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Continuous Improvement with Spirent


Spirent’s SimGEN is built on decades of experience, delivering the power, flexibility, and intuitive ease-of-use needed to develop the next generation of location-aware systems. To ensure our customers stay ahead of the industry, Spirent dedicates a large team to improving the performance and broadening the performance of our flagship simulation control platform.

If you’d like to find out more about renewing your support agreement, and the great value that it provides, get in touch.

NOTE: SimGEN™, SimREPLAYplus™, SimTEST™, and Single Channel Utility are built on Spirent’s SimGEN architecture. References to updates and improvements will refer to SimGEN unless stated otherwise.

Version 8.04 May 2024 (by Mia Swain & Chris Yapp)

New ICDs supported

NavIC_SPS_ICD_L1_V1.0 August 2023 version

Spirent is excited to introduce the new NavIC L1 signal into our simulation capability. NavIC (Navigation with Indian Constellation) provides precise positioning and timing information in the Indian subcontinent and its surrounding regions, offering unique benefits in terms of regional accuracy and signal strength.





New Features

1000 Hz System Iteration Rate on GSS7000 simulator as a licensable feature

In V8.04, an improved system iteration rate of 1000 Hz is introduced to the GSS7000 as a licensable option. This new feature enhances the GSS7000’s performance, addressing vehicle dynamics limitations and improving signal accuracy. The increased SIR also reduces the simulator's system latency to 4ms.

Please click here for the latest GSS7000 performance specifications.

Spyder programming tool

Included in the V8.04 installer, Spirent provides users an open-source Python development environment - Spyder. Combined with pre-loaded gRPC schema, users can now write their own scripts, applications and software add-ons in order to schedule tests, control the scenario execution and manage simulation data.

Spyder enables direct interaction with SimGEN software using Python commands. Even the use of scripts is optional as commands can be sent to the engine as they are typed.


Expanding positioning data with RTCM message type 1032

Introducing support for RTCM message type 1032, a valuable addition enhancing positioning data analysis. This message type is specifically tailored for non-physical reference station scenarios, enabling rovers to reference baseline vectors to physical points rather than non-physical references. This feature is particularly beneficial for post-processing tasks, ensuring precise ECEF location information interpretation. Users can now seamlessly integrate message types 1005, 1006, and 1032 into their systems, catering to diverse deployment requirements and optimizing data accuracy.

Comprehensive DOP logging for enhanced positioning accuracy

With the release of V8.04, bulk logging includes all DOP values (GDOP, PDOP, TDOP, HDOP, VDOP) calculated from both simulated GNSS and visual satellites, offering a more comprehensive and accurate positioning data experience.

Remote Reboot capability

Remote Reboot feature is now supported on the latest GSS7000 simulators (serial number 70001500 onwards), delivering the capability to restart and switch on/off GSS7000 remotely.

For details on how to operate this function, please refer to Appendix B, section b7 of DCS0055J Issue 1-02 Debian GSS7000 Simulator And Embedded Host Update Procedure on the Customer Service Center (supported customers only).

User interface improvement

Accessing bulk logging options has become even more intuitive. Now, instead of navigating through the Options menu on the toolbar, users can conveniently find all bulk logging options directly under Data logging, located beneath the scenario tree. This enhancement simplifies the user experience, making it easier to manage and access logging settings.



32 channels of secure signal support for GSS9000

There is now added support for 32 channels of secure signals, increased from 16, for the GSS9000.

SimREPLAYplus and SimTEST improvements

New licensable features have been added to the SimREPLAYplus and SimTEST catalogue which include:

  • NMEA Output Feature for SimTEST

  • Remote Vehicle Feature for SimTEST and SimREPLAYplus

  • Data Streaming Feature for SimTEST and SimREPLAYplus

  • RTCM Feature for SimTEST

New features for CRPA systems

Extra features have been incorporated into this release for CRPA systems:

  • Remote command syntax:

    • Many remote commands use the V<x>_A<y> syntax and a subset of these commands also supports an 'all antennas' variation, dropping the A<y> part so the command become just V<x>.

