The accuracy of existing UWB range-based indoor localization methods is generally degraded due to the non-line-of-sight (NLOS) situations where a serve bias in UWB range measurements is unavoidable. In this article, we first propose a two-stage NLOS detection method to detect line-of-sight (LOS)-measured distances in mixed LOS/NLOS indoor environments. Then, a high-accuracy UWB/IMU/Odometer integrated localization system is presented using an adaptive multi-algorithm localization framework based on the number of detected LOS-measured distances. Specifically, under conditions of one or two LOS-measured distances, an improved adaptive EKF positioning algorithm (IAEKF) is proposed. Compared with the traditional extended Kalman filter (EKF)-based fusion scheme, the weight function of innovation is exploited to adaptively estimate the measurement noise covariance matrices and further reduce the influence of the changing measurement noise in NLOS conditions. For three or more LOS-measured ranges, a novel tightly-coupled fusion factor graph framework is developed. To further improve the performance of seamless positioning in transaction areas, a strong constraint of trajectory smoothness is designed and added to the factor graph framework by using the weight value of IMU/odometer measurements. The experimental results show that the proposed localization system achieves an average localization error of 0.227 m, which surmounts UWB range-based and integrated methods in LOS/NLOS mixed environments.

The rise of the Internet of Things has spurred the growth of wireless applications, particularly Wi-Fi-based indoor localization, which is gaining prominence owing to its cost-effectiveness. Nevertheless, the accuracy of Wi-Fi-based indoor localization is hindered by signal instability. To address this limitation, we introduce an interval random analysis approach for uncertain Wi-Fi-based indoor localization. Specifically, this approach employs an interval random parameter lognormal shadowing model for radio map enhancement and adaptive Bayesian comprehensive learning (IRPLS-ABCL) particle swarm optimization (PSO) for location estimation accuracy enhancement. The process comprises two stages: offline training and online localization. During the offline phase, we establish the interval random parameter lognormal shadowing model, considering the parameters as interval random variables, rather than precise values, in a sparse reference point scenario. In the online phase, we use a double-panel fingerprint homogeneity model to assess fingerprint similarity and apply the adaptive Bayesian comprehensive learning PSO algorithm to enhance localization precision. The experimental results show that the proposed algorithm can achieve the best performance in terms of localization accuracy based on the predicted average received signal strength (RSS), reaching 1.89 m.

Wireless Fidelity (WIFI) can transmit data efficiently, but it has the advantages of low computing cost and simple deployment. However, the WIFI signal is susceptible to interference from human movement, multipath propagation, and indoor temperature changes, resulting in problems such as low positioning accuracy and poor stability. To improve positioning accuracy and stability, we propose a novel fingerprint positioning technology applying vision-guided definition for WIFI-based localization, defined as KV. There are two stages in localization: WIFI-based coarse localization and fusion localization. In the WIFI-based coarse positioning stage, we propose a two-metric adaptive K-nearest Neighbor (KNN) localization method to improve the accuracy and robustness of WIFI-based localization. Unlike the traditional KNN method, a difference-based search approach is introduced to can obtain the K value intelligently and reasonably instead of manual determination. In the fusion localization stage, we employ an effective multi-angle unsupervised fusion positioning method applying the fusion of WIFI and vision to enhance positioning accuracy and positioning stability further. Experimental results show that our proposed fusion localization method achieves 1.24m in localization accuracy and the positioning error is 60% within 0.8 meters. The performance of the proposed method surmounts other state-of-the-art methods, which proves its effectiveness. This method has important practical significance in multi-source indoor positioning technology.

Currently, most mobile devices have WIFI and camera modules to locate their position. However, there are two main challenges in large, highly similar indoor environments (localization accuracy and localization time). Aiming to balance these problems, we propose a sequential-multi-decision integrated system that combines WIFI and vision to acquire users’ locations. This system has two phases: sequential fusion localization and adaptive multi-decision fusion localization. The former employs WIFI-based localization first, then image-based localization and fusion localization are used within the constraints of WIFI-based localization. In the WIFI-based localization phase, the gaussian process regression (GPR) model is used to construct a WIFI indoor map. Subsequently, we propose to apply the hybrid whale optimization algorithm (HWOA) to WIFI-based localization to improve its accuracy and stability. The latter uses an adaptive multi-decision fusion mechanism that integrates WIFI-based localization, image-based localization, and fusion localization to obtain the users’ location finally. The experiments show the effectiveness of HWOA applied to WIFI-based localization. We also experimentally evaluate the proposed fusion algorithm with other state-of-the-art fusion algorithms (e.g., accuracy and time) in a real environment (an area larger than 10,000 $m^{2}$ ). The experimental results show that the proposed fusion system is competitive.

With the continuous development and improvement in Internet-of-Things (IoT) technology, indoor localization has received considerable attention. Particularly, owing to its unique advantages, the Wi-Fi fingerprint-based indoor-localization method has been widely investigated. However, achieving high-accuracy localization remains a challenge. This study proposes an application of the standard particle swarm optimization algorithm to Wi-Fi fingerprint-based indoor localization, wherein a new two-panel fingerprint homogeneity model is adopted to characterize fingerprint similarity to achieve better performance. In addition, the performance of the localization method is experimentally verified. The proposed localization method outperforms conventional algorithms, with improvements in the localization accuracy of 15.32%, 15.91%, 32.38%, and 36.64%, compared to those of KNN, SVM, LR, and RF, respectively.