Clock frequency synchronization using high-speed digital networks

Abstract

We propose a new method for synchronizing clock frequencies between computers in a distributed system. It uses a framing clock signal, which is a clock signal for network synchronization retrieved using framing bits from a synchronous user network interface of digital networks. Because framing bits are generated using a clock for network synchronization and it is originally a cesium frequency standard oscillator, the framing clock signal should have high accuracy and stability. The clock signal was evaluated in terms of frequency accuracy and stability for the Basic Rate Interface of the Integrated Service Digital Network. The accuracy was 1.7 x 10 -10 , and the stabilities for the intervals of 1.0 x 10 2 and 1.0 x 10 4 were 2.0 x 10 -9 and 2.0 x 10 -11 , respectively. The accuracy and stability of the framing clock signal are better than those of the quartz-crystal oscillators installed in computers by 3 and 2 orders of magnitude, respectively.