GLOBECOM 2005 Tutorial

CANCELLED
Monday, 28 November
Majestic Ballroom H / Level Two / Renaissance Grand Hotel

Title: TU10 Synchronization of Digital Telecommunications Networks

Duration: Half Day/2:00PM-5:00PM

Instructor: Stefano Bregni, Politecnico di Milano, Italy

Abstract:
Network synchronization deals with the distribution of time and frequency over a network of clocks, even spread over a wide area. The goal is to align (i.e., synchronize) the time and frequency scales of all the clocks, by using the communications capacity of links among them.

Network synchronization has gained increasing importance in telecommunications throughout the last thirty years, especially since transmission and switching turned digital. Actually, the quality of most services offered by network operators to their customers is affected by network synchronization performance: digital switching, SDH/SONET, ATM, CDMA, GSM and UMTS are striking examples where network synchronization has been proven to affect quality of service.

A synchronization network is the facility implementing network synchronization. Basic elements of a synchronization network are nodes (autonomous and slave clocks) and communication links interconnecting them. Most modern telecommunications operators have set up synchronization networks to synchronize their switching and transmission equipment.

It is maybe needless to say that quality of service degradations due to some synchronization problem look always sudden, unexpected and of mysterious origin for almost everybody but the (good) synchronization engineer. Rather surprisingly, engineers with a solid expertise on the above mentioned topics are not common. The results are quite evident: gross mistakes in system design and management produce quality-of-service degradations that unfortunately, due to ignorance, are often deemed unavoidable.

In this tutorial lecture, synchronization processes at different levels in telecommunications are first reviewed and fundamental definitions about timing of digital signals, jitter and wander are introduced. Major topics of this tutorial are: timing aspects in SDH/SONET networks; architectures and requirements for timing transfer in PDH, SDH/SONET, ATM and fixed/mobile telephone networks; strategies, standards, architectures and clocks for synchronization networks.

Motivation:
Network synchronization plays a central role in digital telecommunications. Nevertheless, this subject is widely misunderstood. Neither it may be said that such knowledge is common among telecommunications engineers. Actually, it is not easy to find in literature detailed information on several network synchronization issues.