The Internet of Things (IoT) is a concept that has attracted significant attention since the emergence of wireless technology. The knowledge diffusion of IoT takes place when an individual disseminates his knowledge of IoT to the persons to whom he is directly connected, and knowledge creation arises when the persons receive new knowledge of IoT, which is combined with their existing knowledge. In the current literature, several efforts have been devoted to summarising previous studies on IoT. However, the rapid development of IoT research necessitates examining the knowledge diffusion routes in the IoT domain by applying the main path analysis (MPA). It is crucial to update prior IoT studies and revisit the knowledge evolution and future research directions in this domain. Therefore, this paper adopts the keyword co-occurrence network and MPA to identify the research hotspots and study the historical development of the IoT domain based on 27,425 papers collected from the Web of Science from 1970 to 2020. The results show that IoT research is focused on IoT applications for smart cities, wireless networks, blockchain technology, computing technologies, and AI technologies. The findings from the MPA address the need to explore the knowledge evolution in the IoT domain. They also provide a valuable guide to disseminate the knowledge of IoT among researchers and practitioners, assisting them to understand the history, present and future trends of IoT development and implementation.
The concept of the Internet of Things (IoT) has been gaining momentum since the emergence of wireless technology [1,2,3,4,5,6]. The fundamental premise of IoT is to connect multiple devices through tools like Radio Frequency Identification (RFID), sensors, actuators, smartphones, by which these devices can communicate with each other . As a dynamic global network infrastructure, IoT relies on smart devices with several capabilities, including sensing, networking, processing, and actuation, thereby facilitating the ability of people and objects to collaborate in heterogeneous and complex environments [8,9,10]. According to the seminal survey of , concepts and technologies surrounding IoT can be categorised into three main parts. The first part concerns the internet-oriented vision, which corresponds to the development of IP protocol for allowing smart things to communicate over the internet . The second part is related to the things-oriented vision, which considers IoT a network of identifiable things . This vision is achieved by integrating sensors and pervasive technologies to track objects. The third part concerns the semantic-oriented vision, which focuses on how vast networks of heterogeneous devices and the data they are generating can be controlled, monitored, and managed from a technical perspective . As such, raw data generated from sensor-based systems will be processed and churned out to obtain a better understanding and representations. These visions can be realised through the interconnection and interoperability of sensing and actuating technologies, providing the ability to exchange information across different platforms through a unified framework and enable innovative applications .
This paper conducts a retrospective analysis of five decades of research on IoT, where the main objective was to shed light on IoT and determine the pattern of knowledge diffusion, the key roots over the previous decade, and highlight the current research areas and potential opportunities for further academic investigations. In light of this, we used a multi-step approach to the bibliometric examination of IoT research, employing two complementary analytical methods, the keyword co-occurrence network and MPA, and utilizing the software tools VOSviewer and Pajek in the analysis of publications extracted from the Web of Science (WoS). These two methods aim to systematically investigate the entire domain of IoT based on 27,425 papers retrieved from WoS from 1970 to 2020. The idea of blending both methods provides in-depth insights for researchers to enhance their understanding of IoT development over the past fifty years. To our knowledge, this is the first study that uses four different main paths to investigate the knowledge diffusion trajectories in the IoT domain. The results show that there are five main clusters and the most significant clusters are around IoT applications for smart cities, and thus it is labelled as IoT for smart cities, followed by wireless networks, blockchain technology, computing technologies, and AI technologies. This numerical method helps researchers identify important activities in the IoT domain and unearth the routes of knowledge diffusion on IoT systematically. Accordingly, several insights and recommendations are suggested for the scholars and practitioners to understand the history, present and future trends of IoT development in a new review approach, which is more comprehensive than traditional review methods and bibliometric analysis.