# An Automatic Embedded Device Registration Procedure Based on the OGC SensorThings API
## 1 Introduction  
Sensor Web is a widely distributed network connecting different types of sensors [1, 2]. With enough power supply, in-situ or remote sensors can continuously collect observations of instruments and environment [3]. By sharing these large number of observations online via interoperable ICT (Information and Communication Technologies), users can integrate the observations to discover phenomena that were not observable in the past [2]. In recent years, the Internet of Things (IoT), a similar idea to the Sensor Web, attracted much attentions from various fields. While there have been many definitions of the IoT, International Telecommunication Union (ITU) introduced a general yet comprehensive definition. The ITU defines that the IoT is \"a global infrastructure for the information society, enabling advanced services by interconnecting (physical and virtual) things based on existing and evolving interoperable information and communication technologies\", and a thing is \"an object of the physical world (physical things)or the information world (virtual things), which is capable of being identified and integrated into communication networks\". As the Sensor Web and the Internet of Things are similar in terms of their architectures and functionalities, we name them as the SW-IoT (Sensor Web and IoT) in this paper. In general, the SW-IoT provides two main functionalities [4]:  
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2. Sensing capability: SW-IoT devices can monitor their latest status or use embedded sensors to observe properties of their surrounding environment. With the help of communication technologies, users can remotely access these observations for further analysis or decision-making. 3. Tasking capability: Tasking capabilities allow users to remotely control SW-IoT devices. For example, a client can send tasks to turn on/off a device, adjust the sensor's sampling rate, schedule an observation event, etc. The integration of sensing and tasking capabilities helps achieve various applications, such as precision agriculture, Industry 4.0, smart city, home automation, and e-Health, etc. In general, we can summarize the SW-IoT with a three-tier architecture [5], which contains the device layer, the service layer, and the applications layer. In terms of sensing capabilities, devices embedded with sensors can continuously collect and upload observations to services on the service layer. The service layer mainly supports data management and interfacing while the application layer retrieves data from the service layer for further applications. In terms of tasking capabilities, a client in the application layer can first send tasks to the service layer. A service then transforms the tasks into a device request by following a corresponding device protocol. Once the service forwards the request to the device, the device will execute the task accordingly. Besides the three aforementioned layers, an additional gateway layer is commonly applied in the SW-IoT systems (Figure 1). The gateway layer serves as an intermediate between the device layer and the service layer. There are two advantages to applying gateways. Firstly, while most embedded devices are resource-constraint and not able to connect to the Internet by themselves [6], gateways can help devices to communicate with services. Secondly, as directly connecting to the Internet requires higher energy consumption, devices can connect with gateways via low-power-consumption wireless communication protocols [7], such as Bluetooth LE, ZigBee, LoRaWAN, and NB-IoT, etc. With the advance of micro-controller and sensor technologies in recent years, the cost of constructing SW-IoT systems has been significantly reduced. Government agencies, scientists, and developers can customize and deploy embedded systems at a lower cost. However, instead of following open standards, many SW-IoT systems are constructed based on proprietary protocols due to its conveniences.