1. University of Aizu,Department of Computer Science and Engineering,Aizu-Wakamatsu,Japan
2. Research Institute of Electrical Communication, Tohoku University,Sendai,Japan
3. University at Buffalo,Department of Electrical Engineering,SUNY Buffalo,New York,USA
4. Rensselaer Polytechnic Institute,Department of Electrical, Computer, and Systems Engineering,Troy,New York,USA