RUI CHEN1,2, ZHENGKUN MI1,+ AND LIANGBAO JIAO2
1Key Lab of Broadband Wireless Communication and Sensor Network Technology
Nanjing University of Posts and Telecommunications
Nanjing, 210003 P.R. China
E-mail: mizk@njupt.edu.cn
2School of Communications Engineering
Nanjing Institute of Technology
Nanjing, 211167 P.R. China