A new white paper sponsored by the Resilient Navigation and Timing Foundation (RNT Foundation) discusses the need and implementation of a reliable and resilient national timing architecture that will include space-based assets. This system-of-systems architecture — GNSS, terrestrial eLoran broadcasts and fiber — is essential to underpin today’s technology and support development of tomorrow’s systems, according to the executive summary of A Resilient National Timing Architecture.
“Everyone in the developed world needs precise time, all the time, whether they know it or not,” said Marc Weiss, one of the paper’s authors and an internationally recognized expert on timing and synchronization. “It is a foundation of every networked technology, digital broadcast, and most navigation systems, to name just a few critical uses.”
Three Paths to Precise Time
“Precise time is so important that everyone needs at least three independent methods of getting it. So, if one, or even two, fail it is not a national disaster,” said Pat Diamond, co-author of the paper. “Our proposed architecture calls for precise time via GNSS, terrestrial eLoran broadcasts and fiber.” Diamond is a long-time network designer, developer, and entrepreneur. He is also a member of the U.S. National Space-Based Positioning, Navigation, and Timing Advisory Board.
Diamond also pointed out that these three methods should be the backbone for timing distribution in the U.S., but won’t be the only methods. “What we are describing is a baseline architecture that will be added to,” he said. “It is a starting point. We envision in the paper additional distribution methods like time from other satellites, user clocks, and so on, all being part of the mix.”
Government Leadership
The U.S. federal government has a leadership interest and responsibility in all of this, according to the paper. Nations have long recognized the military and commercial advantages of determining and distributing precise time. Great Britain’s Longitude Act of 1714 was really about developing a chronometer to support safe navigation of Royal Navy and British merchant fleet. In the United States, the U.S. Naval Observatory has been keeping and distributing a national time scale time since 1845.
“Just because the feds have an important leadership role, doesn’t mean they have to build and own a bunch of systems,” said Dana A. Goward, the paper’s third co-author and executive director of the RNT Foundation. “There are a variety of ways these systems can be established. Public-private-partnerships, subscription contracts like the FAA did with their air traffic ADS-B system, and cooperative agreements are all examples. As we move forward with 5G telecommunications and perhaps even timing and navigation, it will be increasingly important to have a rock solid timing infrastructure to support it all.”
The National Timing Resilience and Security Act of 2018 requires the U.S. Department of Transportation to establish a terrestrial system to backup GPS timing services by December of this year. While the department does not appear to be on track to meet that goal, it completed a technology demonstration program for GPS backup technologies earlier this year. Two companies demonstrated timing distribution by fiber. Another two demonstrated eLoran.
Many Pieces Already in Place
One of the benefits of the proposed architecture is that much of what is called for is already in place, according to the paper. “We already have fiber networks, NAPs (network access points). eLoran is mature and has been deployed by the Brits. And the U.S. government owns enough former Loran-C sites to establish a nationwide eLoran network,” Diamond said. “All we need is a bit of money and some engineering work to put this all together.”
ViaLite has been asked to supply distributed GPS equipment for the NASDAQ stock exchange in New York for the first time.
Photo: ViaLite
ViaLite’s Distributed GPS System is being used to feed mission-critical timing and synchronization signals over optical fiber to multiple S650 GPS referenced NTP time servers.
Stock exchanges need to offer their clients the fastest possible trading speeds and, for this, their IT systems need to be provided with highly accurate timing signals, which can be obtained from GPS/GNSS satellite networks.
The equipment Vialite supplied included GPS lossless distributed multi-port fiber-optic links, supplied in OEM format to meet NASDAQ’s requirements.
“ViaLite was chosen for its performance attributes that are not readily available elsewhere in the RF over fiber market, as well as for its best in class quality, reliability and support,” said ViaLite director of sales, Craig Somach.
For more information on RF over fiber for data centers, stock exchanges and more, visit www.vialite.com.
Image: ChakisAtelier / iStock /Getty Images Plus /Getty Images
By Eric Colard
Head of Emerging Products, Frequency & Time Systems
Microchip Technology
Mobile operators are investing heavily in the deployment of LTE-Advanced and 5G networks that will transform cellular communications and connectivity.
They face big risks, though: the high-performance mobile services delivered over these networks are extremely dependent on precise time from GPS and other similar regional constellations broadly known as GNSS so they can synchronize radios, enable new applications and minimize interference.
If GPS/GNSS becomes unavailable due to jamming, spoofing, failures or other events, the resulting service disruption would have a catastrophic impact on system performance.
