1. School of Information Science and Engineering, Yunnan University, Kunming 650106, China
2. Glasgow College, University of Electronic Science and Technology of China, Chengdu 611731, China
3. Research and Development Department, Youbei Technology Co., Ltd., Kunming 650011, China
4. Department of Electrical and Computer Engineering, Lebanese American University, Byblos P.O. Box 13-5053, Lebanon