1. Faculty of Electronic Information and Electrical Engineering; Dalian University of Technology; Dalian, 116024 China
2. School of Engineering and Science; Victoria University; Melbourne, Vic 8001 Australia
3. School of Electrical and Electronic Engineering; The University of Adelaide; Adelaide SA 5005 Australia
4. Department of Engineering, Faculty of Engineering and Science; University of Agder; N-4898 Grimstad Norway