GMV uses the flexibility of Skydel SDX to simulate GNSS timing events

The upcoming GPS Week Number Rollover (WNRO) on April 6 is bringing a lot of attention not only in the specialized GNSS media but also in the general media. The WNRO is a known feature of GPS that occurs only every roughly 20 years and thus can be anticipated and tested in a receiver using a GNSS simulator.

A less-known rollover effect is also present in the Week Number (WN) associated to the UTC Offset (UTCO) transmitted by GPS. This WN has only 8 bits, which implies a range of values from 0-255, equivalent to a rollover every roughly 5 years. A possible failure in the receiver interpretation of the UTCO WN would not have such dramatic effects as a general GPS WNRO, but it could seriously affect the output of a GPS timing receiver.

Other than WN rollovers, un-programmed GNSS timing glitches are extremely rare but not impossible. A well known case is the GPS anomaly of 25-26 January 2016, when around half of the satellites in the constellation transmitted an incorrect UTCO value during 12 hours. The transmitted value was of the order of 13 microseconds, when the correct value is usually of the order of just a few nanoseconds. This caused many timing receivers around the world to provide an incorrect timing information or to fail altogether.

Other fields in the GPS navigation message that could potentially be corrupt and cause incorrect timing output are Timing Group Delays (TGDs), and Leap Second information. In general, any event related to the contents of the GPS navigation message can be simulated by editing the associated bits in the message, for each satellite PRN. However this is a cumbersome and prone-to-error task. Skydel/Orolia’s SDX simulator provides an Application Programming Interface (API) that allows to develop SDX extensions to tackle particular simulation problems in an easy and flexible way. By using this API, GMV has developed a “Time Plugin” that allows to edit directly on a user interface the numerical values associated to TGDs, UTCO, and Leap Seconds, per individual satellite PRN. These values are then converted to bits in the GPS message and transmitted in the RF stream to feed the receiver under test. Events like for example the GPS anomaly of 25-26 January 2016 can be easily tested (as shown in the screenshot).

With Orolia's Skydel SDX API, GMV has developed a "Time Plugin" that allows to batch edit the numerical values associated to TGDs, UTCO, and Leap Seconds

We’like to thank Ricardo Píriz from GMV for the content of this post.

Skydel is now part of Orolia!

Skydel becomes Orolia Canada

We’re pleased to announce that Skydel is now part of Orolia, the global leader in Resilient Positioning, Navigation and Timing (PNT) solutions for critical military and commercial applications. This acquisition secures the ongoing development of our GNSS test solutions for the years to come. Moreover, our combined Resilient PNT technologies will deliver unprecedented vulnerability testing and interference protection services for our customers’ most critical GPS/GNSS-reliant systems.

What does this mean for you?

On a day-to-day basis, it will be business as usual. Your current Skydel and your reseller points of contact will not change. We continue to improve and support our products, execute our roadmap, and plan great new additions for our SDX simulator. Also, we can now offer you access to the comprehensive Resilient PNT suite and combined technology solutions from Skydel and Orolia to meet your specific GNSS technology needs. Visit to discover the Orolia technology that is now available to you through our team.

What about us?

Our Skydel team is now part of the Orolia family! Our company name has changed to Orolia Canada Inc, and our head office remains in Montreal as an Orolia Technology Center of Excellence for testing and simulation. As you can see, we will continue to develop and deliver the most innovative testing and simulation capabilities available today to our newly expanded, global service network.

Our story continues…

Skydel set out 5 years ago to revolutionize the GNSS testing and simulation industry with innovative, flexible and cost-effective solutions. I want to take this opportunity to thank each and every one of you for putting your trust in us and bringing us to where we are today. Our commitment to exceptional customer service is stronger than ever during this exciting growth period.

Read the full press release issued today.

Upcoming Spring Events

We’ll be present at two events in Europe early this spring. Here are the details.

We'll be at these locations in March and April 2019

On March 25-27, we’ll be at Munich Satellite Navigation Summit in Germany. If you plan on attending the event and to assist the technical sessions, come by the exhibition space to visit us. We will be on-site with our distributor Noffz, and we will demo our SDX GPS/GNSS simulator running on their sUTP-5015 SDX configuration.

