## 3 Communication in IoT  
Despite significant changes, IoT still evolves, as can be seen from many reviews, to achieve its final form [79]. The configuration of IoT is based on three layers: a network layer (data transfer), a perception layer, and an application layer for data storage and manipulation [80]. The network layer is considered to be the physical layer of the architecture, where the on-field sensors and actuators directly interact with the environment and gather data as per the requirement. Technology such as Wireless Sensor Network (WSN), Radio Frequency Identification (RFID), and recently, Near Field Communications (NFC) are used on the perception layer [79]. Correlation exists between WSN and RFID technology due to semi-passive and active RFID tags which can also be viewed as lower-computing and storage wireless nodes [81]. A wireless sensing node normally consists of more than one sensor module (either external or embedded along with digital sensor devices), a processing module, typically a low-power microcontroller unit, and a Radio Frequency (RF) communication module compatible with low-power wireless communication technology [82]. At the network layer of the IoT, WSN communicates with physical objects and their surroundings, neighboring nodes, or gateways. The network layer is also responsible for building a network paradigm, by using which the data are typically forwarded to a remote storage infrastructure for further analysis and processing [83]. Wireless standards which are used to develop communication protocols, i.e., 802.15.4, bridge the difference among the internet-enabled gateways and the end-nodes. These types of protocols comprise Sigfox, ZigBee, 6 LowPan, WirelessHART, and ISA100.11a. [74; 84]. In addition to this, Bluetooth Low Energy (BLE), Long-Range and Long-Range Wide Area Network (LoRa/LoRaWAN), and low-power WiFi have also been used in the network layer. The application layer is the IoT's third layer. This layer is responsible for getting data downloaded and delivering application-specific service to the users' device via an application programming interface. It is very important, and it promotes the realization of IoT in several respects. The application layer faces a variety of unresolved suits, such as system recognition as a unique device. Identifying and addressing billions of devices around the world would provide them across the future internet with direct internet-like access and power. Identity uniqueness, durability, and scalability are essential characteristics of the approach scheme [83]. IPv6 can mitigate some system recognition problems with its aspects of internet mobility and is expected to play a key role in this sector [85]. The heterogeneity of the wireless nodes, diversity in data types, parallel operations, and integration of data from devices further exacerbate the problem [86]. While numerous theoretical parameters of the WSN have been studied extensively in literature, practical IoT/WSN implementations are very demanding for agriculture and remain a difficult task. Sensor modules must be sufficiently reliable, with the required measuring range available which is protected from environmental factors that either produce false readings or cause malfunctions in the system. As the IoT possesses distributed nature, therefore replacing the power source can be a very tough challenge for battery-operated nodes in open fields or other agricultural facilities. Consequently, very stringent power limitations influence the hardware selection and the low-power characteristics of the chosen peripherals are often taken into consideration when designing a new device. The software components to be implemented must be carefully inspected to incorporate the functionality of a system. The final function code includes a fully integrated understanding of software engineering and adequate testing to prevent field failures [87].