# Designing a C-ITS Communication Infrastructure for Traffic Signal Priority of Public Transport
## 3 Methodology and Results
### Communication Range
#### 3.1.3 Tools and Results  
As described above, the communication ranges were evaluated in two ways:  
1. Simulation of radio propagation via our radio propagation planning tool;
2. On-site radio measurement.  
From a scientific standpoint, it is quite interesting to consider the singular use of only one of these tools; however, for practical implementation, both tools were combined and considered integrally. This scientific approach, i.e., the combination of both tools, is a new approach, on which this paper builds. The combination and fusion of these results for both tools are needed for an optimal result in the course of the deployment. Likewise, the measured data are directly fed back into the planning tool for further evaluation and calibration of the tool itself.  
The following paragraph includes a more in-depth and detailed description of both methods.  
Radio propagation planning tool for C-ITS G5.  
The radio coverage was estimated using the radio propagation planning tool. The analysis was based on a trained model of C-ITS G5-based propagation measurements.  
Thus, potential RSU locations were selected for the estimation of the radio coverage on existing intersections. On the basis of the location of the registration points, their accessibility when using C-ITS G5 was predicted. The representations of the radio propagation planning of the individual RSU locations took place along the entire corridor of railway section U5. For example, the traffic light at the intersection \"Eckenheimer Landstr./Eschenheimer Anlage\" is shown in Figure 1. The map on the left depicts the locations of the intersections on the entire route. The middle figure depicts the results of the radio propagation planning tool. The image on the right visualizes the location of the registration points.  
Radio measurement and evaluation.  
The radio propagation planning tool works on the basis of learned and referenced data sets. Therefore, reception within critical areas needed to be validated by measurements. A mobile setup of a C-ITS G5-based RSU was developed by Fraunhofer IVI for validation. It  
Figure 1: From left to right: U5 railway section with intersections; calculated communication ranges for C-ITS G5 in the area of study, U5 at intersection “Eckenheimer Landstr./Eschenheimer Anlage”; registration point chain shown as red circle for this intersection.  
consisted of a tripod, which could lift the RSU to a height of approx. 4 m, and a mobile power supply. Moreover, a C-ITS G5-based Onboard Unit (OBU) was used in a test vehicle to carry out the V2I-communication measurements. Both components successfully sent and received messages that were transferred to a backend via mobile communications and stored in a separate database. Since the assembly height of the productive RSU as well as the antenna of the OBU on the vehicles of the VGF are higher, it can be assumed that the results of the present measurements currently underestimate the communication ranges that can actually be achieved.  
Result 1:  
From a scientific standpoint, it is quite interesting to consider the singular use of only one of these tools; however, for practical implementation, both tools were combined and considered integrally. Both tools complement each other seamlessly. The data from the radio measurement and evaluation can thus permanently flow back into the planning tool for calibration. This is especially important for data sets in which new areas are being developed.