Density Evolution and Functional Threshold for the Noisy Min-Sum Decoder

This paper investigates the behavior of the Min-Sum decoder running on noisy devices. Our aim is to evaluate the robustness of the decoder to computation noise caused by the faulty logic in the processing units. This type of noise represents a new source of errors that may occur during the decoding process. To this end, we first introduce probabilistic models for the arithmetic and logic units of the finite-precision min-sum decoder and then carry out the density evolution analysis of the noisy min-sum decoder. We show that, in some particular cases, the noise introduced by the device can help the min-sum decoder to escape from fixed points attractors and may actually result in an increased correction capacity with respect to the noiseless decoder. We also point out a specific threshold phenomenon, referred to as functional threshold, which accurately describes the convergence behavior of noisy decoders. The behavior of the noisy MS is demonstrated in the asymptotic limit of the code length through a noisy version of density evolution and is also verified in the finite-length case by Monte Carlo simulations.