1. School of Mathematics and Computing Science, Guilin University of Electronic Technology 1 , Guilin 541004, China
2. Guangxi Wireless Broadband Communication and Signal Processing Key Laboratory, Guilin University of Electronic Technology 2 , Guilin 541004, China
3. Center for Applied Mathematics of Guangxi (GUET) 3 , Guilin 541004, China
4. School of Mathematics and Statistics, Wuhan University 4 , Wuhan 430072, China