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Continuous Improvement with Spirent

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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 7.03 – July 2021 (by Mia Swain & Chris Yapp)

New ICDs supported

QZSS L6 : IS-QZSS-L6-003
RTCM V3.3 : RTCM 10403.3

New features

Premium enhancements to GSS9000 simulator

2kHz simulation update rate on GSS9000 GNSS simulator (on 3rd Gen GSS9000 only)

There is now a licensable option on GSS9000 simulator to achieve a maximum software and hardware update rate of 2 kHz (maximum scenario duration: 24 hours on up to 80 channels. For more details, please refer to the GSS9000 specification datasheet). This improves the accuracy of simulated trajectory for fast moving vehicles and operations such as space missions, hypersonic vehicles and drone testing use cases.

The faster update rate also improves latency for hardware-in-the-loop (HIL) testing, enabling trajectory and motion data from third-party hardware and software systems to be ingested and processed in real time at faster rates.

Extended maximum scenario duration to 65 days

V7.03 extends the available scenario duration to 65 days on GSS9000 and GSS7000 simulators with SimGEN and SimREPLAYplus software platforms (limitation applies on GSS9000 when SIR exceeds 100Hz. For more details, please refer to the GSS9000 specification datasheet).

This will benefit some test cases such as space missions where long-term simulation is needed. Extended scenario duration enables test runs using the same initial conditions – with reduced user inputs – for the duration of the simulation, delivering uninterrupted high-performance testing for longer.

Enhanced Embedded Interference (GTx) Capabilities

In v7.03 release, Spirent has improved support for interference testing on wide spectrum signals, increased bandwidth resolution and repetition rates, and added variable bandwidth control on additive white Gaussian noise (AWGN).

For more details, please refer to the specification datasheets of the GSS9000 and GSS7000 simulators.

New Python example script added to PosApp installer

This new script is a quick setup guideline to help users better compose TCP string commands using Python.

The "posapp_simremote_control_example.py" script exemplifies how SimREMOTE control of PosApp can be achieved via Python. The script contains a series of generic functions to support communication with PosApp over TCP/IP (socket operations).

An example remote control session is included within the script and will take effect once the script is executed. The script requires Python v3 or later to be installed on the remote client end which controls PosApp. Operation is not limited to the commands specified within the example script; any SimREMOTE command defined in the SimREMOTE User Manual can be used to control PosApp by adapting the example Python script to include the required command.

Please contact Spirent support service for more detailed advice on customising the script for your test needs.

Multipath control added to Maximum Simulated Satellites limit

PosApp v7.03 introduces the ability to control whether multipath signals are included the in the limits set by altering the Maximum Simulated Satellites parameter. This control is provided with a remote command and is applicable to SimGEN, SimREPLAYplus, SimTEST and Single Channel Utility.

Maximum Simulated Satellites - accessed from Options > General Options
Default: 999
Used to limit the maximum number of satellites PosApp simulates. Note, if one satellite per constellation is required, see "Single Channel Mode" on PosApp’s "File" menu.

Exclude MP signals - accessed from Options > General Options
Default: Disabled; multipath signals are included in the limit
When enabled, you can control the maximum number of simulated satellites without impacting the number of channels used to produce multipath signals.

Spirent offers several multipath control methods, which allow you to configure the type, offset and quantity of echoed signals, as well as which satellite they originate from.

The Exclude MP signals feature is accompanied by a remote command:
USER_SETTINGS_UPDATE, { "exclude_mp_signals": "<state>" }
Where <state> is either "true" (enabled) or "false" (disabled)

‘Signal Off’ option added to Single Channel Utility’s Power Adjustment dialog

Default: Disabled; all signals are set “On
When selected under the constellation slider, all signals in that constellation are turned “Off”, disabling all power level sliders in that constellation. All signal levels for that constellation display as ‘Off’ in the Power Levels Graph.

When selected under the frequency slider, all signals in that frequency are turned “Off”, disabling all power level sliders in that frequency. All signal levels for that frequency display as ‘Off’ in the Power Levels Graph.

"Import" function added to Source File dialogs

Located alongside the existing “Browse” function present in various SimGEN and SimREPLAYplus dialogs, an “Import” option has been added to v7.03. The text "Linked" is displayed below the file’s path to show that PosApp is using the chosen file in the scenario.
BeiDou Signal Sources File > Rolling Grid File examples are shown below.

Browsing to the file you want to use keeps the chosen file in its original location; PosApp records its path and filename in the scenario. This solution is suitable if the scenario is only to be used on one simulator system, or if multiple scenarios are to use the same file:

Importing the file you want to use makes a copy of the chosen file in your scenario’s folder. This solution is useful if you move scenarios between systems, or share them with partners (including Spirent):

Data Streaming now supports multiple concurrent versions of EthernetShare.h

EthernetShare.h is a C++ header file supplied with PosApp, which, along with your own C/C++ code, allows you to implement data streaming clients. EthernetShare.h enables PosApp to interface with supported third-party software.

The EthernetShare.h file is subject to configuration control. The file has undergone several updates since its first use with PosApp; at the time of writing the file is at version 27. A record of the changes at each release is contained within the EthernetShare.h file. The file's version can be determined my reading the "static const unsigned short" "version_major" and "version_minor" values.

From PosApp v7.03, PosApp can support multiple concurrent versions of EthernetShare.h file. The EthernetShare.h version is chosen from the Data Streaming Definition > General dialog.

To choose the required version, ascertain the "Built with EthernetShare.h version" from the Data Streaming Definition > General dialog.
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If 26 or less, choose the same version
- If 27 or more, choose the version number that matches the version shown in Data Streaming Message Logger

Apply transmission delay to GPS L1 C/A Navigation message

PosApp v7.03 adds the ability to delay the transmission of the GPS L1 C/A navigation message by up to 6 seconds. The delay is applied to the time of action and is specific to the chosen satellite(s) within the GPS constellation to which navigation data modifications are defined.

The Time Delay is configured using the GPS Signal Sources file’s Navigation Data Modification dialog for Legacy NAV Data Mod:


Version 7.02 – March 2021

New ICDs supported
BeiDou B2b signal and Precise Point Positioning service
BDS-SIS-ICD-B2b V1.0
BDS-SIS-ICD-PPP-B2b V1.0

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
RINEX V3.04

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.

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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.