This paper proposes a range free localization scheme based on identifying the overlapped communication regions of reference nodes. In the proposed scheme, an unknown node identifies the communication regions of reference nodes from which it can receive beacon messages. The overlapped region of all the communication regions should be the area where the unknown node is located. First, the intersection points of every two communication circles are derived by using the proposed formula. Then, all the intersection points that are not located in the Estimative Rectangle (ER) are discarded. Besides, an overlap degree, which is the number of the communication regions that include this intersection point, is associated with each intersection point. All the intersection points with degree n, which is the total number of reference nodes that the unknown node can hear, are shown to be the vertices of the overlapped region of the communication regions. Since the overlapped region is a convex, the averaged point of the intersection points with degree n must be located within this region and hence can be a good position estimation of the unknown node. Experimental results show that the proposed scheme outperforms the related works, including Centroid, ER and Grid Scan algorithms, in term of better localization accuracy.
