--- title: "Time as infrastructure | Nexus Observatory" description: "A 5G cell must hold its phase within 3 µs of its neighbours, ±1.5 µs of a common reference; a synchrophasor’s one per cent vector error leaves room for only…" url: https://observatory.global/stories/timing-pnt/ publisher: Nexus Observatory Inc. updated: 2026-10-31 --- [Stories](https://observatory.global/stories/)System: Timing and PNT # Time as infrastructure A 5G cell must hold its phase within 3 µs of its neighbours, ±1.5 µs of a common reference1; a synchrophasor’s one per cent vector error leaves room for only tens of microseconds of timing error2. Most of that time comes from satellites, which can be jammed or spoofed. A national order in 2020 named the problem3. **Systems**: GNSS, Precision time protocol, Holdover clocks **Toward 2030**: Authenticated satellite navigation, Resilient PNT **Figures**: 4, systems diagram, simulator, data story, timeline to 2030 Go to the references **01** Systems diagram ## Where the time comes from. A primary reference time clock disciplined by satellite navigation feeds a grandmaster; the precision time protocol carries time through boundary clocks to the radio and the substation4. An enhanced reference clock adds an atomic standard that can hold time for days when the satellites are lost5. Jam the receiver and see what still has time. Scenario Figure as text: A time distribution chain with an enhanced reference A four-tier diagram: satellite navigation and an atomic clock, reference clocks, boundary clocks, and the radio sites and substations that need time. - **Sources** : GNSS, Atomic clock - **Reference clocks** : PRTC, ePRTC - **Transport** : Boundary clock, Boundary clock - **End applications** : Radio site, Substation 9 links. Scenarios: Satellites available; Satellite signal jammed; Jammed, no atomic reference. **02** Simulator ## How long a clock can coast. Without a reference, a clock drifts by its frequency offset every second. The time it can coast within a budget is the budget divided by the offset: at one part per billion, ±1.5 µs lasts 25 minutes. Reference clocks are specified to their accuracy against UTC6; the network budget is shared between them and the transport7. Figure as text: Holdover time against a time error budget A line chart of time error growing with holdover time, crossing the dashed budget line at the point marked in red. | Frequency offset | 1 ppb | | --- | --- | | Time error budget | 1.5 µs | | Holdover within the budget | 25 min | | Error after one hour | 3.60 µs | | Error after one day | 86.4 µs | **03** Data story ## Holdover by oscillator stability. The same arithmetic for five frequency offsets, from a hundredth of a part per billion to fifty. Each tenfold improvement in stability buys ten times the holdover; this is why atomic references sit at the top of the chain. Figure as text: Holdover within ±1.5 µs by frequency offset A bar chart of holdover hours for five frequency offsets, from about 42 hours at 0.01 ppb to about half a minute at 50 ppb. | Frequency offset | Hours | | --- | --- | | 0.01 ppb | 41.67 | | 0.1 ppb | 4.17 | | 1 ppb | 0.42 | | 10 ppb | 0.04 | | 50 ppb | 0.01 | **04** Timeline to 2030 ## Toward resilient positioning, navigation and timing. Authentication of navigation messages lets a receiver reject forged signals; Galileo declared its open-service authentication operational in 20258. With enhanced reference clocks and terrestrial distribution, it is part of making time a resilient public good3. Figure as text: Timing standards and resilient PNT policy A timeline from 2016 to 2030 with the enhanced reference clock recommendation, the time and phase budget, the precision time protocol revision, the PNT executive order and authenticated Galileo signals. 1. **2016-11** Enhanced reference clocks specified (ITU-T G.8272.1). Atomic-backed reference clocks with long holdover. 5 2. **2020** Network time and phase budget (ITU-T G.8271). Time error limits for telecom networks. 7 3. **2020-02** PNT resilience order. Responsible use of positioning, navigation and timing services in critical infrastructure. 3 4. **2020-06** Precision time protocol revised (IEEE 1588-2019). The 2019 edition of the protocol published. 4 5. **2025-07** Authenticated Galileo signals. Navigation message authentication declared operational. 8 Figure 1 Systems diagram **Sources reaching the end clocks**: 2 of 2 **Longest route**: 3 hops **State**: Satellites available Figure 1. A time distribution chain with an enhanced reference. A four-tier diagram: satellite navigation and an atomic clock, reference clocks, boundary clocks, and the radio sites and substations that need time. ## References 1. [3GPP TS 38.133: NR requirements for support of radio resource management (cell phase synchronisation accuracy)](https://www.3gpp.org/DynaReport/38133.htm) . 3rd Generation Partnership Project, 2024. 2. IEEE C37.118.1-2011: Standard for synchrophasor measurements for power systems. IEEE Standards Association, 2011. 3. Executive Order 13905: Strengthening national resilience through responsible use of positioning, navigation, and timing services. Executive Office of the President of the United States, Federal Register 85 FR 9359, 2020. 4. IEEE 1588-2019: Standard for a precision clock synchronization protocol for networked measurement and control systems. IEEE Standards Association, 2020. 5. [Recommendation ITU-T G.8272.1: Timing characteristics of enhanced primary reference time clocks](https://www.itu.int/rec/T-REC-G.8272.1) . International Telecommunication Union, Telecommunication Standardization Sector, 2016. 6. [Recommendation ITU-T G.8272: Timing characteristics of primary reference time clocks](https://www.itu.int/rec/T-REC-G.8272) . International Telecommunication Union, Telecommunication Standardization Sector, 2018. 7. [Recommendation ITU-T G.8271: Time and phase synchronization aspects of telecommunication networks](https://www.itu.int/rec/T-REC-G.8271) . International Telecommunication Union, Telecommunication Standardization Sector, 2020. 8. [Galileo Open Service Navigation Message Authentication (OSNMA): service declaration](https://www.euspa.europa.eu) . European Union Agency for the Space Programme, 2025. ## Related stories [Place: Airspace and drones **A shared sky below 120 metres** Flying beyond visual line of sight turns a drone from a camera on a stick into infrastructure. 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Observing them is how a distribution grid…](https://observatory.global/stories/suburb-grid-edge/) ## Where this applies [Positioning, navigation and timing](https://observatory.global/#lines)[Connectivity](https://observatory.global/connectivity/)[Security and trust](https://observatory.global/#lines)[Protocol & Grid](https://observatory.global/grid-services/)[Test and qualification](https://observatory.global/#lines)[Telecom](https://observatory.global/industries/telecom/)[Energy](https://observatory.global/industries/energy/)[Transport](https://observatory.global/industries/transport/)[Government](https://observatory.global/industries/government/)[Field tour: ground station](https://observatory.global/environments/ground-station/) © 2026 Nexus Observatory Inc. **Legal** [Privacy notice](https://observatory.global/legal/privacy/) · [Terms of use](https://observatory.global/legal/terms/) · [Cookie policy](https://observatory.global/legal/cookies/) · [Accessibility](https://observatory.global/legal/accessibility/) · [Official languages](https://observatory.global/official-languages/) · [Notices](https://observatory.global/notices/) **Company** [About](https://observatory.global/about/) · [Open governance](https://observatory.global/consortium/) · [Contact](https://observatory.global/contact/)