Performance Analysis, Characteristics, and Simulation of Digital QAM

Quadrature Amplitude Modulation or QAM is a form of modulation which is widely used for modulating data signals onto a carrier used for radio communications. QAM, when used for digital transmission for radio communications applications is able to carry higher data rates than ordinary amplitude modulated schemes and phase modulated schemes. This paper presents the various fields where QAM can be implemented, describes modulator/demodulator block diagrams for transmitters as well as receivers, provides an introduction of certain performance indicators of modulation and a list of applications using alternative implementations of QAM. Also the paper presents a simulation of QAM using Simulink (example of 16-QAM signal) with signal trajectors and constellation plots. It is compared the theoretical and simulated Bit Error Rate (BER) for 16-QAM with Gray coding in an AWGN channel. Some general conclusions are also cited.