    • The new CRPA syntax becomes V<x>_C<y>. This syntax is compatible with:

      • POW_ON

      • POW_LEV



      • MOD

      • PR_RAMP

      • FADER

  • GTx band carrier frequency adjustment.


  • Attitude for GTx


  • GTx ‘direct’ signal strength


  • ‘Comb’ feature - allows the user to configure the output of a chosen interface signal type, with a maximum of 14 tones, at specified frequency offsets for GTx.


  • Ability to add ‘pulsing’ to a signal.

  • Capability to add noise to a spoofing transmitter.


  • Use of a polarisation pattern file - an editable XML file which can be edited using a suitable text editor like Notepad. Further details can be obtained from the SimGEN User Manual.

Version 8.02 October 2023 (by Mia Swain & Chris Yapp)

New ICDs supported




Galileo HAS SIS ICD v1.0


NMEA 4.11

New features

New Ground-reflected multipath model for GNSS reflectometry (GNSS-R)

In PosApp V8.02, an updated ground-reflected multipath model with respect to the WGS84 ellipsoid is introduced for the specular point computations in GNSS-R simulations. This means accurate specular points that mirror real-world reflections. 

The new Ellipsoidal Precision approach ensures your computations are spot-on with reference to the Earth's actual shape. Furthermore, tropospheric and ionospheric delays now mirror the reflected path, accounting for ionospheric passage twice. Specular reflections are now matching angles of incidence and reflection due to realistic smooth surfaces. 

Enhanced RINEX observation output rate

To allow the effortless capture of high-frequency positioning and timing data, in release V8.02 we increase the maximum RINEX observation output rate from 1 Hz to 10Hz, with 5Hz rate available as an option. This enhancement enables users to conduct precise analyses and develop adaptable navigation solutions.

Simulation of radio occultation: RF ‘ray bending’ effect in Ionospheric model

Due to the changing refractive index in the ionosphere, radio signals propagating through the ionosphere are subject to an ‘ionospheric bending’ effect. For receivers operating at high altitudes, some GNSS signals which are transmitted behind the Earth geometrically (so should have been obscured) could be received due to the ray bending.

V8.02 introduces the radio occultation feature, enabling simulation of RF signals that are impacted and refracted around the curvature of the earth. Users can specify the level of solar activity (low, medium or high) to reflect the refraction on the RF rays.

Display of multiple vehicles in the same ground track window

An improvement on the UI has been delivered in V8.02 to select multiple vehicles and their sub-sets of satellites and constellations, these vehicle and satellites can now be displayed on the same Ground Track map.

Users can now effortlessly manage multiple vehicles on a singular map, while still retaining the option to create and switch between various maps. This upgrade allows for the selective display of chosen vehicles, satellites, and constellations on each map, offering a personalized perspective on simulated scenarios.

Scenario export feature

This new feature allows scenarios to be transferred to another system with all modified files.

PosApp's "Export" feature, found in the "File" menu, streamlines the transfer of saved scenarios between systems. It ensures that files from the "Shared" scenario folder and externally linked resources are included. When the scenario is run on a different system, these files remain intact, maintaining all modified settings.

PosApp version selector

More than one version of PosApp is permitted on a simulator (GSS9000 and GSS7000). In V8.02, a new utility is added to the software GUI to enable the ‘straight forward’ switch between versions.

This feature can be found under Tools > General Utilities.

“Apply to all” User Actions file feature when using multiple antennas and vehicles

A new feature added to the V8.02 GUI allows a user to apply any power setting (Power Level, Power Mode, Power On/Off) to all vehicles and antennas, if using a multiple output system, when utilising a User Action file.

Version 8.01 – December 2022 (by Mia Swain & Chris Yapp)

New ICDs supported

IS-QZSS-PNT-004 (QZSS L1C/B signal)

The Japanese QZS-1R satellite was launched on Oct. 26, 2021.It serves as a replenishment for QZSS’s first spacecraft, QZS-1. QZS-1R satellite has the ability to transmit the new L1 C/B signal. This signal is going to replace the current L1 C/A signal. In V8.01 release, this new signal is available on Spirent’s GSS9000 and GSS7000 simulators.

