Line-of-sight identification based on area measurements

Non-line-of-sight (NLOS) propagation is a killer issue in mobile location and line-of-sight (LOS) base stations (BSs) identification method can be used to effectively mitigate the NLOS error. In this paper, a novel method is proposed to identify LOS BSs using range measurements. Because of the measurement noise and NLOS error, the points of intersection of three position circles may construct overlapping area. In most time, the overlapping areas may be small or not being when three BSs are all LOS BSs. On the other hand, when some of these BSs are NLOS BS, overlapping areas may become bigger. The initial identification is made by that principle. However, some cases aren´t subjected to that principle; the initial identification may be misjudgments. In order to reduce those misjudgments, constraint method, which contain residual test and statistical method, are used to make further identification. The proposed method can identify LOS BSs with respect to not only motional MS but also static MS. Simulation shows that the proposed method can successfully identify all of the LOS BSs over 94% of the time.