A GPS (or GNSS) emulator or simulator transmits exactly the same type of GPS signal and data as emitted by the satellites themselves.
These transmission include all the information such locate, date and time that a normal GPS device would.
When a gps enabled device receives data from a simulator it behaves in the same was as if it were receiving data directly from a satellite.
A newly designed device can be tested for stability and issues if it is subjected repeatedly to the same GPS signals that are identical in strength and quality each time.
This is as opposed to the live broadcast from the existing satellite constellation which has a dynamic signal strength that can vary for a variety of reasons.
Why use a GPS emulator?
Regardless of the market, a newly developed GPS/GNSS product will require testing.
For developers of GNSS/GPS-enabled devices, having the ability to reliably test a device in the same way each time will shorten development times, increase product reliability and reduce costs.
Acquisition of signal, data retention and device performance in changing environments are all the key factors of device testing and how successful it will be.
Devices need to be stress tested in the same way that they will be used in a real world environment.
It simply is not enough to go outside, receive gps co-ordinates from satellites and mark the testing as completed.
In the real world, there are detrimental factors to deal with such as obscuration, multipath reflection, and interference.
As a result, it is important to understand how the device will perform in these situations.
Introducing these potential issues and variables into real-world testing will slow down testing immensely, that’s why GPS emulators were designed.
Advantages of an emulator
Using a GPS emulator provides the development team with a multitude of advantages.
The most vitual advantage is the ability to reply raw RF satellite signals within a lab testing environment without having to go outside, or within line of sight of satellites orbiting overhead.
This will ensure that a controlled test environment is maintained, where all your devices and equipment are in the same spot each time, ready to go.
GPS/GNSS Emulator Types
There are three types of emulators: GPS engine emulators, RF signal Record/Replay emulators, and full constellation emulators.
GPS/GNSS Engine Emulators
GNSS engine simulators are the simplest option of all three that are listed here.
The standard message type is a serial NMEA.
To use a GPS engine emulator, the GNSS engine is completely removed from the device being tested and the GPS signals are directly inserted into the circuit.
These devices are mainly used by system integrators who are not concerned regarding the perofrmenace of the GNSS engine.
The connection method is generally through a serial port, and based within software.
GPS RF replaying & recording Systems
A GPS RF Replay/Recording system samples RF signals from a live GNSS system antenna(s) are a rapid rate.
The data is then stored to a hard drive, later retrieved to be replayed directly into the front end of a GNSS engine, reproducing the original signal.
Complete constellation emulators
Full or complete constellation emulators generate all GNSS signals from scratch.
Combined with a user defined trajectory file, an artificially GPS signal is then created.
This method can be created live, in real time using hardware, or alternatively processed offline using a normal computer.
Using a computer to process the offline data will create a GPS data file which is late replayed using a simple recording & replaying system.
Generally GPS emulators are very expensive, used by companies with a dedicated R&D department, and with extremely deep pockets.
Traditional GPS emulators use signals which have been artificially created by computers.
Whilst this method can be repeated by the tester, it is not a real live environment, as the signals themselves do not experience the same obstructions and obfuscations as found in the sky, and on land.
This leaves developers with a quandary: live testing is impractical, as well as time consuming, and consequently very expensive.
All the whilst being expensive and potentially not providing the realistic signal that is required.
The future – GPS emulator artificial intelligence
The future of GPS emulators will see prices reduced,
There are now free applications on your phone as well as software for computers that can create this data for us.
Artificial Intelligence will assist in making GPS data which mimics live systems, creating the perfect test environment without any involvement from satellites at all.