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© 2014 Microsemi Corporation. COMPANY PROPRIETARY 1
Power Matters.TM
Achieving Phase Accuracyfor LTE-A SynchronizationField Measurement Results
Power Matters.TM 2© 2014 Microsemi Corporation. COMPANY PROPRIETARY
Overview• Frequency, Time, and Phase Synchronization• IEEE 1588 Precision Time Protocol Profiles• ITU Standards and Deployment Models
Achieving Phase Accuracy in the Field• Field Testing Overview• Specific test cases• Field Test Results
Conclusions
Agenda
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TA=1/fA
TB=1/fB
fA=fB
Frequency Synchronization
A
B t
t
Frequency, Time and Phase Synchronization
TA=1/fA
TB=1/fB
fA=fB
Phase Synchronization
A
B t
t
01:00:00TA=1/fA
TB=1/fB
fA=fB
Time Synchronization01:00:10
01:00:00 01:00:10
A
B
t
t
E1/T1, SyncE, PTP, GNSS, NTP, 10Mhz, 1PPS
PTP, GNSS, NTP, 1PPS
PTP, GNSS, NTP
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Mobile Wireless Synchronization Requirements
Mobile Technology Frequency Input into Base Station
Inter Cell Phase Alignment
N/A
± 1.5µs
± 1.5µs
± 0.5 to ± 1.5µs
± 1.5µs
± 1 to ± 32µs
16 ppbFDD
LTE-TDD
eICIC
CoMP
MBSFN
MBMS
LTE-A
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IEEE 1588-2008 Profiles
IEEE 1588-2008 …• -2008 defined for all applications …
barrier to interoperability• profiles define application related
features from the full specification, enabling interoperability
Default ProfileDefined in Annex J. of 1588 specificationLAN/Industrial Automation Application (v1)
Power ProfileDefined by IEEE PSRC (C37.238)Substation LAN Applications
Telecom ProfileDefined by ITU-T (G.8265.1, G.8275)Telecom WAN Applications
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PTP (IEEE 1588) Routing Options
Multicast Grandmaster broadcasts PTP packets
to a Multicast IP address Switches/Routers…
• With IGMP snooping, forwards multicast packets to subscribers
• Else traffic broadcast to all ports Multicast Sync Interval:
Fixed rate, example 16Hz
Unicast Grandmaster sends PTP packets
directly to PTP slaves Switches/Routers forward PTP packets
directly to slaves Unicast Sync Interval; Telecom Profile:
• User defined Sync interval up to 128Hz
• Many subscribers supported
Multicast (1:group) Unicast (1:1)
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1. Originate Time Stamp
How Time Offsets are Corrected in Time Transfer
Client
1. Originate Time Stamp2. Receive Time Stamp1. Originate Time Stamp2. Receive Time Stamp3. Transmit Time Stamp
1. Originate Time Stamp 2. Receive Time Stamp3. Transmit Time Stamp4. Client Time Received
ClientTime = (Receive Time – Originate Time) + (Transmit Time – Client Time Received)Offset 2
Assumes symmetric path latency (delay) for outbound and return paths
Server
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• Automatic Path Asymmetry Correction algorithm supplies external correction factor as defined in IEEE 1588 standard.
• Algorithm learns path asymmetries to the north-bound master … even while system may using GNSS as the primary clock source.
• In the event of a GNSS failure, the system will operate revert to using Asymmetry corrected PTP.
• Feature available with the TimeProvider 2700
• Will be added to G.8273.4 APTS
Path Re-arrangement (Ring Topology
Automatic Path Asymmetry Correction
RED: PPS performance with asymmetry correction.
Customer network test environment
BLUE: PPS performance without asymmetry correction.
