1. Achieving Phase Accuracy for LTE-A Synchronization Field Measurement Results

2. Agenda Overview Achieving Phase Accuracy in the Field Conclusions
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

3. Frequency, Time and Phase Synchronization
TA=1/fA
TB=1/fB
fA=fB
Frequency Synchronization A B t
E1/T1, SyncE, PTP, GNSS, NTP, 10Mhz, 1PPS
TA=1/fA
TB=1/fB
fA=fB
Phase Synchronization A B t
PTP, GNSS, NTP, 1PPS
Metaphor:
Frequency: everyone’s wristwatch has the same quality crystal – ticks seconds at same pace, but not necessarily at the identical moment
Phase: everyone’s wristwatch ticks seconds at the identical moment -Time: everyone’s wristwatch ticks second at the identical moment and registers identical time: …1001, 1002, 1003, etc.
Explain Mobile Technologies and synchronization requirements
Some require only Frequency and some require phase/time-of-day.
Briefly mention the typical requirements for
- frequency, eg., well known 50ppb for the ‘radio interface’.
Phase can be 2-3 microseconds of difference between BS.
Some Mobile Operators may have GPS at all base stations. Even then they might prefer backup methods.
Conclusion: Mobile Backhaul Service by MEN Operator has to be offered along with
options to distribute frequency and phase synchronization
traceable to a primary reference clock.
01:00:00
TA=1/fA
TB=1/fB
fA=fB
Time Synchronization
01:00:10 A B t
PTP, GNSS, NTP

4. Mobile Wireless Synchronization Requirements
Mobile Technology
Frequency Input into Base Station
Inter Cell Phase Alignment
FDD
LTE-TDD
eICIC
CoMP
MBSFN
MBMS
16 ppb
N/A
± 1.5µs
± 0.5 to ± 1.5µs
± 1 to ± 32µs
This table shows the sync requirements for different mobile network standards. There is no need to look at this in detail. I will just call your attention to the block on the lower right of the slide. As you can see, as the LTE technologies are deployed through the network, a requirement for phase synchronization is added. And the requirement is very tight, going all the way to 500 nano second precision.
LTE-A

5. IEEE Profiles
IEEE …
-2008 defined for all applications … barrier to interoperability
profiles define application related features from the full specification, enabling interoperability
Power Profile
Defined by IEEE PSRC (C37.238)
Substation LAN Applications
Telecom Profile
Defined by ITU-T (G , G.8275)
Telecom WAN Applications
Default Profile
Defined in Annex J. of 1588 specification
LAN/Industrial Automation Application (v1)

6. PTP Terminology GMC Slave clock Ordinary Clocks Boundary Clocks
Grand Master Clock (PTP server, Typically uses GPS/GNSS source)
Slave clock
PTP client (Optimized for frequency or Frequency/Time-phase)
Ordinary Clocks
GMC (Time stamps, Hardware Time stamping)
Slaves (Various levels of performance, oscillator variables)
Boundary Clocks
Slave/GMC
Transparent Clocks
Switches
Transparent Clock
Residence Time =
Egress Time - Arrival Time
Arrival Time
Egress Time
PTP Packet
Boundary Clock
Slavee
GMC
PTP Flow
New PTP Flow

7. 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
(Internet Group Multicast Protocol, IGMP) The protocol that governs the management of multicast groups in a TCP/IP network. To sign up for a multicast group, a Host Membership Report is sent by a user's machine to its nearest routers, which forward that data to routers outside the local network. The routers are kept current by polling the users' machines with Host Membership Query messages.
Multicast (1:group)
Unicast (1:1)

8. PTP Operation Frequency Time/phase High transaction rate with client
Multiple timing packets/sec (128 maximum)
Small number of clients supported
< 10 to Hundreds
Stringent client accuracy requirements
Microseconds/nanoseconds
PDV impacts frequency
Asymmetry impacts time/phase
Network Engineering
QoS, Highest priority
Majority of Applications are for frequency/phase
Fixed or variable
Multicast = fixed, unicast = variable
High capacity and low capacity GMC
GMC , minimum 8, scalable
Frequency
Stratum 1 with Rubidium oscillator
1PPB with crystal oscillator
Time/phase
+/- 1.5 microseconds
On Path Timing Support
Full or Partial
Circuit Emulation (T1 reconstruction)
LTE enodeb and small cells
SLA verification
One Way Delay measurements

