Aiming at localization problem of cooperative sensor network

propose scheme to estimate multiple nodes positions in the presence of unknown turn-around times（TATs）.In the adopted scheme

each target node can communicate with several anchor nodes and other target nodes

and two-way times-of-arrival between them are measured

which includes processing delays at both channel endpoints.The maximum likelihood estimates（MLE）of positions of target node and turn-around times（TATs） is carried out based on those measurement value

which generate non-convex optimization problem

it is approximated transform to nonlinear least squares problem.Finally

positions and TATs of multiple target nodes are estimated jointly by solving Euclidean distance matrix.Simulation result show that the proposed method has good localization precision

under different scenes

RMSE of the proposed scheme approach the Cramer-Rao lower bound（CRLB）.