5G network architecture will include new functional blocks and interfaces defined by 3GPP. There are several options for deploying 5G, including standalone and non-standalone modes. When adding 5G to an existing multi-RAT site, backhaul capacity will need to be increased to at least 10Gbps to support 5G capabilities like massive MIMO and wider channel bandwidths. Migration from EPC to the new 5G core (NGCN) will require interworking between the networks during transition.

1. 5G Network Architecture and Design
Andy Sutton, Principal Network Architect - Chief Architect’s Office, TSO
25th January 2017

2. © British Telecommunications plc
Contents
• 5G Network Architecture
– 3GPP logical network architecture
– Functional blocks
– Reference points (interfaces)
– RAN functional split
• Adding 5G to an existing multi-RAT site
– RAT types and base station
configurations
– Scaling mobile backhaul and/or
introducing NGFI
• 5G Architecture Options
– Standalone and non-standalone modes
of operation
– EPC to NGCN migration scenarios and
inter-working
• Summary

3. 5G Network Architecture

4. © British Telecommunications plc
3GPP 5G network architecture
UE RAN UPF DN
AMF SMF PCF
UDM
AF
AUSF
NG1
NG7
NG6
NG5
NG4
NG3
NG2
NG8
NG9 - between UPFs
NG14 - between AMFs
NG10
NG11
NG12
NG13
NG15
NR air i/f
Note: Focus on mobile however Access Network (AN) could be fixed

5. © British Telecommunications plc
Functional blocks within 5G network architecture
1. AUSF = Authentication Server Function
2. UDM = Unified Data Management
3. AMF = Core Access and Mobility Management Function
4. SMF = Session Management Function
5. PCF = Policy Control Function
6. AF = Application Function
7. UE = User Equipment
8. ((R)AN) = (Radio) Access Network
9. UPF = User Plane Function
10. DN = Data Network, e.g. operator services, Internet or 3rd party services

6. © British Telecommunications plc
5G interfaces (reference points)
• NG1: Reference point between the UE and the Access and Mobility Management function.
• NG2: Reference point between the (R)AN and the Access and Mobility Management function.
• NG3: Reference point between the (R)AN and the User plane function (UPF).
• NG4: Reference point between the Session Management function (SMF) and the User plane function (UPF).
• NG5: Reference point between the Policy Function (PCF) and an Application Function (AF).
• NG6: Reference point between the UP function (UPF) and a Data Network (DN).
• NG7: Reference point between the Session Management function (SMF) and the Policy Control function (PCF).
• NG7r: Reference point between the vPCF and the hPCF.
• NG8: Reference point between Unified Data Management and AMF.
• NG9: Reference point between two Core User plane functions (UPFs).
• NG10: Reference point between UDM and SMF.
• NG11: Reference point between Access and Mobility Management function (AMF) and Session Management
function (SMF).
• NG12: Reference point between Access and Mobility Management function (AMF) and Authentication Server
function (AUSF).
• NG13: Reference point between UDM and Authentication Server function (AUSF).
• NG14: Reference point between 2 Access and Mobility Management function (AMF).
• NG15: Reference point between the PCF and the AMF in case of non-roaming scenario, V-PCF and AMF in case of
roaming scenario.
• NG16: Reference point between two SMFs, (in roaming case between V-SMF and the H-SMF).

7. © British Telecommunications plc
5G RAN and functional decomposition…
UE RAN UPF DNNG6NG3NR air i/f
DU CUNGFI
? ?
CU = Centralised Unit
DU = Distributed Unit
NGFI = Next Generation Fronthaul Interface

8. © British Telecommunications plc
RAN functional splits and impact on backhaul
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
Option
1
Option
2
Option
3
Option
4
Option
5
Option
6
Option
7
Option
8
End to end
maximum
latency
Capacity
requirement
Higher layer splits Lower layer splits

