1. Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece
2. Institute for Digital Communications (IDC), Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Erlangen, Germany
3. School of Information Science and Technology, Southwest Jiaotong University, Chengdu, China
4. Hilti Corporation, Feldkircher Strasse 100, Schaan, Liechtenstein
5. Department of Electrical and Computer Engineering, Technical University of Chania, Chania, Greece
6. Computer Science Engineering Department, University of Ioannina, Ioannina, Greece