Aiming at localization problem of nodes without identification in wireless sensor networks（ WSNs）

introduce received signal strength（ RSS） data sequence which gathered by mobile anchor node

use unsupervised clustering algorithm to determine the number of unknown nodes

and extract the strongest RSS signal achieved by anchor node at different stationary point

to carry out ring crossing search for identifying the grid overlapping area.Then

pick out the area which may contain unknown nodes by using the maximum value algorithm. Finally

the improved particle swarm optimization（ PSO） algorithm determines the unknown nodes ’ coordinates which is most consistent with the number of clusters. Simulation results show that the algorithm can accurately estimates the number and localization of unknown nodes in the sparse environment.