1. School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
2. School of Communication and Information Engineering and the Chongqing Key Laboratory of Mobile Communications Technology, Chongqing University of Posts and Telecommunications, Chongqing, China
3. School of Microelectronics and Communication Engineering, Chongqing University, Chongqing, China
4. National Mobile Communications Research Laboratory, Southeast University, Nanjing, China