On the Distribution of Extrinsic L-values in Gray-mapped 16-QAM
Paper in proceedings, 2007

In this paper we address the issue of probabilistic modelling of the extrinsic L-values, used as reliability metrics in the context of bit interleaved coded modulation with iterative demapping (BICM-ID). Starting with a simple piece-wise linear model of the L-values obtained via the max-log approximation, we derive the expressions for the cumulative distribution functions of the L-values, that differentiated produce the desired forms of the probability density functions for Gray-mapped 16-QAM. To illustrate the usefulness of our analytical expressions we applied them to efficiently compute the so-called EXIT functions of the demapper for different values of SNR. The proposed analytical expressions are also compared to the histograms of the L-values obtained through time-consuming simulations.


Alex Alvarado

Chalmers, Signals and Systems, Communication and Antenna Systems, Communication Systems

Leszek Szczecinski

INRS-Energy, Materials and Telecommunications

Rodolfo Feick

Universidad Técnica Federico Santa María

AMC International Wireless Communications and Mobile Computing Conference 2007, IWCMC 2007


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