[1] Beijing Jiaotong Univ, Inst Informat Sci, Beijing 100044, Peoples R China
[2] Beijing Key Lab Adv Informat Sci & Network Techno, Beijing 100044, Peoples R China
[3] Univ Illinois, Beckman Inst, Urbana, IL USA
[4] Beijing Inst Technol, Sch Opt Engn, Beijing 100081, Peoples R China