Study and Comparison of Constellation diagrams of 16-QAM in different fading channels

Abstract

In this paper constellations for 16-quadrature amplitude modulation (16-QAM) in Rayleigh and Nakagami-m fading channels is studied. These constellation diagrams are useful for visualizing the effect of fading to the transmitted signal symbols. We simulated 16-QAM technique at different SNR and draw the constellation diagrams for Rayleigh and Nakagami-m fading channels for different values of m. At lower SNR the constellations are more dispersed. It shows that the effect of fading is more dominated at lower SNR. When the SNR is increased the effect of fading is reduced and it can be seen as constellations are less dispersed. We compare the BER versus SNR plot for AWGN and Rayleigh channel and also for AWGN and Nakagami-m fading channels for different values of m. It shows that the when we increase the value of m (nakagami factor) then the effect of fading increases and we need more SNR for reducing this effect of fading. Index Terms: 16-QAM, additive white Gaussian noise (AWGN), fading channels, constellation, BER, SNR