Wei-Lieh Hsu, Hsiao-Rong Tyan**, Yu-Ming Liang+, Bor-Shenn Jeng++ and Kuo-Chin Fan
+Department of Computer Science and Information Engineering
National Central University
Chungli, 320 Taiwan
**Department of Information and Computer Engineering
Chung Yuan Christian University
Chungli, 320 Taiwan
+Institute of Information Science
Academia Sinica
Taipei, 115 Taiwan
++Telecommunication Laboratories
Chunghwa Telecommunication Co., Ltd.
Taoyuan, 320 Taiwan