Modelling Atmospheric Effects on GNSS Reception

No matter how well any GNSS receiver might be designed, there are a number of outside influences that can have major effects on the performance of the receiver in the real world. In particular, atmospheric conditions can significantly degrade performance in some designs, and unless suitable compensatory measures are taken companies can find themselves selling equipment that can only operate accurately under “ideal” conditions. Ionospheric Scintillation is one such phenomenon that is very likely to increase in the next year or so as we enter, what is predicted to be a significant period of solar activity. Previous solar events have led to severe disruption of GNSS systems and technologies that rely on it.

This is hardly a recipe for success in today's market. Users will reasonably expect perfect performance in all conditions, and excuses such as “the wrong sort of atmosphere” are simply not acceptable.

The ability to accurately recreate all possible atmospheric conditions – or rather their effects on GNSS signals – is essential to be able to test the performance of any GNSS receiver design and its ability to compensate for resultant navigation error. This is clearly not possible using live signals from real-world GNSS satellites. Atmospheric conditions vary not only with changing weather patterns, but also with global location, and the effort required to recreate even a representative sample of such conditions is prohibitive.

However, with suitable software control, a GNSS simulator can be programmed to create such conditions. Indeed, simulation of atmospheric condition is one of the standard capabilities enabled through Spirent's SimGEN software, which is in use by GNSS receiver manufacturers worldwide, and with new scintillation modelling being added, the test capabilities offered by the simulator are now better than ever.

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