说明：  Alamouti方案在MISO i.i.d.瑞衰落信道两根发射天线上进行QPSK传输，SNR从0到20dB仿真。
(Alamouti scheme with QPSK transmission over a MISO i.i.d. Rayleigh fading Channel two transmit antennas, SNR from 0 to 20dB simulation.)