1. Key Laboratory of Dynamic Cognitive System of Electromagnetic Spectrum Space, Nanjing University of Aeronautics and Astronautics, Nanjing, China
2. Department Electrical and Computer Engineering, University of Western Macedonia, Kozani, Greece
3. Department of Informatics and Telecommunications, University of Thessaly, Lamia, Greece
4. School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden
5. Department of Electronic and Electrical Engineering, University College London, WC1E 7JE London, U.K.