1. School of Electronic and Information Engineering, Beihang University, Beijing, China
2. School of Computer Science and Electronics Engineering, University of Essex, Colchester, U.K
3. 5GIC & 6GIC, Institute for Communication Systems, University of Surrey, Guildford, U.K
4. Huawei Technologies Canada Company Ltd., Markham, ON, Canada
5. School of Cyber Science and Technology and the Beijing Laboratory for General Aviation Technology, Beihang University, Beijing, China