1. School of Electronic Information and Electrical Engineering Chengdu University Chengdu Sichuan P. R. China
2. China Coal Technology & Engineering Group Chongqing Research Institute Co., Ltd. Chongqi China
3. Dongfang Electric Group Science and Technology Research Institute Co., LTD Chengdu China
4. Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing Guilin China