Performance Evaluation of LoRa ES920LR 920 MHz on the Development Board

This study contains the LoRa ES920LR test on obstruction or resistance conditions and its comparison with Free Space Path Loss (FSPL) using Drone means without obstacles. The ES920LR has 920 MHz frequency channel settings, 125 kHz Bandwidth, and SF 7-12, with 13 dBm Output Power. Comes with Sleep mode operation with Command Prompt based settings. The development board used is a leafony board, Leafony board is a board with a small size that is compatible with Arduino IDE, using a micro ATmega M328P microcontroller, this board is mounted tiled with complete facilities, e.g., a power supply board, four different sensor boards, MCU boards, communication boards e.g., WiFi and Bluetooth, specifically in this article using the LoRa ES920LR on the Leafony board, using LoRa because it requires a long range (km) and low power, and expansion boards that can be developed, Expansion to Leafony boards is expected to reduce the power consumption of the sensor node, lifetime, lif, small size, and lightweight. Furthermore, this algorithm is used to optimize LoRa Coverage and LoRa Lifetime. The results of receiving the FSPL LoRa 920LR have a Power Receiver (Pr) of 30 dB at a distance of 1 meter or A, at 500 meters 85 dB, 1500 meters 95 dB, 2.5km 100 dB. Attenuation is caused by distance, although not significant, other factors are obstacles or obstacles, bad weather (rain, snow). Keywords—Coverage; lifetime; low power; lightweight; long range; development; board; free Space; drone

Furthermore, it is important to pay attention to the Power Consumption factor as in research [5], [6], the results of data compression in wireless sensors nodes that use LoRa technology to transmit data. An energy consumption comparison is made with other data communication protocols used in WSN. In managing the LoRa and LoRaWAN networks, an appropriate protocol is needed in setting the Medium Access Control (MAC) random access, in research [7], using ALOHA protocol analysis, ie, normalizing the communication of LoRaWAN networks using a Reservation-ALOHA (R-ALOHA). With the continued development of LoRa and LoRaWAN-based End nodes, a protocol that is capable of handling millions of end nodes is needed, it also requires continuous renewal in terms of performance, security [8], robustness, in research [9] discussing the revolution of LoRaWAN network technology considering the IoT requirements. In addition to Software Development, Protocols with security and methodology settings, LoRa acceleration is also developed with various devices, such as Leafony Board and PSoC [10]. In this study, a blackboard-based board developed specifically for LoRa ES920LR communication and applied to drones and GPS technology to obtain SF, SNR [17], and RSSI values, the application in subsequent studies is to get patients (Longitude and Latitude) that can be accessed with Google maps, furthermore, it can be seen that each patient's BPM is in a different location. Because of the shape of the Leafony board is small, it can be placed and flown by a drone.

A. Receiver Sensitivity of ES920LR
As the purpose of this research is an analysis of RSSI, SNR, and other parameters such as power consumption, Gain, Power Receiver, obstacles [ Fig. 1], receiver sensitivity, Time on Air, and how to manage the uplink and downlink data on the server or internet gateway and application the server. Moreover, Power Receiver depends on several factors, including receiver gain and lost signal packet factor or attenuation on the Free Space Path Loss. An illustration of the signal reduction can be seen in Fig. 1. The LoRa ES920LR has a transmitting Power (PTX) of -13 dBm, and the Power Receiver depends on the current state of signal propagation including the presence of Obstacles for all circumstances, e.g., bad wheater (snow, rain [18], [21], [22]), the distance that will affect the Time On Air (ToA), The antenna used, Connector Loss and Gain, we can refer to as Receiver Sensitivity (s).The sensitivity of LoRa (-dB) can be seen in equation 1. Where S or sensitivity depends on the value of Bandwidth, Noise Fig. 2, and Signal Noise Ratio (SNR). Table I shows the relationship between SF, S, and ToA. Moreover, the factor to consider is the Fresnel Zone calculation factor [12] if the transmitter and receiver distance is ≥ 5 km [13]. S= -174 + 10 log 10 (BW)+ NF+SNR limit (1)

B. Time on Air (ToA) of ES920LR
The time needed for data from the Transmitter (Tx) to arrive right at the receiver (Rx) while in the air is Time On Air (ToA). [11] ToA is calculated using equation 2 and equation 3. ToA = T preamble + T Payload (2) T preamble = Nb Preamble (8)+symbols added by radio (4.25) x T symbol , Furthermore, the relationship between SF, Chips, SNRlimit, ToA, and BitRate is shown in Table II.
In detail, the ToA of ES920LR with different bandwidths (125, 250, and 500 kHz) is shown in Table III.  13 | P a g e www.ijacsa.thesai.org

