# Analysis of Low Cost Communication Technologies for V2I Applications
## 4 Experimentation  
### Approach  
Once the communication systems were assembled and programmed, the performance of the devices were validated. For that, the modules were submitted to a test bed where a validation methodology was established in order to compare the technologies. The developed validation methodology was based on several studies and articles from others authors. Summarizing the consulted studies, [27] highlights the critical parameter to control in any V2X technology test, but they did not make physical tests. The most important parameters are the latency of the messages, lost, and right messages rate and the range which is covered by the modules. On the other hand, the analysis of the experimental data was based on the methods carried already out by [28] for 802.11p technologies and [29] for C-V2X technologies. Both made latency and range tests, but they did not analyze other parameters which are important, too. The aim of our experimental tests was to provide as much information as possible about the real behavior of the device. To carry it out, it was used the installations of CIDAUT Foundation in the locality of Mojados and in the Technological Park of Boecillo, both in Valladolid (Spain). The schedule of the tests is summarized in Figures 6-8. In the first place, preliminary tests to ensure the operation of the technology, which would be validated later, were carried out. With the algorithm built and modules assembled, the two modules were tested to ensure the correct communication. The design of the test can be seen in Figure 6. They took place in CIDAUT Foundation installations in the Technological Park of Boecillo. The devices were at the same height, avoiding obstacles between them. The distance between them was 20 m, which was a large enough distance to have a reliable operation. Then it was analyzed the capabilities and limitations of the devices with the test bed in the CIDAUT Foundation installations in Mojados, which can be seen in Figure 7.  
The main road had a length of 506 m with available open space at the beginning and end of the road for accelerating and braking to the desired speed. The tests were carried out as a sequence of a round trip in different operation conditions for taking different measures. The equipment was a vehicle, a lifting crane, and a ladder. 1. Maximum distance and kind of signal. The aim was to measure the distance covered and if the distance was constant regardless of the orientation of the module (the vehicle used was moving at 30 km/h). 2. Dependence on vehicle speed. The vehicle was driven at three different speeds: 50, 70, and 90 km/h. 3. Dependence on RSU height. The vehicle was driven at 50 km/h, but the height of the RSU was variable: 2, 5, and 10 m.  
Figure 6: Design of preliminary tests in Boecillo. Figure 7: Experimental design in Mojados. 4. Dependence on RSU position. The vehicle was driven at 50 km/h, but this time the RSU was located in different positions of the road: On one side (0 m), in the center (2m), and on the other side (4 m). 5. Dependence on data rate. If the technology allowed it, the data rate was changed and it was analyzed if it had influence in the module operation. The round trip consisted of six trips, three outward and three return, which was enough to take data and know the capabilities of the devices. The driven car was a Toyota Hybrid Auris, where the communication technology was outside of the car and in its roof. There was one round trip per each variable change. The methodology validation was completed after performing the last test around the CIDAUT Foundation buildings in the Technological Park of Boecillo, which can be seen in Figure 8, where the dependence of the obstacles in the right operation of the devices was analyzed  
During the test, the RSU was in the same place, as can be seen in Figure 8. One side had buildings, while on the other there was a direct line of sight between both. Comparing both data, it can be appreciated the obstacles' influence. The car used was the same as the previous test in Mojados.