MATLAB development of QAM system to transmit data over an audio channel. The receiver is currently unable to detect or correct for constellation rotation errors of -90, 180, or 90 degrees.
QAM4 Screenshot.png (below) shows the simulated result of a simple configuration so that the principle of operation of QAM can be understood from the plots.
QAM64 Screenshot.png (below) shows the result of QAM256 being used to send and receive 96 kb/s through and audio loopback created by connecting the sound card's line in and line out sockets.
Block Diagram.png (below) is a block diagram of the complete system.