Removing Loops from LDPC Codes

Loop Removal from LDPC Codes

Small loops in the graphical representations of lowdensity parity-check codes are hypothesised to be detrimental to the code’s performance. In this paper we demonstrate a procedure for removing such loops from the graphs. An algorithm based on the code’s adjacency matrix is used to locate any unwanted loops, and then certain edges are exchanged within the graph to eliminate those loops (without...

Serial Concatenation and Joint Iterative Decoding of LDPC Codes and Reed-Solomon Codes

In this paper, a serial concatenation scheme and its iterative decoding algorithm between Low Density Parity Check codes (LDPC) and Reed-Solomon codes are proposed. For the decoder, the soft output values delivered by LDPC are used as reliability values to perform the Chase decoding of Reed-Solomon (RS) codes which return soft information to LDPC decoder. This approach presents an option scheme...

On the Grobner Basis of a Family of Quasi-Cyclic LDPC Codes

Semi-random LDPC codes for CDMA communication over non-linear band-limited satellite channels

This paper considers the application of low-density parity check (LDPC) error correcting codes to code division multiple access (CDMA) systems over satellite links. The adapted LDPC codes are selected from a special class of semi-random (SR) constructions characterized by low encoder complexity, and their performance is optimized by removing short cycles from the code bipartite graphs. Relative...

Improving the Rao-Nam secret key cryptosystem using regular EDF-QC-LDPC codes

This paper proposes an efficient joint secret key encryption-channel coding cryptosystem, based on regular Extended Difference Family Quasi-Cyclic Low-Density Parity-Check codes. The key length of the proposed cryptosystem decreases up to 85 percent using a new efficient compression algorithm. Cryptanalytic methods show that the improved cryptosystem has a significant security advantage over Ra...