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

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© 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

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5G Network Architecture

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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

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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

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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).

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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

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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

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

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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

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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)
?

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© 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+)
?

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5G Architecture Options

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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

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© 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

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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

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© 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

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Summary

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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…

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THANK YOU
Questions?