Research On VANET-based Real-Time Navigation Systems

The real-time navigation system based on vehicular ad hoc network (VANET) can provide vehicles with reasonable routes. It warns the vehicles to stay away from the congested roads, as well as avoids the occurrence of congestion through diversion in advance. Consequently, VANET based real-time navigation is regarded as a promising technique to get out of the dilemma caused by excessive vehicle traffic.For lacking of classification and summary of the relevant works about VANET based real-time navigation system, a survey from the perspective of communications around this field is made, with the purpose to provide guidance for future research. Firstly, the currently proposed VANET based navigation systems are classified into infrastructure-based and infrastructure-less, and the impact of the two categories of systems caused by low market penetration is also covered. As the two main functional modules of VANET based navigation system, the key technologies real-time traffic information collection and shortest routing algorithm design are introduced, including the promotion of bandwidth utilization efficiency and the design of the dynamic shortest routing algorithm. On the basis of the existing literatures, several future research directions are presented finally.In order to provide both the low complexity and the high anti-congestion ability of a navigation system, a decentralized roadside unit (RSU)-based real-time path planning algorithm is proposed. Via area decoupling, the path planning is realized in a decentralized manner, and thus reducing the computational complexity to a great extent. The path planning problem is divided into two sub-problems and solved hierarchically. In the upper layer, area path selection is performed to minimize area crossing delay, and thus avoiding the occurrence of regional congestion at the macro level. In the bottom layer, intra-area routing is realized to prevent congestion in a specified road at the micro level, and thus supporting a minimum intra-area travel delay. Numerical results show that the proposed path planning algorithm achieves the similar anti-congestion ability as compared with a centralized algorithm but decreases the computational complexity dramatically.To mitigate the real-time performance loss caused by vehicle data collection process, a data collection delay guaranteed RSU deployment algorithm is proposed, based on the relationship between vehicle data collection delay and RSU deployment scheme. Taking the impact of link-layer communication mechanism on data transmission on the road into account, road information transmission velocity model is established. Then the RSU deployment optimization problem is formulated, with an objective of minimizing the largest network latency. Furthermore, the problem is solved through an efficient heuristic algorithm to obtain the optimal RSU deployment scheme in the sense of delay minimization. Numerical results show that the proposed algorithm outperforms uniform deployment algorithm under any tested parameter settings, especially when road density varies in a large range. Further it provides the almost same performance in terms of delay performance compared with the optimal solution derived by exhaustive search.