TW-TOA based cooperative sensor network localization with unknown turn-around time

This work aims to estimate multiple node positions in the presence of unknown turn-around times within the context of cooperative sensor network localization. In the adopted scheme, each target can communicate with a set of anchors (probably not in sufficient numbers) and a set of other tar- gets. Two-Way Times-of-Arrival between them are measured, which includes unknown processing delays at both channel endpoints. Since finding the Maximum Likelihood Estimates (MLE) of the positions and turn-around times given those measurements poses a difficult nonconvex optimization prob- lem, it is approximated by a Nonlinear Least Squares prob- lem. Then, the positions and turn-around times of multiple targets are estimated jointly by solving an Euclidean Distance Matrix completion problem. Simulations show that the local- ization accuracy of the proposed method is good, providing an initial point that subsequently enables MLE to attain the Cramér-Rao Lower Bound for all considered scenarios.