# LoRa Architecture for V2X Communication: An Experimental Evaluation with Vehicles on the Move
## 6 Outdoor Testing and Analysis of the Prototypes
### Testing in Real-World Scenario without and with Kalman Filter  
Extensive testing is conducted with multiple RSUs placed at 320 m apart from each other with different speeds of the car to analyze the reliability of the communication. Figure 9 shows the testing setup of the track where the RSU 1, 2, and 3 are placed at 160 m, 480 m, and 800 m mark on the track at a distance of 320 m from each other. The whole setup is implemented and tested in the city of Mount Pleasant, Michigan at the campus area of Central Michigan University. Figure 12 shows the testing route of the proposed V2X architecture. The highest speed limit of the chosen road is 50 kmph, thus the architecture is evaluated with the speeds ranging from 15-50 kmph. Figure 12 also shows the starting point and the endpoint along the road. There are different infrastructures, trees, and electric poles alongside the testing route which blocked the direct line of sight from the vehicles to RSUs. The OBUs are placed on top of the car whereas the RSUs are placed at a height ranging from 1-1.5 m and they are connected to the computers for monitoring data packet reception. The lower height of the  
Figure 11: The number of data packets received by each RSU in preliminary testing with Kalman filter. Figure 12: Route of the experimental evaluation. RSUs hampered the direct line of sight in many instances thus also affected the reliable transmission range. The higher reliable transmission range is achievable by placing the RSUs in a higher position and using UFL antennas instead of the wire antennas. The RSUs are placed at a comparatively lower height (1-1.5 m) considering RSUs need to be connected to a computer for data monitoring and there are no infrastructures along the road to place those at a higher position along the road. The car is equipped with OBU and starts from 0 m mark. According to algorithm 1, for 0-320 m, the car should send the vehicle data to RSU 1. When the car reaches the 320 m mark of the track, the car should switch from RSU1 and start sending the data to RSU2. Similarly, the car should switch from RSU2 to RSU3 when it reaches the 640 m mark. Thus, the car should get the coverage of 320 m from each of the RSUs-along 0-320 m from RSU1, along 320-640 m from RSU2, and along 640-960 m from RSU3. Thus, ideally with a smooth transition of RSUs, each RSU should receive an equal number of data points for any given speed. Most of the applications of V2X is time-critical and need instantaneous responses. It is also needed to have a continuous exchange of vehicle data with a short interval of time among vehicles and infrastructures. So, the number of data packets received by any RSU while crossing a particular distance is very important. Moreover, a smooth transition from sending data from one RSU to another RSU is also very important. These factors explain both the reliability and stability of V2X communication architecture. Tests are conducted at different speeds of the car from 15-50 kmph with multiple trials to record the number of data packets received by each RSU. At any particular speed, the test is run 3 times at different locations but with the same setup. This would randomize the factors like the visibility of the RSU, roadside infrastructure, and traffic volume on the road. The average of the three trials is taken into consideration to calculate the number of data packets received by each RSU at any particular speed. Figure 13 shows the number of data packets received by RSU1, 2, and 3 at a speed of 15, 25, 30, 40 and 50 kmph of the vehicle. It shows the transitioning of the RSUs and the data packets received by each RSU without the Kalman filter. As RSU 1, 2, and 3 are of equal distance apart and the speed of the testing vehicle is kept constant on a single run, each of the RSUs should receive an equal number of data packets from the vehicle. But without stabilizing the RSSI values, the transition of the RSUs become more erratic.