1.　　基于simulink搭建一个QPSK发送链路，QPSK调制信号经过了瑞利衰落信道，观察信号经过衰落前后的星座图，观察信道特性。仿真参数：信源比特速率为500kbps，多径相对时延为[0 4e-06 8e-06 1.2e-05]秒，相对平均功率为[0 -3 -6 -9]dB，最大多普勒频移为200Hz。-1. Based on simulink structures, QPSK sent a link, the Rayleigh fading channel after the QPSK modulation signal, were observed before and after signal after the decline of constellation diagram, observation channel characteristic. Simulation parameters: the source is 500 KBPS bit rate, relative multipath time delay of [0 8 e 4 e- 06-06 e-05] 1.2 seconds, the relative average power is [0-3-6-9] dB, most of the doppler frequency shift is 200 hz.