Nullifying Jammer Effects in RIS-Assisted GNSS-Free Drone Localisation

Abstract

A general challenge in drone localisation and navigation is the strong dependence on satellite positioning. Reconfigurable intelligent surfaces (RIS) offer a promising technology for global navigation satellite system (GNSS)-free drone localisation and for the alleviation of the jammer effect by nulling the jamming signal. In this letter, we investigate how to optimise the nullification of the jammer while maximising the desired signal in a double RIS-aided GNSS-free drone localisation setup. The main objectives of the presented procedure are the maximisation of the desired signal received by the drone, minimisation of the jamming signal effect, accurate estimation of the angle of departure (AOD) from RIS to drone, and drone positioning in 3D. To address this challenge, we propose an alternating projection algorithm to perform jamming nullification by optimising the phase shift at each RIS element. Simulations show that by proper RIS element phase optimisation, the effect of the jammer is efficiently reduced, the AODs from RIS surfaces to drone are computed more accurately, and the drone 3D localisation accuracy is improved.