1. Beijing Jiaotong University,Engineering Research Center of Network Management Technology for High Speed Railway of Ministry of Education, School of Computer and Information Technology,Beijing,China,100044
2. Beijing Jiaotong University,State Key Laboratory of Electronic and Information Engineering School,Beijing,China,100044
3. Tsinghua University,Department of Electronic Engineering,Beijing,China,100084
4. Hong Kong University of Science and Technology (HKUST),Department of Electrical and Computer Engineering,Hong Kong