• Francisco Girela Lopez - FPGA Engineer, Seven Solutions

Ultra-accurate time transfer through optical links is now possible in the nanoseconds range thanks to technologies such as White-Rabbit. This allows complementary solutions integrating GNSS references and network time transfer links. Taking advantage these complementarity technologies allows mitigating the vulnerabilities of GNSS (jamming or spoofing attacks, or interferences at local areas) and it also allows implementing fail over mechanisms. Furthermore, GNSS can be used to calibrate long haul network links with dynamic compensation of slow time drifts (for instance due to the impact of temperature changes), in such a way that the GNSS reference is only used for calibration purposes and network asymmetry estimation. Moreover, GNSS provides mechanisms to facilitate traceability to UTC(k) to be used as reference for the network nodes. Finally, having comparable accuracy with both approaches, GNSS time receivers and network time transfer links, allows implementing cross-validation approaches and provide the best performance from both technologies.