Tele-Communication (Telecom) Terms Glossary and Dictionary
Low-Density Parity-Check Code
Low-density parity-check code is an error correcting code used in a method of transmitting information over a noisy transmission path. Low density parity check (LDPC) codes were introduced along with an iterative probability-based decoding algorithm by Gallager in the early 1960's. These codes were constructed using sparse random parity check matrices and showed promising distance properties. However, they went largely unnoticed until the advent of turbo codes, where they were “rediscovered” by MacKay, who showed that they perform almost as close to capacity as turbo codes. More recently, Richardson and Urbanke have developed irregular LDPC codes that perform even better than turbo codes for very large block lengths (n>10^5) and can come within 0.1 dB of the Shannon capacity.