When every nanosecond counts

www.sevensols.com

Ultra-accurate time transfer based on the IEEE-1588 High Accuracy Profile.

A high scalability and resilience approach

Summary

• The road to 5G

• Limitations of the IEEE 1588 – 2008 (PTPv2)

• The upcoming IEEE 1588 revision: High Accuracy profile

• Scalability and resiliency

• Performance data

• Live demo

2

The road to 5G

• Timing and synchronization is critical to improve current telecom service

capabilities

• Dedicated timing network: Necessary? It depends...

– Interconnection with common reference (GNSS, UTC(k), …)

GNSS

Time Server Backhaul Network

CU DU

RRU

±100 ns

±70 ns ±20 ns ±10 ns

< 10 Km < 2 Km

3Data taken from Dr. Han Li, China Mobile. WSTS 2017

Limitations of the IEEE 1588 – 2008 (PTPv2)

• Several “telecom” profiles.

• Per-link calibration is mandatory.

• Accuracy and precision is not enough.

• Heavily affected by Packet Delay Variation (PDV).

• Best Master Clock Algorithm (BMCA) is unsecure. You must trust the

source.

• Asymmetry needs to be measured and taking into account.

4

The upcoming standard: High Accuracy profile

• Main ideas coming from White Rabbit (WR) Protocol

• WR born at CERN and tested through several years

• WR brought to industry by Seven Solutions already in 2010

• IEEE1588 with HA expected in 2018/2019.

• 3rd default PTP Profile included in Annex J of the IEEE1588

• HA allows:

– Clock sync (L1 synchronization)

– Timestamp enhancement through phase detection

– Automatic precise evaluation of link asymmetry.

• Fully compatible with PTPv2

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The upcoming standard: High Accuracy profile

125.00 MHz

124.98 MHZ

125.03 MHz

125.00 MHz

125.00 MHZ

125.00 MHz

• Sub-nanosecond accuracy of synchronization. L1-Sync + Phase difference

measurement.

• Calibration procedures and dynamic evaluation of medium asymmetry.

• Low bandwidth utilization for time synchronization

• Hops of over 80 Km (validated with WR implementation on longer links)

• As with PTPv2, switchover and holdover techniques can be used

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5G Network example

Network frequencyReference

(PRC/Cesium)

Phase/timereference

Fronthaul II Backhaul/core network

RRURRU

CU

CU

CU

Fronthaul I

CU: Centralized UnitDU: Distributed Unit (5-10 per CU)RRU: Remote Radio Unit (10-20 per DU)

DUDU

DU

DU DU

DU

DU

RRU

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Scalability and resiliency

• Possibility to have multiple grandmasters connected to

independent time sources: GNSS, UTC (k), multiport

device. (Maciej. PhD. 2016, J. L. Gutierrez et al. EFTF. 2016)

• 15 hops maintaining sub-nanosecond (Seven Solutions. ITSF

2016, Torres-Gonzalez et al., ISPCS 2016)

• Up to 120Km per hop (see next results)

8

Performance data

Synchronization performance of the current WR implementation

that is representative to the future HA implementations.

24 hours

20 KmHA profile

Compatible DeviceHA profile

Compatible Device

Counter20 ps

resolution

PPS PPS

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Performance data

10

10000 20000 30000 40000 50000 60000 70000 80000

Performance data

1,E-10

1,E-10

1,E-10

2,E-10

2,E-10

2,E-10

2,E-10

2,E-10

3,E-10

1 10 100 1000 10000 100000

Tim

e Er

ror

(s)

Seconds

MTIE

11

Performance data

1,E-12

1,E-11

1,E-10

1 10 100 1000 10000 100000

Tim

e D

evia

tio

n (

s)

Seconds

TDEV

12

Performance data

GM

CU

DU

RRU

16 hours

GPS-DO

PPS

10 MHz

20 Km

20 Km

20 Km

Counter20 ps

resolution

PPS

PPS

HA profileCompatible Device

HA profileCompatible Device

HA profileCompatible Device

HA profileCompatible Device

13

Performance data

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Performance data

1,00E-10

1,20E-10

1,40E-10

1,60E-10

1,80E-10

2,00E-10

2,20E-10

2,40E-10

2,60E-10

1 10 100 1000 10000 100000

Tim

e Er

ror

(s)

Seconds

MTIE

15

Performance data

1,E-12

1,E-11

1,E-10

1 10 100 1000 10000 100000

Tim

e D

evia

tio

n (

s)

Seconds

TDEV

16

Performance data

18 hours

GPS-DO

PPS

10 MHz

50 Km

70 Km

Counter20 ps

resolution

PPS

PPS

HA profileCompatible Device

HA profileCompatible Device

HA profileCompatible Device

17

Performance data

-100

-75

-50

-25

0

25

50

75

100

0 3000 6000 9000 12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000 45000 48000 51000 54000

Tim

e er

ror

(ps)

Seconds

Time Error on 120 Km, 2 hops

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Performance data

1,00E-10

1,10E-10

1,20E-10

1,30E-10

1,40E-10

1,50E-10

1,60E-10

1,70E-10

1,80E-10

1,90E-10

2,00E-10

1 10 100 1000 10000 100000 1000000

Tim

e Er

ror

(s)

Seconds

MTIE

19

Performance data

1,E-12

1,E-11

1,E-10

1 10 100 1000 10000 100000 1000000

Tim

e D

evia

tio

n (

s)

Seconds

TDEV

20

Live demo

Location A Location B

20/50/70 Km

Location A

Location B

GPS-DOPPS

10 MHz

WR-ZEN TP-32BNCWR-SWITCH

SF7322

PTP

WR-ZEN TP-32BNC

WR

WR

PPS

PPS

PPS

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Conclusions

• WR and HA match 5G time transfer requirements

– Distance scalability with low time error budget (nanosecond)

– Validated in the presented results

– Live trials already in place

• High Accuracy profile:

– Intensively based on White Rabbit approach (developed and promoted

by CERN)

– Clock distribution (L1 synchronization)

– Phase offset measurement

• We have a live set up in the booth

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