Dr. Sven-Christian F. Ebenhag: Redundant National Distribution of Time and Frequency
Time and frequency may be invisible, but they are the silent backbone of modern society. Everything depends on accurate, traceable time, from the stability of national energy grids to the precision of communication networks, security systems, and even healthcare infrastructure. For decades, the Global Navigation Satellite System (GNSS) has been the go-to source for this critical resource — inexpensive, easy to deploy, and widely accessible. However, as recent geopolitical developments have shown, dependence on GNSS comes with serious risks.
At BalticNOG 2025, Dr. Sven-Christian F. Ebenhag of Netnod will address these risks and present the latest work on building a redundant, national distribution system for time and frequency in Sweden. His talk will explore why redundancy is vital, how national timescales can be distributed over fiber networks, and what it takes to ensure these systems remain robust in the face of sabotage, denial of access, and other disruptions.
The Problem with Over-Reliance on GNSS
GNSS technology has transformed how we deliver time and frequency signals, but its convenience masks a dangerous fragility. Disruptions to GNSS — intentional or accidental — can instantly undermine systems critical to a country’s functioning. Despite the high stakes, the market has been unwilling to fund the infrastructure needed to ensure fully traceable time delivery. National Metrology Institutes often lack the resources to fill that gap. The result is that many organizations, from utilities to telecoms, depend on GNSS with no backup plan.
A Fiber-Based, Redundant Approach
In Sweden, new research and development efforts are tackling this problem head-on. Dr. Ebenhag will present a system that distributes time and frequency directly from the Swedish national time scale using multiple geographically diverse locations, each equipped with redundant atomic clock-based time scales. This approach creates a resilient, traceable, nationally controlled time and frequency source by leveraging existing fiber infrastructure and ensuring coexistence with regular communication traffic.
This kind of architecture offers protection from GNSS vulnerabilities and ensures that critical services have continuous access to the precise timing they need to operate.
About the Speaker
Dr. Sven-Christian F. Ebenhag joined Netnod in December 2024. He holds a doctorate in photonics from Chalmers University of Technology in Sweden, where his thesis focused on frequency transmission techniques and fiber optic communication systems. His career includes work as a hardware and software consultant for electronics, and leadership roles in time, frequency, photometry, and radiometry at the RISE Research Institute of Sweden. Most recently, he served as a Senior Scientist at RISE, specializing in photonics and implementing time and frequency transmission over national fiber networks. He has also worked with Big Science Sweden to increase the country’s presence at thirteen international research facilities.
📅 When: 25 September 2025, 1:00 PM
📍 Where: BalticNOG 2025, Litexpo, Vilnius, Lithuania — Room 5.1
🎯 Track: Other — Day 2, Session 2
