Tight-bound symbol error probability of high-level QAM in the presence of residual amplitude fluctuation (digital radio)

High-level QAM (quadrature amplitude modulation) system performance degradations caused by residual amplitude fluctuations of the received carrier after AGC (automatic gain control) amplifiers are studied. The authors derive tight-bound average symbol error probabilities of 64, 256, and 1024 QAM systems in the presence of the residual amplitude fluctuations and an AWGN (additive white Gaussian noise). The tight-bound symbol error probability is calculated by taking an average value of the typical symbol error probabilities including the best (i.e. the innermost) abilities. To confirm the accuracy of their results, the authors calculate an exact average symbol error probability of 64 QAM and also perform computer simulations on 64 QAM and 256 QAM systems.<>