1. School of Information and Communication Engineering, Hainan University, Haikou, China
2. College of Information Engineering, Hainan Vocational University of Science and Technology, Haikou, China
3. College of Physical Science and Engineering Technology, Yichun University, Yichun, China
4. Key Laboratory for Ubiquitous Network and Service Software of Liaoning Province, School of Software, Dalian University of Technology, Dalian, China