1. Faculty of Engineering Science, Omdurman Islamic University (OIU), Omdurman, Sudan
2. Univ Rennes, CNRS, IETR-UMR 6164, Rennes, France
3. Wireless Communication Center (WCC), Universiti Teknologi Malaysia (UTM), Skudai, Malaysia
4. Faculty of Engineering and Technology, Multimedia University, Melaka, Malaysia