1. School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai, China
2. National Key Laboratory on Wireless Communications, University of Electronic Science and Technology of China, Chengdu, China
3. School of Mathematical Sciences, University of Science and Technology of China, Hefei, China
4. Theory Laboratory, Central Research Institute, 2012 Labs, Huawei Technology Company Ltd., Kowloon, Hong Kong