## 4 Experimental Results  
To verify that the proposed SAIS-BsDiff algorithm can improve the efficiency of differential compression and reduce time consumption during the OTA upgrade, an OTA hard-in-the-loop simulation test platform was established, as shown in Figure 7. The experimental platform equipment included a notebook computer, a wireless router, an industrial computer, and an STM32F407 ZGT6 development board (STMicroelectronics, Geneva, Switzerland). The laptop serves as an OTA upgrade server. Wireless routers provide mobile network communication for industrial computers. As the upgraded object of industrial devices, the industrial computer can simulate the client and the automatic driving domain controller. It can receive wireless transmission protocol packets and convert them into UDS diagnosis packets through sockets. The STM32 development board serves as the minimum control unit of the object to be upgraded and is used to verify UDS diagnosis and Bootloader program jump functions during the upgrade. The server was connected to the TBOX through a 4G/5G-U wireless connection, the TBOX was connected to the domain controller through an Ethernet connection, and the STM32 development board was connected to the domain controller through a CAN network connection. Table 2 lists the configuration parameters of the test equipment. Figure 6: Induced sorting shortens the problem domain. Figure 7: OTA hardware-in-the-loop simulation test platform. To objectively evaluate the OTA upgrade efficiency, we assumed that the difference in time before algorithm optimization was \(t_{1}\), and the difference in time after algorithm optimization was \(t_{2}\). The difference in the time improvement ratio is as follows:  
\[\eta=(1-\frac{t_{2}}{t_{1}})\times 100\% \tag{1}\]  
According to Formula (1), the higher the improvement ratio, the higher the upgrade efficiency and the better the optimization performance of the difference algorithm. Based on the experimental test bench introduced, the function between modules was realized by an integrated test. First, the upgrade image was selected and downloaded. During the download, the Wireshark running in the background of the domain controller checked whether the network was properly connected and monitored. The Wireshark page displayed that the server IP address and port number were set to 196.168.31.130, 49534, and the client IP address and port number were set to 172.217.160.110, 443. After the HTTP three-way handshake succeeded, the communication was established, and the server started data transmission. In the lower pane of the Wireshark, the packet transmission body was viewable. This enabled the server access required for OTA upgrades. Then, the improved SAIS-BsDiff algorithm was tested using an OTA hardware-in-the-loop simulation test platform. The comparison algorithm used in the experiment was the open-source algorithm BsDiff 4.3. The dependent library, Bzip2, was installed before use, and the function and performance of the SAIS-BsDiff algorithm were tested. The test file was a binary execution file generated for the Keil tool chain. The BsDiff and SAIS-BsDiff algorithms were used to differentiate the same set of upgraded files. The content of the difference files obtained by the algorithm before and after optimization was consistent; there was no file loss or change, and all upgraded packages could be restored to the new version files after the restoration algorithm. It was verified that the SAIS-BsDiff algorithm could realize the correct differential compression function. Figures 8 and 9 show the results of the BsDiff and SalS-BsDiff algorithms for differentiating and restoring the same group of data; the content and structure of the two restored groups of data are correct. Subsequently, the SAIS-BsDiff algorithm was validated using a test platform.