1. Department of Communication Engineering, Institute of Information Science Technology, Dalian Maritime University, Dalian, China
2. School of Software, Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province, Dalian University of Technology, Dalian, China
3. College of Information and Communication Engineering, Harbin Engineering University, Harbin, China
4. School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China