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Spirent GSS6400 Affordable Record & Playback System

Whether developing navigation algorithms, performing vendor selection, evaluating receiver variants or establishing the performance of a PND under real world conditions you will need a repeatable representative high quality GPS signal. And sometimes testing using real world signals is the easiest way to confirm performance in the presence of real world impairments or real world operational challenges.

The GSS6400 complements Spirent's established range of navigation and positioning simulation systems. While simulators generate the specific controlled signals which are needed to develop and test the performance of navigation and positioning systems, the GSS6400 captures the full "richness" of the real world environment which can then be replayed in the lab. The captured data includes real world fades, multipath and in-band interference as well as direct signals from GNSS satellites.

Spirent’s GSS6400 Record Replay System is a complete, standalone system, purpose designed for gathering data in the field and replaying it with optimal fidelity and performance back in the lab.

The loss of signal integrity inherent in 1-bit systems is greatly reduced by use of 2-bit encoding whilst the in-built 500GBs SATA drive provides approximately 30hrs recording time. For extended record capacity an external SATA drive can be used, or take advantage of the convenient USB ports to move files onto other media such as pen-drives.

  • Field trials are never entirely repeatable making accurate comparative evaluation of receivers a challenge. Record and Playback allows exactly the same test conditions to be presented to any number of devices under test whenever and wherever is convenient.
  • Self contained and easy to use, the GSS6400 makes bringing the real world into the lab a doddle. The 2-bit encoding ensures excellent fidelity whilst the built in battery and controller simplifies data collection significantly.
  • Real world impairments such as atmospheric effects, multipath, fades and interference can be captured and repeatably reproduced back in the lab.

Multiple RF Carriers

  • Up to 3 RF carriers, selected from a range of constellations and signals, can be accommodated in a single signal generator chassis

Realtime Simulation

  • Standard capabilities enabled through SimGEN include simulation of atmospheric effects, multipath reflections, terrain obscuration, antenna reception gain and phase patterns, differential corrections, trajectory generation for land, air, sea and space vehicles and comprehensive error generation

Intuitive and Easy to Use Interface

  • An easy to use graphical user interface (GUI) allows modification of a wide range of variables from pre-set defaults, enabling the user to focus their time on the areas of test important to them. Complete scenarios are readily shared between systems, supporting collaborative activities and speeding the R&D cycle

Q. What is the longest single recording possible?
A. In theory the largest possible file is 16TB (about 45 days of GPS data) this is limited by the size of the hard drive which for a 500GB drive gives around 30 hrs.

Q. How can I use the GSS6400 to evaluate sensitivity?
A. Record a signal with a known C/No and at least 10dB higher than the expected sensitivity. Replay into the receiver under test and increase the attenuation setting once signal are acquired until they are lost. Note that the result is repeatable and comparable between units however absolute accuracy depends on the noise figure of the receiver under test.

Q. Why 2 bits instead of 1 bit?
A. Recording at 2 bits adds just less than 1 dB of noise compared to the true signal. Recording at 1bit adds 3db, and is therefore not as good if you are trying to test sensitivity. 2 bits also improve the dynamic range to help cope with jammers.

Q. Can the output be split for distribution?
A. Yes. Please use the DC block provided if the splitter provides DC for an antenna.

Q. The GSS6400 can use passive or active antenna. What is the range of antenna gain that can be accommodated?
A. Up to 27dB gain antennas are supported.

Q. Can I use a splitter before the RF input during record to allow a reference receiver to log NMEA messages?
A. Yes, a dc block may be required on one of the splitter outputs depending on the dc arrangement of the splitter.

Q. Can files be managed remotely? For example if a recorder was left unattended but networked could a remote user start / stop recording and then collect the files?
A. Yes. The web server can be accessed remotely via the internet, depending on you local IT policy. You can also VNC into the box … which is a PC.

Q. Can the username and password be modified by the user?
A. The password can, but the username cannot.

Q. If I want to control a unit from a local laptop what is the best way of doing this?
A. The easiest way is to connect them via an Ethernet hub or switch.

Q. Please confirm that there are 6 ways of controlling the unit:

  1. Front panel
    A. Yes playback/ record etc.

  2. Keyboard / Monitor / Mouse at the rear panel
    A. Yes but to control the pc run scripts, or open a browser and go to http://localhost to run the Webserver interface.

  3. Webserver via the internet (using dynamically assigned IP address)

    A. Yes playback/ record etc.

  4. Webserver locally using crossover cable
    A. Yes playback/record etc. Currently the manual does not include instructions on how to do this. An application note will be produced to detail the process.

  5. VNC remote desktop
    A. Yes but to control the pc run scripts, or open a browser and go to http://localhost to run the Webserver interface.

  6. Linux shell scripts
    A. Yes

Q. If I transfer files to an external hard drive (via SATA or USB) can I then retrieve those files using a PC running Windows OS?
A. Yes

Q. Can I use the USB ports for a flash drive / memory stick?
A. Yes

Q. Can this unit be used for production test?
A. Yes. If for example you take the unit outside and track satellites with a clear view of the sky you can replay this data into the unit under test. The UUT should give the same position or C/No on every receiver under test.

Q. Should I see the same performance on my receiver as I would have done in the real world?
A. Yes. The only difference is that the C/No will be a little lower than in the real world due to the noise figure of the two receiver front ends that have been used, typically <1.5dB.

Q. Can I record L2?
A. No. L2 is a different frequency and the GSS6400 operates at L1 only.

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Documentation

pdf-icon.png GSS6400.pdf

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