3-D Target Localization in Wireless Sensor Networks Using RSS and AoA Measurements

This paper addresses target localization problems in both noncooperative and cooperative 3-D wireless sensor networks (WSNs), for both cases of known and unknown sensor transmit power, i.e., <inline-formula><tex-math notation="LaTeX">$P_{T}$</tex-math></inline-formula>. We employ a hybrid system that fuses distance and angle measurements, extracted from the received signal strength and angle-of-arrival information, respectively. Based on range and angle measurement models, we derive a novel nonconvex estimator based on the least squares criterion. The derived nonconvex estimator tightly approximates the maximum-likelihood estimator for small noise. We then show that the developed estimator can be transformed into a generalized trust region subproblem framework, by following the squared range approach, for noncooperative WSNs. For cooperative WSNs, we show that the estimator can be transformed into a convex problem by applying appropriate semidefinite programming relaxation techniques. Moreover, we show that the generalization of the proposed estimators for known <inline-formula><tex-math notation="LaTeX">$P_{T}$</tex-math></inline-formula> is straightforward to the case where <inline-formula><tex-math notation="LaTeX">$P_{T}$</tex-math></inline-formula> is not known. Our simulation results show that the new estimators have excellent performance and are robust to not knowing <inline-formula><tex-math notation="LaTeX">$P_{T}$</tex-math></inline-formula>. The new estimators for noncooperative localization significantly outperform the existing estimators, and our estimators for cooperative localization show exceptional performance in all considered settings.