On Fault Tolerance of the Gallager B Decoder Under Data-Dependent Gate Failures

In this letter, we characterize the effect of data-dependent gate failures on the performance of the Gallager B decoder of low-density parity-check codes. We show that this type of failures makes the decoder dependent on a transmitted codeword, thus rendering inapplicable the traditional analysis tools such as density evolution and trapping sets. By using Monte Carlo simulations, we identify two operating regions: one in which hardware unreliability leads to significant performance degradation and another in which the performance loss is negligible. Based on these results, we propose a simple modification of the decoder that ensures its fault tolerance.