Row-Boosted Ensemble Belief Propagation for Short LDPC Codes
2026-08-10 • Information Theory
Information Theory
AI summaryⓘ
The authors address a limitation in decoding certain error-correcting codes called LDPC codes, where the decoding process can get stuck or behave unpredictably. They propose a method called row-boosted ensemble (RBE) decoding, which creates diversity by slightly boosting messages from a few parity-check rows, while keeping the main code structure the same. This approach improves error correction performance noticeably compared to some existing techniques, especially on a common 5G test code. The authors also show that increasing the number of boosted versions can further improve results and that the method works well across different code lengths and decoding schedules.
Belief PropagationLow-Density Parity-Check (LDPC) CodesError CorrectionDecoding AlgorithmsEnsemble DecodingParity-Check Matrix5G NR CodesFrame-Error RateMessage PassingLayered Schedule
Authors
Paul Bezner, Felix Krieg, Stephan ten Brink
Abstract
Belief-propagation (BP) decoding of short and moderate-length low-density parity-check (LDPC) codes is limited by finite-length graph effects: a single decoder trajectory can become trapped or oscillatory even when an alternative trajectory would decode the received word. Existing ensemble-BP decoders create the required diversity through multiple parity-check matrices, automorphisms, modified schedules, subcodes, or altered update rules. We introduce row-boosted ensemble (RBE) decoding as a minimal decoder-side diversity mechanism: all ensemble members share the same parity-check matrix and the same BP kernel, and differ only in a small set of parity-check rows whose outgoing messages are boosted. On the 5G~NR BG1 \((144,96)\) code, RBE with \(32\) members lowers the frame-error rate of BP with \(20\) iterations (BP-20) from \(1.6\times10^{-2}\) to \(1.6\times10^{-3}\) at \(E_\mathrm{b}/N_0=4.0\,\mathrm{dB}\), outperforming saturated-min-sum and affine subcode ensembles of equal size. Increasing the ensemble size yields additional gains, indicating that RBE provides a scalable performance-complexity tradeoff. The gains transfer across 5G~NR block lengths and rates, to non-5G short LDPC codes, and across flooding and layered schedules.