Funding for this research was provided by:
National Natural Science Foundation of China (61172055, 61471135)
Guangxi Natural Science Foundation (2013GXNSFGA019004, 2015GXNSFBB139007)
Fund of Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing (CRKL150104, CRKL160105)
Innovation Project of GUET Graduate Education (2016YJCX87)