多径信道仿真 有三条固定路径的AWGN多径信道的QPSK系统进行BER性能方针,并与在理想的AWGN信道中同样系统的BER进(Multipath channel simulation QPSK system with three fixed paths for AWGN multipath channel carries out BER performance policy, and the same system BER advance as in ideal AWGN channel)