# Performance Evaluation of LoRa Considering Scenario Conditions
## 4 Material and Methods  
As stated above, the performance of LoRaWAN PHY layer has been tested in different scenarios characterized by their level of adversity against wireless transmissions. Recall that the configurable parameters of LoRaWAN PHY layer when using the LoRa modulation are SF, CR, and BW. Note that the GFSK (Gaussian Frequency Shift Keying) modulation, also available in the LoRaWAN specification, has not been considered in this work as it has demonstrated poorer performance in comparison with  
Figure 2: LoRaWAN star-of-stars topology. LoRa [2]. These tunable parameters affect the data-rate and the Packet Delivery Rate (PDR) of the transmissions as showed in the cited previous study [2]. In our study, the possible values that were assigned to the different parameters under consideration were: (i) SF: 7 to 12; (ii) CR: 4/5 and 4/8; and (iii) application payload size: 20 and 40 bytes. LoRaWAN transmissions make use of the unlicensed ISM bands, so the European LoRaWAN end-devices must comply with the ETSI 300 220 regulation. This regulation enforces a duty-cycle policy on channels for every sub-band. The LoRaWAN default channels, namely, 868.1, 868.3, and 868.5 MHz use a BW of 125 kHz. Besides, other channels can be manually configured by the user, hence for our tests, the 867.1, 867.3, 867.5, 867.7, and 867.9 MHz channels were employed because they were free of other transmissions during the sampling campaign. The channel employed by the end-device was randomly selected for each transmission. In order to perform the field tests, following the architecture adopted in our previous work [2], the LoRaWAN end-node was placed on the roof of a car, forming part of an On-Board Unit (OBU) that directly communicated with the LoRaWAN base-station. The microcontroller used in the OBU was the Arduino-compatible SmartEverything Fox board by Arrow. Connected to that board, the LoRaWAN radio module was the RN2483 chip by Microchip with an omnidirectional 5 dBi-gain antenna for end-devices, which was kept pointing upwards, favoring the reception gain (see Figure 3). The transceiver chip was a Class A LoRaWAN device with an output power up to 14 dBm. Thus, observe that only LoRaWAN communications were enabled in the OBU. The OBU microcontroller board had an embedded Global Positioning System (GPS) chip that the device used to obtain its location. In addition to the end-device, the other communication end-point, i.e., the base-station, employed the RHF2S008 board by RisingHF, which includes a Semtech SX1301 chip. This module was capable of decoding up to 8 different receptions in different channels employing any SF, simultaneously. Considering these rich features, only one base-station was used in the experimental tests; a sectorial antenna of 8 dBi gain and a far-field beam-width of 65 degrees was attached to the processing board (see Figure 4). A summary of the equipment configuration is shown in Table 2. The base-station relayed the packets back and forth to the LoRaWAN network server, hence the base-station acted as a gateway between the controller and the end-device. In turn, the network server managed the end-device login and acknowledgement (ACK) logics defined in the LoRaWAN specification [4]. Figure 3: On-board unit detail. Besides, the network server also ruled the downlink queue for managing the different higher-layer packets and it stored the frames received from the OBU as well. Now that the hardware setup has been described, next the behavior of the involved devices is presented. The OBU acted as a periodic sender hence no other elements or sensors beyond the strictly necessary were involved in the tests. The overall functioning was as follows. First, the OBU obtained its GPS location and transmitted a packet with the coordinates included in the payload field. After transmitting each packet, the OBU waited for an ACK from the base-station using the first receiving window specified in the LoRaWAN protocol (please, see [4]).