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 7.02 – March 2021

New ICDs supported
BeiDou B2b signal and Precise Point Positioning service

New features

Galileo E6 signals’ PRN code sequence is now supported on the GSS7000

There are two dedicated signals transmitted on Galileo E6 band (1260-1300 MHz): E6-B and E6-C. Both channels allow the encryption of the information at signal level. Spirent’s industry leading GSS9000 simulator continues to provide support for encrypted signals to authorised users, with the GSS7000 now adding the limited capability to support the PRN code sequence without the navigation message.

March PNT update image1

Spectra of Galileo Signals in E6 (source: https://gssc.esa.int/navipedia/index.php/Galileo_Signal_Plan)

Simulation of multiple RTCM reference stations

A new feature introduced in V7.02 enables the simulation of up to 10 RTCM reference stations. Parameters of each reference station, such as location, RTCM version and message type, can be freely edited by the users. NTRIP protocol is supported in SimGEN, meaning all reference stations can be configured as NTRIP Servers streaming correction messages to a designated NTRIP Caster for testing.

This new feature will allow the user to test both rover and Caster’s ability to select/connect to the most suitable reference station and apply its corrections as the rover moves along its trajectory. It could also enable the simulation of a Multi-Base Station (MBS) Real Time Kinematic (RTK) system to help verify the accuracy of Virtual Reference Stations.

Control GPS L1/L2/L5 power levels independently

Applicable to all control software levels, for all supported simulators, SimGEN v7.02 adds a greater degree of power level control while the scenario is running. In addition to altering power levels by Constellation or Channel, you can now change the power level of each frequency within the constellation independently. For instance, the power level for GPS L1 signals can be controlled separately to that applied to GPS L2 or GPS L5 signals.

This is accomplished using either the Power Adjustment window or remote command (SAT_FREQ_POW_OFFSET).

March PNT update image2

March PNT update image3

Simulation of more BeiDou SVs

By the beginning of 2020, there were over 50 BeiDou satellites in space. To enable more realistic simulation of the BeiDou constellation, the default number of BeiDou SVs has been increased to 30. With the ‘extended constellation’ function, SimGEN is capable of simulating 33 additional SVs as specified in BDS ICDs. A total of 63 SVs are now available with the latest software release.

Single Channel Utility Emulator commands

IEEE commands are used by the Single Channel Utility’s (SCU) Emulator to send legacy direct commands to control the GSS7000 simulator system. SimGEN v7.02’s SCU User Manual includes the complete list of Emulator commands, including for:

  • Scenario commands – simulator info, scenario start/stop controls

  • Signal power commands – signal power level controls

  • Signal control commands – constellation, nav data, velocity profile controls

  • Pseudorange commands – initial pseudorange controls

  • Hardware and calibration commands – BITE, reference frequency, error status

The User Manual also provides a comprehensive list of equivalent SCU GSS6300 emulator remote commands.

Version 7.01 – January 2021

New ICDs supported

EUROCAE ED-259 MOPS for Galileo GPS SBAS Airborne Equipment

New features

In-band interference generation on the GSS7000 multi-frequency, multi-GNSS constellation simulator

This capability enables the realistic and precise reproduction of in-band interference signals in the test lab. It allows users to set transmitter locations, trajectories, and antenna patterns, and enables the customer to define interference signal parameters such as centre frequency, signal modulation and power level.

Using embedded interference on the GSS7000, users can take advantage of:

  • 8 transmitters and 16 interference channels in a single chassis

  • Maximum power level of -47 dBm

  • User defined interference transmitter trajectory and antenna patterns

Version 7.01 – January 2021 Img 1

SimGEN now complies to Networked Transport of RTCM via Internet Protocol (NTRIP)

This new feature enables the simulated differential correction data to be streamed over the internet. The SimGEN software simulates the NTRIP Server, with the simulated correction data pushed out from the server to a third-party NTRIP Caster of user’s choice. NTRIP Clients (GNSS rover devices in the field) connect to the NTRIP Caster to receive the correction data for testing, in the same way that they would in the field. Our software simulations are compatible with NTRIP V1.0 and V2.0.

