1. National Key Laboratory of Wireless Communications, University of Electronic Science and Technology of China, Chengdu, China
2. School of Electrical and Electronic Engineering, Nanyang Technological University, Jurong West, Singapore
3. Institute for Infocomm Research (I2R), Agency for Science, Technology and Research (A*STAR), Fusionopolis, Singapore
4. School of Computer Science and Information Technology, University College Cork, Cork, Ireland