Use of GPS to Synchronize the AT&T National Telecommunications Network

Presently, AT&T synchronizes its national networks using analog signals derived from a single cesium clock ensemble having a precision of a few parts in 10 sup -12. These analog signals have served well 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 chose was a new system based on GPS.