USE OF GPS TO SYNCHRONIZE THE AT&T NATIONAL TELECOMMUNICATIONS NETWORK

E.W. Butterline, J.E. Abate, G.P. Zampetti

Abstract: Presently, AT&T synchronizes its national networks using analog signals derived from a cesium clock ensemble having a precision of a few parts in 10-12. These analog signals have well served the need for precise frequency in what was predominantly an analog network. However, the AT&T network is rapidly being transitioned to a digital network which needs precise time rather than frequency. As a result, several alternatives were considered and the one chosen was a new system based on Global Positioning System (GPS). The GPS based system, termed a Primary Reference Clock or PRC, employs a GPS receiver providing long term timing accuracy along with duplicated disciplined rubidium oscillators providing short term (e. one day) stability. Under computer control, these three elements are verified against each other and against identical PRC systems in other parts of the network. The PRC system produces a digital signal used to synchronize a master clock in the node which in turn produces a signal that is (1) used to synchronize all other clocks in the node, and (2) distributed on a digital basis to all neighboring nodes. By use of monitoring equipment at each PRC, the performance of the master clock at every AT&T network node will be verified against the GPS signal at each PRC. For the first time, a national telecommunications network will be monitored and verified to be performing to a precision approaching Universal Coordinated Time (UTC).
Published in: Proceedings of the 20th Annual Precise Time and Time Interval Systems and Applications Meeting
November 29 - 1, 1988
Sheraton Premiere Hotel
Vienna, Virginia
Pages: 65 - 76
Cite this article: Butterline, E.W., Abate, J.E., Zampetti, G.P., "USE OF GPS TO SYNCHRONIZE THE AT&T NATIONAL TELECOMMUNICATIONS NETWORK," Proceedings of the 20th Annual Precise Time and Time Interval Systems and Applications Meeting, Vienna, Virginia, November 1988, pp. 65-76.
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