XPLORA

GNSS stands for Global Navigation Satellite Systems. Every such system consists of several satellites (usually approximately 30), which are moving in precisely defined orbits around the Earth, and continuously send radio signals to Earth (in a frequency range of approximately 1,2 to 1,6 GHz). These signals can be received on and above Earth (for example, in aeroplanes). When receiving signals from at least four satellites the receiver can calculate a position and the time.
There exist several Global Navigation Satellite Systems in parallel: GPS (operated by the US), the European GALILEO, GLONASS (also known as “Russian GPS”), and BEIDOU from China – all of them supplying global coverage. In addition, there exist navigation satellite systems that use the same mechanisms as the aforementioned GNSS, but cover only specific regions on the globe, like the Japanese QZSS system and Navic from India.

A GNSS signal simulator is a system that produces signals equal to real-life GNSS signals based on mathematical models and inputs from users. Such systems can be merely software-based or can also create physical RF signals. The signals produced by a GNSS signal simulator correspond to those a GNSS-based device would receive in real life under the conditions defined in a specific test scenario.

GNSS signals are used in extremely many different applications for the determination of position and or/time. They are used, for example, for navigation in the automotive, maritime or aerospace industry, for precise timing in power distribution networks and the finance industry, for surveying purposes, for tracking valuable assets like cars and machinery, and many other purposes. All devices and systems which use GNSS technology for positioning and/or timing must be tested to ensure a reliable, safe operation.
Products and systems relying on GNSS technology for positioning and/or timing have to be tested thoroughly before putting them into operation. As the possibilities for comprehensive testing in real life are very limited, the use of a GNSS simulation system is the perfect option for ensuring a high coverage of test scenarios, and efficient execution of many test cases, having in mind the requirement to standardize and repeat tests.

For systematic testing standardization and repeatability are key elements. These cannot be achieved in real life. A GNSS signal simulator can expose a GNSS-based device to a wide range of different environmental conditions, like, for example, different atmospheric conditions, obstruction and reflection of GNSS signals in urban canyons, different visibility of satellites in different locations on the globe at different points of time, etc.
In addition to many natural factors, which have a significant influence on the quality of GNSS signals received on earth, there exist also intentional interferences which can seriously put at risk the quality of GNSS signals, like jamming and spoofing. Test scenarios which include jamming and/or spoofing in real life in most countries can be carried out only with specific licences by the corresponding authorities and/or only with specific, cost-intensive infrastructure (like, for example, anechoic chambers). Therefore tests for hardening GNSS-based equipment against such vulnerabilities are much more efficient when using a GNSS signal simulator.
As a resume: GNSS signal simulators contribute to safety, security and reliability of GNSS-based equipment. And they do this in a fast, cost-effective way.