9. Unicast Startup Sequence
Master/Server
Grandmaster
Slave Clock
Slave/Client
IEEE 1588 Processor
Signaling (Request Announce)
IEEE 1588 Processor 10 20 30 40 50 60 70 80 90
100
120
110
130
140
150
Network protocol stack & OS Processing
Signaling (Announce Granted)
Network protocol stack & OS Processing
PROCESS SET’S UP THE RESERVATION.
Sync detector & timestamp generator
Signaling (Request Sync)
Sync detector & timestamp generator
Switch/Router Layer
Physical layer
Signaling (Sync Granted)
Physical layer
Server clock sends:
2. Signaling (Announce granted)
4. Signaling (Sync granted)
6. Signaling (delay_resp granted)
Signaling (Request delay_resp(onse))
Client clock sends:
Signaling (Request Announce)
Signaling (Request Sync)
5. Signaling (Request delay_resp)
Signaling (delay_resp(onse) granted)
Time
Time
Network
The process is repeated before the lease expires (typically halfway through the lease period).

10. How Time Offsets are Corrected in Time Transfer
Client
Server
1. Originate Time Stamp
1. Originate Time Stamp
2. Receive Time Stamp
3. Transmit Time Stamp
4. Client Time Received
1. Originate Time Stamp
2. Receive Time Stamp
1. Originate Time Stamp
2. Receive Time Stamp
3. Transmit Time Stamp
Client
Time = (Receive Time – Originate Time) + (Transmit Time – Client Time Received)
Offset 2
Assumes symmetric path latency (delay) for outbound and return paths

11. Automatic Path Asymmetry Correction
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 APTS
Customer network test environment
Path Re-arrangement (Ring Topology
RED: PPS performance with asymmetry correction.
BLUE: PPS performance without asymmetry correction.

12. Structure of ITU-T Sync Requirements
Definitions / Terminology
G.8260: Definitions and Terminology for Synchronization in Packet Networks
Frequency
Time/Phase
Basic Aspects
G.8261: Timing and Synchronization Aspects in Packet Networks (Frequency)
G.8271: Time and Phase Synchronization Aspects in Packet Networks
Network Requirements
G : PDV Network Limits Applicable to Packet-Based Methods (Frequency)
G : Network Requirements for Time/Phase Full on Path Support
G : Network Requirements for Time/Phase Partial On Path Support
G : Reserved for future use
G.8262: Timing Characteristics of a Synchronous Ethernet Equipment Slave Clock (EEC)
G.8272: PRTC (Primary Reference Time Clock) Performance
G.8263: Timing Characteristics of Packet-Based Equipment Clocks (PEC)
G.8273: Packet-Based Equipment Clocks for Time/Phase: Framework
Clocks
G : Telecom Grandmaster (T-GM)
G : Telecom Boundary Clock (T-BC)
G : Telecom Transparent Clock (T-TC)
G : Telecom Time Slave Clock (T-TSC)
G.8264: Distribution of Timing Information through Packet Networks
G.8274: Reserved for future use
Methods
G.8265: Architecture and Requirements for Packet-Based Frequency Delivery
G.8275: Architecture and Requirements for Packet-Based Time and Phase Delivery
G : Precision Time Protocol Telecom Profile for Frequency Synchronization
G : PTP Telecom Profile for Time/Phase Synchronization, Full OPS
Profiles
G : PTP Telecom Profile for Time/Phase Synchronization, Partial OPS
G PTP Telecom Profile for Frequency #2
agreed
ongoing
options

13. LTE FDD Frequency, Managed Ethernet Backhaul G.8265.1 Architecture
Managed Ethernet Backhaul consistent, known performance
CORE
AGGREGATION
ACCESS
PTP GM
Macro eNodeB
PTP slave/client device
PTP GM
This is the 1st network scenario listed on slide 17
CES/PWE IWF
GPON
Base Station
Media Gateway
Set frequency with PTP (GNSS/GPS primary source)
10 hops with QoS on PTP flow
No on path support (BC/TC) required

