On iterative equalization, estimation, and decoding

We consider the problem of coded data transmission over an inter-symbol interference (ISI) channel with unknown and possibly time-varying parameters. We propose a low-complexity algorithm for joint equalization, estimation, and decoding using an estimator, which is separate from the equalizer. Based on existing techniques for analyzing the convergence of iterative decoding algorithms, we show how to find powerful system configurations. This includes the use of recursive precoders in the transmitter. We derive a novel a-posteriori probability equalization algorithm for imprecise knowledge of the channel parameters. We show that the performance loss implied by not knowing the parameters pf the ISI channel is entirely a loss in signal-to-noise ratio for which a suitably designed iterative receiver algorithm converges.