Choosing the Synchronization Master Source
Rent Synchronization from another Operator
In this case, the operator extracts synchronization from the synchronization network of another operator, and has not installed any synchronization network within its transport infrastructure.
This solution has the four following disadvantages :
It is expensive : The amount is linked to renting a line transporting synchronization, there is no control of the solution.
It is "black-box" : The way synchronization is ensured and transported is generally unknown by the customer :
* Is there redundancy?
* Is there control for critical parameters (jitter and wander)?
* Is there global management and quick intervention time within the synchronization network?
It is not controlled : In case of problem at the "provider operator", not only the "customer operator" cannot respond, but he does not have any alternative solution.
It is "revenue-closed" : Most main accounts of the operator will require by contract a service reliability and quality and for high value added applications, which the operator will not have real control.
Cesium Source(s)
Solution of excellent quality and long term stability (1.10 -11 ), it is expensive (typically a stand-alone solution, with a tube with finite life, and generally in triplicated).
GPS "off air" Source
This solution is cheap and very precise at the same time (based on multi-satellite reception of primary clocks that are installed in them : NAVSTAR program). This solution has a highly accurate long term stability (1.10 -13 ) It obviously requires satellite visibility. Nevertheless, the operator will not be able to fully control it as he would do so for Cesium primary stand-alone solutions, ownership of the GPS system belonging to the American DoD. |
