1. School of Communications and Information Engineering and the Chongqing Key Laboratory of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing, China
2. School of Communications and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
3. CEMSE Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
4. Department of Electrical and Communication Engineering, United Arab Emirates University, Al Ain, UAE