## 6 V2X Testbed Setup and Algorithm Implementation
### Algorithm Implementation  
To ensure a fair comparison of short-range communication performance between DSRC and C-V2X PC5, both technologies were set up to transmit concurrently on distinct channels within the 5.9 GHz ITS band. This approach facilitates the evaluation of their performance under identical conditions, encompassing factors such as the distance between V2X nodes, traffic situation, and obstructions. The investigated ITS channels, 180 (for DSRC) and 184 (for C-V2X PC5), are strategically chosen to be non-adjacent, with the bandwidth between them serving as a guard frequency. We assume that all V2X nodes use these exact channel numbers for DSRC and C-V2X PC5. For 5G long-range transmissions, a licensed  
Figure 10: Tx/Rx and Global Positioning System (GPS) antennas on the roof of OBU2. Figure 9: Mobile unit inside vehicle, referred as On-Board Unit 2 (OBU2). 40 MHz bandwidth with a center frequency of 3820 MHz is used. A MQTT server deployed on the 5G in-a-box setup is used for the long-range C-ITS message exchange between OBUs. Furthermore, each individual test underwent multiple repetitions with consistent settings to assess and validate the reproducibility of results. Both OBUs are provisioned with a Global Navigation Satellite System (GNSS) device for synchronization with respect to time, accomplished by deploying the Network Time Protocol (NTP) [23]. According to the standardization, these GNSS devices provide a time precision of 1 ms. Experiments were conducted in Technology park, Ghent, Belgium as shown in Figure 11. Each test starts from a LOS scenario (co-located OBU1 and OBU2) and then OBU2 moves away (dotted blue points) and then again gets back towards OBU1. At the testing site, LOS is available for every test up to the distance of 150-170 m approximately. All communication after this point is non-LOS. The initial step involves the transmission and/or reception of CAMs and/or DENMs by OBUs, utilizing chosen V2X communication technology(ies), based on the defined selection criteria in alignment with the designated experimental scenario. Logging of messages (transmitted and received) is done at both OBUs, ensuring data integrity. Data could also be logged at a remote repository but this approach can suffer in case of disruptions in connectivity. The orchestration of diverse V2X technologies, the execution of associated services, and the data logging are managed by the internally devised CAMINO framework [16]. Following the experimentation, the post-processing is performed on the acquired data sets for the analysis of predefined KPIs. Throughout each test, both OBUs independently log transmitted and received data locally to mitigate potential data loss from connectivity disruptions. There are separate log files for CAMs and DENMs on each OBU unit. Table 3 provides a snapshot of CAMs logged in a local log file during the test campaign conducted on 20 December 2023. This snapshot shows CAMs being sent from one of the OBU unit via the long-range 5G link (denoted as CELLULAR), as well as the two short-range technologies i.e., DSRC and C-V2X PC5 (denoted as LTE-V2X).The details about CAMINO framework and geocasting for C-ITS long-range message exchange are as follows:  
Figure 11: Location of OBU1 and driving trajectory of OBU2 for experiments conducted in Technology park, Ghent, Belgium.