1. School of Computer Science and Engineering, Southeast University, 12579 Nanjing, Jiangsu, China
2. School of Computer Sicence and Engineering, Southeast University, 12579 Nanjing, Jiangsu, China
3. Department of Computing Technologies, Swinburne University of Technology, 3783 Melbourne, Victoria, Australia
4. Institute of Network and IT Technology, China Mobile Communications Corp, 248888 Beijing, Beijing, China
5. Institute of Network and IT Technology, China Mobile Research Institute, 248889 Beijing, beijing, China