1. School of Electronic and Information Engineering and the National Engineering Research Center of Advanced Network Technologies, Beijing Jiaotong University, Beijing, China
2. School of Information Science and Technology, Beijing Forestry University, Beijing, China
3. School of Traffic and Transportation and Beijing Research Center of Urban Traffic Information Intelligent Sensing and Service Technologies, Beijing Jiaotong University, Beijing, China
4. Department of Systems and Computer Engineering, Carleton University, Ottawa, ON, Canada