Poor synchronization can be caused by differences in timing accuracy among clocks in various network elements (at different levels) or by phase impairments which disrupt the signal frequency.
In this case, the incoming data flow is interfered during transportation. These interferences are called jitters - short-term phase variations (?font face="arial">
Why installing a synchronization network ?
It is necessary for the operator to have control of the synchronization network in order :
- to keep the whole network at the same frequency.
- to assure that the frequency is very closed to the frequency of other operators avoiding loss of synchronization on the border of both networks. For this, a high quality clock, called Primary Reference Clock (PRC), should be used in the synchronization network structure.
- to minimise jitter and wander effects.
- to have, in case of loss of the primary reference in critical nodes - called SSU -, an equipment which ensure a sufficient precision to continue maintaining SSU synchronization output quality. This means using a secondary or tertiary reference (a Rubidium or Quartz clock reference).
All these requirements are fully explained in international recommendations and standards emitted by ITU and ETSI.
In a competitive context, it is obvious that, for the operator, controlling the synchronization network from a technical point of view is a key issue of its business strategy.
