Cooperative localization based on semidefinite relaxation in wireless sensor networks under non-line-of-sight propagation

This paper is concerned with the received signal strength -based cooperative localization problem in a non-line-of-sight (NLOS) environment. A novel cooperative method in terms of the semidefinite relaxation technique is proposed to reduce the influence of the NLOS propagation on the network. First, an objective function is constructed based on various measurements in the NLOS environment, and an identical balance parameter is put forward as the overall estimate of the error under NLOS. Then, characteristics of the collaborative network and the NLOS environment are simultaneously taken into consideration to establish inequality constraints. Furthermore, by means of the semidefinite relaxation method, the localization problem is transformed into a solvable semidefinite programming problem to achieve the position estimation under cooperation. Moreover, the definite Cramer–Rao lower bound of the localization problem is given to evaluate the algorithm performance. Finally, simulation experiments show that the proposed method outperforms some existing state-of-the-art methods.