14. LTE-A, TDD Phase, Retrofitted or New Ethernet Backhaul - G. 8275
LTE-A, TDD Phase, Retrofitted or New Ethernet Backhaul - G Architecture
Retrofit Existing Backhaul or New Build
Managed Ethernet, Synchronous Ethernet, Boundary Clocks
CORE
PTP GM
SyncE
AGGREGATION
ACCESS BC BC BC BC BC Rb
SyncE
SyncE
SyncE
SyncE
SyncE
Macro eNodeB BC BC BC
SyncE
SyncE
SyncE
PTP GM
SyncE BC BC
Metro Small Cells
This is the 3rd network scenario listed on slide 17
SyncE
SyncE BC BC BC BC
SyncE
Small Cell
Agg.
Set time/phase with PTP (GNSS at primary source)
SyncE and Boundary Clock in every node for asymmetry mitigation

15. LTE-A, TDD Phase, Overlay Existing Backhaul G.8275.2 Architecture
Existing Backhaul Edgemaster Overlay with Asymmetry Correction
Macro eNodeB
CORE
AGGREGATION
PTP GM
ACCESS
PTP GM
Ethernet
Microwave
Macro eNodeB
PON
ONU
OLT
PTP GM
This is the 4th network scenario listed on slide 17. There are 3 alternatives to consider in this scenario.
Same segmented network architecture as previous proposal
Clear upgrade path from frequency profile
Strategically-placed GPS/BC at remote office sites
GPS as primary time source, PTP as backup time source
PTP can run current frequency profile with partial support
Symbiotic relationship between GPS and PTP
PTP provides initial time to GPS, enabling better acquisition in low signal-to-noise environments
PTP stabilises local oscillator, allowing less expensive oscillator
GPS allows path asymmetry to be measured, improving PTP accuracy
PTP provides backup in case of GPS failure
Still requires correctionfor asymmetry in access technology
Metro Small Cells
Small Cell
Aggregation
DSL
modem
DSLAM
PTP GM
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
Once time/phase is set asymmetry is not an issue

16. Achieving Phase Accuracy in the Field

17. Field Test – Overview
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 )
Test Case 3: Partial On-Path Support with loss of GPS at the Edge (with Asymmetry Correction).
Test Case 4: Partial On-Path Support rd 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

18. Test Configuration Mobile Switching Office (MSO) eNodeB sites
TimeProvider 5000 (TP-5000) L3 Unicast GM (Telecom-2008 Profile)
eNodeB sites
TimeProvider 2700 (TP-2700) Slave is connected to the CSR via GigE interface.
Generates 1PPS and DS1 output via PTP from MTSO GM.
Agilent Universal Counter to capture phase (1PPS) from TP Slave.
TP-5000 Probe is connected to the CSR via GigE interface.
Measures PDV and provides 10MHz and 1PPS reference to Agilent Counters.
PC with TimeMonitor Measurement Software to capture and analyze phase output of the TP-2700 slave and PDV from TP-5000 probe.
Both TP-5000 GM and TP-5000 Probe are connected to GPS.
Enable QoS (DSCP = 46) on all Microsemi equipment to prioritize PTP traffic.

19. Path PDV Characteristics
- 3rd party backhaul provider with unknown number of hops - “the cloud”.
- A characteristic of an asymmetric path with significant difference in mean packet delay of 850us (delta) between the forward and reverse paths. - High jitter path with packet delay range of 2.61ms of the forward direction, and 1.21ms on the reverse.
Direction
PD Min
PD Max
PD Range
PD Mean
Forward
647us
14,500us
13,900us
709us
Reverse
629us
989us
360us
663us

20. Path PDV Characteristics (Zoom)
- 3rd party backhaul provider with unknown number of hops - “the cloud”.
- A characteristic of an asymmetric path with significant difference in mean packet delay of 850us (delta) between the forward and reverse paths. - High jitter path with packet delay range of 2.61ms of the forward direction, and 1.21ms on the reverse.
Direction
PD Min
PD Max
PD Range
PD Mean
Forward
647us
14,500us
13,900us
709us
Reverse
629us
989us
360us
663us

21. Path PDV Characteristics ( FW floor Zoom)
- 3rd party backhaul provider with unknown number of hops - “the cloud”.
- A characteristic of an asymmetric path with significant difference in mean packet delay of 850us (delta) between the forward and reverse paths. - High jitter path with packet delay range of 2.61ms of the forward direction, and 1.21ms on the reverse.
Mean FPP ( 200sec window) :
10us – 5.88%
100us – 81.94%

22. Path PDV Characteristics ( RV floor Zoom)
- 3rd party backhaul provider with unknown number of hops - “the cloud”.
- A characteristic of an asymmetric path with significant difference in mean packet delay of 850us (delta) between the forward and reverse paths. - High jitter path with packet delay range of 2.61ms of the forward direction, and 1.21ms on the reverse.
Mean FPP ( 200sec window) :
10us – 2.53%
100us – 99.86%

23. Phase Performance Comparison
TC 2: Partial On-Path
TP2700 with GNSS input
TC 1: Partial On-Path
TP2700 with PTP input only (BC)
TC 3: Partial On-Path (Loss of GPS)
TP2700 with Asymmetry compensation
Partial on-path support improved phase performance by 20,000%.
TC 3 Asymmetry correction improved phase performance by 3X compared to TC 1.
TC 4: Partial On-Path
Embedded in 3rd party CSR

24. Test Case 1: Partial On-Path Support without GNSS support
TP-5000
PDV Probe
1PPS & 10MHz Reference
PTP Slave
1PPS
Ref
10MHz
Counter
TimeMonitor
Data collection
and analysis
GPS
Ethernet Backhaul Network
MSO
eNB Site
1PPS Out
TP-2700 w/o GPS
PTP – Reverse direction
Router or Switch
PTP – Forward direction
CSR
TP-5000 GM
Measure phase output performance of the TP-2700 without GPS/no asymmetry correction.
Measure PDV using TP-5000 Probe

25. TC1 Phase Performance 7.86usp-p
Very long convergence time – about 11 hours. => PTP can’t normally compensate network asymmetry
No redundancy.. Use of SyncE will only assist in much faster lock time but won’t help for phase.
7.86usp-p

26. 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-5000
PDV Probe
1PPS & 10MHz Reference
PTP Slave
1PPS
Ref
10MHz
Counter
TimeMonitor
Data collection
and analysis
eNB Site
1PPS Out
TP-2700 w/ GPS
CSR
- TP-2700 with GPS and PTP as backup with asymmetry correctionenabled.

27. TC2 Phase Performance 567nsp-p
One hop on the same site. Performance with “good” client should be in the range of 50ns..
567nsp-p

28. 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-5000
PDV Probe
1PPS & 10MHz Reference
eNB with
PTP Slave
1PPS
Ref
10MHz
Counter
TimeMonitor
Data collection
and analysis
eNB Site
1PPS Out
TP-2700 w/ GPS
CSR
- Loss of GPS on the TP-2700. X

29. TC2 to TC3 – GNSS to PTP fallback
One hop on the same site. Performance with “good” client should be in the range of 50ns..

30. TC3 Phase Performance 1.74usp-p
Performance is within the limits of 3us ( +/- 1.5us ) and between the boundaries
1.74usp-p

31. 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-5000
PDV Probe
1PPS & 10MHz Reference
eNB with
PTP Slave
1PPS
Ref
10MHz
Counter
TimeMonitor
Data collection
and analysis
eNB Site
1PPS Out
CSR
- Loss of GPS on the TP-2700.

32. TC4 Phase Performance 1.25usp-p
Signal looks very good at first glance, but watch for the offset !
1.25usp-p

33. Field Test – Summary
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!

34. Conclusion IEEE 1588 PTP is well established for frequency
LTE-A requires tight Phase synchronization
Filed testing proves PTP performance to meet LTE-A phase requirements
Microsemi portfolio is fully ready for field deployment to deliver LTE-A phase synchronization

35. Thank You Eran Gilat EMEA, System Sales Engineer