1. National Key Laboratory of Science and Technology on Communications, University of Electronic Science and Technology of China, Chengdu, China
2. Institute for Digital Communications, Friedrich-Alexander-University Erlangen–Nürnberg (FAU), Erlangen, Germany
3. National Mobile Communications Research Laboratory, Southeast University, Nanjing, China
4. Center for Pervasive Communications and Computing, University of California at Irvine, Irvine, CA, USA
5. Department of Electronic Systems, Aalborg University, Aalborg, Denmark