9. Adding 5G to an existing
multi-RAT macro-site

10. © British Telecommunications plc
Adding 5G to an existing multi-RAT macro-site
• Current multi-RAT macro-cell sites
typically have backhaul of 1Gbps
• Capacity is shared between RATs and
in many cases, between network
sharing partners (MNOs)
• Note: >1Gbps backhaul is being
deployed to support certain LTE radio
configurations
– 1Gbps and beyond on LTE radio
interface
2G/4G
SRAN
(1/GE)
3G
MORAN
100M/1GE
4G
Net-Share
(1GE)
1GE

11. © British Telecommunications plc
Adding 5G to an existing multi-RAT macro-site
• 5G deployment to macro-cells is very
likely to be <6GHz spectrum bands
• Massive MIMO is a key concept for 5G
– 32/64/128+ antennas
• 5G NR channel bandwidths to be
larger than current LTE channels
• Most spectrum will be unpaired,
therefore phase/time synchronisation
is required for TDD operation
• Assume eMBB is to be the first use
case, the maximum capacity is
required
• Backhaul, or NGFI, will require a
minimum of 10GE local connectivity
with scalable end to end capacity
2G/4G
SRAN
(1/10GE)
3G
MORAN
100M/1GE
4G
Net-Share
(1GE)
5G
gNB
(10GE)
?

12. © British Telecommunications plc
Adding 5G to an existing multi-RAT macro-site
• 5G deployment to macro-cells is likely
to be <6GHz spectrum bands
• Massive MIMO is a key concept for 5G
– 32/64/128+ antennas
• 5G NR channel bandwidths to be
larger than current LTE channels
• Most spectrum will be unpaired,
therefore phase/time synchronisation
is required for TDD operation
• Assume eMBB is to be the first use
case, the maximum capacity is
required
• Backhaul, or NGFI, will require a
minimum of 10GE local connectivity
with scalable end to end capacity
• mm-wave radio backhaul/x-haul will
support 10Gbps+
2G/4G
SRAN
(1/10GE)
3G
MORAN
100M/1GE
4G
Net-Share
(1GE)
5G
gNB
(10GE)
Sub-tended
mm-wave
(10GE+)
?

13. 5G Architecture Options

14. © British Telecommunications plc
5G Architecture Options
12 options identified, not all will be implemented, slides illustrate most likely solutions
(options 5, 6, 8 and 8a considered unlikely and therefore not illustrated (option 1 is legacy))
1: Standalone LTE, EPC connected 2: Standalone NR, NGCN connected
eLTE
EPC
UE
5G NR
NGC
UE
User plane
S1-u
Control plane
S1-c
User plane
NG3
Control plane
NG2
Release 15 UE

15. © British Telecommunications plc
5G migration scenarios
3: Non-standalone/LTE assisted,
EPC connected
3a: Non-standalone/LTE assisted,
EPC connected
eLTE
EPC
5G NR
NGC
UE
eLTE
EPC
5G NR
NGC
UE

16. © British Telecommunications plc
5G migration scenarios
4: Non-standalone/NR assisted,
NGCN connected
4a: Non-standalone/NR assisted,
NGCN connected
eLTE
EPC
5G NR
NGC
UE
eLTE
EPC
5G NR
NGC
UE

17. © British Telecommunications plc
5G migration scenarios
7: Non-standalone/LTE assisted,
NGCN connected
7a: Non-standalone/LTE assisted,
NGCN connected
eLTE
EPC
5G NR
NGC
UE
eLTE
EPC
5G NR
NGC
UE

18. Summary

19. © British Telecommunications plc
Summary
• 5G standards are still under development
within 3GPP
• Final technical contributions for the initial 5G
standards are being discussed (Release 15)
• 5G will support enhanced Mobile Broadband
(eMBB), Ultra-Reliable and Low Latency
Communications (URLLC) and massive
Machine Type Communications (mMTC)
• 5G RAN will be different from previous
iteration of C-RAN and D-RAN
• NGFI will likely be implemented for 5G and
eLTE - exact functional splits tbd
• There is significant complexity to manage in
the core network, including inter-working
with and migration to NGCN
• BT is pro-actively developing 5G solutions…

20. © British Telecommunications plc
THANK YOU
Questions?