Sincronismo de redes de telecom

Páginas: 8 (1755 palabras) Publicado: 5 de diciembre de 2010
IEEE-1588TM Telecommunications Applications
Silvana Rodrigues Phone: +1 613 2707258

Antti Pietilainen Phone: +358(0)718036660

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

IEEE-1588TM is trademark of its respective owner

[Page 1]

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

[Page 3]

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

[Page 4]

ITU-T SDH Timing Distribution ITU-T Recommendation G.803 Hierarchy defines the synchronization
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

[Page 5]

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

Wander Filtering

Phase Transient (Re-arrangement)



+/- 0.016 ppm

0.016 ppm


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


MTIE < 1µs Objective mask 150ns Phase slope 885ns/s No Requirement


+/- 32 ppm

32 ppm


[Page 6]

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

[Page 7]...
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