1. School of Electronic Engineering and Computer Science, Queen Mary University of London, London, U.K.
2. Department of Computer Science, Brunel University London, Uxbridge, Middlesex, U.K.
3. National Mobile Communications Research Laboratory, Southeast University, Nanjing, China
4. School of Information and Communication Engineering, Hainan University, Haikou, China
5. School of Engineering, University of Kent, Canterbury, U.K.