# PC5-Based Cellular-V2X Evolution and Deployment
## 6 Discussion  
C-V2X can improve road safety, traffic efficiency, and distribution of road information. It is relatively low cost and highly effective compared to traditional onboard sensors. Standardization of LTE-V2X and NR-V2X has been actively promoted by 3 GPP, which has motivated many organizations to develop C-V2X technology. However, there are still some challenges in PC5-based C-V2X deployment.  
* C-V2X is an eco-system. There must be robust engagements from industry stakeholders, like road transport authority, autonomous driving developers, network transmission operators, and government. To improve C-V2X, the government needs to push road transport facility development and unify its standards. For example, traffic light control systems need to be upgraded from traditional equipment to higher processing devices. To transmit the traffic information promptly, it requires a traffic  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Performance (between OBUs)** & **Vehicle 1** & **Vehicle 2** \\ \hline Packet Transmission Frequency & 100 Hz & 100 Hz \\ Average Latency & 27 ms & 32 ms \\ Package Drop Rate & 2.47\% & 2.72\% \\ \hline \hline \end{tabular}
\end{table}
Table 2: V2V Test Result.  
Figure 11: Vehicle2 Performance.  
light control system to send signal changing information with a predefined frequency of at least 10 HZ. But existing devices across Taiwan can't meet this requirement. A mediation conversion process must be added. The disadvantage of this process is that it increases the message transport latency. So, there are delays between the traffic light control console and traffic lights, which is against the ITS standard. This problem causes difficulties in obtaining the correct timing information for C-V2X devices to synchronize in the SPAT application. To overcome these problems, the government must develop a unified standard to push the upgrade of traffic light control systems.
* Technical application layer specifications are not standardized in C-V2X. Some organizations follow up European Standard, while some use American Standard or combine both as a national standard. It is still unclear which standard will be adopted globally. Unifying and balancing all the pros and cons should be part of the government's smart city agenda.
* In some regions such as Taiwan, 5G is still a year away from island-wide coverage, though it has completed LTE-V2X service testing and trials. So far, it is only focused on applications with limited KPI (Key Performance Indicator) performance. C-V2X will reach a new level once 5G is introduced, where bandwidth, low latency, and high throughput are critical for the use case. However, the deployment of 5G NR-V2X still needs the entire eco-system to be fully adopted.
* Plenty of privacy and confidential information from vehicles, roadside infrastructure, and IP cameras are broadcast in the public space. Protecting information security is an essential topic for PC5-based C-V2X deployment, as mentioned in [30; 31; 32]. The country needs a standard to define a security policy.
* Autonomous Driving is defined as Level 0-Level 5 according to international specification SAE J3016 [13]. However, there are no international standards for road level definition.
* Regulations and insurance claims for ITS road accident are yet to be defined.