Quadrature Amplitude Modulation (QAM) conveys digital information by modulating both the amplitude and phase of two orthogonal carrier waves (In-phase I and Quadrature Q). In a 16-QAM scheme, the constellation diagram arranges sixteen distinct symbol states across a Cartesian grid, with each state representing a unique 4-bit binary codeword. The receiver demodulates the transmitted symbol by determining the minimum Euclidean distance between the received noisy signal vector and the reference constellation grid points.