L1 C/B has BOC wave form instead of BPSK for L1 C/A, with the same PRN code family and data format: LNAV.

For detailed changes please refer to the Revision History of the ICD.


PosAPP V8.01 introduces the simulation capability of Search and Rescue RLM (Return Link Messages) on BeiDou satellites.

The RLM is on B2b signals which broadcasted by BDS IGSO and MEO satellites. The users should enable the message type 8 on B2b CNAV3 message sequence.


Then edit the Time, Beacon ID, Message content and select satellites for BeiDou RLM.



Galileo FOC SISICD V2.0

New features

Troposphere mapping functions: Vienna Global Mapping Function (GMF)

This model is based on data from the global ECMWF numerical weather model. 

Vertical tropospheric delays are calculated using the Saastamoinen model which takes the user position, atmospheric pressure, relative humidity and temperature as inputs. The Vienna Global Mapping Function (GMF) converts vertical delays into slant delays, depending on the user position and satellite elevation.

This new mapping function provides a way of evaluating the impact of weather conditions on GNSS signals.

New remote command that returns all SVIDs in view

A new remote command is introduced in PosAPP 8.01 to get SVIDs from all satellites in view at the specified time. This covers satellites from all GNSS constellations. There are 2 modes to choose from: mode 1 is to return the SVIDs from signals currently in view, mode 2 allows the return of SVIDs from all simulated signals.

For more details, please refer to the latest SimGEN and SimREPLAYplus user manuals.

Version 8.00 (including service releases) – June 2022 (by Mia Swain & Chris Yapp)

New ICDs supported

Galileo OS SIS ICD V2.0

The new issue of the OS SIS ICD introduces major updates for all Galileo Open Service users.

3 new features are introduced to the I/NAV message transmitted on the Galileo E1-B signal component:

  • Reduced Clock and Ephemeris Data (RedCED);

  • Reed-Solomon Outer Forward Error Correction Data (FEC2); and

  • Secondary Synchronization Pattern (SSP).

These new features represent a major evolution of the Galileo Open Service signals, which will provide all users with a more robust and faster retrieval of the Clock and Ephemeris Data, particularly for users in challenging environments, while at the same time allowing for a faster reconstruction of the Galileo System Time (GST).

As part of our extensive support entitlement, users will gain access to this updated ICD with the latest software update (PosApp V8.00 GAL FOC 2.0).

New features

New Software User Interface

With the release of v8.00, we have updated the look and feel of our GNSS simulation software. As a customer who has previously used version 7 of SimGEN, SimREPLAY+ and SimTEST, or Single Channel Utility, you will notice some changes to the way the user interface looks and works.

The software has been given a fresh new look – to better align with Windows 10’s look and feel, and with other apps in the Spirent product suite.

Continuous Improvement1

Scenario Play Controls

The controls for starting, stopping, rewinding and engaging turbo mode have been simplified and moved. They can now be found in the top-right corner of the app.

The stop button has been removed and merged with the ‘play’ button.

Continuous Improvement2


The buttons are larger, with clear text labels underneath. They work in the same way as before, showing and hiding the various windows below.

Continuous Improvement3

Scenario Tree

The scenario’s attributes and settings – we call these the ‘scenario tree’ – have been simplified. The tree has been tidied, and the buttons below have been simplified, made more concise and clearly labelled.

Continuous Improvement4

Ground Track

The ground track shows where the scenario’s simulated vehicles and satellites are displayed.

We’ve made it easier to tell the difference between land and sea, easier to determine where your vehicles are, and easier to distinguish where satellites are located in the sky.

Green now signifies visible satellites, blue signifies not visible, and red signifies satellites that are not simulated as part of your license.

Continuous Improvement5

Default Layout

We’ve optimised the size and layout of the information panels to better match the Spirent c50 and Full HD 1080 x 1920 displays, in the default layout configuration.

