# Internet of Things: A Scientometric Review
## 4 Research Topics
### Top Trending Topics  
For this analysis, the top trending topics are the authors' keywords, which have higher average growth rate (AGR) over the others. These topics represent concepts that have a large impact on IoT research. To find these trending topics, two-year AGR time periods (2011-2012, 2013-2014, and 2015-2016) were found using the following Equation (1):  
\[AGR=\frac{\sum\limits_{i=Y_{s}}^{Y_{e}}P_{i}-P_{i-1}}{(Y_{e}-Y_{s})+1}, \tag{1}\]  
where:  
\(AGR\) = Average growth rate;  
\(Y_{s}\) = Start year;  
\(Y_{e}\) = End year;  
\(P_{i}\) = Number of publications on year \(i\).  
Figure 9 shows the top eight trending topics with the AGR time periods. Cloud computing leads, with an AGR of 90 publications/year for 2015-2016, 284 documents on 2016, and a constant growth in all time periods. In 2013, [PERSON] et al. mentioned that the integration of IoT with Cloud computing applications can enable the creation of smart environments such as Smart Cities and others [13]. The growth of publications about IoT related to Cloud computing shows that the mentioned integration is currently happening. The second trending topic on this list is security. This topic has a moderate growth in 2011-2012 and 2013-2014 periods (about 18 publications/years), but, in 2015-2016, its growth soared to 83 publications/year. Security backs the industry's concerns about the user privacy and confidentiality [281; 282]. The same way that the communications protocols were analyzed in this paper by layers, [PERSON] et al. divided the IoT into three layers (perception, transportation, and application layers) to analyze features and security issues of each [283].  
IoT is one of many applications of Big Data because the rapid growth of IoT devices further propels the sharp growth of data to be processed and analyzed [70]. Wireless sensors networks (WSN), such as RFID, is one of the most important technologies enabling the IoT [284]. Likewise, security/privacy is a trending topic and also a concern in IoT, which was well summarized in [285].  
Industry 4.0 is a new trending topic, without any growth in the 2011-2012 period, but with a sharp rise in publications from 3 to 66 in 2014 to 2016. Industry 4.0 includes the use of intelligent manufacturing processes, Cyber-Physical Systems (CPSs), and implementation and operation of smart factories [286]. This fourth industrial revolution aims to integrate IoT technologies such as remote control, manufacturing analytic tools and services, supply chains integration, and tracking and tracing inter- and intra-plant logistics [287]. Fog computing is also a new trending topic, with a small growth in 2011-2014 periods, but a large increase in the 2015-2016 period. Fog is a platform that provides compute, storage and networking services between end devices and cloud computing servers, most commonly, but not exclusively, located at the edge of network [60]. For IoT, this new platform is aimed to decentralize the data processing [288], decrease the latency [289], and bring more reliability for WSN [290]. Finally, Software-Defined Networking (SDN) is a novel concept for IoT, without any growth in the 2011-2012 period, but which was gaining popularity from one publication in 2013, and 2014, to 33 in 2016. SDN brings network routing intelligence via a centralized controller that connects to the network switch through the OpenFlow protocol [291], for example. This allows efficient node mobility [292], resource management [293], and improves the security of IoT networks [291,294,295].