Synthetic aperture navigation in multipath environments

Multipath propagation is one of the major error sources for radio navigation systems. While many new applications require ever more precise user positioning in urban and indoor settings, existing receivers are especially vulnerable to severe multipath, which is often present in such environments. This article reviews recent advances in the concept of synthetic aperture navigation, which enables the user to separate co-channel navigation signals, including combating the adverse effects of multipath. A deeply integrated RF receiver and an inertial measurement unit produce an estimate of the user trajectory, which makes it possible to form a synthetic aperture from the user's motion using a single-element antenna. In turn, using the synthetic aperture opens the door to applying modern direction finding and beamforming methods. These signal processing schemes are able to differentiate between the line of sight and multi path signals (or between different signals in the band in general), as they often arrive from different directions. The desired signal can be extracted in the presence of strong multipath, and its delay can be accurately estimated.