1. School of Information and Electronics, Beijing Institute of Technology, Beijing, China
2. School of Electronics and Information Engineering, Beihang University, Beijing, China
3. School of Aerospace, Transport and Manufacturing, Cranfield University, Bedford, U.K.
4. Instituto de Telecomunicações, Aveiro, Portugal
5. Research and Development Department, EXFO, Montreal, Canada
6. China Mobile Research Institute, Beijing, China