1. Department of Information Engineering and Computer Science, Feng Chia University, Taichung, Taiwan
2. Electrical Engineering and Computer Science International Graduate Program, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
3. Department of Communications Engineering, Feng Chia University, Taichung, Taiwan
4. Department of Electrical and Computer Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan