VANET Traffic Control Mechanism Design And Verification Based On Traiectorv Data

Recent years have witnessed worldwide rapid development in automobile industries and growing rate of vehicle ownership. Consequently, the thorny issue of traffic congestion has bothered more and more people. To alleviate traffic jams as well as enhance traffic efficiency, this thesis analyzes trajectory data of vehicles in traffic system and proposes a corresponding traffic control mechanism.At first, we compared two trajectory prediction methods, one is based on Markov chain, and the other is based on PST (Probabilistic Suffix Tree). We have conducted experiments and results show that the trajectory prediction method based on PST can obviously achieve higher prediction accuracy.Then, we propose a cooperative traffic light control mechanism for multiple intersections based on semi-real-time processing by combining the concepts of fixed-time control and traffic-response control. In our mechanism, we set fixed phase duration between traffic light phases in advance. Each intersection has a traffic light controller and each controller can gather traffic data near its intersection within the current phase period by VANET. As the traffic situation for next period will be effected by coming vehicles from neighboring intersections, we let every controller cooperate with its neighboring controllers by sharing with each other their own traffic data within the current period. Combining its own traffic data with neighboring traffic data, each controller will use trajectory prediction method based on PST to predict the traffic situation of the next period, and then make the optimal decision of traffic light phase setting for the next period according to the prediction result.This thesis also proposes a heuristic algorithm for dynamic route planning to enhance individual’s travel efficiency in traffic system. On the basis of Dijkstra algorithm, we adopt a heuristic method to calculate the weight of each road. The weight of each road will be updated according to its current traffic situation at each set interval. After obtaining new weights of all roads in the traffic network, vehicles will re-compute the optimal travel route.With the combination of cooperative traffic light control based on semi-real-time processing and heuristic algorithm for dynamic route planning, we propose a VANET traffic control mechanism based on trajectory data.To verify the performance of our proposed VANET traffic control mechanism, we run simulation experiments by combining SUMO with NS3. In our experiments, we use LFBL as routing protocol to simulate the VANET environment. The simulation results demonstrate that our proposed traffic control mechanism is both effective and practical. It is able to reduce traffic load and average waiting time of vehicles, as well as release traffic jams and divert jammed vehicles, thus can improve road traffic situation of the whole transportation system.