1. Institute of Information Science and Technology, Yanshan University, Qinhuang Dao, Hebei Province, China
2. Computer Department, Xinzhou Teachers University, Xinzhou, Shanxi Province, China
3. Hebei Key Laboratory of Information Transmission and Signal Processing, Yanshan University, Qin Huangdao, Hebei Province, China
4. School of Information Engineering, Inner Mongolia University of Science and Technology, Baotou, Inner Mongolia Province, China