[1] Univ Elect Sci & Technol China, Sch Informat & Commun Engn, Chengdu 611731, Peoples R China
[2] Univ Coll London UCL, Dept Elect & Elect Engn, London WC1E 6BT, England
[3] Univ Essex, Sch Comp Sci & Elect Engn, Colchester CO4 3SQ, England
[4] Brunel Univ London, Dept Comp Sci, Uxbridge UB8 3PH, England
[5] China Univ Min & Technol, Sch Comp Sci & Technol, Xuzhou 221116, Peoples R China