# Internet of Things: A Scientometric Review
## 4 Research Topics
### Device Operating Systems (OS) and Hardware  
The data set analyzed here shows that the investigations used different IoT devices (end devices and gateway devices), operating systems (OS), and hardware. Figure 8 shows the top authors' keywords per year for the most employed OS and hardware. Android is the most used OS for researchers, with 87 documents. This OS is used for IoT gateways [238; 239; 240; 241] or end sensing devices [242; 243; 244]. Contiki is a lightweight OS for memory constrained systems (like microcontroller-based systems) designed for low-power wireless devices [245]. A total of 56 publications were found related to this OS, where the author uses capabilities like embedded protocols: 6 LoWPAN [166; 246], CoAP [247], and RPL [248]. In addition, some publications use the Contiki network simulator Cooja to simulate routing protocols [249] and performance evaluation [250].  
Other operating systems, such as Linux, are used in IoT for image processing [251] and gateway services [252]. The iPhone Operating System (iOS) is used as user interface for presentation, configuration, and remote controlling for IoT environments [253]. Finally, last year, [PERSON] et al. demonstrated the potential of Windows 10 IoT Core ([PERSON], WA, United States), a light-weight version of Windows 10, as an IoT operating system optimized to run on small devices that have no display [254].  
On the hardware side, some authors' keywords detail the hardware devices employed (see Figure 8b). Raspberry Pi is a small single board computer (SBC) capable of supporting operating systems like Linux Ubuntu, Windows, or Android. The Raspberry Pi is the most popular platform employed for IoT, with 88 publications, as a versatile platform for a gateway [255; 256; 257] or monitoring system [258; 259]. Arduino boards are single-board microcontroller kits, in which the developer connects sensors, actuators, or RF communication interface easily using shield boards. For this specific IoT publications data set, 83 documents refer to Arduino hardware. These boards are widely used for IoT learning [253; 260; 261] and monitoring devices [262; 263; 264].  
Figure 8: Internet of Things devices operating systems (OS) and hardware based on authors’ keywords, for the period 2006 to 2016. (**a**) most used operating systems in authors’ keywords per year; (**b**) most used hardware in authors’ keywords per year.  
Presently, smartphones are highly capable embedded systems that run full OS, with integrated sensors. Sixty-six documents were found related to smartphones in IoT, be they used as sensors [265; 266], gateway [267; 268; 269], or user interface [270; 271]. The Field-Programmable Gate Array (FPGA) is a hardware reconfigurable component that contains an array of computational (logic) elements, with a functionality specified by a hardware description language [272]. These FPGAs are used in IoT investigations for data encryption [273; 274; 275], routing algorithms [276], and parallel simulation [277]. A microcontroller (MCU) is a small computer on a single integrated circuit, which includes a processor core, RAM/ROM memory, peripherals, and, in some cases, RF transceivers. For IoT, the MCU plays a fundamental role in sensing end devices [255; 278; 279] and actuators [280].