RINEX improvements

SimGEN V7.01 includes several RINEX improvements, including:

  • Support for RINEX observation data up to V3.04

  • Support for RINEX navigation messages up to V3.04

  • Support for saving orbits in RINEX V3.04 format

  • Support for reading ionospheric data from mixed-constellation RINEX files

    • The header of mixed-constellation RINEX navigation files contain ionospheric data for multiple constellations. SimGEN V7.01 is able to distinguish between the different lines when reading the header. SimGEN then ignores those lines which are not relevant for the current constellation

  • RINEX V3.04 support for NAVIC (IRNSS), including reading of orbits, UTC offset and ionospheric data

  • RINEX support for BeiDou B2a

  • RINEX V3.02 support for Quasi-Zenith Satellite System (QZSS)

  • Support for BeiDou “orbit type” reading from RINEX

    • BeiDou satellites are in either a MEO, IGSO or GEO orbit. Which orbit they are in is important as it determines key aspects of the navigation data. SimGEN V7.01 introduces the ability to set the correct “orbit type” when loading BeiDou orbits from RINEX, along with the typical orbital parameters

Real-time streaming of almanac/ephemeris data on all constellations

GNSS almanacs and ephemerides form the navigation message transmitted by each satellite, containing information such as week number, satellite accuracy and health, and orbital information. This critical navigation data is needed for receivers to compute the position.

The real-time streaming capability of almanac/ephemeris data is now extended to all constellations (GPS, Galileo, BeiDou, QZSS and NaVIC), potentially helping customers with model based software development and testing.

Version 7.01 – January 2021 Img2

Automatically poll the status of connected GSS7765 interference generators

SimGEN V7.01 introduces the facility to automatically poll the status of connected GSS7765 interference generators and report it via the PosApp System Messages window and message logs. SimGEN checks the status of the interference generators at regular intervals and, if the GSS7765 indicates a problem, reports the response as follows:

  • If the scenario is running, PosApp responds with an "Error" message and the scenario continues running

  • If the scenario is not running when a problematic status is received, PosApp responds with a "Fatal" message, and is prevented from running the scenario until the problem is resolved

Increase in available Earth obscuration angle range

An increase in the available Earth obscuration angle range enables greater flexibility and realism for a number of applications. This parameter can be edited at the Constellation signal source file > Earth obscuration page of the Constellation Editors, and can now be set to -10 to 90 degrees (Earth Tangent). In the simulation, SimGEN calculates satellites below a given angle, with those satellites not being simulated.

Many receivers let you specify an angle below which they will not attempt to track satellites. The default 5° is a common value. The extended Earth obscuration angle range helps to simulate a more realistic field of view for receivers at a higher altitude – such as those found in aircraft and LEO satellites.

Version 7.01 – January 2021 Img3

Attitude determination in quaternion angles

SimGEN now supports a new remote command type for attitude determination in quaternion angles. These are utilised through SimGEN’s support for UDP/IP commands that define the vehicle motion.

Previously, vehicle attitude was only represented as the set of Euler angle rotations obtained on moving from alignment with the local geographic frame in the sequence heading, elevation and bank. The new feature could benefit users who represent spacecraft and satellite orientation/rotation motion with quaternion notation.

Version 7.00 – August 2020

Important notice

Following the end of support for Windows 7, SimGEN version 7.00 has been tested under the Windows 10 environment only.

New ICDs supported



NaVIC (IRNSS) L5 - now supported on Single Channel Utility

New features

We are pleased to announce that a graphical user interface (GUI) for Single Channel Utility (SCU) is now available to supported customers with the release of PosApp V7.00.

