This document discusses the architectural and performance enhancements of 5G mobile networks, highlighting key performance indicators such as increased capacity, data rates, and reduced latency. It also elaborates on the evolution of radio access network (RAN) architecture, issues surrounding fronthaul and backhaul, and the shift towards Ethernet-based solutions for 5G transport. The presentation emphasizes the importance of functional splits and new standards in adapting existing infrastructure to meet 5G requirements.

1. A flexible X-haul network for
5G and beyond
OECC/PSC 2019, Fukuoka, Japan
Jörg-Peter Elbers and Jim Zou
This work was supported by the European Union’s
Horizon 2020 Research and Innovation Program
under Grant Agreement No. 762057 (5G-PICTURE).

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5G is more than a new radio …
Key performance indicators (KPIs)
• 1000 times higher cell capacity
• 100 times higher peak data rates
• 10 times lower latency
• 10 times better reliability

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… and offers very different services
source: ITU-R M.2083-0
eMBB
mMTC URLLC

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5G features are covered by 3GPP Release 15 and 16 specifications
5G standardization timeline
Source:XiangLiu,Huawei,OFC2019

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Decomposition into central unit, distributed unit and radio/remote unit
From 4G to a new (5G) RAN architecture
Source:ITU-TG.Sup66

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~10ms round-trip time~1ms round-trip time ~5ms round-trip time
Very low latency Low latencyUltra low latency
There will not be a one-size-fits-all configuration
Latency determines location of RAN functions
RU: radio unit
DU: distributed unit
CU: central unit
MEC: multi-access edge computing
UPF: user plane function
RU: radio unit
DU: distributed unit
CU: central unit
MEC: multi-access edge computing
UPF: user plane function
RU: radio unit
DU: distributed unit
CU: central unit
MEC: multi-access edge computing
UPF: user plane function
~1000
sites
~100
sites
~10
sites
~1000
sites
~100
sites
~10
sites
~1000
sites
~100
sites
~10
sites
Source: NGMN Overview on 5G RAN Functional Decomposition

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[NokiaWhitePaper„EvolutiontoCentralizedRANwithMobileFronthaul“,2016]
CPRI option 10 already defined (V7.0): 24 330 240 Mb/s.
CPRI requires 13-17x higher bitrate than user data rate and very accurate timing
The CPRI fronthaul challenge

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Agreement on higher layer split (F1), but no agreement yet on lower layer (Fx)
Introducing new functional splits in 5G RAN
Backhaul
Higher layer split (HLS) Lower layer split (LLS)
RRC: radio resource control, PDCP: packet data convergence protocol, RLC: radio link control
MAC: medium access control, PHY: physical layer, RF: radio frequency
Similar timing requirements as CPRISimilar timing requirements as backhaul
>10x
user rate
~1-2x
user rate
~1-2x
F1 rate
Source:ChinaMobileResearchInstitute,2016

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3GPP IEEE P802.1CM eCPRI
New standards for 5G fronthaul
O-RAN
Higher layer
functional split
(HLS)
TSN for fronthaul
Ethernet
transport
requirements
Lower layer
functional split (LLS):
O-RAN 7.2x
Ethernet becomes convergence layer for 5G transport

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10Gbit/s and 25Gbit/s interfaces appear adequate for F1 and Fx transport
Illustrative throughput comparison
Radio
configuration
Interface Cell peak rate @
quiet time
Mean cell rate
@ busy time
Aggregate tri-cell rate
(peak + 2x mean)
100MHz carrier,
8 MIMO layers,
64T64R
F1 4.7Gbit/s 2Gbit/s 8.7Gbit/s
100MHz carrier,
16 MIMO layers,
64T64R
Fx
(ORAN 7.2x)
13.1Gbit/s 2.6Gbit/s
(20% of peak)
18.3Gbit/s
100MHz carrier,
16 MIMO layers,
64T64R
CPRI 269.5Gbit/s 269.5Gbit/s 808.5Gbit/s
Source: P. Sehier et al, JOCN, 04/2019

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From CPRI to eCPRI
eCPRI leverages Ethernet transport & OAM and offers ~10x reduction in bandwidth

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Frame delay includes fiber latency (approx. 5µs/km)
eCPRI latency
CoS Traffic
Max. one-
way frame
delay
Use case
Max. one-way
frame loss ratio
High25
User plane (fast)
25µs Ultra-low latency applications
10-7
High100 100µs Full LTE or NR performance
High200 200µs Installations with long fiber links
High500 500µs Large latency installations
Medium
User plane (slow),
C&M plane (fast)
1ms All 10-7
Low C&M plane 100ms All 10-6

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Rule of thumb: A few µs per network element
Ethernet aggregator latencies – examples
Source: iCirrus paper “Fronthaul evolution: from CPRI to Ethernet“, OFT 2015

