1. Department of Electronic Systems, Aalborg University, Aalborg, Denmark
2. Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, SAR, China
3. Communication Systems Department, EURECOM, Biot, France
4. Department of Computer and Information Science, Linköping University, Linköping, Sweden
5. Telecommunication Research Institute (TELMA), Universidad de Málaga, Málaga, Spain