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FrequencyG.8261: Timing and Synchronization Aspects in Packet Networks (Frequency)
Time/PhaseG.8271: Time and Phase Synchronization Aspects in Packet Networks
G.8273: Packet-Based Equipment Clocks for Time/Phase: Framework
Structure of ITU-T Sync Requirements
G.8265.1: Precision Time Protocol Telecom Profile for Frequency Synchronization
G.8275.1: PTP Telecom Profile for Time/Phase Synchronization, Full OPS
Basic Aspects
Clocks
Methods
ProfilesG.8265.2 PTP Telecom Profile for Frequency #2
G.8261.1: PDV Network Limits Applicable to Packet-Based Methods (Frequency)
G.8271.1: Network Requirements for Time/Phase Full on Path SupportNetwork
Requirements
G.8273.1: Telecom Grandmaster (T-GM)
G.8262: Timing Characteristics of a Synchronous Ethernet Equipment Slave Clock (EEC)
G.8263: Timing Characteristics of Packet-Based Equipment Clocks (PEC)
G.8264: Distribution of Timing Information through Packet Networks
G.8275.2: PTP Telecom Profile for Time/Phase Synchronization, Partial OPS
G.8271.2: Network Requirements for Time/Phase Partial On Path Support
Definitions / Terminology G.8260: Definitions and Terminology for Synchronization in Packet Networks
G.8261.2: Reserved for future use
G.8272: PRTC (Primary Reference Time Clock) Performance
G.8273.2: Telecom Boundary Clock (T-BC)
G.8273.4: Telecom Time Slave Clock (T-TSC)
G.8274: Reserved for future use
agreed ongoing options
G.8275: Architecture and Requirements for Packet-Based Time and Phase Delivery
G.8265: Architecture and Requirements for Packet-Based Frequency Delivery
G.8273.3: Telecom Transparent Clock (T-TC)
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LTE FDD Frequency, Managed Ethernet Backhaul G.8265.1 Architecture
Managed Ethernet Backhaulconsistent, known performance
CORE ACCESSAGGREGATION
PTP slave/client device
Macro eNodeB
• Set frequency with PTP (GNSS/GPS primary source)• 10 hops with QoS on PTP flow• No on path support (BC/TC) required
PTP GM
PTP GM
CES/PWE IWF
GPON
Base Station
Media Gateway
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Retrofit Existing Backhaul or New Build
Managed Ethernet, Synchronous Ethernet, Boundary Clocks
CORE ACCESSAGGREGATION
• Set time/phase with PTP (GNSS at primary source)• SyncE and Boundary Clock in every node for asymmetry
mitigation
LTE-A, TDD Phase, Retrofitted or New Ethernet Backhaul - G.8275.1 Architecture
BC
BC BC BC
BCBCBC
BC
BC
PTP GMSyncE
SyncE
SyncE
SyncE SyncE
SyncE
SyncE
SyncE
SyncE
SyncE
Macro eNodeB
RbBCSyncE
PTP GMSyncE
BC BC BC
Small CellAgg.
MetroSmall Cells
BCSyncE
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LTE-A, TDD Phase, Overlay Existing Backhaul G.8275.2 Architecture
AGGREGATION
• Set time/phase in macro/small cells with GMC at edge (asymmetry not an issue)
• Hold time/phase with GMC from MSC using asymmetry compensation
Macro eNodeB
CORE
PTP GM
PTP GM
Existing Backhaul
Edgemaster Overlay with Asymmetry Correction
PTP GM
• Once time/phase is set asymmetry is not an issue
ACCESS
PONONUOLT
Microwave
Ethernet
PTP GM
Small CellAggregation
MetroSmall Cells
DSLmodem DSLAM
Macro eNodeB
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Achieving Phase Accuracyin the Field
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Objective: Confirm that PTP can be used to synchronize eNodeBs • Test Case 1: Partial On-Path Support without GNSS support• Test Case 2: Partial On-Path Support
with GNSS reference on the Edge (as per ITU G.8275.2)
• Test Case 3: Partial On-Path Support with loss of GPS at the Edge (with Asymmetry Correction).
