New error prediction techniques for turbo-coded OFDM systems and impact on adaptive modulation and coding

This paper deals with packet error rate (PER) prediction and its impact on adaptive modulation and coding (AMC) for an OFDM turbo coded transmission on a multipath channel. We compare four link quality metrics (LQM), including the signal to noise ratio (SNR), the capacity, and two LQM which we designed to exploit the soft outputs of the turbo-decoder. Since error prediction is used to perform AMC, we assess the throughput performance of a realistic system employing each of the four LQM. The comparison shows that while SNR performs poorly and capacity remains suboptimum, the two metrics exploiting soft outputs approach the throughput which would be achieved by perfect PER prediction