Submarine operations represent one of the most demanding environments for resilient timing. With no access to GNSS for weeks or months, maintaining nanosecond-level accuracy is critical for secure communications, navigation, and mission coordination, as well as for enabling rapid and accurate GNSS reacquisition once even limited signals become available. The extreme denial durations place unique demands on oscillator stability. These challenges call for innovative solutions that combine high-stability hardware with advanced algorithms to predict, correct, and minimize accumulated timing deviations, as well as fast acquisition. This session will explore the unique timing challenges of submerged platforms and present approaches to extend ePRTC-class performance into truly denied and mobile environments. We will highlight application needs from a defense perspective and then examine algorithmic techniques and simulations that mitigate timing deviation and enhance long-term holdover. The talk will combine operational context with technical solutions, offering fresh insight into timing resilience for critical defense missions.

Civil and Military air traffic control (ATC) systems rely on three core technologies, satellite positioning systems ,radar, and communications (data and voice), to safely manage the congested airspace across the globe.  Due to the density of traffic, and the increased safety risks presented by takeoff and landing, higher resolution and faster update systems are required near airports. Precision frequency and time control is a critical element for all three of these technologies.  Many of these systems are receiving critical upgrades due to the aged infrastructure. This presentation will discuss how various traffic control systems work, and the role and requirements of frequency and time in these systems, including ATC radars, Automatic Dependent Surveillance Broadcast (ADS-B), Wide Area and Local Area Multilateration (WAM/LAM), Satellite Augmentation Based Systems (SBAS), and data and voice communication systems.  Timing architectures solutions that plan for GNSS denial will be presented.

The IEEE 802.1 Time Sensitive Networking TSN profile for Aerospace Onboard Ethernet Communications has just been consented as IEEE802.1DP/SAE AS6675. This profile has been developed jointly by the IEEE 802.1 Working Group and SAE Avionics Networks AS-1 A2 Committee to address the unique requirements of the aerospace and defense industries. IEEE802 TSN has defined a set of standards with several features, options, configurations and protocols for time-sensitive communication over Ethernet. IEEE 802.1AS, which is one of the four pillars of TSN, relies on the generalized PTP gPTP protocol to distribute precise time synchronization across network devices. This paper discusses the main features of the IEEE 802.1 profile for Aerospace Onboard Ethernet Communications.

When the US government announces major efforts like GOLDEN DOME everyone sees dollar signs for their respective products.  But what technologies will be required and how will they be implemented in such a vast protective dome network?  This presentation provides an overview of the types of networks required to implement a Golden Dome protective umbrella, including review of required timing accuracies and methods to achieve them across a nationwide network. Topics include: Golden Dome- what is it? Network requirements for Golden Dome Timing accuracy requirements Typical network topology for a national defense network Timing references for national defense

The current geopolitical landscape is making the topic of timing in aerospace and defense of particular interest within the WSTS community, especially as related to the increasing need for robustness and resiliency in the timing in navigation and guidance systems. Some of the solutions and challenges addressed by the telecom industry, have often been applied to other industries. While solutions applied to the Aerospace and Defense sector are typically developed in isolation from other industries, some of the solutions developed to support the telecom industry can be valuable in also in the Aerospace and Defense context. In particular, being telecom one of the key critical infrastructures, similar challenges related to the needs for an increased resiliency and robustness in timing must be addressed. Starting from inputs from partners that active within the Aerospace and Defense sector, this talk will provide an analyse on how telecom’ solutions and standards related to resiliency and robustness in timing, could be applied to a context as the Aerospace and Defense. Note: speaker to be confirmed

AI/agent pipelines quietly assume trustworthy time: stage ordering, rate limits, cache freshness, and consent/policy expiry all depend on it. When clocks drift or wander, symptoms show up elsewhere—telemetry “holes then bursts,” duplicate side effects, stale responses, or precision/recall drops in abuse detection—so teams chase model or data issues long before suspecting time. This talk presents a practical, vendor-neutral blueprint for timing integrity in production systems. We introduce a TrustedTime client contract that returns (now, confidence, source) so application code can make tiered decisions (provisional vs. final) based on time confidence. We show how to build monotonic, drift-tolerant features—epoch-based counters and windows keyed to a monotonic clock—to prevent skew-induced bucket hopping and sequence errors. We operationalize Clock-Health SLOs (offset, wander, asymmetry; plus a “confidence duty cycle”) as CI/CD and runtime gates that automatically degrade risky actions when time quality drops. An anonymized incident—lagging clock ⇒ telemetry holes ⇒ bot false positives—motivates the design. Results are illustrated with a reproducible skew-injection harness and synthetic data to demonstrate stability and sub-millisecond overhead targets. Attendees leave with SDK patterns, gating policies, and a detection/remediation playbook they can adopt immediately.

The widespread adoption of distributed, GPU-accelerated systems for artificial intelligence (AI) has created a pressing need for advanced profiling and optimization methodologies. Understanding and resolving performance issues in these complex environments is essential. This paper discusses an approach centered on leveraging high-precision time synchronization to improve profiling and debugging in AI clusters.  Standard profiling techniques in distributed settings often struggle with temporal inconsistencies across different nodes. This lack of a common time reference can make correlating events and reliably diagnosing issues difficult. By employing time synchronization mechanisms such as the Precision Time Protocol (PTP), we can achieve precise, unified timestamp alignment across the entire cluster.  We discuss how this synchronized, high-fidelity data enables more effective tracing of AI workload execution. By resolving fundamental temporal ambiguities, this approach enables deterministic, cross-node event correlation. This, in turn, provides a clear foundation for causal analysis and the identification of performance bottlenecks, resource contention, and other operational anomalies with greater clarity.  This methodology underscores the value of precise time data in improving profiling tools for distributed AI infrastructure. Enabling more accurate analysis of system events ultimately supports the development of more reliable and optimized AI applications. 

