1. Department of Electrical Engineering, University of Incheon, 12-1 Songdo-Dong, Yeonsu-Gu, Incheon 406-840, Republic of Korea
2. Department of Information Media, University of Suwon, San 2-2 Wau-Ri, Bongdam-Eup, Hwaseong-Si, Gyeonggi-Do 445-743, Republic of Korea