Performance Analysis of Cross-Entropy Stopping Criterion for Quadrature Amplitude Modulation

The cross-entropy stopping criterion (CE) with binary phase-shift keying can perform well at high sound-to-noise ratio regions in additive white Gaussian noise (AWGN). However, because of the high request of high-speed networks nowadays, the CE must be tested with high order modulation to determine its performance. In this paper, a CE with a threshold equal to 0.0001 was tested in quadrature amplitude modulation (QAM) in the AWGN channel. In addition, the research also tested the CE with various frame sizes, M-ary QAM, and code generators. From the results obtained, the CE is poor in average iteration number (AIN) at a high noisy channel while it can terminate early at a low noisy channel. The CE is also capable of maintaining the bit error rate (BER) performance for various noisy channel stages. Therefore, the CE is suitable to be used with QAM for the low noisy channel to save the AIN and maintain the BER performance of turbo codes.