Just like the energy grid is extremely vulnerable to climate, heat, winds and dry vegetation that can lead to fires on a large scale as seen in California recently, 5G networks are vulnerable to disruptions in the distribution of precise time that can lead to total systems outage.
New technologies enable mobile operators to protect their networks from these threats. These technologies make use of existing deployments while creating new architectures for distributing very high-precision time over long distances. They minimize additional costs while offering the necessary performance to meet the demanding requirements of 5G.
Technology landscape
The latest LTE-Advanced and 5G mobile networks bring tremendous capacity and bandwidth gains that are being used to deliver new services to consumers, industries, cities and specific market segments. From high-bandwidth video delivery for smartphones to autonomous vehicles, smart cities and the internet of things (IoT) for smart factories, these new services all rely on the synchronization of numerous sensors, base stations and other devices.
Accomplishing this requires the delivery of very precise time over long distances. Without it, mobile operators cannot maximize deployment investments by minimizing disruptions and risk.
They also must devise plans they can leverage in case of GPS/GNSS malfunction. At the same time, they need to take advantage of optical networks and other existing infrastructure so that they don’t require expensive new investment in dark fiber.
Photo: iStock.com/NicoElNino
Meeting stringent requirements
Standards bodies have defined stringent requirements for precise time and synchronization such as Prime Reference Time Clock (PRTC), which includes 100-nanosecond (ns) PRTC Class A (PRTC-A), 40-ns PRTC Class B (PRTC-B) and 30-ns enhanced PRTC (ePRTC) performance specifications.
To meet these requirements, a high-quality source of time is an absolute must and a very resilient, efficient and performant distribution mechanism is required to transport time from the source to the various devices consuming time (for example, base stations, sensors and vehicles).
The problem with relying on GPS/GNSS for meeting these requirements is that its deployment can be expensive given the increasing densification of endpoints. There is also a technical vulnerability associated with GNSS receivers located at cell sites.
If the GNSS receiver cannot track satellites properly for whatever reason, the radio must be removed from service quickly to avoid interference issues due to the short holdover period of the oscillator technologies used in the radios. Because of these technical and financial considerations, operators are very motivated to find solutions where GNSS dependency is reduced or even eliminated at many locations.
Another set of considerations for operators includes:
the distribution of time from the source to the endpoints using the network;
the network nodes; and
the various synchronization capabilities these network nodes can support.
Typically, a precision time protocol (PTP) grandmaster is located at the beginning of the timing chain and complies with 100ns PRTC-A or 40-ns PRTC-B so it can deliver precise time to the end of the chain within +/-1.5 microseconds. The network nodes on the path typically embed a Time Boundary Clock (T-BC) capability that meets either Class A (50-ns) or Class B (25-ns).
A new type of time-distribution architecture is needed to address these requirements and considerations so operators can protect their mobile network against GNSS disruption and distribute precise time over long distances for national coverage. This architecture must also deliver the necessary performance to meet end-to-end budgets for 5G needs.
A different time-distribution architecture
There are multiple capabilities a high-precision time-distribution architecture should feature so that operators can most effectively mitigate GPS/GNSS vulnerabilities and solve other challenges in their 5G networks. The architecture should:
leverage the existing optical network (thus avoiding high cost dark fiber expenses)
use a dedicated lambda in order to transport time in the most rapid manner
protect, to the utmost level, a redundant source of time that meets the highest, 30ns ePRTC performance and uses a combination of Cesium and GNSS as the source of time
have two directions for the flow of time (East and West) so that a redundant path can be leveraged in case of any issues along the way from source to endpoint
have a chain of high-precision boundary clocks (HP BCs) that can meet the highest level of performance defined by today’s standards (T-BC Class D 5ns)
A multi-domain architecture of this type offers the redundant, sub-microsecond end-to-end timing capabilities that are required to affordably deliver the high performance, 5-nanosecond per node distribution of precise time over hundreds of miles.
An example of this type of solution is Microchip’s TimeProvider 4100, which can be configured as either an ePRTC at the source of the timing chain with PRTC-A and PRTC-B time-delivery capabilities to various end nodes, or an HP BC on the optical network path.
This type of product can also be configured for application-specific requirements, end to end, with up to nanosecond precision time-delivery capabilities over long distance.
Assuring precise timing
The success of a coming generation of high-performance mobile services will depend on how well operators address today’s critical GPS/GNSS vulnerabilities. Jamming, spoofing, failures or other events can disrupt the precise GPS/GNSS timing that 5G networks need for synchronizing radios, enabling applications and minimizing interference.
