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GNSS Simulation: The General Principles

The core requirement of any GNSS receiver test, whether for development, integration or production purposes, is for a controlled, repeatable signal. For many tests, the signal control includes flexibility over test case, or scenario, conditions that enable performance testing at nominal and extreme or error-state conditions.

Real-world, live-sky testing has significant drawbacks which, in practice, preclude controlled testing. These drawbacks of live-sky testing include:

  • An end user or test site cannot have any control over the GNSS signal being transmitted
  • The signals seen incident to the GPS receiver antenna are constantly changing as the GPS system constantly changes (precesses) 
  • There are occasional signal errors, often unknown to the receiver at the time
  • Atmospheric conditions change significantly and have a significant impact on single frequency systems
  • Testing at multiple geographic locations proves to be expensive

Using a GNSS RF simulator enables the user to define and control all simulated parameters. Advantages of using a simulator include the following:

  • Full control over test scenarios
  • Repeatable
  • Errors can be introduced in a controlled fashion and the way the system under test deals with each error can be optimised
  • Atmospheric conditions can be modelled and even removed from the test
  • Other signal effects can be controlled, such as multipath and antenna patterns
  • Vehicle trajectory and associated dynamics can be modelled
  • Future signals (e.g. Galileo, GLONASS and modernised GPS signals) can be generated to allow testing against new signals before a complete constellation of satellites are transmitting the Signals in Space (SIS)

GPS simulators can be used in various configurations enabling, for example, use of remotely generated trajectories and generation of interference signals as well as simulated GNSS signals.

If you want to know more about why you should choose a simulation solution from Spirent, take a look here.

 

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