Officially, there’s no explanation for what caused the recent disruption at Israel's busiest airport. For three weeks, flights were affected by mysterious disruption to signals from the Global Positioning System (GPS). Pilots reporting navigation system errors with inaccurate “spoofed” locations had to resort to alternative methods to land planes.
Whatever or whoever was behind the disturbance at Ben Gurion International, the one thing that is clear is that this was a perfect demonstration of the danger of reliance on satellite signals alone for critical services.
In aviation, Global Navigation Satellite Systems (GNSS) such as GPS are vital. Pilots need to know their exact position on the globe and air traffic controllers use GNSS signals to coordinate thousands of planes taking off and landing every day. And, while there were no casualties during the disturbances at Ben Gurion, the event illustrates just how easily key infrastructure relying on GNSS can be targeted at scale and for sustained periods.
The alternatives to GNSS
Attacks that supply false location or time data (spoofing), and those that block GNSS signals entirely (jamming) aren’t just a problem for navigation. They can negatively impact other critical application that rely on GPS-based timing from mobile networks to military applications to power utilities. LTE-TDD (4G) base stations, for example, require a reliable source of coordinated universal time (UTC) derived from GNSS satellites, to enable the network synchronization needed for bandwidth-intensive applications.
And with 5G being rolled out across the world, it’s more crucial than ever for telecom network synchronization technology to have an alternative source of UTC that doesn’t rely on satellite signals. Widespread 5G coverage means many more connected devices. If, or indeed when, GNSS attacks happen in the 5G era, operators will need even more accurate alternative timing sources capable of functioning for extended holdover periods.
This is why the ITU-T has created the enhanced primary reference time clock (ePRTC) standard. Unlike the current PRTC technology, ePRTCs are defined in the new G8272.1 recommendation as highly accurate frequency, phase and time synchronization sources able to hold time accurately for at least 14 days, ensuring time service performance during long GNSS outages.
Highly precise autonomous timing
ePRTCs ensure GNSS backup by combining a GNSS receiver with a cesium clock. This creates an outstandingly accurate source of time with guaranteed holdover performance. Cesium clocks are the most autonomous and stable frequency source. However, they are not traceable to UTC. On the other hand, GNSS receivers provide long-term traceability to UTC but can be subject to outages and degradation in performance. The combination of both technologies ensures an accurate, secure and robust UTC traceable time and frequency source. The GNSS receiver makes it possible to align the ePRTC timescale to the UTC timescale. The use of the cesium clock reduces dependency on GNSS and gives operators control of their network synchronization.
Our own ePRTCs offer an effective solution, resolving GNSS dependency while providing higher performance levels than standard PRTC systems. They provide highly accurate frequency, phase and time synchronization and maintain prolonged service performance even without satellite signal availability. Oscilloquartz ePRTC solutions also guarantee much higher levels of accuracy than standard PRTCs, increasing precision to within 30ns of UTC, compared to within 100ns with PRTCs.
They are the ideal choice for modern networks that urgently need to move away from reliance on GNSS alone. What’s more, our OSA 3230B ePRC cesium clock can be combined with either our OSA 5430 or our OSA 5440. This choice of grandmaster clock options means we can offer both a highly compact ePRTC solution and a fully hardware-redundant variant with scalable fan-out, so that operators can select the perfect technology for every scenario.
With our Oscilloquartz ePRTC solution providing new levels of stability, accuracy and reliability in the future, with or without GNSS, airports like Ben Gurion will be safe from costly and dangerous disruptions to satellite signals, whoever may be behind them.