1. School of Elect. Inform. & Commun., Huazhong Univ. of Science & Technology,Wuhan,China
2. School of Mech. Eng. and Elect. Inform., China Univ. of Geosciences,Wuhan,China
3. Peng Cheng Laboratory,Shenzhen,China
4. VTT Technical Research Centre of Finland,Finland
5. University of Oulu,Oulu,Finland
6. Princeton University,Department of Elect. & Computer Eng.,Princeton,NJ,USA