A. Flowchart, Devices and Design
The flowchart in Fig. 6 is the steps used in this research, very clearly illustrated in the flowchart, that the initial step is to build a sensor node. Before using the Arduino Pro Mini, the Arduino board [23] is used to make it easier to get a tx and Rx pin [ Fig. 7]. After success, furthermore, a communication test Between ES920LR LoRa [ Fig. 5] was conducted.     Fig. 7 and Fig. 8 are the steps in making a Sensor Node. Fig. 7 still uses Arduino Uno, while Fig. 8 has been changed to Arduino Pro mini. The transformation of Fig. 7 and 8 was completed in this research objective, namely using the Leafony Board in Fig. 11. Moreover, Fig. 9 is a mesh communication that can be carried out by the ES920LR in collaboration with the ES920GW and Application server. LeafBus in Leafony is shown in Fig. 10, there are 5 pins used by LoRa ES920LR. 14 | P a g e www.ijacsa.thesai.org  The development system can be seen in Fig. 3. Fig. 9 uses the ES920LR Leafony Board that mesh with each other on end-devices and sends sensor data to the edge router or border router to the ES920GW as an Internet Gateway and displays it on the internet server.
The difference between Leafony boards and other boards is the port in Fig. 10. LeafBus Leafony boards are pins that are used to connect with other boards. LeafBus LoRa uses these five LeafBus pins i.e., 3V3, Reset, Pins 8 (F11), and Pin9 (F13) as Tx and Rx, and GND. Fig. 11 is the LoRa ES920LR design on the Leafony board, created using kiCAD Software, as described in Fig. 4, there are five LoRa pins identified i.e., Tx, Rx, 3V3, GND, and Reset Pin. And there is the addition of a 10 k Ohm resistor on the Reset pin to Pin 13 and V3V. Therefore, there were three times the changes in the form of LoRa ES920LR end node, i.e., end node LoRa ES920LR use Arduino Uno, LoRa ES920LR use Pro mini, and LoRa ES920LR Leafony board, as shown in Fig. 12.

B. ES920LR Radio Propagation
Before the ES920LR was made in the form of a Leafony board, the Arduino Pro mini-board was tested first. Please note, the mini-board pro requires FTDI. FTDI functions as a regulator as well as a programmer board to program the Arduino Pro mini. The LoRa ES920LR transmitting data experiment uses drones using the FSPL approach. Moreover, Free Space Path Loss (FSPL) is a condition where the process of sending sensor data from the transmitter to the receiver does not pass through any obstacles, the application of Free Space Path Loss (FSPL) using a drone is one of the right efforts to get the value of Receive Signal Strength (RSS) without obstacles. Furthermore, Fig. 13 Developing an equation for LoRa Path Loss by considering the environment (n or exponent) or data transmission area as equation 7 [20].
Fig. 14 is an example of Lora's ES920LR test area with Obstacle buildings and trees. This will produce a different RSSI (-dBm), RSSI can't experience attenuation even with longer distances, this is wherefore the signal is a combination of reflected and direct signals. FSPL gives the direct signal greater amplitude of the waves which causes RSSI (-dBm) greater than those affected by obstacles that cause reflected, scattered, and diffraction.  An important part of this chapter is an analysis of the signals generated by ES920LR with an approach to Free Space Path Loss. For the signal analyzer used Textronix RSA 3408B, LoRa signal contains preamble and symbol, the amount of bytes of data is 255 bytes, on ES920LR 293 bytes on SF12, seen in Fig. 15 is a chirp which shows the existence of LoRa signal, the resulting chirp is up-chirp and down -chirp. Channel power shows how close the distance between transmittersreceiver, -46.13 dBm shows the value of Signal strength, in general, this value is greater based on the distance of the transmitter-receiver that is increasingly far away until a loss occurs.     Fig. 18 is a real experiment from this research, where the transmitter and receiver have different distances, with the transmitter fixed position, and the receiver moves according to the specified point. RSSI data at a distance of 400 meters to 800 meters do not show regular attenuation, this is due to different levels of obstacles, at a distance of 400 meters there are many obstacles that block the direct signal to the receiver, but at a distance of 700-800 meters, the direct signal is greater than reflected signal. thus producing a combined signal that gives a smaller RSSI (-dBm) value or a stronger signal.
While Fig. 19 is an RSSI and SF approach, there is no equation or relationship between SF and RSSI in the equation, because SF talks about the time between Transmitter-receiver in sending data or signals. This is shown in equation 8. [16].   Time is influenced by SF and BW, the greater SF (12), and the smaller the bandwidth, the greater travel time, and vice versa. This causes attenuation, the farther the distance between the transmitter and receiver (SF12). Then the weaker the signal produced, accordingly, the minimum RSSI is -120 dBm, so the greater the Spreading Factor (Fig. 2) [19], the weaker the signal produced.
Finally, if these signals are combined (Fig. 20), they will produce very different signals, between FSPL and full Obstacle, at a distance of 1000 meters, the full obstacle signal is lost and down. This is why the FSPL approach uses drones, the resulting value is indeed not significant on equations 4 and 5. However, it is close to the RSSI (-dBm) value.
In addition to using drones or FSPL [ Fig. 17], testing is carried out using Tx and Rx ES920LR transmitting in areas of buildings and trees [ Fig. 18]. So that the comparison is obtained as in Fig. 20. Fig. 15 and Fig. 16 are output Chrip and Signal LoRa ES920LR in real-time using Signal Analyzer. The change in the Spreading Factor causes a change in Time on Air and causes an attenuation signal to the receiver (Pr) or RSSI (-dBm) shown in Fig. 19.

V. CONCLUSION
Receiving a Signal Strength indicator (RSSI) on the ES920LR generally decreases based on distance or Time On Air (ToA), so that ToA can cause attenuation signal strength. Free Space Path Loss (FSPL) is a condition where there are no obstacles and signals that are better than this experimental research where experiments are conducted with many obstacles e.g., buildings and trees. Furthermore, drones are the solution to get FSPL values on Propagation radio. In the full obstacle situation the ES920LR loses the LoRa signal at 1 km distance, but can be re-tested by changing the measurement area so that the mileage is in accordance with the LoRa ES920LR specifications.

VI. FUTURE WORK
End node devices have to the ability to long life or survive longer with a Power Supply Battery, and a wide range of distances, small and lightweight e.g., Leafony LoRa board for the drone, in the network design that is made there are additional gateways to reduce the load heavily of the gateway in accommodating the end node sensor data to maintain the stability and value of Packet Receive Ratio (PRR (%)).