Keeping track of the order of events in distributed computing is one of the most fundamental and important problems in computer science. In the past, distributed systems builders have only used wall-clock physical time in features geared for human consumption (like log timestamps and UI presentation). Time, however, is changing, and when clocks can be used at scale with a precision and accuracy good enough for distributed systems, you can approach the system design in new ways. Clock accuracy becomes a feature and benefit, not a bug, in your system design and function, and the aforementioned algorithms can be simplified and new levels of system performance can be unlocked. In 2023, we improved the Amazon Time Sync Service to microsecond-level clock accuracy on supported Amazon EC2 instances. This new capability, the first from any cloud provider, adds a local reference clock to Amazon EC2 instances and is designed to deliver clock accuracy in the low double-digit microsecond range within an instance’s guest OS software. Since this launch, we have brought this capability to global scale at AWS datacenters worldwide. At AWS, we, and our customers, are now able to use real wall-clock time in applications including databases, AI/ML, financial services, broadcast/media, telecommunications, quantum computing, and more to improve both the performance and resiliency of our systems and applications. Democratizing access to good clocks is only the first step for customers. Making it easy for customers applications to ingest and leverage timestamps into their designs is just as important as providing reference clocks. We have done the undifferentiated heavy lifting for customers at the software level by building and sharing updated, open-source software for anyone with a trusted time source to better synchronize and leverage time in their applications. We foresee broader demand from anyone and everyone building distributed applications to need a quality time source, and will be using this talk to share these updates. Included are examples where AWS and our customers are using time as a key primitive in system design.

As enterprises and governments race to deploy AI, sovereignty has become a defining requirement. Regulations increasingly mandate that data, models, and inference remain within defined geographic or jurisdictional boundaries. At the same time, AI workloads are becoming more distributed executed across multi-cloud, edge, and colocation environments. This creates a fundamental challenge: how to ensure deterministic, sovereign AI execution while maintaining resilience and performance in globally interconnected systems. Building on the emerging concept of Neoclouds – distributed, sovereignty-aware cloud environments spanning hyperscaler regions, sovereign data zones, and edge colocation sites, this paper examines their implications for timing and synchronization. While Neoclouds are being discussed in policy and architectural circles, their success depends on synchronization frameworks that can guarantee temporal integrity, data traceability, and deterministic inference pipelines across distributed domains. Our contribution explores three dimensions: Time-Synchronization as a Sovereignty Enabler – how sub-microsecond synchronization supports compliance (e.g., jurisdictional logging, financial traceability) and protects against replay or tampering in sovereign AI environments. Architectural Patterns for Neoclouds – how interconnection fabrics, timing distribution, and policy-based routing can be combined to create jurisdiction-bound yet resilient AI execution environments. Operational Lessons – from hybrid deployments where timing was used to validate locality, detect cross-border data movement, and support AI observability. Key insights include the need for synchronization frameworks that are both technically precise and audit-ready, bridging regulatory compliance with timing science. We show how timing primitives can serve as anchors of trust – verifying where and when AI computations occur, ensuring resilience against both GNSS vulnerabilities and jurisdictional violations. For the WSTS community, this work situates Neoclouds and AI sovereignty as an emerging application domain where synchronization is not a background utility but a frontline enabler. By linking timing, sovereignty, and AI resilience, we highlight an opportunity for standards bodies and timing experts to shape the future of distributed intelligence.

A fundamental milestone for synchronization in data centres will be reached at the ITU-T SG15 (October 2025) with the planned release the first edition of a Supplement on synchronization in data centre. The Supplement puts together considerations on target time sync requirements, suitable solutions, clocks, etc. as agreed by some of the major users and vendors active within the data centre industry. The benefits in distributing synchronizing among servers in a data centre range from minimizing power consumption to guarantee the correctness of operations distributed over multiple servers. These benefits will be particular visible in case such as AI data centres. This talk will summarize efforts done in various bodies, particular focus on the ITU-T Supplement, to define requirements and harmonize solutions that can be implemented within various types of data centres.  The plan is to present in cooperation with partners, the results of an analysis of timing accuracy and latency measurements, with particular emphasis on observability and correlation across distributed systems. These are aspects particularly relevant as data centres evolve toward AI and large-scale distributed systems. Note: speaker to be confirmed

Edge computing for AI autonomy and resilient systems demands sub-nanosecond timing synchronization, surpassing traditional ITU-T G.703 10 MHz clock and standalone 1PPS interfaces for clock distribution. This talk introduces the Embedded Pulse-Per-Second (EPPS), proposed as Annex C to ITU-T G.703, embedding a 1PPS phase-synchronization marker into the 10 MHz clock using a 25% duty cycle modulation (25 ns high, 75 ns low) at the 1PPS boundary. With ±10 ns alignment, <100 ps jitter, and <500 ps transition times (40-60% amplitude) over 50 Ω interfaces with 3 m cabling, EPPS achieves “epsilon”-level precision, complying with G.703 clause 20.2 and Table 19-4 for unified phase and frequency distribution. EPPS extends to edge ecosystems via PCI-SIG CEM 7.0 (draft) and OCP NIC 3.0 standards. PCI-SIG CEM reassigned JTAG pins as FlexIO pins in prior specifications, with some allocated for USB 2.0; CEM 7.0 proposes Timing Synchronization on unallocated FlexIO pins to bi-directionally distribute 1PPS or EPPS, enabling precise timing for AI accelerators in GPU clusters. OCP NIC 3.0 repurposes FlexIO pins for a bi-directional Timing Synchronization interface (including independent frequency and phase/time distribution; important for Telecom), propagating 1PPS and 10 MHz signals to digital phase-locked loops with sub-nanosecond accuracy, supporting Telecom and OCP configurations. The talk proposes a unified timing framework, including standards synergy for precise clock distribution across ITU-T, PCI-SIG, and OCP.

