Low-Activity Gallager-B LDPC Decoding

Reducing the energy consumption of LDPC decoders is an essential step towards increasing the relevance of these codes in energy-constrained applications such as protecting on-chip memories. Gallager-B (GaB) LDPC decoders are well suited for high throughput applications due to their low complexity. We propose Low-Activity Gallager-B (LA-GaB), a functional equivalent to GaB with reduced message switching probability, and an adapted density evolution technique capable of predicting its message switching probabilities. We demonstrate an ASIC implementation of LA-GaB in an unrolled configuration achieving a reduction of more than 50% of dynamic energy and lower surface area compared to standard GaB, with no change in decoding performance. We also propose a high-level energy model of this unrolled implementation based on our activity model for rapid design exploration in the energy domain.