This paper proposes deployment strategies for consumer unmanned aerial vehicles (UAVs) to maximize the stationary coverage of a target area and to guarantee the continuity of the service through energy replenishment operations at ground charging stations. The three main contributions of our work are as follows. 1) A centralized optimal solution is proposed for the joint problem of UAV positioning for a target coverage ratio and scheduling the charging operations of the UAVs that involves travel to the ground station. 2) A distributed game-theory-based scheduling strategy is proposed using normal-form games with rigorous analysis on performance bounds. Furthermore, a bio-inspired scheme using attractive/repulsive spring actions are used for distributed positioning of the UAVs. 3) The cost-benefit tradeoffs of different levels of cooperation among the UAVs for the distributed charging operations is analyzed. This paper demonstrates that the distributed deployment using only 1-hop messaging achieves approximation of the centrally computed optimum, in terms of coverage and lifetime.

The Web of Things (WoT) paradigm was proposed first in the late 2000s, with the idea of leveraging Web standards to interconnect all types of embedded devices. More than ten years later, the fragmentation of the IoT landscape has dramatically increased as a consequence of the exponential growth of connected devices, making interoperability one of the key issues for most IoT deployments. Contextually, many studies have demonstrated the applicability of Web technologies on IoT scenarios, while the joint efforts from the academia and the industry have led to the proposals of standard specifications for developing WoT systems. Through a systematic review of the literature, we provide a detailed illustration of the WoT paradigm for both researchers and newcomers, by reconstructing the temporal evolution of key concepts and the historical trends, providing an in-depth taxonomy of software architectures and enabling technologies of WoT deployments and, finally, discussing the maturity of WoT vertical markets. Moreover, we identify some future research directions that may open the way to further innovation on WoT systems.

The Internet of Things (IoT) envisions a global market in which it would be possible to easily get data from IoT devices across the globe. However, the potential of this idea still needs to be unlocked. Centralized architectures fall short due to their lack of transparency and tendency to create silos. On the other hand, blockchain technology enables the creation of distributed and trustworthy systems, but its integration with the IoT is still a matter of research. IoT-based scenarios often employ numerous devices for the same sensing task, which may be heterogeneous and unreliable by purpose. In our vision, IoT applications should rely on data and its quality rather than on single providers. For this purpose, we propose an architecture that enables a decentralized IoT global market in which clients pay for data and device owners are rewarded for providing it. Our solution employs a distributed oracle layer on top of smart contracts powered by a distributed global network of IoT devices. The system supports IoT data source decoupling since the end-user can perform semantic queries bounded to specific locations and data types without specifying the target devices. In addition, it features automatic discovery, interoperability mechanisms, and reputation algorithms for the selection of trustworthy data sources. Our results show that the proposed system is robust and consistently provides quality data, even with multiple malicious data sources.

The pandemic caused by COVID-19 has shed light on the urgency of bridging the digital divide to guarantee equity in the fruition of different services by all citizens. The inability to access the digital world may be due to a lack of network infrastructure, which we refer to as service-delivery divide, or to the physical conditions, handicaps, age, or digital illiteracy of the citizens, that is mentioned as service-fruition divide. In this paper, we discuss the way how future sixth-generation (6G) systems can remedy actual limitations in the realization of a truly digital world. Hence, we introduce the key technologies for bridging the digital gap and show how they can work in two use cases of particular importance, namely eHealth and education, where digital inequalities have been dramatically augmented by the pandemic. Finally, considerations about the socio-economical impacts of future 6G solutions are drawn.