[1] Beijing Jiaotong Univ, Sch Elect & Informat Engn, Beijing 100044, Peoples R China
[2] Univ Surrey, Fac Engn & Phys Sci, Dept Elect Engn, Ctr Commun Syst Res, Guildford GU2 7XH, Surrey, England
[3] Swinburne Univ Technol, Fac Informat & Commun Technol, Hawthorn, Vic 3122, Australia
[4] Royal Inst Technol, KTH, S-10044 Stockholm, Sweden