Low Density Parity Check Code Implementation

Claude Shannon

In communication systems, forward error correction (FEC) codes have been widely used to battle data transmission errors caused by unreliable communications through a noisy channel. By adding extra bits to the end of message bits, a certain number of bit errors can be detected and corrected without frequent retransmission in case of data errors. Low density parity check (LDPC) is a powerful FEC coding scheme which can achieve good error performance under very low signal-to-noise ratios. [1] A communications system utilizing LDPC code is able to get very close to the channel capacity limit which was established by Claude Shannon in the 1940’s. In addition, LDPC code has less complexity in the decoding process compared with other FEC codes. With the advance in computing power, it has been adopted in many high speed communication standards such as digital video broadcasting, WiMAX, 4G wireless systems, among others.

 LDPC Codes were first developed by Robert G. Gallager (below) in 1960. They were largely forgotten about until the 1990's when advances in computing power allowed them to be utilized.

Robert G. Gallager