smooth evolution path from legacy to ngn synchronization at itsf 2014
DESCRIPTION
Dominik Schneuwly examines how to evolve from legacy to next-generation network synchronizationTRANSCRIPT
Smooth Evolution Path from Legacy to NGN Synchronization
Dominik Schneuwly, ITSF 2014
© 2014 ADVA Optical Networking. All rights reserved.2
Outline
• Drivers of the evolution
• Dimensions of the evolution
• Evolution starting points
• Evolution phases and end points
• Evolution path examples
• Conclusions
© 2014 ADVA Optical Networking. All rights reserved.3
Driver of the evolution
• Network technology evolution from TDM to packet-switched networks, and from fixed to fixed & mobile end sytems
• Synchronization in the past:• Driver: TDM switching (telephony) and transmission (SDH)• Reasons: limit under- and overflowing of frame buffers,
allow crossconnecting (SDH)• Requirements: frequency, accuracy 1·10-11 (relative freq. acc.)
• Synchronization at present and in the future:• Driver: mobile base stations, e.g. 2G BTS, 3G Node B, 4G eNB• Reasons: successful call handover
efficient use of sparse spectrum & channel capacity
etc.• Requirements: frequency (1.6E-8) and phase (1.5 μs ⇾ hundreds ns)
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Dimensions of the evolution
• Change in synchronization needs• Old: frequency for the entire network (1E-11)• New: frequency (1.6E-8) and phase (1.5 μs ⇾ hundreds ns) for the
network edge
• Change in network technology• Old: TDM networks (PDH, SDH)• New: packet-switched networks
• Ethernet, Synchronous Ethernet (SyncE)• IP, IP/MPLS• Etc.
• Change in synchronization technology• Old: SDH/SONET, E1/T1 over PDH• New: SyncE, PTP (IEEE 1588 v2)
Synchronizationtechnology
Synchronizationneeds
Networkcontext
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Once more: frequency, phase and time-of-day
t
t
Clock signal of system A
Clock signal of system B ! !!
t
t
Time signal of system A
Time signal of system B
14/01/0008:34:56
14/01/0008:34:57
14/01/0008:34:55
14/01/0008:34:55
14/01/0008:34:56
14/01/0008:34:57
System A System B
t
t
Clock signal of system A
Clock signal of system B
TA = 1 / fA
TB = 1 / fB
fA = fB• Frequency synchronization
• Phase synchronization
• Time-of-Day synchronization
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Application Radio Interface Backhaul
Frequency Phase Frequency Phase
CDMA 2000 ±50ppb ±3 to 10µs GPS GPS
GSM ±50ppb n/a ±16ppb n/a
WCDMA ±50ppb n/a ±16ppb n/a
LTE (FDD) ±50ppb n/a ±16ppb n/a
LTE (TDD) ±50ppb ±1.5µs ±16ppb ±1.1µs
LTE-A MBMS ±50ppb ±1 to 5µs ±16ppb±1µs
(G.8271)
LTE-A CoMPLTE-A CoMP JT
±50ppb±1 to 5µs± 0.5µs
±16ppb±1.1µs
< 0.5µs (?)
LTE-A eICIC ±50ppb ±1 to 3µs ±16ppb ±1.1µs
Frequency and phase synch. requirements
MBMS: Multimedia Broadcast Multicast Services CoMP: Coordinated MultipointeICIC: enhanced Inter-Cell Interference Coordination JT: Joint Transmission
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Starting point 1: central PRC
PRC
SDH
SSUSSU
SSUSSU
SSU
• Frequency synchronization with accuracy = 1E-11
• Generation: central PRC, typically atomic Cesium clock
• Distribution: SDH, physical layer; sometimes E1/T1 in «last mile»
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Starting point 2: distributed PRCs
SDHSubnetwork
PRC
SDHSubnetwork
PRC
SDHSubnetwork
PRC
• Frequency synchronization with accuracy = 1E-11
• Generation: distributed PRCs, typically GNSS receivers
• Distribution: SDH, physical layer; sometimes E1/T1 in «last mile»
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Transition phases
• Main transition phases:
• A: Frequency over TDM network• SDH/SONET
• B: Frequency over packet network• SyncE• PTP / No Timing Support (G.8265.1)
• C: Phase over packet network• PTP / Full Timing Support (G.8275.1) with SyncE• PTP / Full Timing Support (G.8275.1) without SyncE (ITU-T: «ffs»)• PTP / Assisted Partial Timing Support (G.8275.2)
A B C
(less common)
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Transition A → BB / A SDH & PDH
SyncE X
G.8265.1 X
Transition B → CC / B SyncE G.8265.1
G.8275.1 X X
G.8275.2 X X
Many evolution scenarios
Transitions A → B → C:SDH & PDH → SyncE → G.8275.1
SDH & PDH → SyncE → G.8275.2
SDH & PDH → G.8265.1 → G.8275.1
SDH & PDH → G.8265.1 → G.8275.2
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There are more evolution scenarios than that!
• Already mentioned: Starting point (SDH & PDH) can be with centralized or with decentralized PRCs
• There are multiple mobile systems (2G, 3G, 4G); evolution scenarios may be different for each of them
• Multiple network ownerships (mobile operator, transport provider, etc.)
