[Ji, Jingyu;Mei, Shaohui;Liu, Xiao;Li, Xu] Northwestern Polytech Univ, Sch Elect & Informat, Xian, Shaanxi, Peoples R China.^[Zeng, Shan] Wuhan Polytech Univ, Coll Math & Comp Sci, Wuhan, Hubei, Peoples R China.^[Wang, Zhiyong] Univ Sydney, Sch Informat Technol, Sydney, NSW 2006, Australia.