Cross-Layer Optiminization Of Intelligent Transportation System Based On IEEE1609.4/802.11P

With the rapid increase of the number of motor vehicles in the world, especially in developing countries, a series of problems such as traffic congestion, traffic safety, and environmental pollution has become one of the focuses of national governments and research institutions. As one of the important means to effectively mitigate these issues, Intelligent Transportation Systems (ITS) has become a leading issue in the field of transportation research. In order to achieve high-quality communication for traffic safety-related applications, wireless access in vehicular environment (WAVE) protocol stack, which includes IEEE802.11p/1609.x, has been released in stages by Institute of Electrical and Electronics Engineers (IEEE) since2006. Now, the WAVE protocol system has become one of the most popular protocols in the field of vehicle wireless communication, being highly concerned by the national researchers. At the same time, many research institutions have conducted a variety of in-depth research and improvement based on WAVE.In this paper, we first briefly summarized the WAVE protocol architecture. Then, we analyzed the new features introduced by the IEEE802.11p and IEEE1609.4protocol for vehicular ad hoc network environment. Meanwhile, we also investigated the current research progress about the evaluation metric system of reliability and QoS in the field of vehicular safety-related applications. Through theoretical analysis and matlab simulations, we pointed out two shortages of the current protocols as follows:1) Performance of CSMA/CA mechanism which is used in current protocols will deteriorate sharply when the traffic becomes heavy, and the channel coordination mechanism between CCH and SCH cannot adjust according the real traffic environment adaptively.2) There are few specific evaluation metrics of reliability and QoS for vehicular ad hoc network. To solve the first problem, we proposed a reliable and adaptive MAC mechanism, and a priority-based medium access mechanism. As for the second problem above, a metric system of reliability and QoS, that takes full account of features of vehicular ad hoc network, was proposed to solve it. Finally, correctness and reasonableness of the proposed mechanisms was verified by a series of simulations in matlab.