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When critical infrastructure relies on GNSS as time source, the threat of GNSS spoofing is a challenge that has increased in recent time. Spoofing attacks can originate from bordering areas or even within national boundaries and pose significant threats, particularly to defence and other mission-critical networks. Unlike jamming, which disrupts signals entirely, spoofing is more insidious and can mislead systems into accepting incorrect timing data and degrade network performance or disabling services altogether. We analyze this in the context of CPNT network approach where the network provides an alternative timing source. During Jammertest in Norway, Erillisverkot and Net Insight have focused on the impact of GNSS spoofing on time synchronization and how it can be mitigated. In Jammertest 2024, there were several lessons learnt on spoofing behaviour and impact in a real-world hostile environment. Based on these findings and the implementation of new functionalities, Jammertest 2025 has in turn given new experiences on how spoofing can be detected, and what strategies can effectively mitigate its effects.  This session will share lessons learned from the field, highlighting how spoofing can be identified through synchronization anomalies and incorporated into performance monitoring. It will also explore how critical networks can build greater resilience by integrating spoofing detection capabilities and alternative time sources into the synchronization strategy.

Those attending WSTS are fully aware of the growing RF and cyber threats to GNSS. A world in which GNSS is routinely degraded, disrupted, deceived, or denied impacts critical infrastructure owners and operators across multiple sectors and seriously affects nearly every country’s national defense. This presentation will look at the performance of a complementary PNT service from low-Earth orbit (LEO) in an environment where GNSS has been intentionally compromised. Specifically, this briefing will focus on how the LEO PNT service from Iridium performed during deliberate GNSS attacks (e.g., jamming, spoofing, meaconing, etc.) at Jammertest 2025 in Andøya, Norway. Results from multiple test scenarios will be presented: static timing dynamic timing (i.e., timing on the move) Performance parameters of the LEO PNT service (e.g., signal strength, burst rate, number of satellites in view, etc.) will be presented along with various performance comparisons against signals from GPS and other GNSS. The data will show how a space-based complementary PNT service from LEO can continue to provide an accurate and stable source of time for timing sync applications when GNSS signals are impaired, falsified, or disabled.

Global Navigation Satellite Systems (GNSS) are the backbone of modern infrastructure, supporting applications in aviation, maritime transport, autonomous navigation, geospatial mapping, precision agriculture, and emergency management. GNSS also enables high-precision timing essential for synchronizing telecommunication networks, financial systems, and power grids. Its widespread use stems from its global coverage, cost efficiency, and accuracy. However, GNSS signals—transmitted from medium Earth orbit—are inherently weak upon reaching Earth’s surface, making them vulnerable to jamming, spoofing, and interference [1, 2]. These vulnerabilities pose serious risks to national security and critical infrastructure, underscoring the need for resilient, GNSS-independent alternatives.  A promising solution is the Broadcast Positioning System (BPS), developed by the National Association of Broadcasters (NAB) as a terrestrial Positioning, Navigation, and Timing (PNT) technology [3]. BPS leverages the Advanced Television Systems Committee 3.0 (ATSC 3.0) broadcast standard—widely deployed as NextGen TV in the U.S. and recognized by the ITU. Using existing television broadcast infrastructure, BPS transmits powerful terrestrial signals capable of nanosecond-level timing accuracy [4–8]. Its key advantages include:  Strong signals from high-power terrestrial transmitters, orders of magnitude stronger than GNSS.  Multi-band operation across 54–88 MHz, 174–216 MHz, and 470–608 MHz, enhancing coverage and interference resilience.  GNSS-independent timing when transmitters use local reference clocks.

National Association of Broadcasters (NAB) has won a contract from the U.S. Department of Transportation to demonstrate to demonstrate and test BPS time delivery service to one of Dominion Energy’s power substations located in Fairfax, Virginia. As preparation of the test, NAB has been upgrading the two-tower leader-follower network (WHUT in Washington, DC as leader and WNUV at Baltimore, Maryland as follower) to be totally GNSS-independent. Accurate and traceable time will be delivered from NIST Gaithersburg to the leader station using a dark fiber link and White Rabbit modems. The leader station will send time to the follower station using its broadcast BPS signal. The leader station has cesium clock-based holdover capability to handle accidental loss of dark fiber connection.

In this joint talk, NextNav and Oscilloquartz will demonstrate results from lab and field work showing how 5G based terrestrial Positioning, Navigation, and Timing (PNT) signals can be used as a time source for network synchronization. This 5G terrestrial solution operates at 900 MHz to broadcast a 5G standard Positioning Reference Signal (PRS) which provides an accurate timing signal to provide resilient PNT services when GPS is unavailable. The session will show how PPS/TOD outputs from a NextNav timing receiver connect into a timing grandmaster and show system performance using standard timing metrics. We will present results with timing accuracy in the tens of nanoseconds range, traceable to UTC, and stable operation in both indoor and outdoor GNSS-denied cases. The talk will highlight what worked well, what calibration was required, and the key challenges. The focus will be on practical lessons and why adding terrestrial PNT as another source makes sense for building more resilient sync networks

With vulnerabilities ever more present potentially affecting systems using GNSS as the principal source of accurate time, secondary backup sources have become increasingly critical. Addressing this issue, the ATIS SYNC group has recently completed work on a new technical report “Resilient Timing Architecture for 5G Communications Networks”.  This document considers new tools, particularly those under development at the ITU, in constructing architectural recommendations.  This paper provides details on the topics covered in this important new technical report.

