## 3 Methodology
### Selection of Adequate Parameters for LoRa-Based Communication  
The LoRa-based access networks implemented in open spaces connect sensor nodes in different remote locations to centrally located storage and data-processing servers. The range of communication is an essential parameter when considering the effectiveness of implemented solutions regarding the implementation of sensor networks in remote areas to monitor environmental and agronomic parameters. In most cases, the high data transfer rate is not so significant. However, it is necessary to ensure the energy-efficient transmission of data over relatively long distances. The parameters described hereafter affect LoRa transmission range and energy efficiency [54]. LoRa operates in the sub-GHz unlicensed frequency bands. The LoRa systems operate at the ISM frequency bands, and the carrier frequency (CF), the center frequency used for the transmission band, is 863 MHz to 870 MHz in Europe. Moreover, there are also some regulatory constraints in most countries on the permissible occupied bandwidth (BW) [54]. Increasing the signal bandwidth (BW) allows a higher effective data rate to be used, thereby reducing the transmission time at the expense of reduced sensitivity of the receiver. It is possible to choose between 125 kHz, 250 kHz, or 500 kHz. However, in the multi-data-rate channel mode, the gateway is limited to a 125 kHz bandwidth with typically eight channels, even though the maximum bandwidth of LoRa is 500 kHz. Therefore, if there is a need for a high data transfer rate, the best choice is the value of 500 kHz. On the other hand, if it is necessary to achieve a long communication range, it is necessary to choose the bandwidth value of 125 kHz. The greater the bandwidth, the shorter the time-on-air value, and the sensitivity of the receiver is better. However, a higher time-on-air value will also mean higher energy requirements. The spreading factor and error correction rate allow the optimization of the trade-off between occupied bandwidth, data rate, link budget improvement, and immunity to interference. The spread spectrum LoRa modulation is performed by representing each bit of payload information by multiple chirps of information. A chirp is a sinusoidal signal whose frequency monotonically increases (upchirp) or decreases (downchirp) [60]. A chirp is a pulse that sweeps from f\({}_{\text{Low}}(-\text{BW}/2)\) to f\({}_{\text{High}}(+\text{BW}/2)\)[60]. The number of chirps forms a symbol. For instance, if a symbol value is between 1 and 128, the number would be one of the combinations of \(2^{7}=128\) chirps. The Spreading Factor (SF) represents the number of chirps per symbol. Its value is an integer number between 6 and 12. The values of SF from 6 to 12 represent 64, 128, 256, 512, 1024, 2048, and 4096 chirps/symbol, respectively. The greater the SF value, the more ability the receiver has to remove the noise from the signal. Thus, the greater the SF value, the more time is taken to send a packet, but a higher range will also be achieved because the receiver's sensitivity is better. For example, if the expansion factor is minimal, i.e., SF = 6, a higher speed can be achieved, but with a reduction in the possible range. SF = 6 presents a particular use case for the highest data-rate transmission possible with the LoRa modem. The spreading factor must be known in advance on both transmit and receive sides of the link, as different spreading factors are orthogonal to each other. Generally, according to the LoRaWAN specifications, the spreading factor control is limited to 6 unique spreading factors going from spreading factor 12, or the lowest data rate, to spreading factor 7, for the highest data rate. This means up to six sensor nodes can transmit data simultaneously on the same channel. Due to interference, some of the data bits can be lost, so the error correction bits are used to recover the original lost data bits. LoRa uses Forward Error Correction (FEC) techniques to increase the robustness of radio communication links.