• Networks with equiment from multiple vendors: different equipment roadmaps
• Some operators use CES/PWE for their 2G BTS (PDH over packet network)
• And we haven’t mentioned WDM systems in conjunction with phase synchronization …
• Etc., etc.
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Evolution example 1a: SDH & PDH → SyncE →G.8275.1
Leverage existing PRC and SSUs
SSU
PRC
SDHor
SyncE
SyncE
SSU
PRC
SDH
SDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
© 2014 ADVA Optical Networking. All rights reserved.13
Evolution example 1a: SDH & PDH → SyncE →G.8275.1
Leverage existing PRC and SSUs, just add cards to SSUs for phase
SSU
PRC
SDH
SyncE
SSU
PRC
SDH
SDH & PDH
SSU
SyncE
GNSScard
T-GMcard
GNSS
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
G.8275.1
DeployBoundary Clocks
Add cards
Upgrade toPTP Slave
Upgrade toSyncE
Core
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Evolution example 1b: keep PRC for phase holdover
Leverage existing PRC and SSUs, just add cards to SSUs for phase
SSU
PRC
SDHor
SyncE
SyncE
SSU
PRC
SDH
SDH & PDH
SSU
SyncE
GNSScard
T-GMcard
GNSS
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
G.8275.1
DeployBoundary Clocks
Add cards
Upgrade toPTP Slave
Upgrade toSyncE
PRC
SDHor
SyncEFor Holdover:frequency holds phase & time
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Evolution example 1c: starting with decentralized PRCs
Leverage existing GNSS/SSUs, just add T-GM card to SSUs for phase
SyncESDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
GNSScard
GNSS
SSUGNSScard
GNSS
SSU
Local PRC Local PRC
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Evolution example 1c: starting with decentralized PRCs
Leverage existing GNSS/SSUs, just add T-GM card to SSUs for phase
SyncESDH & PDH
SSU
SyncE
GNSScard
T-GMcard
GNSS
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
G.8275.1
DeployBoundary Clocks
Add card
Upgrade toPTP Slave
Upgrade toSyncE
GNSScard
GNSS
SSUGNSScard
GNSS
SSU
Local PRC Local PRC Local PRTC
© 2014 ADVA Optical Networking. All rights reserved.17
Evolution example 2a: SDH & PDH → SyncE → G.8275.2
Add cards to SSUs and add small APTS units for phase
SSU
PRC
SDHor
SyncE
SyncE
SSU
PRC
SDH
SDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
© 2014 ADVA Optical Networking. All rights reserved.18
Evolution example 2a: SDH & PDH → SyncE → G.8275.2
Add cards to SSUs and add small APTS units for phase
SSU
PRC
SDHor
SyncE
SyncE
SSU
PRC
SDH
SDH & PDH
SSU
SyncE
GNSScard
T-GMcard
GNSS
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P) G.8275.2
Add cards
Upgrade toPTP Slave
Upgrade toSyncE
APTS
GNSS
G.8275.2
Add APTS unit
First Aggregation
node
© 2014 ADVA Optical Networking. All rights reserved.19
Evolution example 3a: SDH & PDH → G.8265.1 → G.8275.1
Leverage existing PRC and SSUs, just add cards to SSUs for phase
PRC
SDHor
Synce
Carrier Ethernet
SSU
PRC
SDH
SDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
G.8265.1
T-GMcard
Add card
SSU
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Evolution example 3a: SDH & PDH → G.8265.1 → G.8275.1
Leverage existing PRC and SSUs, just add cards to SSUs for phase
PRC
SDHor
Synce
Carrier Ethernet
SSU
PRC
SDH
SDH & PDH
SSU
CarrierEthernet
GNSScard
T-GMcard
GNSS
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
DeployBoundary Clocks
Add card
Upgrade toPTP Slave
Upgrade toSyncE
Core
G.8265.1
T-GMcard
Add card
SSU
G.8275.1
© 2014 ADVA Optical Networking. All rights reserved.21
Evolution example 4a: SDH & PDH → G.8265.1 → G.8275.2
Add cards to SSUs and add small APTS units for phase
PRC
SDHor
SyncE
Carrier Ethernet
SSU
PRC
SDH
SDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
T-GMcard
SSU
Add card
G.8265.1
© 2014 ADVA Optical Networking. All rights reserved.22
Evolution example 4a: SDH & PDH → G.8265.1 → G.8275.2
Add cards to SSUs and add small APTS units for phase
PRC
SDHor
SyncE
Carrier Ethernet
SSU
PRC
SDH
SDH & PDH
Ph
ysic
al l
aye
r b
ase
d
Pa
cke
t b
ase
d (
PT
P)
Upgrade toSyncE
T-GMcard
SSU
SSU
CarrierEthernet
GNSScard
T-GMcard
GNSS
G.8275.2
Add card
Upgrade toPTP Slave
APTS
GNSS
G.8275.2
Add APTS unit
First Aggregation
node
Add card
G.8265.1
© 2014 ADVA Optical Networking. All rights reserved.23
Conclusions
• Evolution is driven by changes in synchronization needs, network context and synchronization technologies
• There are many possible evolution scenarios
• Leveraging existing SSUs and PRCs is possible with many evolution scenarios
• Within these scenarios, evolution requires addition on T-GM cards in SSUS, and possibly addition of small APTS units
• Chosen evolution path has important impact on CAPEX
• Optimal planning of the evolution path is a must
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