Design Of WiFi Network Performance Measurement Testbed For Internet Of Vehicles

With the development of economy, the number of cars was rapid increased. This phenomenon cause many problems, such as traffic accidents, traffic congestion and environmental pollution. To solve these problems, Internet of vehicles which interact with each other through vehicles, people, roads, and sensors was produced. Wireless communication technology has laid a foundation for the Internet of vehicles, so the performance of wireless network is crucial for the implementation and development of internet of vehicles. Currently, many countries are building "wireless city", mostly using WiFi networks. In China, many cities have been comprehensive coverage with WiFi networks which adopt international standard unified agreement and the transmission rate is high. It is very meaningful to study Wi Fi networks as the wireless communication subsystem of internet of vehicles.Existing wireless network testbeds are for large-scale static wireless network performance testing and evaluation, without considering mobility of the nodes. One of the most important features of the internet of vehicles is rapid mobility of the nodes, but the existing wireless network testbeds are unable to meet the wireless network performance testing. To solves the problems, this paper presents a WiFi network testbed that can test and evaluate the WiFi network performance.Based on network tomography technology, a WiFi network testbed oriented internet of vehicles was designed and implemented. Aiming at the features of rapid mobility of tested nodes in internet of vehicles, based on RFID technology, it can be detected automatically when the mobile nodes enter and leave the test region. Furthermore, the start up and stop of test process can be controlled automatically. Then, the tested node rapid mobility’s impact on network performance was tested by above testbed. There were two test modes, that is, short data packages test and long data packages test. The network performance test indexes include network round-trip delay, packet loss rate, average throughput. Test results show that the WiFi network performance indexes degrade with the speed increase of tested node. When the speed of tested node is 70km/h, the network performance indexes decrease significantly comparing to the situation of 20km/h. In short data packages test mode, the network round-trip delay increases 2.3 times, the packet loss rate increases 5.5 times, and the average throughput decreases 42% times respectively. In long data packages test mode, the network round-trip delay increases 2.7 times, the packet loss rate increases 6.7 times, and the average throughput decreases 35% times respectively. The results indicate that the wireless network performance indexes of internet of vehicles can be effectively measured and evaluated by this WiFi network testbed oriented internet of vehicles.