1. Faculty of Electronic Engineering and Technology, University Malaysia Perlis, Arau, Malaysia
2. School of Information and Communications Engineering, Xi'an Jiaotong University, Xi'an, China
3. Centre for Wireless Communications (CWC), University of Oulu, Oulu, Finland
4. Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, U.K.