1. School of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China
2. Chongqing Key Laboratory of Image Cognition, Chongqing University of Posts and Telecommunications, Chongqing, China
3. Department of Electronic and Electrical Engineering, Brunel University London, London, U.K.
4. School of Optoelectronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing, China