If you miss or can’t attend in Munich, you’ll have a chance to catch us a few weeks later, on April 9-12: we’ll be exhibiting at European Navigation Conference 2019 in Warsaw, Poland. Don’t miss our booth at the exhibition on-site. Noffz will be exhibiting with us at this event as well.

The Noffz sUTP-5015 GNSS Simulator, powered by Skydel SDX

A Skydel team member will be there at both events: take this opportunity to talk to us about your GNSS testing needs or exchange views about all things GNSS. This is a perfect opportunity to see the latest SDX release in action, and maybe learn a bit more about what’s in the works at Skydel for 2019.

We hope to see you there!

Opening the new year with SDX 19.1

Here at Skydel we’re always working on providing the best GNSS simulator for our clients. To that end, we’re starting off the new year with SDX 19.1, the eighteenth major revision of our GNSS Simulator. This newest GNSS simulator version adds Galileo AltBOC support, atmospheric errors, SBAS improvements, and GNSS satellite antenna patterns.

Galileo AltBOC

SDX now supports Galileo AltBOC as a new GNSS signal type. Current SDX users licensed with the Galileo E5 signal will be able to generate 8 Phase Shift Keying (8-PSK) constant envelope AltBOC after upgrading to SDX 19.1.

Galileo ALTBoc signal generated in SDX

The signal can be generated by selecting both Galileo E5a and E5b in the output - signal selection panel.

Atmospheric Delays and Improvements to SBAS

We’ve added a new error type to all SDX users in release 19.1: atmospheric delays. Moreover, these errors can be compensated with SBAS for those SDX licensees with the SBAS option installed. The SBAS message now broadcasts ionospheric error corrections.

To introduce these new features, let’s briefly review the theory behind ionospheric delays and SBAS. When a signal is broadcast from a GNSS satellite to the surface, a delay is introduced following how the signal propagates in the atmosphere. One of SBAS’ aims is to provide corrections to mitigate these delays (also called errors) in order to achieve a better positioning accuracy. SBAS accomplishes this by creating a virtual grid of points wrapped around the globe. Ground-based SBAS reference stations, located at known positions, compute corrections values for each point, which are in turn sent to, and broadcast by, the SBAS constellation. A GNSS receiver with SBAS enabled can then use the correction data relevant to its current position to compute a more accurate positioning solution. These points are called Ionospheric Grid Points (IGPs) and are organized into bands (numbered 0 to 10).

We’ve added three new interfaces to help create, manage, and use these error values in your simulation scenarios.

Creating and managing ionospheric errors in a simulation scenario

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SDX 18.10 is available now

Today we’re announcing SDX release 18.10, a new version of our GNSS simulator that features improvements to receiver antenna management and a new advanced jammer type.

Antenna model sequence during simulation

Starting with this SDX update is an upgraded paradigm for managing receiver antennas: SDX now supports the management of multiple vehicle antennas within a single scenario. Antennas can now be defined, named, and exported as antenna files that can be re-imported back into other scenarios. This handy feature will speed up antenna reuse and multi-scenario workflows for users managing numerous antenna models in GNSS simulation scenarios.

The new antenna model UI maintains the previous SDX paradigm whereby antenna patterns can be defined for gain and phase offsets.

Moreover, SDX now provides a simple and powerful sequencer for switching from one antenna pattern to another at specific times during a scenario.

The antenna sequencer is simple to use and will be useful for those who need to toggle antennas at various points in the simulation to replicate a real-world scenario.

As we do for every new feature added, the SDX API is updated—and documented—to reflect these latest changes, and these new features can be used in the programming of your automated scenarios.

Also added: IQ File as a jammer type

In addition, with release 18.10, you can now add IQ File playback as a jammer type in SDX. This feature, combined with the IQ File generation capability already available in SDX, opens a new range of possibilities, limited only by your imagination.

Selecting and playing back a IQ file as a jammer type in SDX 18.10

Users who already have the advanced jamming option installed and are eligible for this SDX upgrade can benefit from this new feature immediately by upgrading to SDX release 18.10.

Wrapping up

So far in 2018, SDX has seen the support of anechoic chambers, the support for multiple GPUs, the addition of SBAS support among many other new features in the summer release, and now SDX release 18.10 brings a new way to manage and sequence vehicle antennas.

That’s hardly the end of it: new custom simulation solutions based on SDX are coming soon, along with new features and GNSS constellation support. This is only the beginning!