1. Purple Mountain Laboratories,Nanjing,P. R. China,211111
2. Southeast University,National Mobile Communications Research Laboratory,Nanjing,China,210096
3. China Telecom Research Institute,Beijing,P. R. China,102209
4. Beijing Jiaotong University,School of Electronic and Information Engineering,Beijing,China,100044
5. Beijing University of Posts and Telecommunications,State Key Laboratory of Networking and Switching Technology,Beijing,China,100876