Alternative to GPS

STL (Satellite Time and Location)

A Proven Alternative or Backup Source of Timing for GPS

Satellite Time and Location (STL) from Satelles provides wireless carriers and other critical infrastructure providers with a reliable, secure, and accurate timing synchronization service. You can use STL as an alternative or backup source of timing for GPS to make your services more resilient.

STL signals come from low Earth orbit (LEO) satellites in the Iridium constellation. Since this constellation is just 485 miles from Earth, STL signals are 1000X stronger than GPS signals and can reach areas where GPS isn’t reliable.

GPS provides an essential service to 5G networks and other critical infrastructure. However, you need a backup timing source to keep your infrastructure up and running if your signals are disrupted.

The best part? STL technology is available now.

Speak with an STL Expert

Reliable, Secure, and Available Everywhere

Since the STL constellation is just 485 miles from Earth, its signals provide service in areas where GPS/GNSS doesn’t reach or isn’t available, such as indoors.

STL is a Stratum 0 UTC source of time and is used to create a Stratum 1 timing clock compliant with the ITU-T G.8272 PRTC-A performance standard.

The complex, overlapping beam patterns of the satellites combined with signal authentication techniques allow Satelles to deliver a trusted time and location capability that is highly secure and thwarts disruption or manipulation.


Customers use STL either as a primary source of PNT — for example, 5G deployments where GPS/GNSS is unavailable indoors or when distributed PTP cannot meet needed accuracies — or as an essential contingency capability to protect the operations of PNT-dependent systems and ensure survivability and resilience.

STL offers the advantage of utilizing a small indoor antenna to deliver timing signals that penetrate most structures, including buildings with low-emissivity (Low-E) windows or metal and concrete siding and roofing. This means that in-building wireless installations that leverage STL can maintain synchronous timing without the need for an outdoor GNSS antenna.

STL antennas can also be installed outdoors similar to GPS/GNSS antennas.

GPS is a source of timing, and PTP is used to distribute that timing to locations that can’t get GPS. STL can be that source of time in areas where GPS doesn’t reach, or as a backup in the case of GPS disruption.

With 5G networks, PTP doesn’t always meet the needed accuracy to get to certain locations because of too much accumulated timing error (loss). This is caused by too many switch and router hops – this is very common especially when the fiber is not owned by the service provider. STL provides the timing source closer to the desired location to mitigate these issues.

Using STL, a PTP EdgeMaster can enable 5G to work deep indoors. Standalone receivers that connect to a wireless operator’s RAN gear or router to replace or augment GPS allow STL to provide timing sync whenever and wherever GPS is unavailable.


Use of the L-band frequency plus strength of signal means STL can take advantage of small form factor antenna and receiver size, making it a low-cost alternative or backup to GPS/GNSS.

Satelles works with solution providers and original equipment manufacturers (OEMs) that engineer user equipment (UE) incorporating STL technology.

Expert Findings

Government authorities in the U.S. and Europe—including The U.S. National Institute of Standards and Technology (NIST), the U.S. Department of Homeland Security (DHS), and the U.S. Department of Transportation (DOT)—have tested STL. They confirmed that STL meets 5G timing accuracy specifications, provides signals indoors, and offers resilience in the event of a GPS/GNSS outage. See our expert findings.

Protect Your Critical Infrastructure

Explore how STL can help you meet your 5G timing synchronization requirements when GPS is not available.

Speak with an STL Expert