[1] Tongji Univ, Sch Software Engn, Shanghai 200092, Peoples R China
[2] Middlesex Univ, Sch Sci & Technol, London N17 8HR, England
[3] Indian Inst Technol Roorkee, Dept Elect & Comp Engn, Roorkee, Uttar Pradesh, India
[4] Nanjing Univ Aeronaut & Astronaut, Dept Comp Sci, Nanjing, Jiangsu, Peoples R China
[5] Univ Politecn Valencia, Dept Commun, E-46071 Valencia, Spain