Sincronismo de redes de telecom
Silvana Rodrigues Phone: +1 613 2707258
silvana.rodrigues@zarlink.com http://timing.zarlink.com/
Antti Pietilainen Phone: +358(0)718036660
antti.pietilainen@nokia.com http://www.nokia.com
AGENDA
Telecommunication Synchronization Background
– Telecom Synchronization – North America and International Telecommunication Union (ITUT) TimingDistribution Hierarchy – Synchronous and Converged network model
Telecom Applications Examples using 1588 IEEE-1588TM Standard work to address Telecom Applications
– IEEE-1588 Issues for Telecom – IEEE-1588 Enhancements to support Telecom – IEEE-1588 Standard work to support Telecom
Summary
IEEE-1588TM is trademark of its respective owner
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Telecommunication SynchronizationBackground
Telecom Synchronization
Clock quality levels (stratum for North America and Types and Options for the International Telecommunication Union ITU) are defined by the industry standards organizations to maintain clock quality in the network Time sensitive services need synchronization Synchronization is important to avoid overflow or underflow of slip buffers, bit errors and other adverseeffects
– ITU-T Recommendation G.822 provides criteria for controlled slip rate
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North America Timing Distribution Hierarchy
Stratum 1
Primary Reference Source
Stratum 1: Network Gateway
Stratum 2
Stratum 2: Central Offices
Stratum 2
Stratum 3
Stratum 3
Stratum 3
Stratum 3
Stratum 3: Local Offices
Stratum 3
Stratum 4
Stratum 4: Customer PremisesStratum 4
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ITU-T SDH Timing Distribution ITU-T Recommendation G.803 Hierarchy defines the synchronization
PRC
G.812 Type I reference chain G.812 Type I
G.813 Option 1
G.813 Option 1
G.813 Option 1
Number of G.812 type I clocks ≤ 10
G.813 Option 1
Number of G.813 option1 clocks ≤ 20
G.813 Option 1
G.813 Option 1
G.812 Type I
G.813 Option 1
G.812 Type ITotal number of G.813 clocks in a synchronization trail should not exceed 60.
G.813 Option 1
G.812 Type I
G.813 Option 1
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Clock Level
North America Stratum Level 1 (PRS) 2 Not Defined 3E 3 PRC (G.811) Type II (G.812) Type I (G.812) Type III (G.812) Type IV (G.812)
+/- 1x10-11 N/A +/- 1x10-10 /day
ITU-T Clock Level
Free-run Accuracy
Holdover Stability
Pull-in/Hold-in range
N/A
Wander Filtering
Phase Transient (Re-arrangement)
N/A
N/A
+/- 0.016 ppm
0.016 ppm
0.001Hz
MTIE < 150ns
N/D +/- 4.6 ppm
+/- 2.7x10-9 /day +/- 1.2x10-8 /day +/- 3.9x10-7 /day
0.01 ppm 4.6 ppm
0.003Hz 0.001Hz
MTIE < 1µs MTIE < 150ns Phase slope 885ns/s MTIE < 1µs Phase slope 61us/s Objective: MTIE < 150n Phase slope 885ns/s MTIE < 1µs
+/- 4.6ppm
4.6 ppm
3Hz 0.1Hz (SONET)
Not Defined SMC
Option I (G.813) Option 2 (G.813) 4
+/- 4.6 ppm
+/- 2x10-6 /day +/- 4.6x10-6 /day N/A
4.6 ppm
1 – 10Hz
+/- 20 ppm
20 ppm
0.1Hz
MTIE < 1µs Objective mask 150ns Phase slope 885ns/s No Requirement
4
+/- 32 ppm
32 ppm
No
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Standard Requirements
ITU-T recommendations, G.823 for E circuits andG.824 for T circuits set limits on the magnitude of jitter and wander at network interfaces. The wander may not exceed given values anywhere in the network. Thus, a circuit emulation link, for example, may consume only part of the wander budget GSM, WCDMA, and CDMA2000 require frequency accuracy of 0.05 ppm at air interface CDMA2000 requires time synchronization at ± 3 µs level (±10 µs worst case)WCDMA TDD mode requires 2.5-µs time accuracy between neighboring base stations (i.e. ±1.25 µs of UTC)
– These requirements are too difficult to achieve without good transparent clocks or boundary clocks in each intermediate node – Some cellular operators do have control over the transport network so they could use IEEE1588 compliant switches for achieving time synchronization
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