1. School of Information and Communication Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
2. Engineering Product Development Pillar, Singapore University of Technology and Design, Tampines, Singapore
3. School of Communication and Information Engineering, Chongqing Key Laboratory of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing, China
4. College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China