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Deterministic latency for
high-priority traffic
without central
scheduling
Reduces average frame delay variation, but neither peak
delay variation nor worst case latency
Reduces peak delay
variation
Can in principle eliminate packet delay variation,
but requires network-wide flow scheduling
Scheduled traffic (IEEE 802.1Qbv) Gap preservation (FUSION)
Strict priority queuing (IEEE 802.1p) Frame preemption (IEEE 802.1Qbu & 802.3br)
Ethernet TSN technologies for 5GPartofIEEE802.1CMFurthermeasures

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Requirements holds for clock synchronization, not user or C&M data transport
eCPRI timing accuracy
Category
Maximum time error |TE| at UNI Maximum
time
alignment
error TAE
between
antenna
ports
Typical LTE
applications
Typical 5G NR
applications
T-TSC in radio equipment
T-TSC in
transport
network
T-TSC with
|TEmax|=70ns
(Class B)
T-TSC with
|TEmax|=15ns
A+ (relative) n/a n/a 20ns 65ns
MIMO or TX-diversity transmission,
at each carrier frequency
A (relative) n/a 60ns 70ns 130ns
Intra-band
contiguous
carrier
aggregation
Intra-band
contiguous
carrier aggregation*
(450 MHz – 6 GHz)
B (relative) 100ns 190ns 200ns 260ns
Intra-band non-
contiguous or
inter-band carrier
aggregation*
Intra-band
contiguous
carrier aggregation*
(24.25 – 52.6 GHz)
C (absolute) 1100ns 3µs
Time-division
duplex (TDD),
dual connectivity
Intra-band non-
contiguous or inter-
band carrier
aggregation*,
TDD, dual
connectivity
*With or without MIMO or transmitter (TX) diversity

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Ethernet is simplest; TDM-PON, FlexE and OTN add additional protocol layers
5G transport layer stack
Optical underlay
Backhaul Fronthaul
F1
Fx
eCPRI
CPRI
IEEE1914.3
NGS1
Timing&Sync
Ethernet
802.1 CM
grey optics WDM
Fiber
TDM-PON
FlexE2.1 or OTN
OAM&Serviceassurance

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Ethernet-based network with WDM underlay option
Converged 5G X-haul architecture
RU
RU RU
RU+DU
RU RU+DU
RU+DU
CU
Fx fronthaul F1 fronthaul NG backhaul
Core
RU

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Low-latency Ethernet aggregation
ECOC 2018 Best Demo Award
RoE
BH
TrafficAnalyzer
10G
100G100G
10G
1G
IEEE 1588v2 PTP
(grand master)
IEEE 1588v2 PTP
slave (probe)
10G10G
10G10G
10G 10G
BBU
GNSS
RRH
PTP
10G 10G
Central Office Remote Node
…
RoE
RoE
NETCONF/YANG
Controller
100G100G
FUSION
IP Core
MAC 100G PHY
MAC
10G
PHY
MAC
10G BH
…
x6…8
10G
PHY
100G MAC100G PHY
FUSION
IP Core
MAC
MAC
100G Aggregator Node (time sensitive)
1G PTP
100GMAC 100G PHY
10G PHY MAC10G FH
10G FH
…
x4
1G PHY
10G PHY
…
10G
10G
…
Backhaul
Service Configuration
and Monitoring
…
…
…
PTP
TrafficEmulator
…
Traffic
Generator
100G Transport Node (time sensitive)
…
…
SM
GST 100GbE ingress
treated as GST
FH bounded delay aggregation
Dagg = Store-fw MTU@10G +
serve all other streams
(F  1) MTU@100Gbps +
transmission of packet
MTU@100Gbps 100G
1G
ECOC Paper Tu3B.3
Fronthaul traffic
(1522 Byte MTU)
• <3.1µs agg+deagg latency
(1µs from MAC/PHY)
• <0.6µs transit node latency
• 5µs per fiber-km
IEEE 1588v2 PTP traffic
• <±75ns time error
(w/o additional means)

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Low-cost, auto-tunable transceiver modules are key to operational simplicity
G.metro – passive WDM for mobile fronthaul
Optical network units
(tail-end)
Optical line terminal
(head-end)
RU
Transparent l-services
λ-control and -tuning
Passive
remote node(s)
C-band filters
Single-fiber ops
Remotely controlled
Hardened T-SFP+
CU/DU
DWDM
filter
...
...
...
Linear add/dropOLT
1G-10G
Standards
G.694.1 DWDM grid
G.694.2 CWDM grid
G.698.1 Multichannel DWDM
with single channel
optical interfaces
G.698.4
(G.metro)
Multichannel bi-
directional DWDM
applications with
port agnostic single-
channel optical
interfaces

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NFV and edge compute Passive WDM and fiber monitoring
Ethernet/IP connectivity Precision timing delivery
Summary: With 5G, radio transport goes Ethernet
…
Different solutions depending on fiber infrastructure and network requirements

21. Thank you
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