1. Information and Communication Engineering, DGIST, Daegu, Republic of Korea. E-mails: heejung8@dgist.ac.kr, hk@dgist.ac.kr, son@dgist.ac.kr
2. Robotics Engineering, Hanyang University, Gyeonggi-do, Republic of Korea
3. School of Information Systems and Applied Technologies, Southern Illinois University, Carbondale, IL, USA. E-mail: SamChung@siu.edu