1. T-BERD/MTS 5800 + TEM Introduction to Sync/Timing for LTE Advanced Mobile Networks
Joe Gomez
May 2017

2. Agenda Application Overview Measurements & Options Applications
Use Cases

3. What is driving timing & sync field testing
Application Overview
What is driving timing & sync field testing

4. Mobility Market is Mature
LTE and 4G is widespread - worldwide.
Almost 1.5 Billion subscribers worldwide are on LTE
- Global Mobile Suppliers Association
Next challenge is LTE Advanced and getting to 5G.
When are people moving to LTE-A? – Now
“37% of the world’s LTE carriers are in the process of deploying LTE-Advanced technologies in 84 countries.”
- telecoms.com, August
5G is farther out
2018 – standards finalized
2020 – first networks go live

5. Why is Timing Important?
LTE Advanced (LTE-A) has more stringent Timing and Synch requirements than LTE
New techniques are heavily dependent on phase synchronization – Phase Sync is new
Today most Mobile Network Operators (MNOs) do not test timing and sync at all
So Timing testing is not a question of better …
… it’s a question of new
Driving LTE-A / 5G …
IoT – requirement for massive number of connections
Low Latency – support for autonomous vehicles

6. The New Wave of Timing & Sync Measurements
Top 3 Drivers of Sync Requirements
LTE-TDD
CoMP
eICIC
Most field trials to occur
Techniques requiring
phase synchronization
LTE-TDD
eICIC
CoMP
MBSFN
Coordinated
Scheduling
LTE Advanced Technologies
New Recommended Field Tests
One Way Delay
SyncE Wander
PTP Time Error
PTP Wander
PTP Clock cTE 5G
2011
2016
2017
2018
2019
2020

7. Synchronization Problems Cause Interference
Everything is “A-OK” – cells can overlap
With Time & Phase Sync problems overlapping cells interfere with each other
Interference
Interference = Dropped Calls
Same as 10+ years ago when moving around meant your call would drop
Timing/Sync – New source of interference!
Interference

8. Keep the Mobility Network Healthy
Everything is “A-OK”
Cells interfere with each other
Stay Here
All-In-One, Easiest to Use
Timing/Sync
PTP
SyncE
Wander Analysis
OTDR, Microscope
CPRI
Ethernet (RFC 2544, Y.1564)
T1/E1
Interference
Identify Problems
… and how to fix them

9. T-BERD/MTS with Timing Module – Product Highlights
Miniature Atomic Clock!
Rubidium-based MAC; Industry leading stability and accuracy
Advantage: Test for longer when out of satellite line of sight
72 Channel GNSS Receiver
Concurrent reception of GPS, GLONASS and SBAS constellations; BeiDou and Galileo supported
Advantage: find more satellites in more places, including urban canyons
PTP Check
Workflow based Time Error Measurement that ensures easy of use and repeatability of test
Advantage: Every tech is now a PTP expert
SyncE and 1588v2 (PTP) Wander Analysis
With ITU Masks
Advantage: Conform to standards based measurements
10GE 1588v2 (PTP)
For troubleshooting timing at aggregation locations such as CRAN hubs/hotels
Advantage: solve PTP problems anywhere in the network
Affordable solution for basic Lab testing
1 PPS Wander Analysis accurate to 1ns
Advantage: Standard for network performance troubleshooting
All-In-One, Easiest to Use
Timing/Sync
OTDR, Microscope
CPRI including RFoCPRI
Ethernet (RFC 2544, Y.1564)
T1/E1

10. Timing/Sync Measurements & Options
Timing/Sync options, measurements and PTP architectures

11. What needs to be measured?
Frequency Syntonization
Time Synchronization
Phase Synchronization

12. Network Operator Options for Managing Timing / Sync
Technique
Frequency Synch Capable
Phase Synch Capable
Time Synch Capable
Notes
IEEE 1588v2 – Precision Time Protocol (PTP) √
Asymmetric delay unaware; accuracy dependent on network architecture
SyncE – Synchronous Ethernet X
Cannot convey time or phase but can be used to assist time accuracy in holdover
Network Time Protocol (NTP)
Accuracy degrades during congestion; slow start up; inherent equipment oscillator accuracy affects performance
Global Navigation Satellite Systems (GNSS)
Susceptible to jamming; atmospheric conditions affect CNR
Hybrid Options
Provide maximum flexibility based on network architecture
Common Backup
Common Primary

