Comparisons of PSK, APSK, and QAM over AWGN and fading channels

Abstract

In addition to the thermal noise, communication systems can normally experience various fading because of objects reflecting the signal. PSK, APSK, and QAM modulation schemes are widely used in communication systems. It is thus essential to know how well these schemes can perform in different fading channels. This research explores the BER performance of these modulation schemes in common and typical channel models including AWGN, Rayleigh fading, Rician fading, and Nakagami fading channels by simulations in MATLAB. The BER curves over a range of SNR and symbol constellation diagrams are obtained. It is found that Rayleigh and Nakagami fading distort signals most and impacts of Rician fading in LoS case and AWGN can be mitigated significantly by increasing the SNR. Furthermore, the QAM has better BER performance in fading channels while PSK and APSK perform better in AWGN channels when the number of bits of one symbol is relatively small. Selections of modulation schemes should depend on the specific circumstances and the optimization of them is required when large numbers of bits are transmitted by one symbol.