Abstract
IoT presents a new technology that aims to interconnect numerous smart devices to provide operators with many smart services. Generally, wireless sensor networks (WSNs) are the key paradigm that ensures Internet of Things (IoT) applications. Due to the limitation of energy sensor resources, the IoT-based WSN is an energy efficiency strategy. In this context, many strategies for energy conservation have been proposed in the literature. Due to the absence of a comparative study of these methods in the literature, the present paper proposes to study 60 recent energy-efficient methods dedicated to IoT applications based on WSNs. Paper selection is accomplished based on the best citation through the Web of Science, Scopus, and SCI indexed databases. First, the different approaches proposed in the literature are classified into three categories: routing methods, clustering methods, and miscellaneous methods. Routing methods are classified into seven types: multipath routing, distributed routing, centralized routing, survivable path routing, opportunistic routing, SDN- based routing, and QoS-based routing. Moreover, clustering approaches are organized into four types: fuzzy clustering, random clustering, weighted clustering, and hybrid clustering. For the Miscellaneous part, three phases are discussed: the physical layer, MAC layer, and security. Furthermore, a comparative study is performed concerning types, performance metrics, applications, simulators, and future research directions. This analysis helps field researchers to learn the latest methods in this field. Established methods or testing those inside a testbed may be an essential path for potential studies.