A novel NLOS mitigation approach for TDOA based on IMU measurements

The location estimation of a mobile station (MS) is becoming more and more important in many applications. By using the time difference of arrival (TDOA) method, the position of a MS can be determined based on the relative time difference measurements. However, the accuracy of the position estimation suffers from Non-line-of-sight (NLOS) errors. In this paper, the influence of the main base station (BS) selection for the position estimation accuracy is discussed. It is shown that the selection of the accurate range differences is more important for position estimation than the detection of the NLOS BSs for TDOA method. A novel accurate range differences selection approach based on IMU measurements is developed. Instead of selecting the BSs under line-of-sight (LOS), the accurate range differences are chosen for calculation. The selection method is combined with Iterative Extended Kalman Filter (IEKF) to effectively mitigate the NLOS measurement errors. The IEKF performance difference, with and without the selection approach, is analyzed. The performance of ultra-wideband/inertial sensor (UWB/INS) tightly coupled approach and Taylor approach are discussed. Among all the approaches, the IEKF with selection approach shows better accuracy both in simulation and real field tests.