HAIXIA HOU1,*, DAOJUN LIANG2,3,*,
MINGQIANG ZHANG3,4 AND DONGFENG YUAN3,+
1College of Science and Information Science, Qingdao Agricultural University, 266109 China
2School of Information Science and Engineering, Shandong University, Qingdao, 266299 China
3Shandong Key Laboratory of Wireless Mobile Communication Technologies, Jinan, 250000 China
4School of Cyber Science and Engineering, Qufu Normal University, 273165 China
E-mail: hxhou@qau.edu.cn; {liangdaojun; mqzhang}@mail.sdu.edu.cn;
+dfyuan@sdu.edu.cn