This document discusses synchronization techniques for 5G networks. It explains that frequency synchronization is established over mobile networks using SyncE and PRCs. Time synchronization is introduced using PTP and PRTCs sourced from satellite clocks, achieving moderate accuracy. Boundary and transparent clocks can improve PTP delivery accuracy when used in the packet network. The document outlines increasing synchronization accuracy requirements for newer technologies. It proposes using enhanced PRTCs combining GNSS and atomic clocks to achieve sub-100ns accuracy required for applications like 5G and fronthaul.

1. Synchronizing 5G networks
May 2020
Time accuracy within 100ns at the cell site

2. © 2020 ADVA. All rights reserved.22
Historically, SDH/SONET delivered
frequency synchronization
Ethernet reuses this technology
with SyncE
Central primary reference clocks
(PRCs) provide precise
synchronization signal
Cesium atomic clock / GNSS
receivers for frequency accuracy
Distribution over SyncE-capable
network elements
Frequency synchronization is well established over mobile transport networks
Frequency synchronization in 3G, 4G and LTE
Ethernet with SyncE
PRC
Edge of
mobile core

3. © 2020 ADVA. All rights reserved.33
Primary reference time clocks
(PRTCs) deliver PTP-time based
on satellite-synchronized
oscillators
PTP packets delivered over
existing packet-based network
Accuracy depends on network
asymmetry and PDV
Accuracy achieved at base station,
subject to network delay
characteristics
Moderate phase and time-of-day synchronization from central timing source
Introducing time synchronization in mobile RAN
Edge of
mobile core
Ethernet with SyncE
IEEE 1588 PTP
PTP
grandmaster
PRTC

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Delivery of PTP over packet
networks is improved by
boundary/transparent clocks
Transparent clock: compensates
for delay of switches/routers
Boundary clock: terminates PTP
on slave port (before input
queuing delays) and generates
PTP on master ports (after output
queuing delays)
This architecture achieves sub-
1.1µs accuracy at base stations
Adding PTP “awareness” to the packet network improves time delivery
Improving accuracy of PTP delivery
Boundary/transparent clock
Edge of
mobile core
PTP
grandmaster
PRTC

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Synchronization requirements
2G/3G – frequency synchronization
3G TDD: 5µs time synchronization (large cells)
LTE – multicast: several µs time synchronization
LTE Advanced CoMP, TDD: 1.5µs time synchronization
5G – positioning: <100ns time sync (cluster)
5G – CA, IoT: several 100ns time sync (cluster)
Fronthaul eCPRI: <100ns time sync (cluster)
Accuracy needs to
improve further

6. © 2020 ADVA. All rights reserved.66
ITU took action and tightened
specifications of clocks and time
clocks
G.811.1: improving accuracy of
PRC -> ePRC
G.8272: improving PRTC with
class B accuracy (with MB GNSS)
G.8272.1: improving accuracy of
PRTC by defining ePRTC using
atomic cesium
G.8273.2: improving BC with class
C/D accuracy
OSA54XX rel. 10.5.1. comes with BC class C,D and improved ePRTC capability
Towards <100ns accuracy
Edge of
mobile core
ePRTC
OSA 542x
OSA 5430/40
GM, combiner
TC/BC class C/D
OSA 3XXX Cs atomic
clock

7. © 2020 ADVA. All rights reserved.77
ePRTC- Combining best GNSS technologies with most accurate atomic clocks
ePRTC block diagram and evolution
Single-band
GNSS receiver (PRTC)
OSA 3230B – dual
cesium clocks (PRC)
Enhanced PRTC combines PRC and
PRTC with atomic clock
Multi-band, multi-constellation
GNSS receiver (PRTC-B)
Dual cesium
clocks (ePRC)
ePRTC– uses ePRC and MB GNSS with
higher accuracy + redundancy
Clock
combiner
Clock
combiner
PTP
SyncE
ToD
PPS
10MHz
PTP
SyncE
ToD
PPS
10MHz
OSA
5430
OSA
5430

8. © 2020 ADVA. All rights reserved.88
Highly scalable PTP grandmaster supporting 2x 1024 clients
@ max 128pps (1024 per CSM)
Telecom grade fully redundancy hardware
First PTP telecom grandmaster featuring 10G interface
Highly scalable fan-out:
• Up to 48x 10G ports
• Up to 48x 1G ports
• Up to 160 BITS ports
• Up to 100 composite clock ports
Simultaneously providing PTP and NTP as well as physical
layer frequency synchronization
Multi-band, multi-constellation GNSS input options including
GPS, GLONASS, Beidou, and Galileo
PTP input and SyncE input as backup to GNSS
ePRTC and PRTC-B options
BC type D
OSA 5430/40 multi-technology core grandmaster
OSA 5440
OSA 5430

9. © 2020 ADVA. All rights reserved.99
OSA 542x – the “Swiss Army Knife“ of synchronization
PTP
GM/BC type D / slave
NTP
server
SSU
Multiple I/F
fan-out
Sync probe
G.8265.1 EnterpriseG.8275.2 G.8275.1
2G/3G/
4G/5G
FDD BS
DOCSIS 3.1 MIFID ii
5G-NR/LTE
TDD/LTE-A BS
NTP61850-9-3/
C37.238
Smart grid

10. Thank you
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