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 /spl rho/ 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 the 16-state code with modified set partitioning labeling and power correlation /spl rho/=0.95, a BER of 10/sup -6/ can be achieved at E/sub b//N/sub 0/=11 dB, with 4 passes of soft feedback. This corresponds to about 3.5 dB increase in the required E/sub b//N/sub 0/ compared to that of perfect CSI.