LMMSE turbo equalization based on factor graphs

Qinghua Guo, L. Ping

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    74 Citations (Scopus)
    426 Downloads (Pure)


    In this paper, a vector-form factor graph representation is derived for intersymbol interference (ISI) channels. The resultant graphs have a tree-structure that avoids the short cycle problem in existing graph approaches. Based on a joint Gaussian approximation, we establish a connection between the LLR (log-likelihood ratio) estimator for a linear system driven by binary inputs and the LMMSE (linear minimum mean-square error) estimator for a linear system driven by Gaussian inputs. This connection facilitates the application of the recently proposed Gaussian message passing technique to the cycle-free graphs for ISI channels. We also show the equivalence between the proposed approach and the Wang-Poor approach based on the LMMSE principle. An attractive advantage of the proposed approach is its intrinsic parallel structure. Simulation results are provided to demonstrate this property.
    Original languageEnglish
    Pages (from-to)311-319
    JournalIEEE Journal on Selected Areas in Communications
    Issue number2
    Publication statusPublished - 2008


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