Location: Investigation of Real Interference Effects on Conventional GNSS Receivers

High performance GNSS receivers are the basic element for the deployment of location-based services and novel applications in several fields ranging from personal communication to geodesy, timing and many others.

Together with the growth of interest towards navigation and positioning, always more demanding requirements are being put on the user side, on accuracy, continuity and integrity of the positioning services.

In order to match such requirements, advanced signal processing techniques are being designed to improve all the different signal processing stages of the receiver architecture, and novel technological solutions are being studied for the implementation process to cope with flexibility, reconfigurability and upgradeable requirements.

Despite of these improvements that are being put in place for all the classes of receivers, ranging from mass-market to professional or safety-of-life, there is one phenomenon that cannot be neglected, and that is becoming more and more relevant as far as other corrupting effects are being mitigated.

In fact the low received signal strength that characterizes the signal at the input of the receiver for both the GPS and Galileo, keeps the power spectral density at approximately 20 dB/Hz below the thermal noise floor [6].

The presence of other signals with very different power level, even on carrier frequencies outside of the GNSS bands, due to implementation loss, could be very dangerous for the performance of the navigation receivers. Such signal could, in fact, bound the achievable accuracy performance, limiting also the development of effective applications. For these reasons, a growing interest towards the design of interference monitoring, detection and mitigation techniques is experienced for a large class of receivers and applications.

Several different electromagnetic sources, that populate the crowded radio frequency spectrum might be potential interferers on the GNSS bands. (Fig. 1)
The final effect of the potential interference on the positioning accuracy could be different and depends on many elements (e.g. interference signal characteristics, interference frequency components, GNSS receiver features).

Fig. 1: Interference signals over GPS and Galileo bands