Table of Contents

5G Timing Synchronization

Every network—from wireless communications to IoT sensors—contains nodes that make them work. All the nodes in a network must sync within precise time measurements so they can transmit and receive data accurately.

Coordinating timing among the nodes within a network is called timing synchronization. It is required for all 5G networks to operate and meet their strict timing criteria. If the timing isn’t precise, the network can’t operate.

People often think of GPS/GNSS as a navigation tool, but it goes far beyond that. GPS provides positioning, navigation, and timing (PNT). Positioning is the blue dot on your phone that shows your location on a digital map. Navigation helps you travel to another location. Timing is necessary for all the various nodes within a network to communicate and therefore operate.

Today, every element of critical infrastructure, for example 5G networks, power grids, financial transactions, water treatment, transportation, etc., relies on GPS for timing synchronization. Each device has a receiver in it to get the GPS signal.

This reliance can create problems if we lose GPS. Critical infrastructure can fail if GPS is unavailable or denied. A study commissioned by the National Institute of Standards and Technology (NIST) found that the loss of GPS would cost the U.S. $1 billion per day. Even though GPS is an amazing service, it is never a good idea to rely on a single source of technology.

With 5G networks, wireless operators moved from frequency division duplexing (FDD) to time division duplexing (TDD). TDD offers some technical advantages over FDD but has more stringent timing requirements. If an operator doesn’t meet these timing requirements, its network will shut down nodes to preserve functionality.

This could create a regional outage.

5G networks offer higher data speeds and lower latency than 4G networks. They can process large files quickly and support bandwidth-intensive applications, such as IoT sensors and smart appliances.

Timing synchronization doesn’t directly impact how fast a network processes files. However, 5G networks require timing synchronization to work at maximum performance levels. To utilize the benefit of 5G processing speeds, each 5G node must maintain this stringent timing synchronization.

GPS satellites are over 12,000 miles away in space, and their signals are weak by the time they reach Earth. Tree canopies, structures, and even walls often block GPS signals—which is why you might lose satellite radio while driving under a bridge or can’t navigate accurately on your phone map in a city filled with skyscrapers.

In the past, all the cellular nodes were towers. They were open to the sky outside and could receive GPS consistently. As the industry moved to a higher volume of smaller cells, such as those mounted on telephone poles and indoors, for example, wireless operators started to have trouble getting the GPS signal with the same consistency. This was because of tree canopies and buildings blocking GPS.

Today cellular networks rely on GPS for their timing synchronization, and so without a GPS signal, timing synchronization can’t happen and 5G networks won’t work. As cellular networks upgrade to 5G, the lack of GPS signal availability in certain places is hindering a fuller roll-out.

Precision Time Protocol (PTP) allows you to transfer timing from one location to another. This enables you to use a GPS signal from one location and transfer it to a GPS-challenged location. This is often used to help get GPS to indoor nodes, where GPS doesn’t reach. For example, you can put a GPS antenna outdoors, such as on a nearby building roof, then using PTP, and a fiber connection, you can transfer the timing synchronization to your GPS-challenged location.

However, PTP doesn’t work in all situations. Often the fiber path that connects the originating and terminating ends of the PTP connection creates degradation of the timing signal. For example, the fiber route may not run directly from point A to point B, such as when a fiber provider routes the fiber to optimize its fiber business without necessarily providing the shortest path for each customer’s use. This inserts connection points that increase the number of network hops, which when combined can accumulate delays that use up the timing budget allowed for that initial PTP connection. This can be challenging to identify in advance and can delay the turn up of the 5G node and/or create service issues down the road.

In addition to the technical challenges, PTP devices can be several thousand dollars and fiber connections quite costly.

With PTP, your timing synchronization can travel to another area of a building or a different building altogether, which can be very valuable if you cannot get GPS directly to those areas. However, it is important to know if the accuracy of your timing will still meet your requirements once it goes through this process. In the past the timing requirements for 3G and then 4G weren’t strict enough to run into many problems, but with 5G the timing accuracy requirements are more stringent and therefore create a new set of challenges. Many cellular carriers have started asking companies to come in and test their accuracy levels and have been surprised to find them to be out of spec, leaving them vulnerable to outages.

STL is a complement, backup, or alternative to GPS. It provides the same timing synchronization that GPS provides today needed to operate 5G networks and keep so much of our nation’s critical infrastructure running.

The constellation that STL uses is 485 miles from Earth, 25 times closer than GPS. Since STL signals are much closer to Earth and have other broadcast advantages compared to GPS, they are 1,000X stronger than GPS and can provide service to places GPS doesn’t reach—such as deep inside buildings or in occluded areas with dense tree canopies or other obstructions. STL and GPS use similar receivers, making it very easy to integrate STL into any equipment that currently has a GPS receiver. Additionally, you can set up the two systems to work in tandem, setting either one as primary and the other as secondary, for full redundancy. In the event of an outage, the timing synchronization fails over to the other. Other alternatives to GPS have significantly different form factors and service delivery models, making it more challenging to roll out a redundant solution compared to STL.

