1. Purple Mountain Laboratories, Nanjing, China
2. School of Information Science and Engineering, Shandong Normal University, Jinan, China
3. School of Information Science and Engineering, Shandong University, Qingdao, China
4. Department of Engineering, University of Durham, Durham, U.K
5. Sensor Networks and Cellular Systems Research Center, University of Tabuk, Tabuk, Saudi Arabia