Two-Way Satellite Time and Frequency Transfer (TWSTFT) has been used as a trusted time transfer and synchronization for a long time, and this approach typically provides timing accuracy of 100 ns or better. However, TWSTFT comes with high implementation costs and a complicated setup, from precisely pointing the dish to align with a satellite in geostationary orbit, to configuring many different devices to interoperate for time transfer to function. At the US Department of Energy’s (DOE’s) Center for Alternative Synchronization and Timing (CAST), we are identifying and assessing alternative timing and synchronization technologies, and among our goals is to lower cost and ease integration for industry, to hasten adoption and improve resilience. This paper highlights research into TWSTFT operational performance and efficiency compared against terrestrial links between mirrored grandmaster and slave clocks more than 1000 miles apart. We evaluate the performance of precision time protocol (PTP)-based clock synchronization using DOE’s Energy Sciences Network (ESNet), compared with TWSTFT, for wide area synchronization between clock implementations at Oak Ridge National Laboratory (ORNL) and Idaho National Laboratory (INL). Outcomes of this research will highlight the performance, accuracy, cost, and efficiency trade-offs between terrestrial and space-based approaches for time transfer to inform capital and architectural investment decisions at energy utilities.  

Vescent Technologies, in partnership with the Danish National Metrology Institute (DFM), presents an overview of the Timekeeper for Optical and Radio frequencies using C2H2 (TORCH) – a prototype optical molecular clock designed to be environmentally resilient, cost-effective, and integrated within a compact chassis. This system is intended for deployment in both governmental and commercial advanced timekeeping applications. The abstract outlines system capabilities, initial instability metrics, and projected performance targets. Previous demonstrations of an optical clock based on acetylene (C2H2) molecules using commercial-off-the-shelf hardware, including robust optical frequency comb technology and optical frequency references based on narrow linewidth lasers stabilized to acetylene transitions. These results are documented in prior publications (https://vescent-production-media.s3.us-west-2.amazonaws.com/files/675222b6883975273c5a46bb.pdf). Vescent has conducted a long-term measurement campaign where two acetylene optical clocks are compared with a Rb-disciplined GPS unit to characterize both short- and long-term performance. This campaign has been operating for over 45 days (3,888,000 seconds) in a well-trafficked laboratory setting without phase-slips, environmental shielding, or user intervention. Short-term instability of a single acetylene clock is below 3×10-13/τ1/2 and reaches a flicker floor of 2×10-14 at 100 seconds and beyond 1,000,000 seconds. No drift beyond the error bars has been measured to date. Notably, the acetylene clock out-performed the Rb-GPS system at averaging times up to 200,000 seconds. Performance data from these systems operating for over 90 days will be presented at the conference. Based on these findings, Vescent and DFM have designed TORCH – an integrated and automated version of the acetylene optical clock. Housed in a 3U rackmount enclosure, the system operate on standard AC power and supports remote operation via Ethernet. The 10 MHz and 100 MHz RF outputs are designed to support ADEVs < 4×10-13/τ1/2 with a flicker floor of <2×10-14 at timescales longer than 1,000 seconds; the system will also support TDEVs below 10 picoseconds at 1 hour and 450 picoseconds at 1 day. The 100 MHz output is engineered to exhibit phase noise below -80 dBc/Hz at 1 Hz offsets. The system features a warm-up time of less than 30 minutes and supports turn-key operation. Its projected operational lifetime exceeds 10 years, leveraging robust telecommunications-grade components, with early estimates suggesting significantly longer lifespans without requiring subcomponent replacement. Initial performance data from alpha prototype units and results from environmental sensitivity testing will be presented.

As critical infrastructures increasingly depend on precise and trustworthy time synchronization, the need for strong cryptographic protection of timing protocols has become paramount. The Network Time Security (NTS) protocol, developed within the IETF to secure the Network Time Protocol (NTP), provides a modern, standards-based framework for authenticating time sources and mitigating spoofing and replay attacks. NTS introduces a two-step mechanism that separates key establishment from time exchange, using Transport Layer Security (TLS) for the former and authenticated extension fields for the latter. This approach delivers strong cryptographic assurance while maintaining backward compatibility with existing NTP deployments. Building on the success of NTS for NTP, current research and standards work are focused on extending similar security properties to other time synchronization protocols. This presentation explores the application of NTS to the IEEE 1588 Precision Time Protocol (PTP) and the IEEE 1588.1 Client-Server Precision Time Protocol (CSPTP), each of which presents unique challenges in design and deployment. PTP and CSPTP operate in high-precision and often hardware-assisted environments where introducing authentication, key management, and replay protection must not compromise sub-microsecond accuracy. The talk will provide a concise overview of NTS for NTP, outline motivations for extending its concepts to PTP and CSPTP, and describe design approaches under discussion in the IETF and IEEE communities. It will also present a possible timeline for the ongoing work, review the current state of specification development, and identify early prototype implementations and interoperability testing efforts. Particular attention will be given to deployment models, scalability considerations, and coordination between standards bodies to ensure cohesive security across protocol layers and use cases. By integrating NTS with PTP and CSPTP, the time synchronization ecosystem can move toward a unified, scalable, and cryptographically strong security model that meets the demands of modern networked systems—from industrial automation and telecommunications to finance and power distribution. Attendees will gain an understanding of how NTS-based mechanisms can enhance trust, resilience, and precision across the entire spectrum of time synchronization technologies.

