Synchronization Architectures
The most widespread and effective synchronization network tree has been standardized by ETSI and ITU.
This architecture consists in distributing a frequency reference very closed to the nominal frequency to all network elements through different synchronization elements. These elements are organised in tree as shown in the Fig.3 :
A Primary Reference: HPS which will provide the pilot frequency to the whole network. This reference should be carried out using a Cesium atomic clock or the GPS. The Cesium primary source has a stability that is sufficient for interconnecting the network to other international networks. For security reasons, the synchronization network can have two or three primary clocks, each being isolated geographically. The Cesium primary source has a high cost, but is installed in 1 up to 3 units only and allows an operator to fully control the network. While the GPS solution is cheaper, even if it抯 completely dependent on the US DoD. This last solution, based on a GPS as Primary Reference Source (PRS) together with a Rb-Qz clock has very good price and performance ratio.
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