仿真4-PAM载波调制信号在AWGN信道下的误码率和误比特率性能，并与理论值相比较。假设符号周期为1s，载波频率为10Hz，每个符号周期内采样100个点。 -Simulation 4-PAM modulation signal in AWGN channel bit error rate and bit error rate performance, and compared with the theoretical value. Assuming symbol period for 1s