PERFORMANCE AND ERROR PROPAGATION OF 2 DFE CHANNELS

We compare performance and error propagation of DFE with and without a d = 1 RLL code, at 2.67 user density and with a single coefficient FI R phase equalizer. Performance without error propagation is slightly b etter with d = I in spite of the rate loss, because precursor ISI can be completely eliminated. We develop a model to estimate the effects o f error propagation for both d = 0 and d = 1. The model is in good agr eement with a 20db SNR simulation. For an overall error rate of 10(-6) , the probability of a burst of length 50 in the decoded data is 10(-1 3) for d = 1 and 10(-8) for d = 0. This large difference is due both t o the higher code rate and to the larger postcursor cancelation for ed = 0. In the model, we rigorously compute burst error probabilities us ing a Markov chain derived from our channel assumptions. We also use t he model to compute the decay rate of the burst error probability and to identify the set of infinitely propagating sequences. In the simula tions, we use random data and a commonly used (1,7) code for DFE17, to which we added AWGN noise at SNR 20db. Finally, we compare the result s of the model with the simulations.