# Review of V2X-IoT Standards and Frameworks for ITS Applications
## 5 Discussions  
Most of the published research is focused around a single V2X technology and/or isolated use case scenarios where technologies are compared to one another. Results of the review of currently commercially available V2X products also match with the latter findings. The V2X products, frameworks and/or developments kits that are currently available on the market are mostly suited for the applications with a small selection of predefined technologies. Even so, published research data have shown that the performance of the two main V2X technologies degrades as the number of connected devices increases. Application of the upgraded transceivers, which are based on IEEE 802.11 ax, could increase the capability of the load handling for the DSRC technology based on IEEE 802.11p standard. It still remains unclear whether the current mobile, cellular network infrastructure will be capable of transmitting data via C-V2X technology within the permissible latency and throughput. It is expected that the gradual deployment of the next-generation cellular network infrastructure, like 5G NR, will increase the capacity and throughput and decrease the latency. Due to the requirement of backward compatibility, communication based on C-V2X will have to include handover procedures between network equipment from different cellular generations, which will increase deployment costs and design complexity of the system  
Due to aforementioned reasons, it is necessary to develop solutions, based on highly versatile hardware from analog and digital processing point of view, that enable reliable and efficient technology \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Standard** & **Frequency, MHz** & **Range** & **Transfer Rate** \\ \hline Zigbee & 915, 868 & 10–100 m & 20–250 kb/s \\ LoRaWAN & 169, 433, 868, 915 & 2–45 km & 3–50 kb/s \\ LTE-M & 700–2100 & Global & 100–380 kb/s \\ NB-IoT & 450–2100 & 1–10 km & 28–250 kb/s \\ IEEE 802.11 af (White-Fi) & 470–790, 54–698 & 1 km & 1.8–35.6 Mb/s \\ IEEE 802.11 ah (HaLow) & 863–868, 902–928 & 1 km & 0.15–347 Mb/s \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Summary of common wireless standards for IoT. insensitive V2X communications. Since the two main V2X technologies share some of the frequency spectrum, solutions of hybrid ITS network architecture, which combine DSRC, C-V2X or other complementary wireless solutions (for example IoT-based), are the next logical step. Here, the V2X technology between users is chosen according to the network load, quality, application or other critical parameters and is not limited by the hardware. IoT technologies should also be integrated into the hybrid ITS network. They could be used for offload of the non-critical sensor data, which can help to identify and plan traffic flows, analyze and inform on-road events, and so on. It can be concluded that merging V2X and IoT technologies is a necessity that can help manage and add new features into ITS solutions. Summing up the overview of DSRC, C-V2X, IoT technologies and their standards, regulations and hardware specifications of the commercial products, it can be concluded that a highly versatile framework that supports several wireless technologies and the extremely wide 54-7125 MHz frequency spectrum is needed for the development of a modern ITS solution. There is no sufficiently flexible framework at the time that can be used to develop new transport communication networks or their architectures and concurrently verify them at the hardware and software level. Conceptualization, K.K. and V.B. ; investigation, M.J., K.K., V.M., A.V. and L.K. ; resources, J.R.; writing--original draft preparation, K.K. and V.B. ; writing--review and editing, M.J., V.M., R.N., J.R., A.V. and L.K. ; visualization, K.K. and V.B. ; project administration, R.N. ; funding acquisition, R.N. All authors have read and agreed to the published version of the manuscript. This research was funded by Research Council of Lithuania, grant number DOTSUT-235, No. 01.2.2-LMT-K-718-01-0054.