说明：  为了使数字信号在有限带宽的高频信道中传输，必须对数字信号进行载波调制。就频带利用率和抗噪声性能（或功率利用率）两个方面来看， QPSK系统最佳。QPSK是利用载波的四种不同相位差来表征输入的数字信息，是四进制移相键控（QPSK）。本项目用MATLAB软件对四进制移相键控信号在AWQN信道中传输进行了建模和仿真，通过对仿真得到的误码率和理论误码率进行比较和分析，从而证明了MATLAB软件仿真QPSK调制解调的可行性。
(In order to make the digital signal in the high-frequency channel of limited bandwidth transmission of digital signal carrier modulation. Two in terms of bandwidth efficiency and anti-noise performance (or power utilization), QPSK system the best. QPSK, four different phase characterized by the input digital information using carrier quaternary phase shift keying (QPSK). This project using MATLAB software quaternary phase shift keying signal channel transmission in AWQN modeling and simulation, to compare and analyze the error rate obtained by the simulation and theoretical bit error rate, thus proving the simulation of MATLAB software QPSK modulation and demodulation of feasibility.-)