The Common Time Module, a Robust Time Maintenance System

The Common Time Module CTM is being developed by Symmetricom with support from the US ArmyCERDEC. The goal is to implement timing services for mobile systems that demand a high degree of reliability and precision. The system is based around a core module that implements a time and frequency server with provisions for legacy time protocols. To address the rigors of a mobile and dynamic environment, the CTM manages multiple connections to the common time reference UTC-USNO. Either GNSS signals GPS or a network connection IEEE-1588 can synchronize local time services. In addition, the CTM integrates a low-power atomic resonator for extended holdover capabilities. By dynamically managing these technologies, the CTM can supply accurate time and frequency in a wide range of deployment scenarios. Furthermore, improvements in low-power technology such as Chip-Scale-Atomic-Clock CSAC will dramatically reduce power requirement, which is a significant advantage to mobile systems. Finally, this paper will examine how standardized IEEE-1588 network techniques will be applied to support redundancy with the CTM.