Download or read book Low Density Parity Check Codes Based on Finite Geometries written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-09-15 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low density parity check (LDPC) codes with iterative decoding based on belief propagation achieve astonishing error performance close to Shannon limit. No algebraic or geometric method for constructing these codes has been reported and they are largely generated by computer search. As a result, encoding of long LDPC codes is in general very complex. This paper presents two classes of high rate LDPC codes whose constructions are based on finite Euclidean and projective geometries, respectively. These classes of codes a.re cyclic and have good constraint parameters and minimum distances. Cyclic structure adows the use of linear feedback shift registers for encoding. These finite geometry LDPC codes achieve very good error performance with either soft-decision iterative decoding based on belief propagation or Gallager's hard-decision bit flipping algorithm. These codes can be punctured or extended to obtain other good LDPC codes. A generalization of these codes is also presented.Kou, Yu and Lin, Shu and Fossorier, MarcGoddard Space Flight CenterEUCLIDEAN GEOMETRY; ALGORITHMS; DECODING; PARITY; ALGEBRA; INFORMATION THEORY; PROJECTIVE GEOMETRY; TWO DIMENSIONAL MODELS; COMPUTERIZED SIMULATION; ERRORS; BLOCK DIAGRAMS...