Target localization with NLOS circularly reflected AOAS

Bearings-only localization with light-of-sight (LOS) propagation is well understood. This paper concentrates on bearing-only localization with non-line-of-sight (NLOS) measurements, where the target radiation arrives at the sensor after a specular reflection. The wrinkle is that the reflecting surface is circular (inner side of a circle), and is assumed known. Since the target-sensor geometry has multiple configurations, the maximum likelihood (ML) solution may not exist. However, if a concentric opaque circle (such as the earth) exists within the reflecting one, the propagation path is unique; a grid search based ML is available for such a circumstance. Since ML is computationally consuming, two suboptimal algorithms based on small angle approximation are developed. Their performances are numerically compared.