Performance analysis of turbo-equalized systems over frequency-selective block-fading channels

In this paper, we investigate the finite-length system performance of turbo-equalized systems over frequency-selective block-fading channels for packet data transmissions. First, we derive a tight upper bound on the frame error rate (FER) performance of the system under maximum-likelihood sequence estimation based on an approximation of the Euclidean distance distribution at the output of the noiseless inter-symbol interfering channel. Then, we show that the intersymbol interference can be viewed as an additional fading factor depending on the channel selectivity, but also on the coding scheme and the interleaver type. By introducing the interference-to-fading ratio, we evaluate the impact of the interference in the performance degradation compared to the effect of the fading. We show that a two-stage interleaver structure is needed to achieve coding diversity and turbo-equalization gain.