Oven-Controlled Crystal Oscillators (OCXOs) have long been regarded as the gold standard for frequency stability, delivering ppb-level stability required in timing-critical applications. However, their traditionally high power consumption and bulky thermal control systems limit their use in modern power- and size-constrained domains such as unmanned aerial/underwater vehicles (UAVs), drones, portable instrumentation, and long-term test and measurement platforms that operate without continuous power access. This paper presents the design, optimization, and performance evaluation of a next-generation low-power, low-profile OCXO architecture that addresses these constraints while maintaining excellent frequency stability and phase noise performance. Reducing OCXO power consumption poses several technical challenges. The largest contributor is the oven control loop, which maintains the crystal at a constant elevated temperature above ambient to minimize frequency drift. Lowering heater power without compromising temperature uniformity demands a rethinking of oven design, including advanced thermal insulation materials, minimal thermal mass enclosures, and adaptive temperature control algorithms. At the same time, the crystal’s cut, drive level, and aging characteristics must be optimized for stable operation over a reduced thermal gradient. Achieving this balance requires co-design of the crystal blank and oven controller. The performance demonstrates superior warm-up characteristics (<3 minutes to stability) and a profile height below 7 mm, making it compatible with airborne and handheld systems. Applications extend to timing references for UAV/UUV navigation payloads, autonomous sensor nodes, and portable test instruments used in field environments lacking stable power sources. The example provides a possibility of future OCXO miniaturization, offering a practical pathway toward ultra-low-power precision timing in edge and mobile systems. 

As access equipment such as cellular RAN Distributed Units become more critical to network operation there are increasing demands for improved availability, including extended local time holdover in the event of synchronization source failure. However, commercial pressures typically don’t allow the budget to provide this in traditional ways, so alternative novel solutions must be found. This paper shows how the latest generation of “smart” temperature compensated and controlled oscillators can be used in conjunction with the high precision measurement capabilities and fine resolution frequency control provided by modern digital phase locked loops, and advanced oscillator modeling software, to implement a robust compensation scheme enabling extended time holdover within budget.

As the demand for secure and autonomous timing sources grows, robust time scale systems are increasingly being adopted beyond metrology laboratories, extending into defense, research, and telecommunications sectors. The primary function of a time scale system is to deliver a highly stable and accurate reference to UTC, enabling precise synchronization and secure operations across diverse applications. While metrology laboratories utilize these systems to uphold national standards and ensure measurement traceability, other organizations depend on them for mission-critical operations, network reliability, and data integrity. Establishing a traceable reference to UTC without reliance on GNSS helps mitigate risks and ensures uninterrupted service. This paper examines the evolving landscape of time scale systems, outlines best practices for maintaining a continuously operating UTC-traceable reference including mission-critical redundancy and security measures, and highlights new technologies and innovations shaping the future of time scale systems.

From ultra-high frequency communications to AI-driven applications, the demand for precise timing is expanding across both wired and wireless domains. This presentation summarizes the practical needs for synchronization from the device edge to the network edge and introduces a clock module configuration designed to meet these requirements. Specifically, we will address the following three points: Distributed MIMO technology and time synchronization in ultra-high frequency communications The need for high-precision local oscillators (LOs) in such communications The importance of time stamping at the device edge in AI/digital twin applications and the corresponding device technologies We will also present our development activities and results. In recent years, the practical application of optical frequency standards, such as optical lattice clocks, has advanced significantly. In Japan, “optical internet” technology—combining these standards with photonics-electronics convergence devices—is being developed. Optical lattice clocks have already begun steering the distribution of standard time, and improved time synchronization accuracy is becoming a reality. In parallel, technological development is progressing for non-terrestrial networks (NTN), including High Altitude Platform Stations (HAPS) as disaster response platforms. These efforts are closely linked to the future vision of wireless cell towers. Together, these trends are forming the foundation of Japan’s next-generation infrastructure, enhancing the stability of standard frequencies in wired systems and building a robust communications environment independent of GNSS in wireless systems. To connect these technologies to societal implementation, it is essential to explore industrial and application fields. High-performance infrastructure only gains social value when it meets real-world needs. Without a clear vision, technological development cannot accelerate. As mentioned earlier, improvements in performance from the backhaul side are now reaching the network edge. However, accurately understanding the on-site needs and technical requirements from the device edge—and identifying specific challenges in each application field—is crucial to driving future development. This presentation aims to offer a new perspective on the intersection of technological advancement and societal implementation, considering these factors.

The intrinsic value of high accuracy time transfer is that it’s not enough to have the right time one must also have the right time at the right place. The right place could range from data centers requiring precise event timestamping to efficiently support artificial intelligence to coordinating radio assets such as cell towers to support every increasing demand for capacity, bandwidth and speed. Optical networks and associated clock systems play a key role already.  The optical networks are already well established and the growing need for accuracy and resilient time can be supported with existing deployed network in a cost effective and scalable manner. This presentation shows real world examples of high accuracy optical time transfer relating to both current high accuracy time transfer standards such ITU and G8271.1 as well as emerging coherent network time standards that can operate without satellite dependencies.  Operational aspects such as performance under fiber cuts and power outages are explored as well as alternative distribution approaches to support cost effective operation over real-world optical networks.

