# State-of-the-Art Internet of Things in Protected Agriculture
## 1 Introduction  
The Internet of Things (IoT) was first developed in 1999 by the network radio frequency identification (RFID) system proposed by the Massachusetts Institute of Technology (MIT) Auto-ID Labs [1]. With the application and development of new information technologies, the connotation and extension of IoT have undergone major changes [2]. IoT can be defined as a huge internet-based network connecting physical and virtual \"things\" with standard and interoperable communication protocols. To be specific, everything, such as a sensor and an actuator possessing unique identity and attribute, exchange messages and communicate with each other to realize intelligent positioning, tracking, identification, perception, monitoring and management via kinds of networks anytime and anywhere [3]. IoT has penetrated pervasively most aspects of human life everywhere such as health care, smart home, smart city, industrial control and so on. Agriculture is an ideal candidate for the deployment of IoT solutions because it occurs in wide areas that need to be continuously monitored and controlled [4; 5]. The concept of protected agriculture is relative to open-field agriculture. It uses artificial techniques to change climatic factors such as natural light, temperature and humidity to create environmental conditions suitable for the growth of animals and plants, enabling them to grow around the clock. The environment of protected agriculture is completely or largely artificially controlled andwhich has broken the limits of climate and land conditions for the growth of animals and plants to a certain extent. So it is also called controllable agriculture. Compared with open-field agriculture, protected agriculture has more potential to apply IoT technology, because it is less affected by climatic and geographical factors. Some mature IoT solutions in other fields can be transferred directly to protected agriculture [6]. With the development of agricultural sensor, wireless communication, cloud computing, machine learning and Big Data technologies, IoT technology has emerged and is gradually being promoted and applied in the protected agriculture field [7; 8; 9]. It is playing an important role in various areas of protected agriculture as it is capable of helping farmers monitor soil condition, climate change and animal and plant health [10]. When the environmental factor change beyond the set threshold, IoT will automatically send a warning message to the administrator to remove the hidden danger. It can also control environmental factors such as temperature, humidity, carbon dioxide concentration and illumination according to the condition of crop growth in real time [11; 12]. In addition, cameras in the IoT system are able to capture crop diseases and insect pests in the greenhouse in real time, helping farmers find problems and take targeted preventive measures [13]. Through GPS, RFID and other location-based sensors, goods such as vegetables can be tracked and monitored visually during transportation and storage. Supermarket managers use smart phone or PC to monitor and predict product status and the demand for getting product on shelves. At the user or consumer end, people can query the variety, origin, processing and other farm product information by means of the QR code, barcode, etc. IoT for protected agriculture can help create an informed, connected, developed and adaptable rural community. Low-cost embedded devices can improve the interaction between humans and the physical world. Cloud computing, edge computing, and Big Data can provide valuable analysis and support for decisions. In summary, IoT will become an important tool in the next few years to engage people in embedded agriculture which includes suppliers, farmers, technicians, distributors, merchants, consumers and government representatives [14; 15]. On the basis of the potential of IoT applications in protected agriculture described in the previous paragraphs, this paper aims to identify the current state of solutions in these fields.