BER Transfer Chart Analysis of Turbo Frequency Domain Equalization

In this paper we analyze the performance of a turbo frequency domain equalizer using the BER transfer chart. This tool evaluates the signal to noise ratio improvement at the decoder input during iterations. We derive a formula for the variance of the equalizer output at each iteration as a function of the error probability of the previous iteration. By defining an equivalent SNR based on the equalizer output mean and variance, and knowing the decoder bit error rate curve, we are able to evaluate the bit error rate of the decoder output in each iteration. Compared to the initially proposed BER transfer charts, this method gives us a more accurate curve for the equalizer and follows the dynamic of the process. Simulation results show that this method can predict the performance of the system with reasonable accuracy.