Device-to-device (D2D) communication is one of the most promising innovations in the next-generation wireless ecosystem, which improves the degrees of spatial reuse and creates novel social opportunities for users in proximity. As standardization behind network-assisted D2D technology takes shape, it becomes clear that security of direct connectivity is one of the key concerns on the way to its ultimate user adoption. This is especially true when a personal user cluster (that is, a smartphone and associated wearable devices) does not have a reliable connection to the cellular infrastructure. In this paper, we propose a novel framework that embraces security of geographically proximate user clusters. More specifically, we employ game-theoretic mechanisms for appropriate user clustering taking into account both spatial and social notions of proximity. Further, our information security procedures implemented on top of this clustering scheme enable continuous support for secure direct communication even in case of unreliable/unavailable cellular connectivity. Explicitly incorporating the effects of user mobility, we numerically evaluate the proposed framework by confirming that it has the potential to substantially improve the resulting system-wide performance.
As mobile communications technology is completing its fifth-generation (5G) cycle, it becomes increasingly capable of supporting novel usage scenarios with stringent performance requirements. Beyond seamless broadband connectivity for humans, 5G systems are preparing to enable a wide range of machine-type applications, thus advancing the vision of the Internet of Things (IoT). Facilitated by the rapidly converging 5G-IoT ecosystem, next-generation industrial IoT services, however, pose unprecedented research problems, primarily along the lines of providing wireless connectivity with ubiquitous availability, extreme reliability, and ultra-low latency. To this end, the first part of this paper presents a concise update on the novel requirements and challenges in the context of the emerging Industrial Internet infrastructure. In the second part, we introduce and solve a new optimization problem formulation aimed at improving performance reliability for advanced IoT devices equipped with several radio access technologies. We argue that by intelligently leveraging such heterogeneous multi-connectivity, future 5Ggrade IoT applications will be able to improve their levels of operational reliability. Our conclusions are corroborated by rigorous mathematical derivations as well as several realistic numerical examples.