Impact Study of Unintentional Interference on GNSS Receivers

This work has been performed in the context of an Administrative Arrangement for DG HOME. The overall scope is to perform an impact assessment of radio frequency (RF) interference on critical infrastructures relying on GNSS-services for timing and synchronization purposes. In WP3, the analysis has been divided into the impact of intentional interference on critical infrastructures presented in WP3.1 and the analysis of unintentional interference, covered in this report. DVB-T has been identied as the most important source of unintentional interference in the GNSS frequency bands and therefore a special attention is paid to this interference source. The main motivation to assess the performance reduction of receivers due to unintentional interference, is related to the high probability of these events. Unintentional interference stems from out-of-band emissions or spurious transmissions. Four different scenarios have been considered in this work, covering (i) additive white Gaussian noise, (ii) continuous wave interference, (iii) pulsed continuous wave nterference and (iv) interference that stems from the third harmonic of DVB-T transmissions. All these scenarios are highly relevant and are frequently observed in realistic signal conditions. The scenario of DVB-T interference receives most of the attention in this work, since DVB-T has become the most widely adopted digital terrestrial television broadcasting standard in the world. Harmonics of the DVB-T signal could possibly fall together with the GPS L1 or Galileo E1 bands and as such become a threat. DVB-T services are operational in more than 40 countries, with more than 75% of the deployment in Europe. In the coming years, DVB-T is expected to be deployed in more than 100 countries. In the frame of this work, different tools have been developed to quantify the impact of unintentional interference. First, a laboratory testbed has been set up, that allows to take real GPS L1 signals, combine them with synthetic interfering signals and test the robustness of different commercial and professional receivers. Further, in order to have a full control of the signal characteristics and the implementation details of the receiver, a simulation platform has been developed. This simulation tool generates GNSS as well as interfering signals, and observes consequently the impact on the acquisition or tracking performance for different receiver implementations. Finally, since it is difcult to reach statistical signicance for the acquisition performance, an analytical tool has been developed allowing to evaluate the effects of interference. This report summarises the relevant results for the four considered scenarios. For the assessment of the acquisition performance the analytical tool and the simulation platform have been used. In order to evaluate the tracking performance, experimental work has been conducted with real receivers and simulations have been performed. For the acquisition, the report quanties how much the probability of detection and the probability of false alarm are affected by the presence of interference. For the tracking, the main result of this report is the quantication of the signal degradation in terms of C=N0 and in terms of the variance of the position solution. In the scenario of DVB-T Page 2 of 94 WP3.2 interference, the degradation of the signal quality has been determined as a function of the DVB-T third harmonic power and the distance between the victim receiver and the DVB-T base station.JRC.DG.G.6-Security technology assessmen