SDX Release 18.7

Once again, our summer SDX update is a big leap forward. Is it becoming a tradition? We’ll know next year for sure, but until then, let’s unpack the details of SDX 18.7.

Introducing SBAS and satellite errors

SDX implements support for satellite-based augmentation systems (SBAS), enabling the replication of an augmented GPS constellation using an SBAS such as WAAS, EGNOS, MSAS, GAGAN, and SDCM.

A SDX simulation scenario with the SBAS constellation

Within SDX, SBAS can be activated for a given simulation as an additional constellation via the Output panel.

In the new SBAS settings panel, you can configure the augmentation system as you would with other constellations, with fine control over its message content, multipath signals, and more.

In SDX, configure SBAS like you would do with other constellations

Developed along with SBAS, and available for all SDX licensees, we have added new settings that permit you to simulate various GNSS satellites error sources.

Pseudorange errors

Discrepancies in PRN pseudoranges can occur, and could be caused for example by a recurring error in a satellite’s on-board clock. SDX 18.7 enables simulation developers to create randomized errors using Gauss-Markov First Order processes, or an error pattern using sine waves.

The new pseudorange errors in SDX 18.7

As always, we like to implement new features in an innovative and thoughtful way: pseudorange errors are plotted on a graph to provide a quick visualization of the error in function of the time.

In addition, a pseudorange offset can also be set in this new panel.

Ephemeris (orbital) errors

In a perfect world, orbital parameters would match perfectly the satellites’ orbits. But in reality, there is always a variation. So now with SDX 18.7, you can specify orbits’ offsets using the RIC (radial, in-track, cross-track) frame:

Orbital errors can now be specified for a satellite in SDX 18.7

These two new error types can be automatically corrected by SDX’s SBAS module, if activated (i.e., if you selected SBAS in the output panel, and opted to correct errors). In this case, pseudorange errors will be corrected during simulation by SBAS fast corrections (FCs), while SBAS long term corrections (LTCs) will rectify ephemeris errors.

Otherwise, these new errors options can be used—uncorrected—as a step closer towards simulating real-world conditions for a wide variety of scenarios.

Multiple GPUs are now supported

Unless you are new to SDX GNSS simulation, you know that SDX uses GPUs to pack a lot of power in a very cost-effective package. The architecture behind our GNSS simulator delivers unique scalability, especially in terms of signal generation. Starting with this release, we take this vision further by enabling multiple GPU cards to be used in SDX configurations.

More GPUs adds a lot of power while retaining a small simulator form factor

SDX can now drive multiple Nvidia GPUs concurrently, making for a GNSS simulator with an impressive size-to-power ratio. For example, adding a second GPU does not add to the form factor of our popular USRP-based hardware configuration, while adding a lot of power under the hood.

While having two GPUs enables computation that can unleash capabilities for the most demanding scenarios, SDX can now drive up to four Nvidia GPUs concurrently for multi-antenna simulators.

Adding GPUs enables the simulation of even more signals making possible the following example scenarios:

  • Multipath - generate a high volume of echos
  • Simulation of GEO orbits for all constellations, on multiple bands, with even more visible satellites at all time
  • Even larger multi-constellation scenarios, featuring multiple vehicles
  • Highly complex spoofing mitigation and testing setups
  • Complete anechoic chamber simulation

New Software-Defined Radio (SDR) Supported: DekTec DTA-2115B

With this release of SDX, we’re also adding a new SDR option for building a SDX hardware configuration: the single-output DTA-2115B is a PCIe card radio that combines interesting RF capabilities with a reduced form factor.

SDX now supports a new SDR: the DekTec DTA 2115B

Capable of 72 MHz of bandwidth, it is more than enough for generating RF for the wider GNSS signals, while its PCI Express interface makes it a very interesting option for racked or desktop PC-based simulators.

The DTA-2115B supports synchronization using 1PPS or 10MHz; multiple SDR cards can be used to create multi-output configurations for those requiring a small-scale, large-capabilities GNSS simulator.

A 4U systems with 4 SDR (top), and a very compact single-output 2U racked simulator (bottom)

We’ve updated the SDX turnkey configurations page to include a configuration based on the DTA-2115B. Moreover, more details about the DTA-2115B SDR can be found on our supported SDR page.

