## 2 Related Studies
Therefore, the current consumption of the sensor node is 81.5 mA. When a solar cell with DC charging is adopted, the power efficiency is improved by 31%. However, power efficiency increases to 98% when MPPT is used. [PERSON] et al. [29] developed a WSN application for crop protection from animal intrusion in a farming field. A sleep/wake scheme was adopted to conserve the power of the WSN. Successful results were obtained from laboratory-level trials of the systems. However, the authors discovered a few technical faults in the circuit components. The power consumption of the system was 27 W/h, but the calculations of the current consumption of the nodes in the WSN were not considered in their study. [PERSON] et al. [30] constructed practical organizations of agents that can connect with one another while observing crop irrigation. Fuzzy logic was adopted to accurately control watering quantities. The major finding of this research was that heterogeneous data from the surrounding can be merged via sensor node measurements. The proposed system based on fuzzy logic consumes 4.5 L of water per day relative to traditional operation, which consumes 7.3 L a day. Thus, 37% water saving is achieved over 30 days. The use of a solar cell also allows the continuous charging of the sensor node battery. [PERSON] et al. [31] monitored soil water status and irrigation water by developing a practical application to optimize water resources in irrigated agriculture. They adopted a sleep/wake scheme to reduce the power consumption of the General Packet Radio Service (GPRS) node. The sending and sampling rates in the achieved tests were adjusted to 30 min and 15 min, respectively. The disadvantage of this system is its short life span of 13.35 days. However, the average current consumption of the entire GPRS node is 5.93 mA relative to that in traditional operation, where the GPRS modem alone consumes 400 mA during data transmission. [PERSON] et al. (2016) presented an efficient WSN platform that is appropriate for agricultural applications and can be used in remote areas. A sleep/wake algorithm was proposed to limit the energy consumption of the WSN platform. The results showed that the nodes are autonomous, scalable, and easy to locate and relocate. However, the proposed system has a limited communication range because the transceiver uses an omnidirectional antenna. Nevertheless, the sensor node captures and transmits an image for 6 min and then sleeps for 54 min, with a low power consumption of 0.8 \(\upmu\)A. Subsequently, sensor node life is extended to 8 days. Moreover, current consumption is improved to 4.427 mA compared with that in conventional operation, where the current consumption of the camera and CC1110 is 270 mA and 31 mA, respectively, in the transmission mode. [PERSON] et al. (2016) discovered, examined, and auto-calibrated imbalances in the pH levels of the nutrient solution used in hydroponic agriculture. The results indicated that the design of the system improved water quality in hydroponic agriculture by implementing and testing a smart system for bicarbonate control in irrigation. The advantages include low power consumption, low cost due to the use of a low-power wireless protocol (i.e., nRF24L01) while ensuring the adopted coverage area, and the provision of multimedia services because of the adoption of mobile devices or computers. However, the number of nodes in the network is limited to five. Each node wakes up for 15 s to transmit their data and then returns to sleep for 255 s (i.e., DC is equal to 15/270 = 5.555%). Accordingly, the power consumption of the sensor node is reduced from 49 mA (in traditional operation) to 2.807 mA (with the sleep/wake strategy). [PERSON] et al. (2016) monitored environmental parameters for greenhouse applications. They used the MoniSen module to introduce a new granularity level for PA monitoring applications. They adopted a distributed sensor architecture for large-scale applications by developing fully functional software and hardware.