1. Department of Computer and Information Communications Engineering, Hongik University, Sejong-si 339-701, Republic of Korea
2. Department of Information and Communication Engineering, Yeungnam University, Gyeongbuk 712-749, Republic of Korea
3. School of Information Science and Technology, University of Science and Technology of China, Hefei, Anhui 230027, China
4. Department of Computer Science, Texas Southern University, Houston, TX 77004, USA