STL is comparable to GPS and provides the timing synchronization accuracy that 5G operators need. In certain conditions, GPS may be more accurate by a small fraction, for example 10 nanoseconds.

We rely on GPS for many critical functions in society, but it has some serious shortcomings such as not working indoors, being susceptible to degradation, and vulnerable to signal disruption and manipulation.

STL was created to help fill in those shortcomings, being purpose-built to complement GPS and provide solutions where GPS falls short. For example, STL has cryptographic security that prevents bad actors from interrupting the signals the way they do with GPS. STL also uses a separate satellite constellation that’s not impacted if a GPS signal is lost.

STL is a seamless and rapid means of building redundancy into technologies that rely solely on GPS today.

Low Earth Orbit (LEO) Positioning, Navigation, and Timing

The Global Positioning System (GPS) and other Global Navigation Satellite System (GNSS) constellations are in Medium Earth orbit (MEO). It is about 12,000 miles away from Earth.

Low Earth orbit (LEO) is where the satellite constellation that broadcasts STL is located. Since this constellation is just 485 miles away from Earth, its signals are much stronger than GPS. LEO satellites also travel much faster than MEO satellites, traveling horizon to horizon in eight minutes. This means you only need one satellite in view at a time to provide the same service as with four or five GPS satellites.

Positioning is your location, which is important for tracking devices and equipment.

Navigation gives you directions based on your current position and where you want to go.

Timing provides the world with a single, accurate source of time—down to the nanosecond. The world’s critical infrastructure sectors, such as telecom, finance, and power, rely on precise synchronized timing to operate.

Traditionally GPS is used to provide all three: positioning, navigation, and timing.

LEO PNT simply means that the position, navigation, and timing are being provided from satellites in low Earth orbit, instead of GPS. Since LEO satellites have a strong signal that penetrates indoors, they can serve as a primary PNT source. You can also use them as a backup PNT source if you want resiliency so that if your GPS signal gets disrupted or manipulated, you can derive your PNT from STL instead.

Yes. Satelles is currently the only commercial provider of LEO PNT, and our service has been tested thoroughly. The U.S. National Institute of Standards and Technology (NIST) has conducted extensive research and published papers that discuss STL’s PNT quality and accuracy.

The U.S. Department of Transportation, U.S. Department of Homeland Security, and the European Commission have also completed studies about our LEO PNT service. They’ve published reports that provide details about their tests and analysis.

Many organizations rely on GPS for PNT. However, GPS was not developed for this purpose, while LEO PNT from Satelles was developed exclusively to provide position, navigation, and timing.

LEO PNT has security advantages, as the stronger signals are much more difficult to disrupt or manipulate. LEO satellites are also less vulnerable to solar storms than GPS satellites due to their lower orbital altitude.

Satelles leverages an existing constellation, Iridium, to make a commercially available, cost-effective LEO PNT service.

One difference between the various MEO PNT constellations is the country that hosts them. The United States owns the GPS constellation, while Galileo is owned by Europe, GLONASS by Russia, and BeiDou by China. There are some differences in features and capabilities.

STL is the only commercially available  PNT service using a LEO constellation. Iridium® owns and operates the constellation and provides a variety of communications services. Satelles has a unique relationship with Iridium which enables Satelles to offer PNT services, known as STL. Iridium’s coverage is worldwide, including the poles.

Recently, other companies have launched LEO constellations but are focused on broadband communications services, and do not offer PNT. Some use small, cost-effective satellites called cube sats. Some use much larger, heavier satellites. Most of these satellites only last a few years before they run out of fuel, burn up in the atmosphere, and need replacement. These satellites also have less power than Iridium satellites and may not produce strong signals that can penetrate buildings. They are also more susceptible to space storms and getting knocked out of orbit without the ability to steer themselves back in.

No. Satelles has an exclusive agreement with Iridium and is the only company that can provide PNT through its constellation.

Yes. All constellations need ground infrastructure to communicate with satellites. Satelles maintains a robust ground network around the world as part of its delivery of STL.

L band is a range of frequencies in the radio spectrum that includes the specific frequencies used by GPS. Satelles also uses L band for our LEO PNT services.

Since STL is in the same band as GPS, it can use receivers and antennas that complement GPS equipment. This enables the use of dual-purpose equipment, making it far simpler to use STL as an automatic backup source of timing if the GPS signal is unavailable or denied.


Alternatives to GPS

GPS is one of the most frequently used sources of time in the world. All critical infrastructure—including power grids, emergency services, communications systems, and financial services networks—rely on it for precise timing. Consumer smartphones and other electronics also use GPS receivers for accurate positioning, navigation, and timing (PNT).