There’s more! Additional improvements and new features in SDX 18.7

This version of SDX brings many additional features available for all licensed users eligible to upgrade:

Almanac data importation: it’s now possible to import YUMA and SEM files in addition to RINEX for GPS satellites.

Geo satellites: make any GPS, Galileo, or BeiDou satellite geostationary by simply providing a longitude and SDX will do the rest. This can be handy for specific testing purposes.
Hop! Make it geo.

Message modification for Galileo: change or corrupt the Galileo navigation message

Logging improvements: log simulated downlink data for all signals in hex format

New library for downlink data: use the provided Python scripts to parse the simulated downlink data for easy manipulation or to output it in a more human-readable format.

It goes without saying that all of SDX 18.7 changes and upgrades are 100% reflected in the SDX API, ensuring that you can use the new features in your automated scenarios.


SBAS, satellites errors, multiple GPUs, new SDR and more: all in all, this is another substantial version of SDX, and it’s available now.

Do you want to learn more about SDX and these new features? A great opportunity to do so is meeting us at ION GNSS+ in Miami, at the end of September. Come by our booth to see a demo of the latest improvements to our GNSS Simulator, and take a moment to have a chat with us! We’re always eager to learn about your GNSS projects. Also, we MIGHT have a few more things to showcase at the show, but that’s a secret for now…

Announcing Partnership with GMV and Tecnobit

We’re excited to announce a partnership with GMV and Tecnobit to work on enhancing SDX to support the upcoming evolution of Europe’s Galileo GNSS! Read the full press release below:

GMV and Tecnobit partners with Skydel

GMV and Tecnobit to tailor Skydel SDX GNSS simulator for Europe

Montreal and Lisbon, 18 July 2018 - GMV, Tecnobit and Skydel today announced that they are working to adapt Skydel’s Global Navigation Satellite System (GNSS) simulation solution to support the latest developments of the Galileo GNSS, synchronizing with the European efforts to bring a modern, highly-accurate and secure positioning system to the market. GMV, Tecnobit, and Skydel aim to provide corporations, universities, and research labs with a reliable, advanced simulation system that closely follows the latest Galileo capabilities.

“Together with our partners at Tecnobit, and taking advantage of SDX’s unique software-defined architecture, we are currently working to add Public Regulated Service (PRS) support to Skydel SDX”, says Manuel Toledo, Head of GNSS Advanced User Segment Solutions Division at GMV. PRS provides position and timing data for sensitive applications that require the highest level of service continuity.

Skydel and GMV are also joining efforts on developing SDX’s capabilities for signal authentication with Galileo Commercial Service (CS) and Open Service (OS). The goal of such authentication is to increase the safety level of signals and to avert their falsification or fraud and is currently a unique feature that only the Galileo constellation can provide.

Skydel and GMV are also collaborating on projects that aim at providing signal simulation solutions for Galileo’s second generation (G2G). Galileo’s second-generation satellites are scheduled to be launched in 2025 and beyond.

“With Galileo’s Full Operational Capabilities approaching soon, we must focus on the system’s upcoming G2G services.”, said Pierre-Marie Le Véel, business development director at Skydel. “Skydel’s top priority for the European market is to provide simulation tools for the design of these next-generation GNSS devices.”

The partnership among the three companies truly unites the unique strengths of each organization. While GMV brings its expert knowledge of both the European market and the Galileo system and Tecnobit brings its expertise as developer of cryptographic systems, Skydel adds its versatile and extensible GNSS simulator, resulting in a solid technical and commercial synergy for establishing an improved GNSS service offering for Europe.

About Skydel
Founded in 2014, Skydel offers GNSS test solutions to scientists and engineers who develop navigation systems. Skydel’s flagship product is SDX, a multi-constellation, multi-frequency, software-defined GNSS simulator. Skydel continually improves and deploys SDX for worldwide clients in the military, aeronautics, and automotive, as well as industrial and academic research sectors, through a network of resellers and partners.

About GMV
GMV is a privately-owned technology business group founded in 1984 and trading on a worldwide scale in the following sectors: Aerospace, Defense and Security, Cybersecurity, Intelligent Transportation Systems, Automotive, Telecommunications and IT for public administration and large corporations. Currently, GMV is the world’s first independent supplier of satellite control centres for commercial telecommunications satellite operators and a European leader in satellite navigation systems (inc. EGNOS and Galileo).

