G - Next Generation Core (NGC)

13

RU CU

RU

N2/N3 interface

DU

RU DU

D-RAN with AAU/RRU

C-RAN with option 2 split

C-RAN with option 7/8 split

and further CU centralisation

DUCPRI

eCPRI

CU N2/N3 interfaceF1CPRI

eCPRI

CU N2/N3 interfaceF1CPRI

eCPRI





Note: In full C-RAN configuration the DU and CU may be co-located or on separate sites (as illustrated)



14

RRC

SDAP/PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

RRC

SDAP/PDCP

Data

Low-RLC

High-MAC

High-PHY

Low-MAC

Low-PHY RF

High-RLC

Option1

Option2

Option3

Option4

Option5

Option6

Option7

Option8




N2-N3

CPRIeCPRIF1


RAN access network connectivity

15

RU DU CUS1 or N2/

N3 interface

F1CPRI

eCPRI

Terms; Fronthaul, mid-haul and backhaul as defined by MEF (Metro Ethernet Forum)

Fronthaul Mid-haul Backhaul

Backhaul (in common use)

CPRI, eCPRI orNon-ideal fronthaul


5G within a multi-RAT network deployment - DRAN scenario

16

3G

4G1

5G

CSGOSA-FC

OSA-FC

21CMSE

DWDM

DWDM

21CMSE

Mobile core

networks2

21C IP/MPLS network (P routers not illustrated)

Openreach Point to point DWDM solution

Future-proofed for network sharing and RAN evolution

n x λ(can bypass

CSG)

1 - 2G is supported on the same base station as 4G (SRAN/Multi-RAT)2 - Includes RNC for 3G and IP Sec GW for 4G and 5G

PRTC sync source



17

3G

4G1

5G

CSGOSA-FC

OSA-FC

21CMSE

DWDM

DWDM

21CMSE

Mobile core

networks2



n x λ(can bypass

CSG)


PRTC sync source

E-Band



18

3G

4G1

5G

CSGOSA-FC

OSA-FC

21CMSE

DWDM

DWDM

21CMSE

Mobile core

networks2



n x λ(can bypass

CSG)


PRTC sync source

E-Band

E-band link(s) could connect directly to a wavelength on OSA-FC product


5G demo at Canary Wharf

19

Highlights• 1.3Gbps to test equipment (30 MHz LTE + 40 MHz NR)• 600Mbps to Huawei 5G CPE (5 MHz LTE + 40 MHz NR)• 4T4R LTE (15 MHz 2100 + 15 MHz 2600) with 64T64R NR


Summary

• The functional decomposition of the RAN is at an advanced stage in standards,

industry fora and implementation (XRAN/ORAN, 3GPP, ONAP)

• Traditional 4G centric CRAN (CPRI based) is popular in Asia due to availability of dark

fibre, this brings radio optimisation benefits through centralised scheduling etc.

• CPRI doesn’t scale for 5G due to amount of spectrum and antennas therefore eCPRI

was developed by the same industry partners who developed CPRI

• Several industry groups are working towards a virtualised RAN to disaggregate the

hardware from software for many functions, also enables innovative new entrants to

market

• Major RAN vendors offer a range of different RAN architectures to meet various

deployment scenarios

• BT is currently rolling out the radio, backhaul and core network infrastructure

necessary to be a leader in 5G and converged networks

20

https://www.ngmn.org/fileadmin/ngmn/content/downloads/Technical/2018/180226_NGMN_RANFSX_D1_V20_Final.pdf

https://www.ngmn.org/fileadmin/ngmn/content/downloads/Technical/2018/180226_NGMN_RANFSX_D1_V20_Final.pdf


Thank YouAny questions?

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ran functional decomposition the options and interfaces… · nodeb iub interface rnc nokia umts...

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