The effect of imperfect CSI on QAM bit-interleaved coded modulation with iterative decoding in fading

We study the impact of imperfect channel state information (CSI) on the bit-error rate (BER) of QAM bit-interleaved coded modulation with iterative decoding (BICM-ID), in flat Rayleigh fading. The key parameter characterizing this effect is the power correlation coefficient p between the fading gain and its estimate. An accurate and efficient bound is developed to predict the asymptotic BER. We also show simulation results for QAM BICM-ID with 8-state and 16-state convolutional codes to provide the performance evaluation. For 16-state code with the modified set partitioning labeling, and power correlation p = 0.95, a BER of 10(-6) can be achieved at E-b/N-o = I I dB, with 4 passes of soft feedback. This corresponds to about 3.5 dB increase in the required E-b/N-o, compared to that of perfect CSI.