This gives you more room for your power level and received signals panels, while also fixing the date/time and position details panels for consistency and clarity.

Continuous Improvement6

Antenna configuration window

V8.00 introduces a set of new features that focus on customer experience. One of these features is the antenna configuration window, a tool that has been designed to accurately recreate and represent the position and orientation of the antennas with respect to the vehicle in the scenario.

This tool allows users to prepare their antenna set-up before the simulation starts. It helps to visualise the active configuration in a dynamic 3D plot as one edits parameters such as antenna offsets, heading, elevation and bank angles. Whether the user is running a single or multi-antenna scenario, the antenna configuration window enables them to create, edit or delete their vehicle antennas as well as easily share settings across SimGEN scenarios.

Continuous Improvement7

For the most advanced use-cases, a CRPA definition tool has been also incorporated. In 2 steps, users can now create antenna arrays and uniformly space the individual elements based on half wavelengths or precise distances. This capability comes with the associated 3D plot that enables the visualisation of the relative distances between the different antenna elements.

Continuous Improvement8

Once a CRPA antenna is created, SimGEN will holistically identify the individual elements as part of a CRPA entity and will always reflect it within a single instance of the software. This allows users to modify in-run parameters such as power levels for the whole CRPA antenna using the sliders within SimGEN.

Spoofing Capability

Release v8.00 Spoofing introduces the embedded spoofing feature (licensable), Spirent’s new all-in-one spoofing solution.

The new spoofing feature comprises powerful built-in and user configurable capabilities to generate spoofing scenarios. It covers most spoofing attacks such as trajectory spoofing, navigation data spoofing and meaconing attacks, and works on all GNSS constellations and frequencies. For increased realism, the spoofing signals are now transmitted from ground-based transmitters.

Fully embedded into SimGEN, the user can easily define, amongst other parameters, the number of spoofer transmitters and their location (absolute or vehicle relative, static or moving), the spoofer power levels, the false vehicle position (spoofed position) and the spoofing signal content, including navigation data and errors. The resulting spoofer RF signal will be automatically calculated based on user scenario settings, with the correct spoofer signal arrival angle and spoofer signal content.

The new feature is available on GSS9000, GSS7000 SimGEN and SimREPLAY+.

Continuous Improvement9


V8.00 introduces significant updates for SimSENSOR and SimINERTIAL (via new version v5.05). The inertial error model (shared by the two inertial sensor simulation solutions) has been enhanced with the addition of new embedded vibration and temperature models. SimINERTIAL and SimSENSOR users will now be able to test their inertial sensors and INS against the effects of these environmental errors.

The vibration-induced errors affecting accelerometers are simulated via a vibration model based on MIL-STD-810-H. The model includes the pre-defined vibration profiles defined in the standard (e.g. aircraft, helicopter, shipboard), as well as user-defined ASD vs. frequency vibration profiles. Multiple vibration profiles can be applied at different time in a given scenario.

The temperature model is based on two industry-recognized research papers and simulates the effects of temperature on MEMS-based accelerometers and gyroscopes. The user can define the scenario temperature profile and set the values of critical temperature parameters.

SimSENSOR will also benefit from new embedded and pre-defined error models, for Consumer/Automotive, Industrial, Tactical and Navigation performance grades of IMUs, for an easy and more realistic simulation of common IMU models.

Continuous Improvement10

Improved remote control

V8.00 adds further sophistication to SimGEN’s remote-working functionality. From v8.00, you can remotely restart the SimGEN engine via a command-line interface. Engine control has long been a facet of the Host Controller Utility, which also includes the ability restart the firmware and configure network ports for remote control of the software. This is in addition to recent improvements made to the utility that enable both the GSS9000 and its Host Controller to be turned on, rebooted, and powered off from a remote computer.

Version 7.04 (including service releases) – December 2021 (by Mia Swain & Chris Yapp)

New ICDs supported


GLONASS CDMA signal system V1.0

  • Spirent has led the way with the first commercially-available GLO CDMA simulation solution. For more information on GLONASS CDMA signals and Spirent’s implementation, please visit our blog.

