The new “enhanced” primary reference time clock (PRTC) recommendation from the International Telecommunication Union (ITU), G.8272.1, looks set to be one of this year’s key innovations in the world of network synchronization. Aimed at producing the levels of accuracy necessary for 5G, enhanced PRTCs (ePRTCs) go far beyond the current technology. While the time output of today’s PRTCs should be accurate to within 100ns of Coordinated Universal Time (UTC), this new generation of clocks promises to deliver time to within just 30ns. ePRTCs also offer a greater level of reliability – unlike current PRTC technology, which has no holdover specifications, the emerging enhanced clocks are able to hold time accurately for 14 days, ensuring time service performance during GNSS outages.
The new technology achieves enhanced performance by using highly stable cesium clocks to filter the wander out of the GNSS-based timing. This enables the ePRTC to utilize the advantages of both timing methods, ensuring the long-term accuracy of GNSS alongside the short-term stability of a cesium beam atomic clock. The use of these cesium-based timing sources is also the key to enabling stringent holdover capabilities when GNSS is not available. Combining a GNSS receiver with at least one cesium clock creates a phenomenally accurate source of time with guaranteed holdover performance. This reduces dependency on GNSS and gives operators control of their network synchronization.
The improved accuracy and the protection against GNSS outages are both features that will provide significant advantages in real-world applications. As well as the telecommunications industry, areas such as metrology and utility networks are set to benefit from the more than three-fold improvement in timing accuracy. And, as GNSS vulnerabilities have increased in recent years due to deliberate spoofing and jamming attacks as well as the natural threats of solar flares and space weather events, a move away from reliance on GNSS alone is seen as a mandatory step toward more secure network synchronization solution.
G.8272.1 demands that ePRTCs be able to hold time within 100nsec for up to 14 days (when verified against a primary time standard such as UTC). Enhanced reference clocks that are traceable to UTC but stable in both the short and long term will become more and more essential in telecommunications as end applications demand stricter accuracy and more operators roll out LTE-Advanced. 5G requirements are the ultimate target of the new enhanced clocks.
At Oscilloquartz, we’re working continually to help create the set of ITU specifications needed to deliver the required levels of stability, accuracy and resiliency for this and other groundbreaking timing innovations. In fact, this year may be the era of “advanced everything”. As well as ePRTCs, we’re also heavily involved in the development of other enhanced clock specifications such as enhanced Ethernet equipment clocks and the enhanced PRC clock. Additionally, an advanced cesium beam clock technology based on optical pumping will soon be introduced to bring superior stability, accuracy and resiliency to the next generations of ePRTCs and ePRCs. Watch this space for further updates.