## 4 Results and Discussion
### Overview of Simulation Results
After receiving 20 uplink messages, the network will respond with adequate ADR parameters to accommodate non-optimal propagation [88]. For larger payload sizes, this implies that more bytes have been sent before the LoRa parameters are adjusted to the channel. In addition, ADR changes the parameters in steps, which causes an even slower adaption to the propagation environment for larger payload sizes. This effect is notable when observing the energy consumption of nodes with a slow data transmission rate. This results in higher energy consumption. Therefore, LoRa devices should send smaller packets to adapt to the channel faster since this will reduce air time and energy consumption for packets sent with non-optimal parameters. The energy per useful bit is a function of the maximum range and different payload sizes. With high SF values and an increase in the payload size, the energy per useful bit decreases. Also, with low SF values, the payload variation does not substantially affect energy per bit. In extension to these analyses, the analyses carried out as part of this work consider fixed, predefined payload sizes when estimating the transmission rate values. Therefore, the corresponding transmission rate calculated is used for each scenario related to the estimation of energy consumption based on the selected packet size. The conclusions based on the obtained results fulfill those obtained in [3; 4; 15], and indicate that, regardless of SF  
Figure 7: Consumed energy per byte for different packet payload sizes. values, if the payload size decreases, the energy per useful bit also decreases, as well in the chosen scenarios of optimal packet sizes in bytes for the given case study. Delivering a large number of packets in a short time by a more significant number of nodes causes bursts of collisions, as presented in Figure 8.  
In LoRaWAN, the reliability of packet delivery is achieved through the acknowledgment of packets in the downlink. However, sending confirmation increases the energy consumption in the network. Therefore, when there is a certain tolerance for packet loss, as is the case when sending not so time-critical data, for instance, data related to the state of the environmental and agronomic parameters, it is possible to omit sending confirmations. This is especially appropriate in cases of implementing sensor networks with a smaller number of nodes and sending data less often, where the frequency of possible collisions is reduced. Moreover, this is also appropriate in cases where high signal quality is ensured and there are no significant losses during packet transmissions. Considering what has been stated, it can be concluded that in some cases, acknowledgments of packet delivery are not sent due to savings in energy consumption. However, to ensure the successful delivery of the amount of data needed to gain insight into the value of environmental and agronomic data necessary for crop condition assessment, it is recommended to use packet sequence numbers nevertheless. In this way, the server could check the received traffic, and in the critical case of a more considerable difference between the sequential numbers of the two successively received packets, it can inform the sensor node that ADR should be applied and continue sending data according to its recommendations. The LoRa network server can monitor the detailed radio information from all gateways that receive a given frame. These data include information about the gateway, extended unique identifier (EUI) of the networking devices (sensor node), server timestamp, acknowledgment flag as set by the device, frame counter (FCnt), and encrypted data payload. In addition, some extended radio information such as the radio frequency, spreading factor, bandwidth, coding rate, the gateway's Rx UTC and GPS time, and the gateway's position (latitude and longitude) can also be added. According to this information, the network server can control the sequence number of the particular packet received from the selected sensor node.