VIAVI Launches Cesium-Free ePRTC360+ Timing Solution for Critical Networks
VIAVI Solutions Inc. has introduced its patent-pending Cesium-free ePRTC360+ holdover solution designed to protect critical infrastructure such as power grids, transportation systems, aviation, public safety networks, 5G mobile networks, and AI data centers from growing risks related to GNSS timing interference. The solution is positioned as the only non-Cesium alternative capable of complying with ITU-T G.8272.1 requirements.
The ITU-T G.8272.1 specification mandates that Enhanced Primary Reference Time Clock (ePRTC) systems maintain a short-term drift below 30 nanoseconds when transitioning into holdover and a long-term drift of less than 100 nanoseconds over a 14-day period, all traceable to UTC. Until now, these benchmarks were achievable only with Cesium atomic clocks, but VIAVI’s ePRTC360+ now meets the same criteria without Cesium.
According to Doug Russell, Senior Vice President and General Manager of Aerospace and Defense at VIAVI, the Cesium-free ePRTC360+ delivers performance comparable to advanced Cesium-based systems at a significantly lower cost, enabling broader deployment across synchronization networks, including edge locations that previously could not justify Cesium clock investments.
The ePRTC360+ has undergone testing in real-world defense and commercial environments involving GNSS jamming and spoofing and has been incorporated into the VIAVI SecurePNT 6200 product line. It can sustain 100-nanosecond accuracy during GNSS outages using the resilient altGNSS GEO-L service with no time limitations. The system integrates an enhanced SecureTime GEO anti-jamming antenna and a GNSS anti-spoofing antenna that supports eGNSS GEO services with authentication capabilities to detect and mitigate spoofing threats.
Unlike traditional omnidirectional GNSS signals that are vulnerable to interference, VIAVI’s proprietary GEO-L service uses encrypted, highly directional L-band transmissions from geostationary satellites. Combined with the SecureTime GEO antenna, this approach strengthens anti-jamming resilience and provides a reliable timing source for the ePRTC360+’s internal Rubidium oscillator. It also supports seamless switching between multiple orbital sources when primary GNSS signals are compromised by jamming, spoofing, or advanced meaconing attacks.
Because ePRTC360+ clocks are more cost-effective than Cesium systems, operators can deploy them throughout the network rather than only at core sites. They also work alongside non-RF Cesium clocks at the network core, improving synchronization resilience through meshed PTP backups, particularly during localized or regional GNSS disruptions.
The solution also overcomes several limitations associated with Cesium-based timing systems, including vulnerability to physical shock, complex startup procedures, lengthy GNSS learning periods, export licensing requirements, strict shipping and storage regulations, and periodic Cesium tube replacement. Disposal of Cesium clocks is also classified as hazardous due to their material composition.
By removing these challenges, the ePRTC360+ is designed for straightforward integration into any vendor’s grandmaster clock platform, helping operators meet strict ePRTC timing standards while lowering overall operational costs.
VIAVI will showcase the ePRTC360+ for the first time at Mobile World Congress (MWC) Barcelona 2026, taking place from March 2 to March 5, at Stand 5B18 in Barcelona, Spain.
The ITU-T G.8272.1 specification mandates that Enhanced Primary Reference Time Clock (ePRTC) systems maintain a short-term drift below 30 nanoseconds when transitioning into holdover and a long-term drift of less than 100 nanoseconds over a 14-day period, all traceable to UTC. Until now, these benchmarks were achievable only with Cesium atomic clocks, but VIAVI’s ePRTC360+ now meets the same criteria without Cesium.
According to Doug Russell, Senior Vice President and General Manager of Aerospace and Defense at VIAVI, the Cesium-free ePRTC360+ delivers performance comparable to advanced Cesium-based systems at a significantly lower cost, enabling broader deployment across synchronization networks, including edge locations that previously could not justify Cesium clock investments.
The ePRTC360+ has undergone testing in real-world defense and commercial environments involving GNSS jamming and spoofing and has been incorporated into the VIAVI SecurePNT 6200 product line. It can sustain 100-nanosecond accuracy during GNSS outages using the resilient altGNSS GEO-L service with no time limitations. The system integrates an enhanced SecureTime GEO anti-jamming antenna and a GNSS anti-spoofing antenna that supports eGNSS GEO services with authentication capabilities to detect and mitigate spoofing threats.
Unlike traditional omnidirectional GNSS signals that are vulnerable to interference, VIAVI’s proprietary GEO-L service uses encrypted, highly directional L-band transmissions from geostationary satellites. Combined with the SecureTime GEO antenna, this approach strengthens anti-jamming resilience and provides a reliable timing source for the ePRTC360+’s internal Rubidium oscillator. It also supports seamless switching between multiple orbital sources when primary GNSS signals are compromised by jamming, spoofing, or advanced meaconing attacks.
Because ePRTC360+ clocks are more cost-effective than Cesium systems, operators can deploy them throughout the network rather than only at core sites. They also work alongside non-RF Cesium clocks at the network core, improving synchronization resilience through meshed PTP backups, particularly during localized or regional GNSS disruptions.
The solution also overcomes several limitations associated with Cesium-based timing systems, including vulnerability to physical shock, complex startup procedures, lengthy GNSS learning periods, export licensing requirements, strict shipping and storage regulations, and periodic Cesium tube replacement. Disposal of Cesium clocks is also classified as hazardous due to their material composition.
By removing these challenges, the ePRTC360+ is designed for straightforward integration into any vendor’s grandmaster clock platform, helping operators meet strict ePRTC timing standards while lowering overall operational costs.
VIAVI will showcase the ePRTC360+ for the first time at Mobile World Congress (MWC) Barcelona 2026, taking place from March 2 to March 5, at Stand 5B18 in Barcelona, Spain.
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