# Distributed Edge Computing to Assist Ultra-Low-Latency VANET Applications
## 4 Latency-Aware Offloading Algorithm for Multilevel MEC VANET System
### Annotation
However, the three considered cases, in each scenario, indicate different values of the cars' mobility. The considered value of flow rate for each scenario is indicated in Table 4. Table 5 indicates the value of cars' mobility considered in each case for the three considered scenarios. \begin{table}
\begin{tabular}{c c} \hline \hline Bandwidth & 6 Mb/s \\ Packet generation frequency & 1 Packet/s \\ Transmitter power & 23 dBm \\ Packet size & 255 byte \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Key operating parameters of the VANET segments. Figure 3: Bandwidth performance of the considered VANET system. Scenario (A): In this scenario, three cases were considered with a flow rate of 2000 cars per hour and respective speeds of 30 km/h, 50 km/h, and 60 km/h; the size of packets was 30 bytes. Figure 4 illustrates the different values of packet delivery time with the different distances between RSU stations. Results indicated that, with the increase of distance between RSU stations the value of the packet delivery time is increased; for all considered cases (i.e., various considered speeds). Moreover, with the increase of car mobility, the average value of packet delivery time was reduced. Based on the data obtained, the best packet delivery time was observed at a speed of 60 km/h. Figure 5 illustrates the amount of offloaded data to the backhaul network with the distances between RSU stations. As the distance between adjacent RSU stations increased, the amount of data offloaded to the backhaul was increased, which degrades system performance. Moreover, with the increase of cars' mobility, the amount of data passed to the core network was reduced. \begin{table}
\begin{tabular}{c c} \hline
**Scenario** & **Value of Flow Rate** \\ \hline Scenario (A) & 2000 car/h \\ Scenario (B) & 3000 car/h \\ Scenario (C) & 4000 car/h \\ \hline \end{tabular}
\end{table} 
Table 4: Specifications of the three considered scenarios. Figure 4: Packet delivery time with the distance between roadside unit RSU stations for scenario (A). Figure 5: The rate of data offloaded to the backhaul network for scenario (A). \begin{table}
\begin{tabular}{c c} \hline
**Case** & **Mobility Value** \\ \hline Case (1) & 30 km/h \\ Case (2) & 50 km/h \\ Case (3) & 60 km/h \\ \hline \end{tabular}
\end{table} 
Table 5: Mobility value for each considered case. Scenario (B): In this scenario, the considered flow rate is 3000 cars per hour. Figure 6 illustrates the obtained values of the packet delivery time for different values of distance between RSU stations, for the considered value of flow rate. With the increase of flow rate of cars the average value of the packet delivery time was reduced. This can be clearly seen, by comparing Figures 4 and 6. The packet delivery time results for cars with speeds of 50 km/h and 60 km/h were almost the same; the longest package delivery time will be for cars moving at a speed of 30 km/h. This can be interpreted as that of scenario A. Figure 7 illustrates the mound of offloaded data to the backhaul network for the second scenario. Results indicate that the amount of data offloaded to the backhaul increases with the increase of distance between adjacent RSU stations. Moreover, with the increase of car mobility, the amount of data passed to the core network was reduced. Comparing results for scenario A and B, we can conclude that the amount of data offloaded to the backhaul increases with the increase of low rate of cars. This is because of the increase of number of cars produces much data that cannot be handled by the MEC servers due to the limited computing capabilities, which in turn, is moved to the core network. Scenario (C): In this scenario, the considered traffic intensity was 4000 cars per hour. The measured values of packet delivery time for different values of distance between RSU stations, for this scenario, are indicated in Figure 8. The average value of packet delivery time for this scenario was approximately the same as of scenario (B).