At WSTS 2025 we presented a summary of what we may expect in terms of synchronization requirements of 6G networks, targeted for commercial deployment in 2030. One topic that was briefly discussed was Integrated Sensing and Communications (ISAC). Historically, the requirements for network clocks were based on performance impairments that could directly relate to either an end service (e.g. DS-1 slip objectives) or the performance of the underlying infrastructure (e.g. jitter and wander). Coordinating the performance of the network resulted in the current clock hierarchy that has largely been caried over as the network evolved from TDM to packet.  As the network evolved towards higher bit rates and reliance on services at the upper (data) layers we began to see a growing gap in the spectrum (the gap between jitter and wander) we consider for timing and synchronization. Further compounding the synchronization “problem” was the increased reliance on time-of-day, for certain services and  now new infrastructures (data centers).   Note, this is being submitted to “Telecom”, but it could also be an emerging topic. Sensing and communication is seen by some to be a critical capability in future networks, but are we defining a service or an infrastructure, and what is the impact of the existing synchronization capabilities needed to manage this service/infrastructure? This presentation will build upon some of the material that was presented at WSTS2024 and examine the interactions between the system clocks with the view of understanding if the existing performance models used are valid and what additional control or synchronization measurement systems may be required for deployment. Enter description here.

The first PTP Protocol defined for time and phase transfer in telecom, G.8275.1, requires that all network switches and routers act as Boundary Clocks with respect to PTP.  This allows for network architects to estimate the accumulated time transfer error in the network path between the Grandmaster clock and the radio heads that need time synchronization from the Boundary Clock performance specifications.  Recognizing that many telecom networks would not immediately upgrade all switches and routers to support PTP, G.8275.2, Precision time protocol telecom profile for phase/time synchronization with partial timing support from the network, was also defined.  Here the presence of packet delay variation (PDV) is expected due to variable queueing delays in switches and routers that do not support PTP.  Such PDV is known to result in time transfer errors that are statistically non-Gaussian, typically exhibiting skewed error distributions with long tails in the distribution and non-stationary properties. Standard PLLs such as PI filters or Kalman filters are based on averaging to remove noise. However, such methods perform poorly when noise is skewed or with long tails in the distribution, and the non-stationary results in no static mean value to stabilize on.  Even robust statistics like the Allan Deviation do not always converge as more data points are added when there are long tails in the distribution. To manage PDV, PTP time receivers implement nonlinear PLLs that use prefiltering—commonly referred to as lucky packet filters—to select received timestamps, forwarding only packets with minimal delay for averaging.    More complex variations of lucky packet filters are also in use, but the idea is always to pick the Sync messages and Delay Request messages with the least PDV. Another problem with large networks using G.8275.2 is changes to PTP message latencies resulting from traffic engineering mechanisms.  This can result in two problems: PLL transients due to step changes in the network delay Large PTP errors due to asymmetry when the Sync and Delay Request messages take different routes through the networks, In this presentation we present: An analysis of the limitations of the lucky packet filters A description of network properties where partial timing support PTP will work well Additional capabilities that are required to overcome partial timing support challenges in larger networks Enter description here.

Precise and resilient time distribution is a critical enabler for 5G, future 6G networks, financial systems, power grids, and critical infrastructure. Today, global synchronization architectures remain largely dependent on GPS/GNSS, creating significant vulnerabilities against jamming, spoofing, and geopolitical supply constraints. Our presentation presents a national strategy for achieving true GNSS independence by generating a BIPM-registered UTC(k) reference at the national timing laboratory and distributing it nationwide through Enhanced Partial Timing Support (ePTS), a new ITU-T supplement currently under standardization. ePTS builds on IEEE 1588/G.8275 concepts while introducing advanced mechanisms for asymmetry calibration, route compensation, and dynamic error budgeting in existing MPLS/IP infrastructures. This allows highly accurate time transfer without requiring full on-path support or satellite reliance. Field results from Türk Telekom’s nationwide backbone demonstrate sub-100 ns performance over 1500 km, validating that UTC(k) can be securely extended to all network domains with carrier-grade resilience. The approach ensures robustness against GNSS disruptions, lowers operational costs by reducing satellite dependencies, and provides a sovereign timing infrastructure essential for critical sectors. Thepresentation will highlight architectural principles, deployment lessons, and integration with national metrology institutes, positioning ePTS as a foundation for GNSS-independent 5G/6G rollouts and a blueprint for other nations seeking strategic timing autonomy.

The Bulk Electric System (BES) is a key critical infrastructure element necessary for the operation of nearly every industry in the United States. Modern power system applications, such as phasor measurement units , require highly accurate time-of-day  synchronization, typically within ±1 µs. Some applications demand even greater precision, with time signals coordinated across multiple locations. Currently, coordinated universal time via Global Positioning System signals is the primary source of precise timing for control, protection, and disturbance analysis in the BES. However, reliance on GPS as a single source introduces risks. To address this, the Pacific Northwest National Laboratory (PNNL) is leading an effort for the U.S. Department of Energy to identify alternative and complementary timing sources for the electricity industry. The effort includes test and evaluation of non-GNSS solutions, industry outreach, and updates to the DOE PNT Profile for the energy sector. This presentation will: Describe the timing threat to the BES, how our project partner, the Bonneville Power Administration, a federal Power Marketing Administration operating much of the BES in the Pacific Northwest, identified the weakness of GPS as a single timing source several years ago, Detail BPA’s response, which included integrating an alternative timing source and distribution method (using IEEE 1588) to their protection roadmap. BPA has completed three phases of test and evaluation, with the latest phase involving at-scale testing on their transmission system. Additionally, the presentation will highlight a PNNL developed testbed designed to evaluate the performance and compatibility of various timing systems, both sources and distribution methods, against the specific needs of the electricity sector. The testbed uses a hybrid hardware-in-the-loop simulation environment to evaluate how various approaches work with real-world scenarios including: The effects of jamming and spoofing of PNT sources The impacts of timing disruptions on both local applications (transmission line protection), and wide-area applications (control center operations). The presentation will explain how additional users, technologies, and vendors can become involved in the testing. Lastly, this presentation will cover PNNL’s involvement in standards development, including contributions to: IEEE P1952, Standard for Resilient Positioning, Navigation and Timing (PNT) User Equipment IEEE P2030.101, Guide for Designing a Time Synchronization System for Power Substations. Following the presentation, attendees will have a better understanding of the timing needs of the electricity sector and the risks posed by inaccurate time, which can lead to unintended operations or inefficient use of resources.