Spirent’s PosApp software supports the generation of a single channel output for each licenced signal. The Single Channel Utility allows individual control of several parameters including: a satellite’s carrier frequency, power level, velocity profile and PRN, secondary code and navigation data. Single Channel Utility GUI provides a user interface to all current SCU remote commands on GSS7000 and GSS9000 simulators, and any PosApp product (SimGEN, SimREPLAYplus, SimTEST) can operate in single channel mode.


All PosApp products (SimGEN, SimREPLAYplus, SimTEST) can be switched to operate in single channel mode via "Options" -> "Control Options" -> "Single channel mode":


The new 2-Vehicle 1-RF trajectory spoofing licensable feature allows 2 vehicles to be defined with independent trajectories at the same RF output. To simulate a trajectory spoofing attack, 2 sets of GNSS signals are generated at a single output to simulate 2 different vehicle trajectories (static or dynamic). These two trajectories could be aligned originally with one set of GNSS signals then altered to simulate one trajectory gradually diverted from the ‘truth’ trajectory. The receiver can be spoofed to follow the altered signal set, diverging from the truth data according to the user-controlled parameters.

Applicable to GPS, GLONASS, Galileo and BeiDou constellations (plus their respective ground-transmitter interference constellations), the multi-copy constellation feature for receiver anti-spoofing tests enables the generation of up to 10 copies of any licenced constellation – each with full manipulation of parameters via the signal sources file (1 source file for each copy).

By using the multi-copy constellation feature, users can:

  • Have more than one satellite constellation per GNSS type

  • Choose whether the satellite constellation uses traditional orbits or has fixed, ground-based positions

  • Treat the first constellation for each GNSS type as ‘truth’

  • Modify constellation parameters based on intended signal attack simulation

Signal Flexibility allows the user to select an existing GNSS signal and replace its standard (ICD-defined) content with user-defined values. With this feature, an open API and flexible system architecture turns the GSS9000 into an arbitrary waveform generator (AWG).

Fundamentally, this feature allows built-in user-configurable setup and control

  • Experimental and pre-operational SIS ICD PRN codes

  • Navigation data content and rate

  • Chipping rate

  • Edge-shaping

  • Modulation types

New support of ‘rolling’ SP3 files and navigation data generation by curve-fit adds realism to GNSS satellite orbit simulation. To enable this function, go to “Options” -> “General options” -> “generate nav data by curve-fit”.

SimGEN will interpolate between records and, if required, extrapolate beyond the ends of the files. Navigation data is generated using a curve-fitting process similar to that used by GNSS Control Segments, meaning users will see ephemeris and clock errors which are highly representative of those observed under live-sky conditions. This is PosApp’s most realistic simulation to date, allowing users to:

  • See the increased accuracy of modernised ephemerides

  • Observe the degradation of accuracy that occurs outside of an ephemeris’ validity period

  • See the different precision of different almanac messages

  • Test receiver performance across discontinuities at ephemeris cutovers

  • Quickly and simply exercise all available orbit and clock parameters in each navigation message

The maximum number of GTx (Ground Transmitter) channels permissible on the GSS9000 has been increased from 16 to 64 simultaneous embedded interference channels from a single constellation. The 64-channel maximum can consist of 64 channels of one signal type or up to 32 channels of two GTx signals and so on. For example, “64 GTx_GPS_L1” or “32 GTx_GPS_L1 and 32 GTx_GPS_L2”.


The GTx dialogue menus have been improved to include a field to specify the “max transmitters” and the fixed attenuator value for each simulated GTx signal. The increase enables larger or denser jamming fields to be produced. The position, motion, power, and signal type of each Ground Transmitter can be independently controlled.

As of V7.00, the External Power Gain range has been increased to -30dB to +130dB. Accessible as a parameter on the General Options menu, it is used to change the reference level seen in the Power Levels Graph to display the actual power level experienced by the device under test. It is intended to allow the user to show the effect of cables, amplifiers and attenuators between the simulator and the device.

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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.