All of the objects in the real world are envisioned to be connected and/or represented, through an infrastructure layer, in the virtual world of the Internet, becoming Things with status information. Services are then using the available data from this Internet-of-Things (IoT) for various social and economical benefits which explain its extreme broad usage in very heterogeneous fields. Domain administrations of diverse areas of application developed and deployed their own IoT systems and services following disparate standards and architecture approaches that created a fragmentation of things, infrastructures and services in vertical IoT silos. Coordination and cooperation among IoT systems are the keys to build “smarter” IoT services boosting the benefits magnitude. This article analyses the technical trends of the future IoT world based on the current limitations of the IoT systems and the capability requirements. We propose a hyper-connected IoT framework in which “things” are connected to multiple interdependent services and describe how this framework enables the development of future applications. Moreover, we discuss the major limitations in today’s IoT and highlight the required capabilities in the future. We illustrate this global vision with the help of two concrete instances of the hyper-connected IoT in smart cities and autonomous driving scenarios. Finally, we analyse the trends in the number of connected “things” and point out open issues and future challenges. The proposed hyper-connected IoT framework is meant to scale the benefits of IoT from local to global.

Location-based services (LBSs) typically crowdsource geo-tagged data from mobile users. Collecting more data will generally improve the utility for LBS providers; however, it also leads to more privacy exposure of users’ mobility patterns. Although the tension between data utility and user privacy has been recognized, there lacks a solution that determines how much data to collect—in both spatial and temporal domains—is the “best” for both mobile users and the service provider. This article proposes a strategy toward making an optimal tradeoff such that a user submits data only if her mobility privacy will not be compromised and the data utility of the LBS provider will be sufficiently improved. To this end, we first define and formulate a concept called privacy exposure , which incorporates both the spatial distribution and the temporal transition of a user’s activity points . Second, we define and quantify data utility in terms of spatial repetitions and temporal closeness among data based on an economic principle. Then, we propose a PRivacy-preserving and UTility-Enhancing Crowdsourcing (PRUTEC) algorithm to determine, on behalf of each mobile user, whether a newly sensed piece of data should be submitted to the LBS provider. Our simulation demonstrates that PRUTEC improves the data utility of the service provider with a much less amount of data to collect and reduces privacy exposure for mobile users while collecting useful data continuously.

Human mobility information is widely needed by many sectors in smart cities. This work designs lightweight algorithms to perform stop detection, passenger flow tracking, and passenger estimation in an automated train. The on-board learning and detection algorithms are running on an edge node that is integrated with Wi-Fi sniffing technology, a GPS sensor, and an IMU sensor. The stop detection algorithm determines if the automated train is static at which train station based on GPS and IMU data. When the train is moving, the correlations between statistical properties extracted from Wi-Fi probes and the actual number of passengers change. The passenger flow tracking algorithm analyzes the number of incoming and outgoing passengers in the train. The passenger estimation algorithm approximates the number of passengers inside the train based on a multidimensional regression model created by statistical properties extracted from different device brands. The prototype is deployed in an automated train to conduct real-world experiments. The experimental results indicate that the passenger flow tracking algorithm reduces the average errors of 62.5% and 70% compared against two clustering algorithms. Compared with two counting-based approaches, the passenger estimation algorithm results in lower errors with a mean of 3.15 and a variance of 9.29.

Many indoor localization techniques have been widely investigated. As the proportion of people with multiple mobile devices is increasing, an interesting research challenge arising from this growth is how to integrate data from multiple devices carried by a mobile user for localizing her/him. This work designs a multi-device joint localization system, called JoLo , to realize the idea using a group of off-the-shelf mobile devices carried by a user. The proposed system collects wireless fingerprints at the predefined training locations in the environment. Then, the system fuses the real-time wireless measurements observed by the multiple devices of a user into a summary list for localization reference. Finally, three fusion-based positioning algorithms are proposed to determine the user's location based on the fused summary list. The three proposed algorithms reduce mean distance errors in localization to less than one meter in a lab environment. One of the fusion-based algorithms, namely cluster-based DF algorithm, can even improve the performance by 50% on average compared to the existing single-device localization techniques.

The goal of sensor-assisted emergency guiding systems is to guide people to exits as soon as possible in emergencies (e.g., fires in buildings). Sensors are deployed in a smart environment to monitor and detect hazards. Sensors collaborate with each other to compute guiding paths for people in case of emergencies. To achieve this goal, this paper focuses on the sensor-assisted guiding problem, which studies how to guide people to exits quickly. Thus, the sensor-assisted guiding problem is analyzed from two different aspects: the sensor-centric guiding problem and the user-centric guiding problem. The former is to find a guiding direction for each single sensor for evacuating people nearby, whereas the latter is to find a personalized guiding direction for each individual user. In other words, the number of guiding directions provided by each single sensor in the sensor-centric guiding problem is limited, whereas this constraint is relaxed in the user-centric guiding problem. This paper proves that the sensor-centric guiding problem is NP-hard. When the constraint is relaxed, a user-centric guiding system is more efficient. Then, this paper designs a localized user-centric guiding protocol, which allows each sensor to provide more than one guiding direction for personalized guiding. The key idea of the proposed protocol is to estimate the evacuation time in a distributed manner. Extensive simulation results show that the proposed solution can significantly reduce the evacuation time by 15% compared to typical sensor-centric approaches. Finally, the implemented prototype indicates that proposed protocol is lightweight and can work with real sensor platforms.

People usually form a social structure (e.g., a leader-follower, companion, or independent group) for better interactions among them and thus share similar perceptions of visible scenes and invisible wireless signals encountered while moving. Many mobility-driven applications have paid much attention to recognizing trajectory relationships among people. This work models visual and wireless data to quantify the trajectory similarity between a pair of users. We design a visual and wireless sensor fusion system, called ViWise, which incorporates the first-person video frames collected by a wearable visual device and the wireless packets broadcast by a personal mobile device for recognizing finer-grained trajectory relationships within a mobility group. When people take similar trajectories, they usually share similar visual scenes. Their wireless packets observed by ambient wireless base stations (called wireless scanners in this work) usually contain similar patterns. We model the visual characteristics of physical objects seen by a user from two perspectives: micro-scale image structure with pixel-wise features and macro-scale semantic context. However, we model characteristics of wireless packets based on the encountered wireless scanners along the user’s trajectory. Given two users’ trajectories, their trajectory characteristics behind the visible video frames and invisible wireless packets are fused together to compute the visual-wireless data similarity that quantifies the correlation between trajectories taken by them. We exploit modeled visual-wireless data similarity to recognize the social structure within user trajectories. Comprehensive experimental results in indoor and outdoor environments show that the proposed ViWise is robust in trajectory relationship recognition with an accuracy of above 90%.