Accurate time synchronization is essential for digital substation automation, enabling precise coordination of protection, control, and monitoring systems in power grids. The Precision Time Protocol (PTP), as defined by IEEE 1588-2019, provides sub-microsecond accuracy and includes an authentication feature to secure time synchronization against network-based attacks, such as network spoofing and man-in-the-middle attempts, which could compromise time synchronization and therefore decrease the grid reliability.   Current substation time synchronization using PTP is limited to the substation’s LAN, requiring physical presence for access. In future digital substations, PTP synchronization will extend to WAN communication. Securing WAN communication including PTP is critical for the reliability of the time infrastructure of the digital substation, and overall grid. Additionally, implementing PTP security in the LAN provides an extra layer of protection.   This paper presents the integration of a Time Synchronization clock system, serving as a PTP grandmaster, with the Group Domain of Interpretation (GDOI) security concept to enhance the security of time synchronization in digital substation automation. The GDOI security concept, which utilizes Key Distribution Center (KDC) servers for key management and KDC clients embedded in PTP-enabled devices for secure key distribution and authentication, ensures the integrity and authenticity of PTP messages, preventing unauthorized access and packet tampering. While the system effectively mitigates network-layer threats, it does not address GNSS spoofing or jamming, which require separate countermeasures. This presentation is finalized with experimental results demonstrating synchronization accuracy within 100 nanoseconds and robust protection against common cyber threats, ensuring reliable operation of critical power infrastructure.    

Time synchronization has long been used in substations for sequence of events reporting and post event analysis. This has been important for compliance, but protective functions could still operate with a loss of time synchronization. Modern digital substations have introduced protection signals that are distributed over an Ethernet based network, that must be synchronized to a high accuracy within 1 microsecond. A loss of synchronization under these conditions can disable critical protection elements, particularly differential schemes. To mitigate this risk, redundancy is commonly implemented using multiple clocks managed by the Best Master Clock Algorithm (BMCA) in PTP, along with redundant Ethernet connections through Parallel Redundancy Protocol (PRP). This paper serves to analyze the effects on protection of the recovery scenarios that would be encountered from a clock or network failure. Although BMCA enables automatic changeover to a new master, recovery can introduce complications. End devices may experience a time jump if its internal oscillator is inaccurate, or the new master has a significantly offset time reference. Also, the time that is taken for new master selection and synchronization may be longer than the device is capable of providing holdover. By examining these scenarios, the paper highlights the practical considerations needed for designing and implementing protection systems utilizing redundant time synchronization.

Authors: Tahmina Hoque, Doug Arnold Increased use of alternate energy sources with intermittent production, makes balancing energy flows in power grids more complex.  This has led to an increased dependency on synchrophasor measurements of current and voltage throughout the network to detect energy flow instabilities before they lead to a cascade blackout.  Grid operators need to compare the measurements throughout the grid on the same timescale, The IEEE Standard for Synchrophasor Measurements for Power Systems (IEEE C37.118) establishes a time synchronization requirement of 1us to UTC for all phase measurement units.  This specification ensures that the contribution to measurement error remains significantly below 1% of the total vector error.  Typically, in substations UTC is derived from a GNSS receiver (or two) and distributed using PTP and IRIG-B. For resilience against GNSS failures, including those caused by jamming and detected spoofing attempts, holdover oscillators and alternative sources of time are desired.  One such source can be PTP from a nearby substation, which is unaffected by the GNSS disturbance due to distance.  Also, since power grid substations are typically connected to a telecom-like network, the use of a telecom profile for this purpose is an attractive option.  Time received in this fashion can be converted to power profile PTP using an inter-working function (IWF), as defined in ITU-T G.8275.    The IWF was created by the ITU for translating between different telecom PTP profiles, but the concept is adaptable to translating from the G.8275.2 telecom profile to the IEC 61850-9-3 power utility profile, for example.  Using the IWF approach the two profiles operate in different PTP domains, so the Grandmaster (GM) of the substation domain is combined with a timeReceiver in the telecom domain.  In this presentation, we will propose guidelines for proper PTP protocol translation, including how the power profile Grandmaster (GM) clock quality attributes are determined. 

