## 4 Results and Discussion
### Evaluation and Optimization of Energy Consumption in Simulated LoRa Networks  
Considering everything stated so far, a prime focus of the conducted research in the following part of the paper is on a detailed analysis of the impact of payload size on energy consumption based on simulation process conducted using simulator [87]. Input values used in the simulation are the ones presented in Section 3.2 describing energy profile of LoRa sensor node, as well as all parameters presented in Sections 3 and 4.1. The selected payload sizes correspond to real-life applications related to monitoring environmental parameters used in precision agriculture. Therefore, the maximum possible payload size of 51 bytes, an average size of 11 bytes (used in most commercially available applications), and a minimum size of 6 bytes (proven optimal for the chosen precision agriculture application) are considered. Figure 5: Comparison of measured RSSI and SNR values. Thus, the analyses are conducted to quantify the impact of relevant LoRaWAN parameters and mechanisms on energy consumption in the scenarios in which different packet payload sizes are used. In order to save energy, non-time-critical data can be accumulated. Furthermore, by increasing the payload size, the overhead related to header information decreases, and the number of retransmissions in a stable propagation environment reduces. For this reason, it was assumed that the grouped measurements of different parameters are sent within the same packet for the analyses conducted in this paper. Typical applications of sensor networks in precision agriculture for environmental monitoring are time-related. Collecting current data is essential to obtain more detailed information about specific agrometeorological parameters, for example, the amount of precipitation, such as rain, in specific, more frequent periods. Hence, it is vital to provide a considerable amount of helpful information. As opposed to the default transmission rate (\(\lambda\)) of 0.02 bits per second, equivalent to transmitting a 9-byte message every chosen hour, for instance, in [3], the data transmission rate is adjusted to the quantity of data that should be transmitted, i.e., to the actual packet size, as well as the packet transmitting interval. The interval is set to 10 min. This means the packet is transmitted every 10 min, so six packets are transmitted per hour. Moreover, the overhead data are considered for assessing the accurate transmission rate, as presented in Table 9. Unlike the previously conducted analyses [3,4], in which the transmission rate does not match the size of the packet and is set to a fixed rate of 0.19 \(\times\) 10\({}^{-3}\), this approach considers the actual packet size in determining the transmission rate. This is the main difference between the previously conducted analyses in [3,4], and the analyses conducted in this work, which result in more precise results of the subsequent simulation procedures. One of the possible energy efficiency mechanisms is reducing the total volume of sent data and an adaptive data sampling process. With less frequent data transmission, the overhead of starting and initializing a transmission is also lower. As already proven, approaches based on reducing the number of packets transmitted can improve the success rate of packet delivery. According to the TTN Fair Access Policy, for a maximum packet size of 51 bytes, a total of 10 packets/hour cannot be exceeded. Therefore, the transmission interval is set to 10 min, which means that data is transmitted every 10 min, so six packets are transmitted per hour. Although the sampling period of 10 min is more extended than the minimum of approximately 5 min, determined by considering duty cycle regulations, it is still short when energy savings are considered. However, it is coordinated with the necessary data related to measuring the amount of precipitation, especially in the case of short-term intense precipitation, after which the need for irrigation can be significantly reduced.