Galileo High Accuracy Service testing ICD V1.2

  • Galileo HAS will provide free-of-charge high-accuracy Precise Point Positioning corrections through the Galileo E6-B signal, with accuracy under two decimeters, offering real-time improved user positioning performance.

  • Working with GMV, Spirent has developed the industry’s first commercially available simulation test solution for the Galileo HAS, via a beta interface implementation based on HAS ICD version 1.2.

  • As part of our extensive support entitlement, all existing Galileo E6 customers will gain access to this functionality with the latest software update (V7.04 SR01 HAS).

New features


Software tool SimOSNMA is designed to work with Spirent’s market leading GNSS simulation platforms to test Galileo Open Service Navigation Message Authentication (OSNMA ICD V1.1) signal conformance, which will bring new levels of robustness for both civilian and commercial GNSS uses.

SimOSNMA has been developed together with Qascom, a leader in GNSS resilience and a significant contributor to the development of Galileo OSNMA. For more information, please refer to Spirent’s press release, or contact your local Spirent representative.

Premium enhancements to the GSS9000 Series

1. Rolling RINEX (also available on GSS7000 with SimGEN Software)

As spoofing techniques become more sophisticated in the real-world, Spirent remains committed to bringing the most advanced anti-spoofing test techniques to the lab.

For this purpose, from V7.04 release, all Spirent GNSS constellation simulators are capable of updating ephemeris data on user demand based on existing RINEX files. This feature permits a close alignment between the simulator and the live-sky signals during the scenario run.

2. Enhanced embedded multipath

Achieving greater realism is a key aspect and a common theme for most of today’s simulation test tools. In the GNSS domain, multipath plays an important role in realism due both to the low power of the signals received, and the diversity of the scenarios where receivers operate.

In the V7.04 release, new functionality is added to the GSS9000 Series embedded multipath feature. Users can now control the power levels and code delays of each multipath signal in real-time, enabling the creation of more complex and dynamic scenarios for greater representation of the real world.


3. 32-channel interference channel banks

The V7.04 release unlocks another new feature of GSS9000 Series simulator. The number of simultaneously generated GNSS and interference signals is expanded to 32 per channel bank, enabling a 2RF interference-capable GSS9000 Series to simulate up to 160 GNSS signals (RF1) and 160 interference signals (RF2). This was previously limited to 160 GNSS signals and 80 interference channels.

Increased antenna power level control

V7.04 adds the ability to apply power level changes to all vehicle antennas in a single action. This feature is applicable to scenarios with more than one antenna defined, whether the antennas share a vehicle, or are spread across multiple vehicles. With a multi-antenna scenario loaded, the “All antennas” option can be accessed from the Power Adjustment dialog. For scenarios containing multiple vehicles, the “All vehicles” option is also made available.

Enabling the “All antennas” feature ensures any power level changes are applied to all the vehicle’s antennas configured for the signal being adjusted. By selecting “All vehicles” as well, the same changes can be cascaded to every antenna, irrespective of which vehicle they are assigned to:


GSS9000 Simulator and Host Controller remote power on / off / reboot

V7.04 adds the capability to remotely control power to the simulator and its C50r Host Controller. Functionality to power on, reboot and shutdown both the GSS9000 Simulator and C50r Host Controller is provided via the Host Controller Utility when used with a supported IP power switch. This enables essential maintenance and power conservation to be conducted remotely.

To further enhance the remote-working experience, the Host Controller Utility is now present in the Remote PC instance of PosApp. To install, select the SimREMOTE option during the installation process on your Remote PC.

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Mia Swain
Mia Swain

Mia Swain is a Product Manager working on simulator products and PNT solutions within the Spirent Positioning Technology business unit. She has an academic background in Physics and worked in R&D, applications engineering and then product management. Mia Swain’s current focus is managing the commercial status and development lifecycle of Spirent’s commercial grade GNSS simulator and its software platform, ensuring that the products maximize their commercial value and next generation products meets the needs of the market.