说明：  The digital simulation system using MATLAB to illustrate the Quadrature Amplitude Modulation (QAM). QAM is a modulation scheme to convey two digital bit streams which can be converted to symbol signals by modulating the amplitudes and the phase of two carrier waves. First, we transmit a signal composed of two different 1024 bit streams and modulate them using QAM. Next, at the receiver, we demodulate them using an orthogornality of two carriers and matched filters. We also conduct the error analysis of two sampled signals in order to observe how the probability of making bit errors changes depending on the inverse of Power Spectral Density (PSD) of Additive White Gaussian Noise (AWGN).