Optimum reference node deployment for TOA-based localization

While achieving localization using wireless networks, the positioning accuracy of a target device is highly sensitive to the placement of reference nodes. As a result, an in-depth analysis on the optimal placement of reference nodes is extremely useful in order to improve deployment outcome. In this paper, we propose an optimum reference node deployment scheme for Time of Arrival (TOA)-based localization by minimizing the Cramer-Rao Bound (CRB) of localization error. In order to find the global minima of the CRB which is highly nonlinear, a novel method is developed to solve the corresponding optimization problem. The essence of our method is to express the CRB in complex coordinates, and then to minimize the CRB with respect to the angles of reference nodes. The mathematical solution provides an interesting result indicating that the highest localization accuracy is achieved when the reference nodes have uniform angular distribution around the service area where the target is expected. We compare several different reference node deployment schemes through simulations, and the results show our derived optimum deployment provides the best performance.