Analysis of linear turbo equalizer via EXIT chart

Abstract

We propose a method for the analysis of linear turbo equalization based on extrinsic information transfer (EXIT) charts. Given channel knowledge, and therefore the optimum linear equalizer coefficients, the evolution of soft information of the soft-input soft-output (SISO) equalizer can be estimated by computing bit error rates (BER) analytically. Compared to conventional analysis methods, the proposed method predicts the linear turbo equalizer performance without running extensive simulations to obtain the SISO equalizer EXIT charts. Using an empirically generated SISO decoder EXIT chart, convergence analysis can be undertaken. Further, the method provides a bound on the achievable BER for given channels and an estimate of equalizer complexity. These approximate analyses are validated via computer simulations.