Simultaneous localization and tracking is studied to solute the problem of tracking a moving target in wireless sensor networks（ WSNs） while simultaneously localizing the nodes of WSNs

while position information is uncertain. RSSI is used to measure distance between node pairs

multidimensional scaling techniques are used for the initial position of WSNs based on distance matrix. Then the compression EKF filtering is used to estimate and update sensor node position and target position. Simulation results show that the algorithm has high accuracy of localization and tracking under low network coverage rate. Although the initial positioning error is 5m

the node and the tracking error is less than 3 m especially for long distance tracking

this algorithm has good accuracy and realtime performance.