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Analysis of wireless localization using non-line-of-sight radio signals

One of the important issues in wireless localization is concerned with the identification of non-line-of-sight (NLOS) radio signal propagation, since NLOS propagation is considered the dominant source of localization error. The existing identification methods focus on "consistency" tests, based on the assumption that localization involving the use of NLOS radio signals cannot be performed in a consistent manner. However, the validity of the foregoing assumption has not been properly investigated. This paper presents a theoretical analysis of the localization using NLOS radio signals, and shows that the assumption would no longer be valid when the mobile user is located outside the convex hull of the underlying beacons. As a result, existing NLOS identification methods, as well as many localization approaches, could perform unsatisfactorily. The importance of the proposed convex hull condition for NLOS identification is confirmed by extensive simulation results.