1. Nanjing University of Posts and Telecommunications, Institute of Signal Processing and Transmission, Nanjing 210003, China
2. National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
3. Sunwave Communications Co., Hangzhou 310053, China
4. Nanjing University of Posts and Telecommunications, Key Lab Broadband Wireless Communication and Sensor Network, Ministry of Education, Nanjing 210003, China