# A Design of a Lightweight In-Vehicle Edge Gateway for the Self-Diagnosis of an Autonomous Vehicle
## 4 The Performance Analysis
Overall, the transmission delay time about message translation and transmission is reduced by an  
Figure 11: The transmission delay and the Stabilization Time when The CAN messages are translated. (**a**) From CAN to FlexRay, (**b**) From CAN to MOST, (**c**) From CAN to Ethernet. average of 10.83%. That is, if the lightweight method is used, transmission delay is reduced and data processing is improved. Figure 12 shows the average transmission delay by overhead happening when continuous messages are transferred from a CAN bus to a destination protocol. When messages are transferred from the CAN to the FlexRay, Figure 12a shows an average transmission delay according to network traffic increase. In the case the network traffic is 25%, the transmission delay of the existing method was measured as about 275 \(\upmu\)s and that of the proposed method was measured as about 250 \(\upmu\)s. In the case the network traffic is 85%, the transmission delay of the existing method was measured as about 656 \(\upmu\)s and that of the proposed method was measured as about 670 \(\upmu\)s. Therefore, when traffic increase is low, the proposed method is faster by about 9% than the existing method. However, when traffic increase is high, there is no difference between the methods. When messages are transferred from the CAN to the MOST, Figure 12b shows an average transmission delay according to network traffic increase. In the increase the network traffic is 25%, the transmission delay of the existing method was measured as about 2 ms and that of the proposed method was measured as about 2.5 ms. In the case the network traffic is 85%, the transmission delay of the existing method was measured as about 7.9 ms and that of the proposed method was measured as about 8.1 ms. Therefore, when traffic increase is low, the proposed method is faster by about 20%  
Figure 12: The transmission delay as traffic is increased. (**a**) CAN to FlexRay, (**b**) CAN to MOST, (**c**) CAN to Ethernet. \begin{table}
\begin{tabular}{c c c} \hline
**Direction** & **The Improvement Rate of Transmission Delay** & **The Improvement Rate of Stabilization Time** \\ \hline From CAN to FlexRay & 2\% & 25\% \\ From CAN to MOST & 7\% & 0\% \\ From CAN to Etherney & 11\% & 20\% \\ \hline \end{tabular}
\end{table} 
Table 3: The improvement rate of the proposed method. When messages are transferred from the CAN to the Ethernet, Figure 12c shows an average transmission delay according to network traffic increase. In the case the network traffic is 25%, the transmission delay of the existing method was measured as about 0.9 ms and that of the proposed method was measured as about 0.7 ms. In the case the network traffic is 85%, the transmission delay of the existing method was measured as about 2.26 ms and that of the proposed method was measured as about 2.24 ms. Therefore, when traffic increase is low, the proposed method is faster by about 20% than the existing method. However, when traffic increase is high, there is almost no difference between the methods. In brief, the transmission delay of the proposed method is lower as traffic value gets smaller. There is almost no difference between the two methods as traffic value gets larger, which it means that the two methods have the same transmission delay characteristic. When messages are sent and received between a CAN bus and a FlexRay bus, Figure 13a shows the error rate according to the number of messages. The error rate was measured as follows. First, the error rate was measured when the CAN messages are transferred to a FlexRay bus. In the case 50 messages were transferred, the proposed method showed an error rate of 0% and the existing method of 2%. In the case 100 messages were transferred, the proposed method showed an error rate of 1% and the existing method of 2%. In the case 340 messages were transferred, the proposed method showed an error rate of 0.88% and the existing method of 1.47%.