1. Division for Electricity Research, Uppsala University, Box 534, S-751 21, Uppsala, Sweden
2. School of Information and Communication Technology, KTH Royal Institute of Technology, Isafjordsgatan 22-26, Electrum 229, 16640 Kista, Sweden
3. ECE Department, Engineering Faculty, University of Tehran, Tehran, Iran
4. Element Six Ltd, King's Ride Park, Ascot, Berkshire SL5 8BP, United Kingdom