1. Department of Information & Communication Systems, Hohai University, Changzhou 213022, China
2. Changzhou Key Laboratory of Photovoltaic System Integration and Production Equipment Technology, Changzhou 213022, China
3. Institute of Telecommunications, University of Beira Interior, 6201-001 Covilhã, Portugal
4. Department of Computer and Communication Engineering, Northeastern University, Qinhuangdao 066004, China