Towards Energy Efficiency in the Internet of Wearable Things: A Systematic Review

Personal mobile devices such as smartwatches, smart jewelry, and smart clothes have launched a new trend in the Internet of Things (IoT) era, namely the Internet of Wearable Things (IoWT). These wearables are small IoT devices capable of sensing, storing, processing, and exchanging data to assist users by improving their everyday life tasks through various applications. However, the IoWT has also brought new challenges for the research community to address such as increasing demand for enhanced computational power, better communication capabilities, improved security and privacy features, reduced form factor, minimal weight, and better comfort. Most wearables are battery-powered devices that need to be recharged therefore, the limited battery life remains the bottleneck leading to the need to enhance the energy efciency of wearables, thus, becoming an active research area. This paper presents a survey of energy-efcient solutions proposed for diverse IoWT applications by following the systematic literature review method. The available techniques published from 2010 to 2020 are scrutinized, and the taxonomy of the available solutions is presented based on the targeted application area. Moreover, a comprehensive qualitative analysis compares the proposed studies in each application area in terms of their advantages, disadvantages, and main contributions. Furthermore, a list of the most signicant performance parameters is provided. A more in-depth discussion of the main techniques to enhance wearables' energy efciency is presented by highlighting the trade-offs involved. Finally, some potential future research directions are highlighted.