Performance analysis of the bit-interleaved coded modulation using turbo equalization with single carrier frequency domain equalization using subblock signal processing over fast fading channels

We investigate the impact of the subblock signal processing on the performance of the bit-interleaved coded modulation using turbo equalisation with single carrier frequency domain equalisation (BICM TE-SC-FDE) over frequency selective fading channels. We focus on the impact of the subblock signal processing to mitigate the impact of the residual intersymbol interference (ISI) on the convergence behaviour using the extrinsic information transfer (EXIT) chart technique. We first show that BICMTE-SC-FDE with subblock signal processing can effectively mitigate the residual ISI impacting not only the error floor but also the convergence behaviour. Then, we show that the Gaussian assumption modelling of the soft information within the TE-SC-FDE with subblock signal processing can accurately track the flow of the extrinsic information in the iterative procedure. We parameterize the inter-subblock interference as a function of the ratio between the channel´s length and fast Fourier transform blocksize, channel´s power delay profile and the soft estimate obtained from the channel decoder. This leads to an analytical model where the product of the Doppler spread and transmit block length and the number of subblocks signal processing are crucial parameters affecting the transfer function of the equalizer and hence the convergence behavior of the TE-SC-FDE with subblock signal processing. The accuracy of our EXIT chart prediction is verified by the simulation. Performance evaluation using the EXIT chart analytical technique is much faster than the exhaustive BER simulation of the overall system.