The classic fusion localization techniques based on the Kalman filter (KF) framework have been a focus of research community in the past decades, due to the limited computing power of the mobile devices. However, with computing-efficient and sensor-rich smartphones now being a commonplace, it is convenient and meaningful to provide more accurate positioning services for smartphones in an indoor environment. In this paper, we design and develop a tightly coupled fusion platform of Wi-Fi RTT, RSS, and data-driven PDR based on factor graph optimization for locating the consumer-grade smartphones in indoor environment. As compared to the existing PDR solutions, including step model-based approaches and data-driven approaches, the proposed PDR solution with magnetic information constraint can track the relative position change of pedestrians at 20 Hz, while supporting multiple smartphone usage poses. A comprehensive comparison between factor graph optimization (FGO), KF frame and its variants is also performed. The experimental results demonstrate that the proposed fusion platform achieves an average positioning accuracy of 0.39 m. In addition, it also improves the accuracy of EFK and ARKF by 45.83% and 27.78%, respectively. The analysis shows that as the smartphone computing performance continues to improve, the FGO-based sensor fusion gradually replaces the KF frame and its variants.

With continuous and accelerated urbanization, a large number of location-based services (LBS) have shifted from outdoor to indoor. The pervasive smartphone-based localization has been the subject of extensive work, including signals, algorithms, technologies, solutions, and applications. However, no single ubiquitous technology or solution exists for performing indoor positioning similar to the global navigation satellite system (GNSS) in the outdoor environment. The aim of this work is to develop a practical, precise, and economic smartphone-based localization solution. In order to address the challenges of utilizing the limited audible-band acoustic signal in pervasive smartphone localization, i.e., signal detection, correction, and evaluation, we present a low-cost anchor hardware, two-step signal detection method, data-driven pedestrian dead reckoning (PDR), and robust positioning algorithm. Moreover, we further propose acoustic measurement compensation approaches and measurement quality evaluation and control strategy (MQECS) to improve the performance of position estimation. Six phones, including Huawei Mate9, P9 Plus, OnePlus 6, Honor 8, Mi 10, and Google Pixel 3 are used to evaluate the localization performance in three typical wide area indoor scenarios (i.e., convention center, parking lot, and dining-hall). The total testbed area is accumulated to more than 8,800 square meters. The experimental results demonstrate that the proposed method achieves average positioning accuracies of 0.34 m (static) and 0.67 m (dynamic). In addition, the results show that the overall performance, repeatability, and stability are superior for different scenarios and devices.

Indoor navigation and location-based services increasingly show promising marketing prospects. Indoor positioning based on Wi-Fi radio signal has been studied for more than a decade because Wi-Fi, a signal of opportunity without extra cost, is extensively deployed for internet connections. Bayesian fingerprinting positioning, a classical Wi-Fi-based indoor positioning method, consists of two phases: radio map learning and position inference. Thus far, the application of Bayesian fingerprinting positioning is limited due to its poor usability; radio map learning requires an adequate number of received signal strength indication (RSSI) observables at each reference point, long-term fieldwork, and high development and maintenance costs. In this paper, based on a statistical analysis of actual RSSI observables, a Weibull–Bayesian density model is proposed to represent the probability density of Wi-Fi RSSI observables. The Weibull model, which is parameterized with three parameters that can be calculated with fewer samples, can calculate the probability density with a higher accuracy than the traditional histogram method. Furthermore, the parameterized Weibull model can simplify the radio map by storing only three parameters that can restore the whole probability density, i.e., it is not necessary to store the probability distribution based on traditionally separated RSSI bins. Bayesian positioning inference is performed in the positioning phase using probability density rather than the traditional probability distribution of predefined RSSI bins. The proposed method was implemented on an Android smartphone, and the performance was evaluated in different indoor environments. Results revealed that the proposed method enhanced the usability of Wi-Fi Bayesian fingerprinting positioning by requiring fewer RSSI observables and improved the positioning accuracy by 19–32% in different building environments compared with the classic histogram-based method, even when more samples were used.

In the applications for mobile sensing, the trustworthy of sensed data should be put on the first place. The identification of participants can ensure data trustworthy but will reveal the privacy of the participants to a great extent. In this paper, we propose a privacy-preserving identification mechanism for mobile sensing systems to select sensed data dynamically to protect participant’s sensitive information. It solves the contradiction between “privacy protection” and “identification”. It divides data privacy sensitivity of the data sensed from the task that participants attended, allowing participants to define their own privacy sensitivity, then selects sensed data dynamically and uses differential privacy to process the data with high privacy sensitivity. It can not only protect participants’ privacy, but also identify participants’ IDs. In order to achieve identification, a two-layer neural network model is used to train and learn the participant's style of action and generate an identity feature database. The experimental results show that the proposed mechanism can provide a trustworthy platform for mobile sensing systems.

Currently, indoor localization technology and indoor location-based services are becoming increasingly important in the area of mobile and ubiquitous computing. However, the design of an indoor location-based system confronts two challenges: achieving high-precision location recognition and identifying what indoor objects actually are (which is called semantic labeling). In this paper, we propose AtLAS, an activity-based indoor localization and semantic labeling mechanism. The key idea is that some objects in an indoor environment, such as doors and toilets, determine predictable human behaviors in small areas, which can be reflected in unique sensor readings. AtLAS leverages this idea to determine a user’s accurate location by identifying users’ activities. Furthermore, we leverage the topological structure of indoor objects to mine the semantic knowledge and label the objects through gained knowledge automatically. To the best of our knowledge, AtLAS is the first attempt to build a system that leverages users’ activities to conduct a high-precision indoor localization and semantic labeling system for the case of residences. Experimental results show that AtLAS can achieve a median localization accuracy of 0.57 meters, and the system can localize the landmarks with a median accuracy of 0.43 meters on average without 5% worst errors. AtLAS can label the objects semantically with a 5.7% false positive rate and a 5.8% false negative rate on average.