# V2X Communication over Cellular Networks: Capabilities and Challenges
## 4 Delay Analysis for V2X Communications
### UC Delay Evaluation  
The purpose of the previous analysis was to identify which of the UCs described by 3 GPP and 5 GAA can be covered by the existing systems and the gaps. Considering the analysis on LTE and 5G and comparing the results to the UC requirements as they have been described in Table 2, we produced Tables 10 and 11. The former considers the 3 GPP delay requirements and captures the achievable delay with LTE-A solutions, whereas the latter considers the same requirements that can be achieved by the 5G-NR. \(\checkmark\) means that the requirements are successfully met, whereas \(\times\) is used for failures. Note here that for some UCs, there are different scenarios with regard to the automation levels. For instance, Infrastructure-based Perception Environment considers 3 ms for full automation and 100 ms for partial automation. \(\checkmark\) indicates that the specific UC can only be fulfilled for a lower level of automation. As can been seen in Table 10, LTE-A can serve only a few of the advanced driving UCs. Some of them can indeed be supported, but only for the lower levels of automation. This was to be expected as the advanced V2X UCs are expected to require E2E delay values that are much lower compared to what LTE-A systems can offer. In the case of 5G-NR, we have selected the following numerology, which is one of the potentially good candidates for V2X communication according to [40]. We have assumed resource mapping of type B, a zero initial error probability, 2 OS, and 30 KHz SCS. We have also used the assumption from a packet that faces a 3 ms delay each time it crosses a network interface (e.g., gNB to UPF). To obtain a complete picture, we have assumed delays of LTE-A in the case of multicast communication as there is currently no such capability in 5G networks. In all cases, we also consider a link to the V2X application server. Table 11 presents the expected delay in the case of (a) E2E unicast communication (packets are crossing two UPFs), (b) a local breakout scheme being used (only one UPF is used), (c) Multicast through the MBMS, and (d) Multicast through SC-PTM. The results are compared against the V2X requirements. Based on this assumption, we observe that compared to the results of LTE-A, 5G-NR can indeed support many more UCs. However, it is worth noting that even with a small core network delay, many of the 3 GPP UCs cannot be covered, even by 5G networks. This is \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Uu Interface**} & \multicolumn{3}{c}{**PC5 Interface**} \\ \cline{2-7}
**UC** & **Unicast** & **MBMS** & **SC-PTM** & **Mode** & **Mode** & **Mode** \\  & & & & **3 DS** & **3 SPS** & **4** \\ \hline
**Delay (ms)** & 35.8 & 54.5 & 35.5 & 26.5 & 56 & 55.5 \\ \hline Platooning & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline Sensor and State Map Sharing & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline Remote Driving & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline Lane Change & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline Infrastructure-based Perception of & & & & & & \\ Environment & & & & & \\ Collision Avoidance & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline Collective Information Sharing & & & & & & \\ See through for Passing & & & & & \\ Emergency Trajectory Alignment & & & & & \\ Intersection Crossing & - & - & - & - & - & - \\ \hline Cooperative Driving & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline \hline \multicolumn{7}{c}{\(\times\) Cannot fulfil. \(\bigtriangledown\) Fulfil only the lower levels of automation. \(\bigtriangledown\) Fulfils} \\ \hline \hline \end{tabular}
\end{table} 
Table 10: 3 GPP use case (UC) evaluation for LTE-A.