13. Types of PTP Network Implementations – Phase Sync
PTP Unaware Networks do not have Boundary Clocks (T-BC) or Transparent Clocks (T-TC)
Boundary Clocks clean up timing fluctuations in the network
PTP Aware Network includes Boundary Clocks (T-BC) and/or Transparent Clocks (T-TC)
In a PTP Network with Partial Timing Support a Boundary Clock is used between network segments
T-GM
PRTC
PTP Unaware Network
End Application
T-GM
PRTC
T-TC
PTP Aware Network
T-BC
End Application
T-GM
PRTC
End Application
PTP Unaware Core
PTP Unaware Backhaul
T-BC
Greenfield
Most Common

14. Inside a PTP Aware Network
Multiple Boundary Clocks are used to regenerate timing
Each T-BC should not contribute more than 50ns constant time error cTE to the end-to-end path
T-GM
PRTC
PTP Aware Network
T-BC

15. PTP Aware Networks – Time Error Budget Overview
ITU has recommended a total End-to-end time error budget of ±1.5μs
ITU recommends maximum time error (max|TE|), dynamic time error (dTE) - time error noise - and constant time error (cTE) measurements.
A PTP Check workflow is ideal for measuring maximum absolute time error (max|TE|).
A PTP Wander Analysis with a G mask measures dynamic time error (dTE).
The BERT UI graphs measure constant time error (cTE) and are included in all PTP results.
±100 ns
±1,100 ns (1.1μs)
±1,500 ns (1.5μs)
T-GM
PRTC
T-TC
PTP Aware Network
T-BC
End Application

16. PTP Aware Networks – Time Error Budget Detail
1.5μs (1500ns) Time Error Budget
Measure with PTP Check
Dynamic Error (dTE (t))
Control the max |TE| in the 200 ns range
Measure with PTP Wander
Constant Time Error (cTE)
Rearrangements/Holdover: 250 ns
End Application: 150 ns
Constant Time Error per node: 50 ns
Graph cTE
Link Asymmetries: 250 ns
Measure with One Way Delay Test
PRTC to T-GM: 100 ns
Measure with PTP Check; verify antenna installation
Budgeting Example (10 hops)
Holdover PTP Rearrangements
250ns
End Application
150 ns
1,100 ns
Dynamic Noise accumulation
200 ns
BC Internal Errors (Constant)
550 ns
Link Asymmetries
250 ns
PRTC
100 ns

17. Critical Measurements
Applications
Critical Measurements

18. GPS Antenna Placement Recommended Test Construction / Installation
Commissioning
Acceptance
Maintenance
GPS Antenna Placement – ensure the GPS antenna is positioned properly, working fine, cabled properly and that it supports at least 4 satellites with sufficient signal strength to be useful for accurate position. This is needed for accurate time and 1 PPS calculation.
Contractors
NEMs, Service Provider Cell Operations / RF Techs
Service Provider Cell Operations / RF Techs
Partial obstruction:
Satellites present –
No signal
Standard Skyplot shows instantaneous satellite obstruction
Long-term Skyplot data is captured to ensure satellite signal strength can support cell site over standard 12 hour satellite orbits
Standard C/No table shows instantaneous satellite signal strength

19. Timing/Sync Recommended Test Construction / Installation Commissioning
Acceptance
Maintenance
Timing/Sync –
PTP as a backup to GPS
Measure PTP Maximum Time Error max|TE|
Measure PTP Wander per ITU-T
Applicable to Troubleshooting
1PPS Wander Analysis
PTP One Way Delay
PTP Wrap Measurements
NEMs, Service Provider Cell Operations
Service Provider Cell Operations

