要求对有3条固定路径的AWGN多径信道中的QPSK系统进行BER性能仿真，并与在理想的AWGN信道中同样系统的BER性能进行比较。熟悉瑞利平坦衰落、莱斯平坦衰落与频率选择性衰落的特点，比较这些衰落信道的误码率。-Required to have three fixed-path AWGN multipath channels of QPSK system BER performance simulation, and in an ideal AWGN channel with the same system BER performance comparison. Familiar with the Rayleigh flat fading, Rice flat fading and frequency selective fading characteristics, compare the bit error rate fading channel.