Since GPS is so critical, it has become a bigger target for malicious attacks. Governments worldwide are concerned about what would happen if we lost GPS signals. They are calling for industry to adopt other sources of timing that can keep critical infrastructure running if GPS signals are disrupted. Additionally, GPS is not a very powerful signal so is difficult to receive indoors and in certain environments. More and more critical technology now relies on GPS. As a result, a greater percentage of these technologies are in environments where GPS isn’t available.

STL (Satellite Time and Location) provides an alternative or backup source of timing for GPS, using a Low Earth Orbit (LEO) constellation, which is a different constellation than GPS or GNSS, and one that is much closer to Earth, making its signals much stronger. STL signals can reach indoors and other places that aren’t accessible by GPS. But it isn’t just about having an alternative source of timing. The timing must meet very precise levels of timing accuracy and stability for utilization by critical infrastructure. STL does this, providing synchronized timing within 100 ns of Coordinated Universal Time (UTC).

Several other companies are working on GPS alternatives, but their products are not yet on the market. Many of these companies have significant infrastructure costs and seek government funding for their initial build. It could be years before their products are viable and available.

Cesium clocks also serve as a GPS backup. These clocks provide stable and precise timing when GPS signals are temporarily unavailable. But they are large, expensive, can’t be moved easily, and only provide a backup for a finite period.

GPS (and other GNSS constellations) are 12,000 miles away in space. So, by the time these signals reach Earth, they are not very strong and have trouble penetrating walls and tree canopies. With GPS, you must put an antenna outside even if you need timing indoors. However, this process is costly, sometimes requires coring through floors and the roof, as well as getting zoning and landlord approvals.

The satellite constellation that provides STL has an orbital altitude of just 485 miles. Since these satellites are much closer to Earth, their signals are 1,000X stronger than GPS and can penetrate walls and areas with dense tree coverage and other environmental obstructions. This enables you to put an STL antenna inside a building, making it a cost-effective alternative to GPS.

With so many critical technologies relying on GPS to work, there are widespread vulnerabilities across all sectors. If someone wanted to disrupt our society, they could focus on disrupting the many GPS-dependent elements of our infrastructure.

There are two key methods that are used today to maliciously affect GPS/GNSS signals:

  • Disruption occurs when someone uses a device that deliberately interferes with the GPS signal, thereby preventing the signal from getting to the devices that rely on it. Devices that block the GPS signal are illegal but can be found online, some as low as $40 that simply plug into a USB outlet in your car. There are more expensive and highly sophisticated devices as well. Even inexpensive devices can deny GPS in large areas and impact critical infrastructure.

A significant amount of disruption of critical infrastructure occurs from unintentional uses of this illicit equipment. For example, a New Jersey man used such a device to prevent his employer from tracking where he drove a company vehicle. Unfortunately, this device blocked not only his vehicle tracker but all GPS signals around his vehicle, thereby affecting any technology relying on GPS. In this case, among many other devices, the degraded signal impacted the Newark Liberty International Airport, and it took weeks for government officials to determine the source of the interference.

This problem magnifies when many people use signal blockers like this, thinking they are only affecting their own GPS-based tracking equipment. Networks anywhere in the vicinity stop working properly while GPS is unavailable.

  • Manipulation is intercepting a GPS signal and replacing it with a counterfeit signal to make a device look like it is located elsewhere.

STL has a much stronger signal than GPS, making it extremely difficult to disrupt. A malicious actor would need a very expensive GPS interference device or to be incredibly close to the targeted area they want to disrupt.

STL has several security features built into it that makes it virtually impossible to manipulate, making data centers ideal users of STL.

To receive a GPS signal, you need a GPS chip. These can be as small as the size of your fingernail. These chips are in many devices—from smartphones to watches.

STL uses the same type of chip for its receivers. You can place STL and GPS receivers in the same device to have a backup timing source without needing a totally separate device in your network.

STL antennas are much smaller than GPS antennas. They are the size of a small salt or pepper shaker. Since they are so small, and because they work indoors, they can be mounted discreetly. You likely don’t need a landlord’s permission to install them, and customers won’t notice them in retail spaces. GPS antennas are large and must be installed outside, which can impact a building’s aesthetics. Tenants with requirements for an outdoor GPS antenna too often need an approval from a building owner or property manager to mount it and are commonly expected to pay a hefty monthly fee for the privilege.

Some companies make antennas that capture both GPS and STL, providing another option to meet your timing synchronization needs.

STL is an excellent backup for GPS. You can place STL and GPS receivers side by side, so they work in concert. One can be set as your primary source of timing and the other as your secondary. If your primary source loses its signal, it will automatically fail over to your backup timing source.

Let's Talk!

Contact us to learn more about how STL from Satelles can help you meet your timing synchronization needs.

Contact Us