Performance comparison of transformed-domain techniques for pulsed interference mitigation

With the growth of a new European Satellite Navigation System and with the modernization of the currently existent Satellite Navigation Systems as the American GPS or Russian GLONASS, a wider range of new signals will guarantee better performance enabling a plethora of new applications. However, due to the weakness of the GNSS signal reaching the antenna users and a crowded frequency spectrum, GNSS-based services will be always vulnerable to the presence of interfering signals generated by other communication systems. A recent example of these risks was the Lightsquared case in the USA, where the GPS receivers operations in L1 GPS band have been seriously threatened. The new modernized GPS L5 and the Galileo E5 frequency bands, which will be the frequencies allocated for GNSS-based aviation aids, will deal with a harsh interference environment in the airport areas due to the sharing of the bandwidth with other Radio Navigation Systems (RNSS) The issue of the interference potentially affects all the frequency bands allocated to GNSS, and for this reason it is crucial to provide the user receivers of proper countermeasures, in particular if devoted to support services related to personal safety. In the last years, the research on new interference detection and mitigation techniques has been focused on more complex algorithms working at higher rate with measurements performed by the receiver and not only assessing the reliability of the position solution. A recent class of such signal processing algorithms aims at processing the received digital signals in domains different from the classical time or frequency representation. In this paper, a general classification of possible unintentional interference for GNSS receivers will be provided, focusing on the aeronautical environment. Then, a comparative analysis of different transformed-domain techniques will be presented. A wavelet-based mitigation approach will be introduced, as well as a new Karhunen-Loève Transform based algorithm and their application on pulsed interference will be described.