Small cells and LTE-TDD/LTE-A base stations rely on stringent phase synchronization. But packet delay variation and asymmetry make it problematic to deliver accurate phase from the core. In this ITSF presentation, Nir Laufer explained how a new level of precision and reliability can be achieved by locating a “sync pill” (a grandmaster and primary reference time clock in miniature form factor) closer to the end application. The "sync pill" can also be used for network sync probing and assurance with minimal footprint and cost.

1. Jagged little (sync) pill
Enabling installation-based networks for
accurate phase delivery and assurance
Nir Laufer, director PLM
ITSF 2017

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This presentation will not be about Alanis
Morissette’s iconic album ...

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Jagged little (sync) pill
• Imagine we could have a jagged little sync pill …
• A pill that can be swallowed by any network element that requires
accurate frequency and phase …
• A pill that can be swallowed by any network element that requires sync
probing and assurance …

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SyncPill example
SyncPlug
GM
PRTC/PRC
BCSlave
SyncProbe
GNSS input
PTP/Sync-E
in/out

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Game of the day: Find the SyncPill …

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Grandmaster clock and PRTC enabler
• LTE-TDD/ LTE-A base station and small cells require stringent phase synchronization
• Delivering accurate phase from the core is challenging due to PDV and asymmetry
• Problems can be bypassed by locating our “SyncPill” GM/PRTC closer to the end
application, e.g., in first aggregation node
T-GM
GNSS
PTP
grandmaster
Packet-based backhaul network
T-SC
T-SC
First aggregation node
T-SC
GNSS
High PDV
asymmetry

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How can we use core GM for backup?
• We can use PTP input from the core GM as backup to the SyncPill GM
• Asymmetry between the SyncPill GM and the core GM can be calibrated
using GNSS
• How can we improve the frequency stability (MTIE/TDEV) of the clock
recovered from the PTP backup?
T-GM
GNSS
PTP
grandmaster
Packet-based backhaul network
T-SC
T-SC
First aggregation node
T-SC
GNSS
High PDV
asymmetry
GM/APTS

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How can we use core GM for backup?
• PDV typically accumulates exponentially as a function of number PTP unaware hops; adding
BCs between the GM and slave can reduce PDV significantly (increasing the probability of
lucky packets)
• We can use our SyncPill as BC enabler to existing network elements – no GNSS is necessary!
• The BC will not eliminate the static asymmetry – which can be compensated by the SyncPill
GM, but it will improve the frequency stability
T-GM
GNSS
PTP
grandmaster
Packet-based backhaul network
T-SC
T-SC
First aggregation node
T-SC
GNSS
GM/APTS
BC
High PDV
asymmetry

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Sync-E “pseudo wire” using PTP
• How can we bridge Sync-E unaware networks?
• SyncPill can function as GM and slave
• SyncPill can translate between Sync-E and PTP (freq) and vice versa
• No GNSS is necessary!
Packet-based backhaul network
First aggregation node
Translate from
PTP to Sync-E
Sync-E
unaware
network
SyncPill
PTP slave
PTP
PRC/PRTC
GNSS
Translate from
Sync-E to PTP
Sync-E Sync-E Sync-E
PTP

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• What is the minimal HW needed in a SyncPill to allow in service
sync monitoring and assurance?
• Reference (e.g., from GNSS)
• Signal under test (SUT)
• Time error (TE) / time interval error (TIE) counters
• Networking capabilities which allow to send the collected data for
analysis in the cloud
• Everything else can done in the cloud SyncDoctor
Sync probing and assurance

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Syncjack in SyncPlug …
• GNSS/PTP/SYNC-E/PPS/CLK as source
• GNSS/PTP/SYNC-E/PPS/CLK as reference

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Probing third-party BC/slave
• SyncPlug is used for sync
assurance of third-party
physical clock
• Slave/BC
1PPS/10MHz/2.048MHz/Sy
nc-E/PTP can be monitored
vs. SyncPlug using GNSS
as reference
• Collected TE/TIE data is
sent from SyncPlug to a
server for analysis and
reporting
GNSS
SyncPlug
BC/slave
clock
(DUT)
10MHz/2.048MHZ/PPS
PTP/Sync-E
Sync-E/PTP
Master
Network TE/TIE
raw data
SCP/FTP
TE/TIE raw data packets
Analysis
TE/MTIE/TDEV/
reports/alarms …
PTP/Sync-E

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Probing a third-party master port
• The SyncPlug is used
for sync assurance of
a third-party BC or
GM master port (DUT)
• The SyncPlug
functions as slave
clock / active probe
and performs
measurements
simultaneously (active
PTP probe)
• Collected timestamps
(packet TE/TIE , T2-
T1 ,T4-T3) data is
sent from SyncPlug to
server
GNSS
SyncPlugBoundary
clock
(DUT)
PTP
Master
Network TE/TIE
raw data
SCP/FTP
T1 T2
T4 T3
TE/TIE raw data packets
PTP packets
Analysis
TE/MTIE/TDEV/
reports/alarms …
PTP

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Active probing of the network
• SyncPlug functions as
active probe and uses
the internal telecom
slave packets exchanged
via the network (IP
unicast –
G.8265.1/G.8275.2)
• The SyncPlug can probe
the network and recover
the clock simultaneously
• Timestamp (T2-T1 and
T4-T3) data is sent from
SyncPlug to server
SyncPlug
(SUT)
PTP
Master
Network TE/TIE
raw data
SCP/FTP
T2
T3 TE/TIE raw data packets
PTP packets
T1
T4
PTP
Analysis
TE/MTIE/TDEV/
reports/alarms …
GNSS

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Come and pick your SyncPill ...
Many sicknesses – one cure
Remember to take your Sync Pill!

16. IMPORTANT NOTICE
The content of this presentation is strictly confidential. ADVA Optical Networking is the exclusive owner or licensee of the content, material, and information in this
presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited.
The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or
implied. ADVA Optical Networking shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental,
consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation.
Copyright © for the entire content of this presentation: ADVA Optical Networking.
Thank You
IMPORTANT NOTICE
The content of this presentation is strictly confidential. ADVA Optical Networking is the exclusive owner or licensee of the content, material, and information in this
presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited.
The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or
implied. ADVA Optical Networking shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental,
consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation.
Copyright © for the entire content of this presentation: ADVA Optical Networking.
nlaufer@advaoptical.com