Estimation of indoor location is a key capability for indoor location-based services. Among various solutions, single-chip low-cost millimeter-wave radar as an emerging technology are getting more and more attention due to their inherent advantages such as penetration ability, low-power consumption. Currently, the vast majority of work is focused on hybrid positioning based on millimeter wave radar with other sensors, and there is a lack of research on single radar indoor positioning. In this paper, we propose a novel indoor positioning system based on single-radar sensor, which determines the trajectory by estimating the velocity and heading of moving radar from sparse point clouds. Doppler velocity of detected object can be able to feedback the radar velocity, and for another hand, the proposed Cluster Center Association method combined with Normal Distributions Transform (NDT) can be used for heading estimation. In addition, we proposed the motion consistency constraints to enhance the robustness of the system. The experimental results show that the traditional NDT algorithm will fail due to the sparse point cloud and severe indoor multipath, and the proposed algorithm can provide the positioning accuracy within 1 meter and the heading estimation error of 3 degrees.

Geomagnetic indoor positioning is an attractive indoor positioning technology due to its infrastructure-free feature. In the matching algorithm for geomagnetic indoor localization, the particle filter has been the most widely used. The algorithm however often suffers filtering divergence when there is continuous variation of the indoor magnetic distribution. The resampling step in the process of implementation would make the situation even worse, which directly lead to the loss of indoor positioning solution. Aiming at this problem, we have proposed an improved particle filter algorithm based on initial positioning error constraint, inspired by the Hausdorff distance measurement point set matching theory. Since the operating range of the particle filter cannot exceed the magnitude of the initial positioning error, it avoids the adverse effect of sampling particles with the same magnetic intensity but away from the target during the iteration process on the positioning system. The effectiveness and reliability of the improved algorithm are verified by experiments.

Robust human tracking in indoor environments is an important feature of location-based service applications, including security surveillance, elderly monitoring etc., yet the advanced technology offered by camera-based device-free tracking systems can raise privacy concerns. To address this problem, we propose a low-cost, low-power device-free human tracking system based on millimeter-wave radar that can provide rich ranging and radial velocity information. In order to achieve continuous tracking, we propose a multi-radar cooperative sensing scheme; with the help of the double segmentation method, we overcome the user proximity problem that prevents multiple humans from being recognized using point cloud location information. Finally, we propose a tracking and trajectory optimization algorithm that considers both spatial information and probability distribution of moving direction to output human trajectory. Experimental results show that the proposed human tracking system provides single-human tracking error of 8.5cm and multi-human tracking error of nearly 10cm.

Device-free wireless localization based on Wi-Fi channel state information (CSI) is an emerging technique that could estimate users’ indoor locations without invading their privacy or requiring special equipment. It deduces the position of a person by analyzing the influence on the CSI of Wi-Fi signals. When pedestrians block the signals between the transceivers, the non-line-of-sight (NLOS) transmission occurs. It should be noted that NLOS has been a significant factor restricting the device-free positioning accuracy due to signal reduction and abnormalities during multipath propagation. For this problem, we analyzed the NLOS effect in an indoor environment and found that the position error in the LOS condition is different from the NLOS condition. Then, two empirical models, namely, a CSI passive positioning model and a CSI NLOS/LOS detection model, have been derived empirically with extensive study, which can obtain better robustness identified results in the case of NLOS and LOS conditions. An algorithm called SVM-NB (Support Vector Machine-Naive Bayes) is proposed to integrate the SVM NLOS detection model with the Naive Bayes fingerprint method to narrow the matching area and improve position accuracy. The NLOS identification precision is better than 97%. The proposed method achieves localization accuracy of 0.82 and 0.73 m in laboratory and corridor scenes, respectively. Compared to the Bayes method, our tests showed that the positioning accuracy of the NLOS condition is improved by 28.7% and that of the LOS condition by 26.2%.

With the growing demand for positioning services, angle-of-arrival (AoA) estimation or direction-finding (DF) has been widely investigated for applications in fifth-generation (5G) technologies. Many existing AoA estimation algorithms only require the measurement of the direction of the incident wave at the transmitter to obtain correct results. However, for most cellular systems, such as Bluetooth indoor positioning systems, due to multipath and non-line-of-sight (NLOS) propagation, indoor positioning accuracy is severely affected. In this paper, a comprehensive algorithm that combines radio measurements from Bluetooth AoA local navigation systems with indoor position estimates is investigated, which is obtained using particle filtering. This algorithm allows us to explore new optimized methods to reduce estimation errors in indoor positioning. First, particle filtering is used to predict the rough position of a moving target. Then, an algorithm with robust beam weighting is used to estimate the AoA of the multipath components. Based on this, a system of pseudo-linear equations for target positioning based on the probabilistic framework of PF and AoA measurement is derived. Theoretical analysis and simulation results show that the algorithm can improve the positioning accuracy by approximately 25.7% on average.