The latest high-precision time-distribution architectures mitigate these risks with minimal additional cost and give operators the performance they need to support demanding new 5G services ranging from IoT-based applications to receiving high-bandwidth video on smartphones.
Microchip has released version 2.1 for its TimeProvider 4100 timing grandmaster.
Eric Colard leads product line management for Microchip’s TimeProvider 4100 and Integrated GNSS Master solutions for the telecom, utility and other industries. Colard’s leadership includes product definition, customer interaction, outbound promotions and business development.
He has held successive technical and leadership roles at technology companies in the U.S. and Europe. He began his career as an engineer in the networking arena on X.25, frame relay and other protocols at companies including Alcatel and Cap Sesa Telecom. He later held successive product management and business development leadership roles in networking, security, and other areas at Novell, Tumbleweed, FaceTime and Vernier Networks.
As the industry rapidly progressed, Colard increasingly became involved in wireless data compression and TCP/IP optimization. In 2007 he joined Symmetricom and architected and built the SyncWorld ecosystem with partners Alcatel-Lucent, Ericsson, Nokia Siemens and Cisco. Through acquisition Symmetricom became part of Microsemi, which today is part of Microchip.
Colard holds bachelor of science and master of science degrees in computer science, both from Ecole Nationale Superieure des Telecommunications (now Telecom ParisTech) in Paris, France. He is a member of the Metro Ethernet Forum (MEF), Open Compute, Telecom Infra Project and Small Cell Forum. He has received an award for his industry contributions from the Small Cell Forum.
The National Aeronautic and Space Administration (NASA) is readying for an ultra-precise atomic clock that could not only transform the navigation of deep space missions, it could also improve the accuracy of GPS timing and thus GPS positioning. It is expected to launch in June.
Drawing of the DSAC mercury-ion trap showing the traps and the titanium vacuum tube that confine the ions. The quadrupole trap is where the hyper-fine transition is optically measured and the multipole trap is where the ions are “interrogated” by a microwave signal via a waveguide from the quartz oscillator. (Image: NASA.)
The Deep Space Atomic Clock (DSAC) is a very small (the size of a toaster) mercury-ion atomic clock that is as stable as a highly precise ground atomic clock, yet small enough to fly aboard a spacecraft, and rugged enough to operate in deep space. Current ground-based atomic clocks that locate and navigate deep space missions are too massive to fly in space themselves.
Thus, tracking data from the far-flung spacecraft must be collected and processed on Earth, meaning a two-way tracking link. DSAC will enable NASA to improve tracking data precision by an order of magnitude for its deep space missions out to Jupiter, Saturn — and beyond.
It could also be used to improve the accuracy of GPS. DSAC is more stable and accurate than the atomic clocks currently aboard GPS satellites. As system modernization proceeds, use of a DSAC aboard future satellites holds out many promises. DSAC technology uses the property of mercury ions’ hyperfine transition frequency at 40.50 GHz to steer the frequency output of a quartz oscillator to a near-constant value.
The clock confines the mercury ions with electric fields in a trap and protects them by applying magnetic fields and shielding. It is anticipated that DSAC would produce only 1 microsecond of error over 10 years.
For further details on NASA’s Deep Space Atomic Clock project and detailed callouts on the diagram above, look here.
It happened in the blink of an eye. Less than a blink. Far less, actually. Slightly more than one one-thousandth of an eye blink, according to calculations. In that amount of time, one of your eyelashes traverses 10 micrometers on its journey toward your lower eyelid.
And yet it was long enough to throw computers and communications systems around the world out of whack, generate thousands of alarms, and pull engineers from their beds at 2 a.m.
One occurrence might have been enough to do all that. I’m not sure. But it kept happening over and over again. Thus the alarms, the out-of-whackness, the sleep deprivation. At least it did not generate massive financial trading sell-offs, blow holes in national security, or shut down Facebook, Instagram and Snapchat. For that, we may be thankful.
But it might have.
The plot shows how the anomaly event impacted one GPS timing receiver during the day. (Click to enlarge | Chart: Chronos Technology)
“On 26 January at 12:49 a.m. MST, the 2nd Space Operations Squadron at the 50th Space Wing, Schriever Air Force Base, Colo., verified users were experiencing GPS timing issues. Further investigation revealed an issue in the Global Positioning System ground software which only affected the time on legacy L-band signals. This change occurred when the oldest vehicle, SVN 23, was removed from the constellation. While the core navigation systems were working normally, the coordinated universal time timing signal was off by 13 microseconds which exceeded the design specifications. The issue was resolved at 6:10 a.m. MST, however global users may have experienced GPS timing issues for several hours.” (This excerpt from an U.S. Air Force communiqué appears in a brief news account.)
