Iterative equalization and decoding using reduced-state sequence estimation based soft-output algorithms

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Title: Iterative equalization and decoding using reduced-state sequence estimation based soft-output algorithms
Author: Tamma, Raja Venkatesh
Abstract: We study and analyze the performance of iterative equalization and decoding (IED ) using an M -BCJR equalizer . We use bit error rate (BER ) , frame error rate simulations and extrinsic information transfer (EXIT ) charts to study and compare the performances of M -BCJR and BCJR equalizers on precoded and non -precoded channels . Using EXIT charts , the achievable channel capacities with IED using the BCJR , M -BCJR and MMSE LE equalizers are also compared . We predict the BER performance of IED using the M -BCJR equalizer from EXIT charts and explain the discrepancy between the observed and predicted performances by showing that the extrinsic outputs of the $M $ -BCJR algorithm are not true logarithmic -likelihood ratios (LLR's ) . We show that the true LLR's can be estimated if the conditional distributions of the extrinsic outputs are known and finally we design a practical estimator for computing the true LLR's from the extrinsic outputs of the M -BCJR equalizer .
URI: http : / /hdl .handle .net /1969 .1 /283
Date: 2004-09-30

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Iterative equalization and decoding using reduced-state sequence estimation based soft-output algorithms. Available electronically from http : / /hdl .handle .net /1969 .1 /283 .

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