• Test Case 4: Partial On-Path Support 3rd party embedded PTP in CSR
Satisfy LTE-A Phase Requirements ±1.5µs (3µs total) Measure PTP Phase Performance to the eNodeB. Measure Packet Delay Variation (PDV) Backhaul Path
Field Test – Overview
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Path PDV Characteristics
Direction PD Min PD Max PD Range PD Mean
Forward 647us 14,500us 13,900us 709us
Reverse 629us 989us 360us 663us
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Path PDV Characteristics (Zoom)
Direction PD Min PD Max PD Range PD Mean
Forward 647us 14,500us 13,900us 709us
Reverse 629us 989us 360us 663us
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Path PDV Characteristics ( FW floor Zoom)
Mean FPP ( 200sec window) : 10us – 5.88%
100us – 81.94%
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Path PDV Characteristics ( RV floor Zoom)
Mean FPP ( 200sec window) : 10us – 2.53%
100us – 99.86%
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Phase Performance Comparison
TC 2: Partial On-PathTP2700 with GNSS input
TC 3: Partial On-Path (Loss of GPS)TP2700 with Asymmetry compensation
TC 1: Partial On-PathTP2700 with PTP input only (BC)
TC 4: Partial On-Path Embedded in 3rd party CSR
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Test Case 1: Partial On-Path Support without GNSS support
TP-5000PDV Probe1PPS & 10MHz Reference
PTP Slave
1PPS Ref
10MHz Counter Ref
TimeMonitorData collectionand analysis
GPS
Ethernet Backhaul Network
MSOeNB Site
Counter
1PPS Out
TP-2700 w/o GPS
PTP – Reverse direction
Router or Switch
PTP – Forward direction
CSR
TP-5000 GM
GPS
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TC1 Phase Performance
7.86usp-p
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Test Case 2: Partial On-Path Support As per ITU G.8275.2
Wireless Ethernet Backhaul Network
MSO
PTP – Reverse direction
Router or Switch
PTP – Forward direction
TP-5000 GM
GPS
TP-5000PDV Probe1PPS & 10MHz Reference
PTP Slave
1PPS Ref
10MHz Counter Ref
TimeMonitorData collectionand analysis
GPS
eNB Site
Counter
1PPS Out
TP-2700 w/ GPS
CSR
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Test Case 3: Partial On-Path Support Loss of GPS at the Edge (Asymmetry Compensation)
Wireless Ethernet Backhaul Network
MSO
PTP – Reverse direction
Router or Switch
PTP – Forward direction
TP-5000 GM
GPS
TP-5000PDV Probe1PPS & 10MHz Reference
eNB withPTP Slave
1PPS Ref
10MHz Counter Ref
TimeMonitorData collectionand analysis
GPS
eNB Site
Counter
1PPS Out
TP-2700 w/ GPS
CSR
X
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TC2 to TC3 – GNSS to PTP fallback
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TC3 Phase Performance
1.74usp-p
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Test Case 4: Partial On-Path Support 3rd party embedded PTP in CSR
Wireless Ethernet Backhaul Network
MSO
PTP – Reverse direction
Router or Switch
PTP – Forward direction
TP-5000 GM
GPS
TP-5000PDV Probe1PPS & 10MHz Reference
eNB withPTP Slave
1PPS Ref
10MHz Counter Ref
TimeMonitorData collectionand analysis
GPS
eNB Site
Counter
1PPS Out
CSR
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TC4 Phase Performance
1.25usp-p
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All TP2700 Test Cases met and exceeded ±1.5µs (3µs total) for LTE-A phase performance.
Combining GNSS and PTP with Asymmetry correction give fastest reference switchover and good performance.
Many embedded PTP clients fail to compensate the network asymmetry. Phase accuracy isn’t the only important parameter!
Field Test – Summary
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Eran GilatEMEA, System Sales EngineerEran.gilat@microsemi.com+972.52.342.4718
Thank You