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 η 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 (η>0 dB), while indifferent to underestimation in a fairly large region (η∈[-6,0] dB). The accuracy of our EXIT chart prediction is verified by simulation.