Advances in Single and Multi-Antenna Technologies for Energy-Efficient IoT

The advent of the Internet-of-Things (IoT) has paved the way for a diverse set of new applications such as Industry 4.0 and environmental monitoring. While newly introduced IoT protocols gain traction, these networks can still be improved in order to support the next generation of IoT. The aim of this work is lowering the energy expenditure of remote energy-constrained IoT devices, by addressing the highest energy consumer, i.e., the wireless transmission. To this end, a full-stack approach considering physical, multiple-access and application layer is followed to advance energy-efficient IoT. The work is conducted from two perspectives. First, the commercially deployed IoT networks are studied and improvements were proposed to the protocol and application design. Secondly, massive MIMO, a multi-antenna technique used in 5G for high-throughput communication, is assessed in the context of IoT. In massive MIMO, the gateway -- or base station -- is equipped with a large antenna array. In contrast to their current application, this work investigates the applicability of this technology for low-power and wide-area IoT applications. To enhance the current IoT networks, a fine-grained energy profile of the protocols is derived, based on realistic conditions such as real hardware and network deployments. Next, a simulation framework is designed to study how these networks can be improved and to evaluate the proposed solutions. One of the solutions exists in intelligently combining different wireless technologies, allowing to make context-aware protocols to dynamically select the best-suited technology. Furthermore, a path loss model is derived for low-height devices and gateways to support upcoming network topologies, i.e., point-to-point and mesh. The derived models and the presented simulation framework are fundamental for designing energy-efficient protocols, as evidenced by their adoption by the research community. A second perspective looks at the use of antenna arrays at the gateway. The potential energy reduction at the IoT device, while simultaneously increasing the number of connected devices, is explored. This is done in two steps. First, the wireless propagation conditions are evaluated by means of several measurement campaigns using 32 antennas. Secondly, after demonstrating its relevance in an IoT context, a novel initial access algorithm is proposed exploiting the antenna array and the static nature of IoT devices. The results demonstrate the viability of massive MIMO for IoT even with a low number of antenna elements and a high number of devices.

Publication year:2021

Accessibility:Closed