20. What to Measure and where
Use Cases
What to Measure and where

21. One Way Delay (OWD) PTP Aware Network T-GM PRTC T-TSC T-BC
A OWD test let’s you measure the asymmetrical delay and packet jitter of an End-to-End link or segment
Tx and Rx fibers could be of different lengths
Tx and Rx traffic could be following different paths
Routers, switches and Ethernet aggregation equipment could have different uplink & downlink latencies
Based on different traffic prioritization
Based on different shaping and policing policies
Based on traffic (OTN) multiplexing at aggregation points
T-GM
PRTC
T-TSC
PTP Aware Network
T-BC
End Application

22. PTP Time Error PTP Aware Network T-GM PRTC T-TSC T-BC End Application
Max Time Error Max |TE| measures the maximum time difference between two clocks
Time reference required (5800+TEM) – only 1 tester is required
When connected to GNSS, TEM accuracy is as good as a grand master
Measure PTP max |TE| at the grandmaster, (T-GM), every boundary clock (T-BC) or transparent clock (T-TSC) to ensure the maximum time error for the segment has not been exceeded
T-GM
PRTC
T-TSC
PTP Aware Network
T-BC
End Application

23. PTP cTE PTP Aware Network T-GM PRTC T-TSC T-BC End Application
ITU Recommendations expect that 50ns cTE is the maximum time error introduced per node (T-BC or T-TSC).
Measure cTE at every T-BC or T-TSC in the network
T-GM
PRTC
T-TSC
PTP Aware Network
T-BC
End Application

24. PTP Wander Analysis PTP Aware Network T-GM PRTC T-TSC T-BC
PTP can be used to distribute frequency , time and phase sync in the network
ITU recommends using PTP Wander Measurements to establish dynamic Time Error (dTE)
Per ITU, and in order to support LTE Advanced applications, End-to-End dTE should not exceed 200ns
Measure dTE (PTP Wander) at T-TSC in the network
T-GM
PRTC
T-TSC
PTP Aware Network
T-BC
End Application

25. SyncE SSM & Sync E Wander
SyncE can be used to distribute frequency sync in the network similar to the way SONET/SDH and T1/E1 are used
SyncE Wander Analysis is required to measure dynamic frequency error in the network
SSM analysis & decode helps establish whether the device under test is transmitting the proper Quality Level (QL) to slave devices
Analyze SSM Messages at every T-BC or T-TSC
Measure SyncE Wander at every T-TSC
T-GM
PRTC
T-TSC
PTP Aware Network
T-BC
End Application

26. 1 PPS Measurements PTP traffic Clock 1 PPS Clock Output
Use 1 PPS Wander measurements to troubleshoot & calibrate boundary clocks
Test Steps
Emulate an up-stream PTP grand master
Compare the clock’s 1 PPS output to the 1 PPS signal received from satellite
PTP traffic
T-BC or T-TSC
Clock
1 PPS Clock Output
Grandmaster Emulation
Wander
Analysis
1 PPS from GNSS signal

27. PTP Wrap Measurements PTP traffic PTP Traffic ToD from GNSS source
Use PTP Wrap measurements to troubleshoot & calibrate boundary clocks
Test Steps
Emulate an up-stream PTP Grand Master
Emulate a downstream PTP Slave
Run a PTP Check to verify m|TE| injected by the Clock
PTP traffic
T-BC or T-TSC
PTP Traffic
PTP Slave Emulation
Grand Master Emulation
Wander
Analysis
ToD from GNSS source

28. GNSS Antenna Installation Verification
Check Sky Plot for obstructions
Observe where the satellites are located. If you see satellites in a portion of the plot with “No Signal”, you could have a partial obstruction
Verify Satellite Signal Strength
For best performance look for CNR* values greater than 35
Verify Number of Satellites Acquired
A minimum 4 satellites are required. As satellites move through the sky this number will vary, but a minimum of 4 are always required.
Partial obstruction:
Satellites present – No signal
Verifying Antenna Installations allow us to troubleshoot problems at the Grandmaster (T-GM) and PRTC points of the network
*CNR: the carrier-to-noise ratio, is a measure of the received carrier strength relative to the strength of the received noise. High values indicate better quality of reception.