Research On Key Technologies Of Wireless Communication For Cooperative System

The wireless communication technologies in the Cooperative System(CS) has become one of the most important fields of research for Intelligent Transportation Systems (ITS) in recent years. Now,there is a trend to import wireless communication technology to improve the condition of diving safety and the effectiveness of transportation system all around the country, especially in the international traffic development planning for construction of information. With the well designed standard system as a basis, many advanced safety related applications and functions for road network management can be done deep analysis and communicated under the same framework, although the effective evaluation methods are still insufficient. As the challenge of increasing traffic congestion to be faced, the large-scale application potential of wireless technologies in the CS and to simulate the whole system comprises heterogeneous components effectively have been mentioned as immediate areas of research focus.According to the technical status of current CS, this paper investigated the wireless communication modeling, the wireless network awareness, the wireless network congestion control and awareness control, the vehicular cooperative positioning and other problems urgent need to be resolved under the large-scale application of CS.First, the models of digital baseband signal processing for OFDM system, network node and competition mechanisms have been established with the results of related standards' analysis. By the test results from real traffic environment, the wireless channel model in 5.8GHz has been improved. The whole wireless communication model which includes above submodel meets the three-layers protocol structure of DSRC and was utilized for the verification of other research issues.Second, Hidden Markov Model for estimating the number of transmitters in the current signal conflict time which is inspired by the analysis results of broadcast communication on control channel in CS has been founded. The network awareness can be acquired without increasing any channel load by the method. And its effectiveness for the urban traffic congestion scenario has been proved by simulation.Third, to improve the adaptability of the network congestion control mechanism for current urban traffic environment, a random time-slot selective method was designed. At the same time, the wireless communication model has been developed according to the standard of network congestion control. The results show its effective balance between network awareness and network congestion control in the urban traffic congestion scenario.Finally, on the base of academic literature studies, the scenario of cooperative positioning application for vehicles in the CS network which comprised kinds of on-board sensors and vehicle movement model was analyzed with the simulation mechanism for hybrid system of discrete-event system and continuous system. A kind of cooperative positioning method based on distance measurement was prove to be feasible for improving the accuracy of positioning by fusing multi-sensors data information under network's congestion control.