1. State Key Laboratory of Networking and Switching; Beijing University of Posts and Telecommunications; 100876 Beijing China
2. China Telecommunication Technology Labs; China Academy of Information and Communications Technology; 100191 Beijing China
3. Department of Electronic Engineering; Tsinghua University; 100084 Beijing China
4. InterDigital Communications; King of Prussia PA 19406 U.S.A.
5. Department of Computer Science; Tongji University; 200092 Shanghai China