White Rabbit (WR) Ethernet enables picosecond-range synchronization of network clocks to a grandmaster (GM).  Since WR devices lock their clocks only to a single GM they have resilience problems.  Resilience requires multiple reference clocks combined to synthesize a single, uniform network time.  We have extended WR with the capability to measure the offsets of an arbitrary number, N, of GMs.  This allows us to compute a time scale based on the N-1 comparisons using ensemble algorithms. The algorithms estimate the N time offsets between each clock and the time scale, and steer the WR network to the ensemble time. We implemented a four-clock ensemble (two cesium and two rubidium clocks), connected to a metropolitan fiber-optic network in Amsterdam, the Netherlands, and assessed its performance. The testbed was built in a redundant way to demonstrate the possibility of multiple WR ‘comparator’ switches, multiple instances of the ensemble algorithm, and geographic redundancy. When we discovered that one of the ensemble algorithms, as published, produced nanosecond-range errors between different physical realizations, we devised a modification that removes these differences. With this modification, different ensemble realizations stay synchronized with static offsets of 0.1 ns, with time deviations in the low picosecond range. This performance agrees well with the expectations based on simulations of the clocks and the ensemble algorithm. We also verified the improvement in frequency stability offered by the ensemble algorithm. To this end, we used a 110-km WR link, provided by the Dutch network SURF, to the Dutch metrology institute VSL, who operate UTC(VSL). Since UTC(VSL) is based on a steered active hydrogen maser we were able to use this to represent ‘true time’, even across the WR link. We experimentally verified the superior stability of the WR link compared to the cesium and rubidium reference clocks by comparing UTC(VSL) locally to the output of a frequency comb laser, locked to an ultrastable optical reference laser. Using the WR link to UTC(VSL), we found that the two ensemble realizations in our network perform close to the theoretically best stability expected from the combination of the four reference clocks. This, in combination with the observed 0.1-ns time offsets, indicates the formation of a networked, all digital ‘atomic super flywheel’ with picosecond-range performance, which furthermore offers redundancy in every respect. In conclusion, we have implemented and demonstrated a fully digital, picosecond-range network time scale based on White Rabbit and an ensemble of atomic clocks.

The emergence of higher accuracy methods for time transfer is resulting in confusion over which solutions are appropriate for differing network configurations.  This presentation provides an overview of White Rabbit (WR) and IEEE1588 High Accuracy (HA) including intended use cases, network requirements and anticipated results.   Chronology of the talk:   Overview of White Rabbit (WR) & IEEE1588 HA (HA) Use cases for WR/HA Network requirements for utilizing WR/HA Measurement of WR/HA accuracy Future expectations for WR/HA uses

The constant concern over GNSS jamming & spoofing is causing many network operators to utilize other trusted references for synchronization, relegating GNSS as a tool for measurements only.  This presentation describes how one US agency has decoupled network synchronization from GNSS with multiple trusted references across the enterprise network. Topics include: World view of GNSS jamming & spoofing events Review of GNSS alternative trusted references Sync planning for non-GNSS strategies Safely utilizing GNSS references with protections  

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The IEEE P1952 standard, formally known as the “Standard for Resilient Positioning, Navigation, and Timing (PNT) User Equipment,” is an ongoing IEEE initiative dedicated to establishing comprehensive technical requirements and operational guidelines for user equipment (UE) that processes PNT data. Its primary objective is to bolster the resilience of PNT systems against a range of threats, including jamming, spoofing, and other disruptions that can affect Global Navigation Satellite Systems (GNSS) as well as complementary and alternative PNT services. This project originated from the collaborative efforts of the U.S. Department of Homeland Security (DHS) and the Cybersecurity and Infrastructure Security Agency (CISA) to address and mitigate PNT-related risks to critical infrastructure. In 2021, the initiative was transitioned to the IEEE under the Communications Society, where active working group meetings continue to drive its development. The standard is designed to address the needs of a diverse set of stakeholders, including: PNT user equipment capable of detecting and responding to adversities, System integrators tasked with combining multiple redundant PNT devices to achieve higher levels of resilience, End users across various sectors, such as power generation facilities, autonomous vehicles, aviation, and even individuals seeking optimal navigation routes. A key feature of the standard is the definition of resilience capabilities through clearly delineated resilience levels. This paper presents an update on the ongoing development of the IEEE P1952 standard and offers an overview of its principal clauses, with particular emphasis on the latest definitions and frameworks for resilience levels.

Alternative PNT (Alt-PNT) systems are growing rapidly in importance and small, light, low-power clocks are becoming essential to this development.  It is well-known now that while GPS/GNSS have pushed new technologies and economic growth, they also have significant vulnerabilities.  Alt-PNT systems are required as layers with the GNSS to provide resilience.  Just as ultra-stable atomic clocks on GNSS were central to its performance and adoption, ultra-stable clocks will also be needed for Alt-PNT.  Moreover, Alt-PNT systems are being designed for drones and Low-Earth Orbit (LEO) satellites.  This is a major driver for the development of low size, weight, and power (SWAP) clocks. The authors are developing an ensemble of micro-electromechanical systems (MEMS) oscillators with stability better than most clocks with similar SWAP.  Time scale ensembles have been used in timing at national metrology institutes (NMIs) for some time, including for the generation of International Atomic Time (TAI) and Coordinated Universal Time (UTC).  MEMS oscillators have improved recently such that an ensemble of them can be more stable than similar Quartz oscillators or even chip-scale atomic clocks.    In this paper we discuss the details of the performance of our ensemble clock, and how we have used artificial intelligence and machine learning (AI/ML)-driven sensor fusion along with clock steering algorithms to optimize the performance of the ensemble compensating for the MEMS aging and the variations in temperature due to external environmental conditions, including those of LEO satellites.  Temperature variations of LEO satellites can vary by +/- 40 Degrees C or more in a matter of 10-20 minutes, depending on the satellite’s thermal mass, power, reflectivity, insulation, spin and orbit, etc.  AI/ML-driven sensor fusion compensates for the LEO environment. We include in this submission a Modified Allen Deviation (MDEV) plot of of the MEMS ensemble clock steered in real-time, showing the ensemble improvement (and the impact of the reference clock, in this case a traditional Rb-based GPSDO).