“The Joint Space Operations Center at Vandenberg AFB has not received any reports of issues with GPS-aided munitions, and has determined that the timing error is not attributable to any type of outside interference such as jamming or spoofing. Operator procedures were modified to preclude a repeat of this issue until the ground system software is corrected.”
Companies and their time-servers around the world were subsequently hit by up to 12 hours of system warnings after 15 GPS satellites broadcast the wrong time, according to Chronos, a UK-based time-monitoring firm.
Telecommunications companies constitute only a small part of industry users who rely on the highly precise accuracy of time measurements — supplied by GPS — to control data flow through their networks. Global financial networks and trading markets similarly depend on GPS, as do electrical power grids and many other sectors of critical national infrastructure. These companies and networks invest significantly in highly sophisticated equipment to monitor said timing accuracy as conveyed by GPS signals. Because billions, make that trillions — or actually even more — are riding on it.
A week after the eye blinks, Chronos Technology released a white paper describing the ensuing fallout for its clients, who are timing equipment users in more than 50 countries around the world. Table 1 from the white paper reports the experience of a few during the event. One company registered nearly 2,500 alarms from its timing equipment during the outage.
Click to enlarge. (Table: Chronos Technology)
At one point during the crisis, according to the white paper, “it appeared that the GPS error had cleared and the Chronos SSP Manager was able to force the units out of holdover. However the scale of the problem escalated as these sites went back into holdover along with dozens of other sites suffering GPS-based timing issues. It was apparent at this point that there was something amiss with the GPS constellation itself.”
Later on, the report states, “This event linked to SVN23 has been one of the most significant service affecting issues for GPS timing users and sits alongside the April 1st 2014 GLONASS outage in scale — however its impact on global timing services is much more extreme.”
Ominously, “Chronos is aware of other more catastrophic impacts to networks and non-telecom applications which were not under supply and support contracts.”
As Loran Is Our Savior. At least one timing-reliant company was not disturbed by the problems, because it was testing an alternative timing service provided by enhanced Loran (eLoran) signals.
Unfortunately for them — and for the rest of us — eLoran has a very uncertain future. In fact, they were lucky to have an eLoran signal at all on January 26, because it was supposed to have been turned off on December 31. Somebody must have forgotten to tell the operators at the Anthorn giant antenna field in Cumbria to go home.
France, Norway, and the United Kingdom, three countries that had been keeping eLoran alive, officially abandoned the effort at the end of last year, reportedly because of lack of leadership from the United States.
The U.S. government decommissioned all its Loran stations a few years ago, even going to the extent of blowing some of them up (perhaps to prevent them from falling into the hands of subversives). Despite a recent reinvigorated interest in enhanced Loran technology, it may be too little, too late.
Whoa, Nellie. The first recorded use of the term “back-up technology” occurred in 1892, when farmers were urged not to prematurely abandon their mules in favor of John Froehlich’s new gasoline tractor.
Dan Albone on his prototype Ivel Agricultural motor. (Image: North Bedfordshire Gazette, 1903)
That admonition, however prudent, has since passed from view. But the concept remains sound. It has surfaced many, many times in GPS World magazine. Certainly not the first incidence, but the farthest back that I can retrieve via search on our website, came in 2007 from Defense contributing editor Don Jewell. “Why do we need a backup? Here is a classic case in point.” He describes a Joint Navigation Conference briefing on a surprise jamming incident that had occurred in January of that year.
In 2009, we reported on an Independent Assessment Team (IAT) report that “unanimously recommends that the U.S. government complete the eLoran upgrade and commit to eLoran as the national backup to GPS for 20 years.” The report was written in 2007, but quashed by the Department of Transportation and Department of Homeland Security (DHS) Executive Committees that commissioned it. Its public release came only after an extensive Freedom Of Information Act (FOIA) battle.
The U.S. government proceeded, despite its paid experts’ recommendations, to blow up those old Loran stations. The current renewed interest and the Wildwood experiment are worthy — more than worthy. Can they prevail? Can they survive blind reliance on a single string of vulnerable technology?
Indubitably, the critical role of GPS back-up was advanced prior to 2007, I just can’t document it this morning by deadline. For the sake of argument, let’s take April 12, 2007, as our start.
We are now 3,229 days out. That’s 77,496 hours, or nearly 279 million seconds. Correct me if wrong, but that appears to make 21.5 million-million times the length of January’s GPS timing error. Surely sufficient to blink a few times, scratch one’s head, and wonder.
