Assessment of RFI Geolocation Using Modern Android Smartphones

This paper assesses radio frequency interference (RFI) detection and crowdsourced RFI geolocation on modern Android smartphones. Three indicators for RFI are investigated: the number of satellites used in the positioning solution (#SV), automatic gain control (AGC), and carrier-to-noise density ratio (C/N0). These are examined across seven different phones in a total of 13 different tests, including four outdoor real-world benchmarking tests, and nine jamming tests performed inside an anechoic chamber with a small consumer off-the-shelf (COTS) jammer acquired on the internet. The results of these tests, and the behavior of each of the three indicators is presented and analyzed to show some of the limitations and issues that will naturally be involve in using smartphones for this purpose. Such issues include the limited abilities of the GNSS hardware in smartphones, and the dynamical nature of ordinary smartphone usage. Based on these tests a new and reliable RFI detection method is proposed and tested on the available data. This method relies on both the AGC and C/N0 indicators to compute a reliable RFI detector which registers all events in all devices in the anechoic chamber, and has no false detections in the benchmarking tests, in which no RFI is present. Finally, a method for geolocating RFI using crowdsourced smartphone data is presented and assessed. The assessment is done through simulation and gives an indication of the number of smartphones necessary to accurately location a jammer or a similar RFI source.