About Tecnobit
Tecnobit is a Spanish Aerospace & Defence company with deep knowledge & background in Crypto Systems. Tecnobit became involved in Galileo PRS activities several years ago and has since developed the Galileo PRS Security Module for the Spanish PRS Receiver in partnership with GMV.

GPS week rollover — are you ready?

In the GPS L1 C/A navigation message, the week number is contained in a 10-bit binary number. This limits the maximum week number to a total of 1024, effectively making 1023 the maximum week after it loops back to 0. Hence, the event named “week rollover” occurs every 19.7 years. Modernized signals solve, or reduce significantly the occurrence of week rollover by using more bits, but many receivers rely solely on the original L1C/A signal to determine the current time.

The first ever GPS week started on January 6, 1980. The weeks counter already rolled over on August 21, 1999, and is scheduled to reach its limit again on April 6, 2019, roughly 10 months from now.

A week rollover is a great example of a difficult, if not impossible, event to test without a GNSS simulator. Testing with the live sky, in this case, is definitely not applicable. Waiting for the event to occur with fingers crossed is not a great idea either.

So, what are the implications?

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Revamping the GNSS Frequency Spectrum Reference Sheet

In 2015, we created a GNSS signals overview document and we called it the GNSS Spectrum Cheat Sheet. It was meant to offer a quick, general view of all GNSS signals aligned on their respective bands, and it proved to be a reference we would use a lot in the Skydel offices and around the lab.

After a bit more than 2 years, the sheet was due for an update. First, the GNSS landscape is evolving with new and growing satellites constellations, and the document was missing a few signals. We also gathered internal and external comments about the sheet, and we had some things noted that we would have liked to see in a new version. We went back to the drawing board, we did some research, improved what was working on the previous version and removed what was not.

And, as we were going, we worked on making something that would look good and that we’d like to print, hand out and share.

So here’s the new and improved GNSS Spectrum cheat sheet! It features all GNSS signals, color-coded and aligned on their central frequencies, and most importantly, every signal is depicted on the same scale, making everything nicely proportional.

The whole sheet uses vector graphics, meaning it can be resized without losing integrity. Since the GNSS spectrum is getting pretty crowded, it’s better to print the sheet on tabloid (11” x 17”) paper format. It can then be folded into letter format.

We even printed it as a poster in our office!

Download the new sheet

You will find a high-quality downloadable PDF version in the resources section of our site. If you have any comment, or spot an error, please let us know! We hope you will enjoy and use it as much as we do.

Closing out a productive year with SDX release 17.12

The year 2017 will soon be coming to an end and looking back at the many improvements we’ve built into our GNSS simulator, we can safely say, “mission accomplished”. Yet there are still a few days remaining to roll out one final “17” release of SDX… so here it is!

So what’s in store for users of SDX 17.12?

Support for 3D antenna patterns

Engineers working with GNSS-enabled technology are often obligated to implement a broad range of antenna patterns, from simple to complex ones. Examples that come to mind are when designing optimal antenna form factors, testing anti-jamming capabilities, or creating equipment for specific environmental applications.

With release 17.12, all SDX users benefit from a 3D upgrade to gain antenna patterns, as well as—new feature!—custom 3D phase offset antenna patterns. These new options replace the previous ones found in the vehicle’s antenna settings.

The new graph UI for 3D Antenna Patterns

A 3D gain or offset antenna pattern is expressed with a graph displaying either the gain or the phase offset, through the 360 degrees azimuth and -90 to 90 degrees elevation, thus creating a full 3D sphere mapping around the antenna.

The CSV import-export options bring customization control over the 3D antenna patterns as well. CSV files are composed of a two-dimensional matrix of values; SDX interpolates between specified azimuth/elevation points thus covering the whole 3D space. The matrix can be of any size; SDX automatically detects the number of rows and columns while importing your data, thus offering convenient flexibility.

The CSV Import/Export function for 3D antenna patterns in SDX 17.12

This enables quick and easy setups, while providing fine-grained control to users requiring large mappings that depict complex patterns.

Master → Slave Configuration Broadcast

One of the most powerful features of SDX is its synchronization capabilities. Along with the timing improvements that were part of the last release, we continue to further refine this feature set in this latest version of SDX. As a result, it is now possible to push a SDX scenario configuration from the master instance to all slave instances. This unique feature brings obvious workflow improvements to any simulation setup.

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