1. Telecommunication Systems Division, Samsung Electronics Co., Ltd., Dong Suwon P.O. Box 105, 416 Maetan-3dong, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-742, Republic of Korea
2. Department of Ubiquitous Computing, Hallym University, 39 Hallymdaehak-gil, Chuncheon-si, Gangwon-do 200-702, Republic of Korea