关键词: 非视距定位, 直接位置确定, 多目标, 波形已知, 克拉美罗界

Abstract: To realize localization in mixed Line-of-Sight and Non-Line-of-Sight (LOS/NLOS) environments with high precision, this paper proposes a Direct Position Determination (DPD) algorithm for multiple targets with known signal waveforms received by an antenna array. By relating the arrival angle and arrival time of the multipath signal to the positions of the obstacles (reflectors), receivers and targets, we derive the Maximum Likelihood (ML)-based functions in terms of 3D target positions in both cases of known and unknown transmitting times. The proposed algorithm can skip the estimation of intermediate parameters, thus solving the problems of NLOS identification and data association inherent in traditional two-step localization methods. To avoid multi-dimensional nonlinear optimization which is frequently encountered in localization of multiple targets, the proposed algorithm decouples the locations of multiple targets into several location problems of each target by exploiting information of uncorrelated known waveforms. By making the approximation of the objective function, only a 3D grid search is required in both cases of known and unknown transmitting times. Therefore, our algorithm is computationally more attractive compared with two-step localization methods. Additionally, we derive the compact Cramér-Rao Bound (CRB) expressions for target positions based on the multipath model when the transmitting times are known or unknown. Simulation results demonstrate that the performance of the proposed algorithm can reach the associated CRB, and is superior to traditional two-step localization methods and existing subspace-based DPD algorithms.

Key words: Non-Line-of-Sight (NLOS) localization, Direct Position Determination (DPD), multiple targets, known waveform, Cramér-Rao bound