EXIT chart analysis of BICM-ID over AWGN channels with SNR mismatch

We use the extrinsic information transfer (EXIT) chart to analyze the convergence of iteratively decoded bit-interleaved coded modulation with channel signal-to-noise ratio mismatch. For additive white Gaussian noise channels, we develop a generalized model for the a priori inputs, which is parameterized by the ratio 77 between the noise variance estimate and its true value. We show that the demapper and decoder transfer functions are very sensitive to overestimation of the noise variance (eta > 0 dB), while indifferent to underestimation in a fairly large region (eta is an element of [-6, 0] dB). The accuracy of our EXIT chart prediction is verified by simulation.