## 2 Materials and Methods
### Data Collection and Analytical Procedure  
The experimental greenhouse was divided into three vertical planes, and each plane was divided into three layers. All measurements were taken in these three vertical planes of the greenhouse. The bottom, middle, and top layers of each plane were located 0.50 m, 1.75 m, and 3.0 m above the ground, respectively, and each layer was also divided into three points for sensor placement, which were 1.0 m, 4.0 m, and 7.0 m from the north wall. The bottom and middle layers contained three temperature and humidity sensor nodes each, and the top layer contained one sensor node at the center point. Each plane contained seven temperature and humidity sensor nodes. A total of 21 temperature and humidity sensors (Figure 3a, numbered 1-21) were placed inside each greenhouse. One CO\({}_{2}\) sensor and one light intensity sensor were placed in the center of each layer of the middle plane. A total of three CO\({}_{2}\) and three light intensity sensors were placed inside each greenhouse. Five sensors for measuring the outside air temperature, humidity, airflow and airflow direction, solar radiation, and light intensity were placed 0.5 m above the top of the greenhouse. Figure 3a shows the positions of the data acquisition sensor nodes in different cross-sections of the greenhouse as well as those for the outside data. Figure 3b shows the distance and height between sensors in a cross-section of the greenhouse. All sensors were installed inside and outside of the Chinese solar greenhouse, and data were collected. The experiment was conducted in two selected CSGs during November and December 2018, which lasted for approximately three weeks. This period was chosen because it allowed for the cultivation of strawberries at different growth stages, facilitating comparative analysis. Due to the consistency in parameter fluctuations seen from the preliminary test on various days, a day with the maximum solar radiation was selected for this analysis [23; 40]. Descriptive statistical analysis methods (average, one-way ANOVA, and least significant difference (LSD) all-pairwise comparisons test) were used in this study. A software package, Statistix 10 (Analytical Software, Tallahassee, FL, USA), was used for the statistical analysis.  
During the experiments, the WSN recorded all the data from the inside and outside of the greenhouse. The sensor nodes consisted of Arduino UNO 328 microcontrollers, sensors, power sources, and nRF24L01 2.4 GHz wireless transceiver modules. After wiring the sensors with Arduino UNO, a code for each of the sensor nodes was sketched in the Arduino software IDE 1.8.7 (Arduino, arduino.cc). This was uploaded, and the program was run for data collection. Real-time data were collected from the sensors and were then remotely and directly plotted in an MS Excel sheet using the parallax data acquisition tool (PLX-DAQ, Parallax Inc., Rocklin, CA, USA) through serial communication. The transmitter nodes were referred to as slaves, and the receiver nodes were referred to as masters. The slaves transmitted the sensor data, while the receivers received it from the slaves.  
The sensor nodes were calibrated after the system was fabricated, as some of the sensors from the same manufacturer might vary in their readings. To calibrate the sensors, data were taken for approximately 15 min under known temperature and humidity conditions. Three replications of this calibration were performed. Figure 4a shows the schematic diagram of the data receiving, processing, and transmission process when using Arduino Uno microprocessor and wireless transceiver modules, as well as the visualization and monitoring that was conducted through the PLX-DAQ tool. Figure 4b shows the data visualization using PLX-DAQ from the sensor nodes and gateway.